1
Download Certus Standard
Transcript
Certus Standard Scanning Probe Microscope with optical video microscope User manual Nano Scan Technologies Ltd. Zavodscaya St 7, Dolgoprudniy, Russian Federation, 141700 Pnone: +7 (495) 665-00-85 +7 (495) 642-40-68 +7 (495) 642-40-67 E-mail: info@nanoscantech. com web: www. nanoscantech. com 2011 This user guide is intended for installation and operation of a Scanning Probe Microscope Certus Standard. Scanning Probe Microscope Certus Standard is a combination of XYZ scanner, cantilever tip sensor (deflectometer), SPM controller EG-3000, software Nspec and optical video microscope. Before installation and operation this appliance, please read the manual. On all matters related to technical support and upgrades for this product, under the additional features, contact the following addresses: Phone: +7 (495) 665-00-85 +7 (495) 642-40-68 +7 (495) 642-40-67 E-mail: info@nanoscantech. com web: www. nanoscantech. com Skype: NanoScanTech «Nano Scan Technologies Ltd.» User manual 2 Read this first! Laser radiation. When you work in certain modes, using a scanning probe microscope (SPM) Certus Standard, laser light sources of varying power and wavelength are used. Before working with SPM Certus Standard, we encourage you to read the documentation for the specified source of laser radiation and safety for the class of the laser source. In the case of an external laser in the recording system of the microscope or with a combination of SPM Certus Standard with external laser sources, we recommend that you study the documentation and safety for your laser source. Precautions. SPM Certus Standard – this is a complex research tool. Strong physical impacts, operation in hostile environments, changes in the structure during use, storage or transportation can result to device damage. Modification and user self-alignment of SPM Certus Standard with research equipment. In the case of user self-alignment of SPM Certus Standard with research equipment, or modification to the specific research tasks recommended to agree the matter with the company "Nano Scan Technology", because the user self-interference in the construction without the agreement deprives the warranty. «Nano Scan Technologies Ltd.» User manual 3 Contents Contents Introduction.................................................................................................9 1. Basic information...................................................................................10 1.1. Field of applications of the SPM Certus Standard........................................10 1.2. Overview of the SPM Certus Standard..........................................................11 1.3. Specification......................................................................................................12 1.3.1. Data Sheet...................................................................................................12 1.3.2. Sample size..................................................................................................13 1.3.3. Deflectometer lasers....................................................................................13 1.3.4. SPM Certus Standard dimensions...............................................................14 1.4. Operating conditions........................................................................................15 1.5. Safety regulations..............................................................................................16 1.6. Terms of storage and transportation..............................................................17 1.6.1. Storage........................................................................................................17 1.6.2. Transportation.............................................................................................17 1.7. Description of basic units.................................................................................18 1.7.1. Scanning head Certus.................................................................................20 1.7.2. Controller EG-3000....................................................................................24 1.7.3. Certus Standard microscope base...............................................................26 1.7.4. Videomicroscope.........................................................................................27 1.7.5. NSpec Software...........................................................................................28 2. Operating principles..............................................................................29 2.1. SPM common principles..................................................................................29 2.2. Probe scanning/positioning..............................................................................31 2.2.1. Scanning......................................................................................................31 2.2.2. Piezoelectric phenomena............................................................................32 2.2.3. Lever translation systems............................................................................33 2.2.4. Displacement sensors..................................................................................35 2.3. Probes.................................................................................................................36 «Nano Scan Technologies Ltd.» User manual 4 Contents 2.3.1. Basic probe parameters..............................................................................36 2.3.2. Probe drawings...........................................................................................37 2.4. Cantilever Z position detection system...........................................................38 2.4.1. Deflector registration system......................................................................38 2.4.2. “Shear-force” registration system..............................................................40 2.5. Feedback............................................................................................................42 2.6. Combining optical and scanning probe microscope......................................42 3. Start operation.......................................................................................44 3.1. SPM Certus Standard installation..................................................................44 3.2. Installation of vibration protection.................................................................44 3.3. Installation SPM Certus Standard base and videomicroscope....................45 3.3.1. Installation of the stand...............................................................................46 3.3.2. Installation of the arm.................................................................................46 3.3.3. Installation of the microscope mover..........................................................47 3.3.4. Installation of the videomicroscope............................................................48 3.4. SPM Certus installation...................................................................................49 3.4.1. SPM Certus head description......................................................................49 3.4.2. Probe holder connection.............................................................................52 3.4.3. Installation SPM Certus on the base...........................................................54 3.5. EG-3000 controller connection........................................................................55 3.6. PC connection...................................................................................................56 3.7. Videocamera connection to the computer......................................................56 3.8. Remote controller connection..........................................................................56 3.9. NSpec software installation..............................................................................57 3.10. SPM Certus Standard «on/off» regulation...................................................58 3.10.1. «On» rules.................................................................................................58 3.10.2. «Off» rules.................................................................................................59 3.11. NSpec basic options........................................................................................59 4. Working with SPM Certus Standard...................................................62 «Nano Scan Technologies Ltd.» User manual 5 Contents 4.1. The list of base operating modes.....................................................................62 4.2. Basic SPM Certus Standard operations (atomic-force microscope techniques)..................................................................................................................62 4.3. Adjustment of range and bias of the capacity sensors..................................63 4.4. Adjustment of PID control...............................................................................64 4.5. Probe installation..............................................................................................65 4.6. Sample mounting..............................................................................................67 4.7. Information about NSpec software required for SPM Certus Standard adjustment..................................................................................................................69 4.7.1. Plot mode control........................................................................................70 4.7.2. Cantilever resonant frequency acquisition..................................................70 4.7.3. Oscilloscope mode......................................................................................71 4.7.4. Land/lift curves............................................................................................72 4.8. Deflectometer system adjustment...................................................................73 4.8.1. Laser beam alignment to cantilever bulk....................................................73 4.8.2. PSD (position sensor diode) alignment.......................................................75 4.8.3. Search of the reflected beam.......................................................................76 4.8.4. Alignment the reflected beam with the PSD center.....................................77 4.8.5. Probe resonant frequency acquisition.........................................................78 4.9. Feedback parameters.......................................................................................80 4.9.1. Additional scan parameters........................................................................83 4.9.2. General recommendations of feedback parameters....................................83 4.9.3. Setpoint tuning............................................................................................83 4.9.4. Probe Z axes control...................................................................................84 4.10. Sample stage positioning................................................................................84 4.11. Probe approaching to the sample..................................................................85 4.11.1. The control of the stepper motors..............................................................85 4.11.2. Stepper motors settings..............................................................................87 4.11.3. Remote control adjustment........................................................................88 4.11.4. Tip approaching.........................................................................................90 «Nano Scan Technologies Ltd.» User manual 6 Contents 4.11.5. Head leveling.............................................................................................90 4.11.6. Head tilting and coarse approaching........................................................90 4.11.7. Fine approaching......................................................................................91 4.11.8. Approaching by remote controller.............................................................91 4.12. Sample positioning..........................................................................................92 4.13. Adjustment of scan parameters.....................................................................92 4.13.1. Signal description......................................................................................95 4.13.2. Multi-pass technique.................................................................................97 4.13.3. Additional scan parameters......................................................................97 4.13.4. Selection of scanning parameters.............................................................99 4.13.5. Scanning conditions..................................................................................99 4.14. Scanning........................................................................................................100 4.15. Primary image processing and saving........................................................101 4.16. Precise probe positioning.............................................................................102 4.17. Scanner calibration.......................................................................................103 4.18. Calibration procedure..................................................................................106 4.18.1. Calibration mode....................................................................................106 4.18.2. Piezostack calibration.............................................................................107 4.18.3. Sensors calibration..................................................................................107 4.18.4. Tool panel Settings..................................................................................108 4.18.5. Calibration coefficients obtaining...........................................................109 5. SPM Certus head application with external optical equipment......113 5.1. Basic principles of optical equipment application.......................................113 5.2. Example...........................................................................................................114 5.3. Video-videocam mode adjustment................................................................114 5.4. Video unit basic functions..............................................................................115 5.5. Lenses calibration...........................................................................................118 5.5.1. Settings panel main functions....................................................................118 5.5.2. Tools panel Settings...................................................................................119 «Nano Scan Technologies Ltd.» User manual 7 Contents 5.5.3. New lens calibration.................................................................................120 5.5.4. Scan field selecting....................................................................................120 5.6. Microscope positioning...................................................................................122 «Nano Scan Technologies Ltd.» User manual 8 Introduction Introduction This user guide describes SPM Certus Standard, specifically designed for work with optical equipment, such as optical microscopes, spectrometers and other similar devices. Universal SPM controller EG-3000 and software NSpec is required for SPM Certus operation. «Nano Scan Technologies Ltd.» User manual 9 Basic information 1. Basic information 1.1. Field of applications of the SPM Certus Standard Certus Standard – specialized scanning probe microscope (SPM), specially designed to work with optical equipment for combining the techniques of scanning probe microscopy and optical microscopy and spectroscopy. XYZ scanning head with piezoceramic stacks is a base of the system. SPM Certus Standard is designed for imaging and studying the surface properties of various substances, materials and structures, both natural and artificial. For example, the study of surface properties of polymer, biological, inorganic, and semiconductor materials, biological cells, tissues, individual biological structures and biomolecules, covered, electronic equipment, etc. With SPM Certus Standard you can solve the following problems: • Topography imaging; • Surface roughness determination; • Surface force spectroscopy; • Nano lithography; • To obtain relevant information about the physical and chemical properties of the sample surface; • Obtain optical microscopic images of reflected light; • Precise SPM probe positioning with optical microscope. General list of tasks implemented by the SPM Certus, determined by the used method. «Nano Scan Technologies Ltd.» User manual 10 Basic information 1.2. Overview of the SPM Certus Standard Fig. 1.1 Overview of the SPM Certus Standard. «Nano Scan Technologies Ltd.» User manual 11 Basic information 1.3. Specification 1.3.1. Data Sheet Main data sheet 1 1.1 SPM scanning head Built-in XYZ scanner (flat stage) 1.1.1 Range 100x100x15 μm 1.1.2 XY resonant frequency 1 kHz 1.1.3 Z XY resonant frequency 7 kHz 1.1.4 Lateral (XY) resolution <1 nm 1.1.5 Vertical (Z) resolution <0.1 nm 1.1.6 Residual non-linearity <0.3% 1.1.7 Minimum scanning step 0.1 nm 1.2 Displacement sensors 1.2.1 Sensors type Capacitance 1.2.2 Operation principle 1.3 Scanner material 1.4 Landing system TDC (time to digital convertors) Aluminum alloy 1.4.1 Minimum step 1 μm 1.4.2 Implementation of the landing system 1.4.3 Number of stepper motor 1.5 Stepper motor 3 Sample positioning 1.5.1 Coarse sample positioning range 5x5 mm 1.5.2 Implementation of the coarse sample positioning 1.5.3 Positioning error 2 Microscrews ~5 μm Optical microscope 2.1 Implementation 2.2 Zooming 2.3 The range of fine-tuning 2.4 Video registration 2.5 Lighting 2.6 Video system optical parameters Digital video microscope Manual 5 mm Digital color video camera Fiber illumination 2.6.1 Numerical aperture 0.3 2.6.2 Camera sensor size 1/3” 2.6.3 Camera sensor resolution, px 1280x1024 2.6.4 Magnification 85x/1050x «Nano Scan Technologies Ltd.» User manual 12 Basic information 2.6.5 Field of view 4.50/0.37 mm 2.6.6 Interface USB 1.3.2. Sample size min Any max without SPM Up to Ø 230 mm and 30 mm height. max with SPM Up to Ø 125 mm and 16 mm height. 1.3.3. Deflectometer lasers Default 650 nm, <1 mW, Class II IR 1300 nm, <1 mW, Class II External User defined «Nano Scan Technologies Ltd.» User manual 13 Basic information 1.3.4. SPM Certus Standard dimensions Fig. 1.2 SPM Certus Standard dimensions «Nano Scan Technologies Ltd.» User manual 14 Basic information 1.4. Operating conditions SPM Certus Standard is a complex, high-precision research instrument. To ensure normal operation of the device are advised to observe the following conditions of use and storage: 1 Temperature 1.1 Range 10÷50°С 1.3 Optimum 22±3°С *When delivered, SPM Certus Standard scanner adjusted to the optimum operating temperature. When the room temperature is different from the optimum, but within the permissible operating temperature range, neces sary to calibrate the scanner at current temperature in the room. 2 Humidity 2.1 Maximum 80 % 2.2 Optimum 65±15 % 3 Atmospheric pressure, mm. Hg 760±30 4 Power requirements 4.1 Voltage, V 4.2 Frequency, Hz 4.3 Ground 5 110/220 (+10%/-15%) 50/60 required Noise and vibration 5.1 Vibration sensitivity range, Hz 1÷100 5.2 Maximum vibration magnitude in range 0.5 μm 5.3 Maximum sound pressure within 10000 Hz 35 dB 6 Shield from: 6.1 Direct sun light required 6.2 Heating required 6.3 Electromagnetic radiation required 6.4 Air/gas flow required 7 Extra recommendation 7.1 Frequent and abrupt changes in temperature and humidity, affect to performance and the quality of the results. 7.2 Running compressors, traction control, laminar boxes, cooling devices, and similar sources of periodic or random noise can create background noise. 7.3 Recommended to place Certus Standard with maximum possible distance from the computers, monitors and peripheral devices. 7.4 Avoid strong mechanical influences on Certus Standard, as this may lead to failure of the mechanics and control electronics unit. «Nano Scan Technologies Ltd.» User manual 15 Basic information 1.5. 1 Safety regulations Safety regulation 1.1 Ground Recommended to check equipment ground 1.2 Opened parts Work is prohibited, with the removed cover and the casing. 1.3 Cables connect/disconnect Cables connecting/disconnecting to device connectors can be done while device is off. 1.4 mount/dismount device units Only specialists of «Nano Scan Technology», certified specialists, in consultation with «Nano Scan Technology» 1.5 External equipment connec- Only in agreement with the company «Nano Scan Technology» tion 1.6 Liquid 2 Not accepted. Laser radiation sources 2.1 Deflectometer laser In accordance with the class of security established by the laser safety class and characteristics of the laser described in the SPM head under the label shown in Fig. 1.2. 2.2 External lasers In accordance with the marking on external sources of laser radiation Fig. 1.3 The warning label on the laser source. «Nano Scan Technologies Ltd.» User manual 16 Basic information 1.6. Terms of storage and transportation 1.6.1. Storage The device should be stored in compressed form in a special room with no abrupt changes in temperature and humidity. 1 Temperature 2 Humidity 22±10°С Maximum 80% 1.6.2. Transportation When transporting, instrument should be packed in the original package or in any other package, which excludes the damage. After transport at temperatures below 0°C, before starting the device, wait 3 hours. «Nano Scan Technologies Ltd.» User manual 17 Basic information 1.7. Description of basic units SPM Certus Standard includes the following parts: • SPM head Certus; • Optical microscope with illumination and video camera; • Base with mechanical motions for samples and optical video microscope positioning; • EG-3000 Controller; • NSpec software. A Scanning head Certus B Optical microscope C Digital video camera D Base with mechanical motions for samples and optical video microscope positioning Fig. 1.4 Basic units of the SPM Certus Standard. «Nano Scan Technologies Ltd.» User manual 18 Basic information A Scanning head Certus B Base with the mechanical movers for samples and an optical video microscope positioning C Optical microscope D Digital video camera E Illumination device F Vibration protection (in the base set - granite slab) Fig. 1.5 Overview of the SPM Certus Standard «Nano Scan Technologies Ltd.» User manual 19 Basic information 1.7.1. Scanning head Certus The basis of the scanning probe microscope Certus Standard is a scanning head of the new generation. The main distinguishing features of SPM Certus are: • Built-in XYZ flat scanner (scanning stage) with capacitive displacement sensors; • Modular architecture, allows to use different lasers for deflectometer, including external laser sources; • easily removable probe holder, which allows to use of fundamentally different types of probes; • open work area (the contact point of the probe and the sample), which provides easy monitoring of the probe, the input of external radiation, etc.; • parallel to the probe to sample approach system with the ability to automatically align the head over the plane of the sample; • Full digital connection between the head and the controller. Plane scanner (stage) is a monolithic metallic body (made of high quality Al alloy), in which with EDM and other methods of precision machining, formed channels for piezoelectric actuators (piezoelectric stacks), moving parts of the scanner, etc. This design provides excellent linearity and flatness of travel, in contrast to piezoelectric tubes, a scan surface which is a sphere. In addition, the plane-scanners have high mechanical stability compared to the brittle piezoelectric-tubes. In the basic mode SPM Certus operate as atomic-force microscope (AFM). As additional modes are implemented: scanning tunneling microscope, scanning Hall probe, Kelvin mode and other modes of scanning probe microscopy. «Nano Scan Technologies Ltd.» User manual 20 Basic information A Certus head body with built in XYZ flat scanner (stage). B Probe holder. C Screws for laser beam to cantilever bulk alignment. D Screws for reflected laser beam to PSD diode alignment. E High precision actuators for approach system. Fig. 1.6 SPM Certus head. Certus head scanner is equipped with capacitive displacement sensors. The measuring method is based on TDC (time-to-digital converters), that are physically located as close as possible to the sensors, that give digital signal proportional to measured capacitance. This method enables high-precision measurements and transmission current sensors position to the controller, with long cables without sacrificing the quality of measurements. In the standard configuration deflectometer diode laser with a wavelength of 650 nm is used. At the request of the customer may use another, for example infrared, laser. In addition, fiber optic port can be installed for connecting an external laser. The head comes with several detachable probe holders: standard cantilevers, tun«Nano Scan Technologies Ltd.» User manual 21 Basic information ing-fork type probes with a vertical or horizontal orientation. Probe holders for any original probes can be developed by the request of customers. Unique "open design" of the SPM Certus enables high multiples of the external lenses, illuminations, condensers microscopes, etc. to illuminate the work area, to view the sample and the probe, to take stock of the radiation to the point of contact tip and sample. For the Certus head control, universal the controller EG-3000 and the software NSpec are using. Fig. 1.7 SPM Certus drawings. «Nano Scan Technologies Ltd.» User manual 22 Basic information Basic technique 1 1.1 1.2 SPM Certus Atomic-force microscopy (AFM) 1.1.1 Contact AFM In base configuration 1.1.2 Resonance semicontact (AFM tapping mode) In base configuration 1.1.3 Resonance noncontact In base configuration 1.1.4 Phase imaging In base configuration 1.1.5 Adhesion force imaging In base configuration 1.1.6 Force spectroscopy In base configuration 1.1.7 Lateral force microscopy In base configuration Magnetic Force Microscopy* 1.1.1 Magnetic Force Microscopy 1.3 1.4 1.5 1.6 * In base configuration Scanning Tunneling Microscopy (STM)* Requires STM probe holder 1.3.1 Constant current mode With STM probe holder 1.3.2 Work function imaging With STM probe holder 1.3.3 Density of state imaging With STM probe holder 1.3.4 STM spectroscopy With STM probe holder Scanning current and capacitance probe micro- Requires special probe holder scopy* 1.4.1 Scanning capacitance microscopy With special probe holder 1.4.2 Kelvin Probe Microscopy With special probe holder 1.4.3 Electric Force Microscopy With special probe holder 1.4.4 Spreading Resistance Imaging With special probe holder Multipass techniques* For the implementation of combined techniques 1.5.1 Two-pass techniques (АСМ+МСМ and etc) Implemented 1.5.2 Constant Height mode (AFM, STM and etc) Implemented Lithography* 1.6.1 AFM Lithography in contact mode Implemented 1.6.2 AFM Lithography in dynamic mode Implemented 1.6.3 STM Lithography Implemented 1.6.4 AFM Oxidation Lithography Implemented Probes and probe holders «Nano Scan Technologies Ltd.» Many techniques require specialized probes and probe holders User manual 23 Basic information 1.7.2. Controller EG-3000 EG-3060/3060A controller designed to control the operation of scanning probe optical or confocal microscope. The controller collects data from various sensors and external devices and provides control outputs to the piezoelectric positioning devices, in addition, all the gathered information is to be sent to the control computer for subsequent processing and visualization. Also, computer controls all parameters of movement and scanning. Exterior view of the controller is shown in Fig. 1.8: Fig. 1.8 EG-3000 SPM controller. For the control of positioning devices system uses a digital feedback and the original scheme for measuring capacitance displacement sensors, based on the TDC (time to digital converter). Capacitance measurement is carried out in the scanning device and controller receives a digital signal. Such a system increase accuracy and significantly improve the device immunity. Any of the signals available in the system can be used to operate the feedback of the tip-sample distance. The controller keeps the feedback on the six channels simultaneously, which allows to scan by tip or by sample. In order to implement the modulation technique microscopy (such as, for example, non-contact atomic force microscopy), controller provides dual-channel lock-in amplifier, equipped with a highly stable master oscillator which is made on the basis of the digital frequency synthesizer. High-speed digital data processing implemented using programmable logic (FPGA), allows synchronous detection of signals at frequencies up to 1.5 MHz. Controller provides stepper motors control, allowing to connect from 4 to 12 drives in a micro stepping mode. The device has additional analog inputs and outputs for connecting external devices, as well as inputs and outputs for synchronization with external equipment. «Nano Scan Technologies Ltd.» User manual 24 Basic information USB interface is used for communication with the host computer. The controller is managed by the specialized software NSpec and EG3000 Dll. EG-3000 detailed information is described in the manual: “SPM controller (model EG-3060 and EG-3060A)”. 1 1.1 Data sheet General characteristics 1.1.1 CPU 1.1.2 PC Interface 1.1.3 Other interfaces 1.1.4 Size 1.2 32 bit; RISC USB 2.0 RS 232, RS485, SYNC I/O 440 х 285 х 90 mm High-voltage outputs 1.2.1 Voltage 1.2.2 Noise (RMS) 1.2.3 Number of channels 1.2.4 Resolution (digital-analog converters) 1.3 -10…150 V < 5 ppm 6 18 bit Stepper motors control unit 1.3.1 Number of channels 1.3.2 Power supply 24V, 3A 1.3.3 Microstepping mode support 1/16 step 1.4 4 Lock-in amplifier 1.4.1 Number of channels 2 1.4.2 Preamplifier gain 1-100 1.4.3 Input voltage range ±10 V 1.4.4 ADC resolution 16 bit 1.4.5 Frequency range of input signals 1.4.6 Frequency range of main oscillator 1.4.7 Output voltage amplitude 1.4.8 Frequency stability 1.4.9 Additional channels ADC / DAC 0-1,2 MHz 10 Hz – 3 MHz 10 mV-10 V < 5 ppm 1.4.9.1 Number of input channels 4 1.4.9.2 Voltage range ±10 V 1.4.9.3 ADC resolution 16 bit 1.4.9.4 Number of output channels 2 1.4.9.5 Voltage range ±10 V 1.4.9.6 DAC resolution 16 bit «Nano Scan Technologies Ltd.» User manual 25 Basic information 1.7.3. Certus Standard microscope base The Certus Standard microscope base is used for placing SPM head Certus, sample positioning and for optical microscope mounting and positioning. A Base plate B The installation location for the SPM head Certus C The platform for the installation and mounting of samples D The knobs for the sample stage positioning E The knob for the microscope arm mounting and positioning F The knob for the microscope vertical mounting and positioning G Tilted mounting for microscope H Microscope mount I The knobs for the horizontal microscope positioning J Retractable handle for the base transfer Fig. 1.9 SPM Base Certus Standard. «Nano Scan Technologies Ltd.» User manual 26 Basic information 1.7.4. Videomicroscope Optical microscope with a digital camera is used for obtaining magnified images of objects of study sites and for the images latching, SPM probe positioning relative to the sample surface. Optical microscope data sheet 1.1 Visualization 1.2 Magnification adjustment 1.3 Fine adjustment range 1.4 Image visualization 1.5 Illumination 1.6 Optical parameters Digital video microscope Manual 5 mm Color digital video camera Fiber illuminator 1.6.1 Numerical aperture 0.3 1.6.2 Camera sensor size 1/3” 1.6.3 Camera sensor resolution, px 1280x1024 1.6.4 Magnification 85x/1050x 1.6.5 View field 4.50/0.37 mm 1.6.6 Interface USB A Microscope B Objective C CCD matrix camera D Illumination side port Fig. 1.10 Videomicroscope «Nano Scan Technologies Ltd.» User manual 27 Basic information 1.7.5. NSpec Software NSpec software is used to control scanning probe microscope Certus Standard. Basic functions: • • • • • SPM parameters adjustment; optical system parameters adjustment; scanning parameters adjustment; scanning; data processing. The program is based on multythread kernel, written in C++ and built by compiler GCC4. The program interface is built using cross-platform libraries and libraries QT4, QWT. The program is compatible with all current versions of OS Windows (XP, 2003, Vista, 7). Upon request, the program can be transferred to the operating system Linux, * BSD, MacOS. Only basic functions of data processing are implemented to NSpec software, and tools for optimal adjustment of scanning parameters. Specialized software is recommended to use for full data processing, such as Gwyddion. For processing the spectral data is also recommended to use specialized programs such as GRAMS. To facilitate the transfer of data to other applications NSpec program supplied by the filters of import/ export formats ASCII, gwy (Gwyddion), spc (GRAMS). «Nano Scan Technologies Ltd.» User manual 28 Operating principles 2. Operating principles 2.1. SPM common principles The Scanning Probe Microscope — the device for surface imaging and local properties information. In basic case Scanning Probe Microscope (fig. 2.1) includes: • Probe; • XYZ scanning/positioning system; • Probe sensor for determination interaction with surface. Fig. 2.1 SPM basic system. The operation of a scanning probe microscope based on the principle of obtaining information about the interaction of the probe to the surface at one point. At a small distance between the surface and the probe, one can fix the forces of interaction (repulsion, attraction, and other forces) and the appearance of different effects (for example, tunneling of electrons). These interactions and effects can be detected with modern means of registration. To register, use different types of sensors, whose sensitivity allows you to record such disturbances. To construct a bitmap image uses a system of probe movement (scanning system) relative to the surface in XY or XYZ coordinates. The recording system records the value of the parameter. The parameter value depending on interaction between the probe and the sample surface is recorded. The surface topography is constructed during scanning based on known or suspected dependen«Nano Scan Technologies Ltd.» User manual 29 Operating principles cies of the interaction of the distance between the tip and the surface (3-D image in XYZ coordinates). Fig. 2.2 Common principles of SPM surface imaging. The main difference between scanning probe microscopy techniques is in registration parameters and registration methods selecting. «Nano Scan Technologies Ltd.» User manual 30 Operating principles 2.2. Probe scanning/positioning XY (XYZ) scanning process is used to get image in scanning probe microscopes. 2.2.1. Scanning The scanning process proceeds as follows. The scanner performs a raster movement of the object (Fig 2.3). System takes signal measurement and digitizes data at nodes of the raster to receive information about the surface characteristics. The direction of lines along which scanner moves is called the fast scan direction. Perpendicular direction is called slow scan direction. The resulting image is based on the data obtained in fast scan direction on forward or backward pass. Fig. 2.3 Scanning process illustration. One can write data on direct or on reverse the course of scanning producing a shift in the perpendicular direction. In this case, the speed of image acquisition increases two times. However, for scanners without sensors such scanning method is not applic«Nano Scan Technologies Ltd.» User manual 31 Operating principles able, since for scanning probe microscopes there is difference between the surface profile at the forward and backward course because of the nonlinear properties of piezoelectric ceramics, and this is usually essential. Scanners with sensors also have a distinction between "direct" and "reverse" profile, although not always visible. This caused by feedback errors in the direction of fast scanning. These errors are reduced with decreasing scanning speed. As a result, it often turns out that to obtain the desired image quality is advantageous to use record data only on direct or reverse course. 2.2.2. Piezoelectric phenomena All modern scanning probe microscopes, scanning/positioning systems, regardless of design, uses the inverse piezoelectric effect for positioning and movement. Inverse piezoelectric effect – the effect of mechanical strain in dielectrics under electric field. It occurs in crystals, which cells have no center of symmetry, resulting to permanent electric dipole in the cells. When applying external electric field for the such crystal, occurs dipoles deformation, leading to a change in crystal size. Since the monocrystal growing of materials with piezoelectric properties is considerable difficulty, usually use polycrystalline materials – ceramics. In this ceramics dipoles in the crystals are oriented predominantly in one direction of polarization in a Fig. 2.2 Piezoelectric phenomena. strong magnetic field. Accordingly, it changes own size, caused by appearance of electric field (Fig.2.2). Piezoelectric properties of the materials described by a set of piezoelectric constants. These constants describe relationships between applied voltage and material deformation. As a rule, even for a relatively small extension, high voltage should be attached to the material. For example, for lead titanate (PZT, Pb(Zr0,55Ti0,45)O3 with additions of Nb, Cr, La, Fe, etc.) piezoelectric constant d33=374×10-12 m/V (for PZT-5A). To reduce the voltage control signal, serial connection of layers of piezoelectric ceramics with electrodes on each layer are used (Fig. 2.3). In more advanced systems, solid array of piezoelectric ceramics with electrodes in the piezostack body is used. «Nano Scan Technologies Ltd.» User manual 32 Operating principles Fig. 2.3 Piezostacks diagram. 2.2.3. Lever translation systems In general, the displacement caused by the inverse piezoelectric effect, relative to the size of the piezoceramic element is a very small amount. The strain usually does not exceed 0.1% of total elongation of the device, displacement value is several tens of micrometers. To increase the displacement, variety of mechanical devices such as levers, hinges (Fig. 2.4), and bending devices (Fig. 2.5) are used. «Nano Scan Technologies Ltd.» User manual 33 Operating principles A Piezo stack. B Elastic Point. C Lever. A Piezo stack. B Bulk. Fig. 2.4 Bending displacement system diagram. Fig. 2.5 Bending displacement system diagram. Typically, the piezoelectric driving element is used only for forward movement. The used material is subjected to Hooke's law in the range of applied loads, i. e. the strain is directly proportional to the applied voltage. The material of the device undergoes only elastic deformation. As a result, after the termination of the external force elements of a such system take initial size, shape and, accordingly, the position in space. This fact is used for backward movement. In the real devices scanner elements are combined to build kinematic structure for «Nano Scan Technologies Ltd.» User manual 34 Operating principles plane-parallel movement in XY plane or XYZ space. 2.2.4. Displacement sensors Because of the nonlinear properties of piezoelectric ceramics, obtained image contains distortions. It is important to understand features of the dependence between the control electric field and the deformation of the piezoceramic sample, namely, non-linearity and ambiguity of this relationship. Usually, the nonlinear properties of ceramics are divided into creep, hysteresis and non-linearity itself. Also nonlinear properties includes volatility and sensitivity of the piezoceramic. Non-linearity and ambiguity of the dependence of the control voltage – the situation often leads to significant distortions of the image. For the correction of displacement, many types of displacement sensors can be used. It can be optical, inductive, magneto, capacitor, etc. Capacitive sensors are used in the two-dimensional scanning stage Ratis and in SPM head Certus. The operating principle of such sensors are displayed in Figure 2.6. Fig. 2.6 Capacitance sensors diagram. Since, the capacity of a flat capacitor consisting of two parallel plates is given by 2.1: С= 0 S d (2.1) C – capacitance, S – capacitance plates square, d – plate distance, ε – dielectric factor, ε0 – dielectric constant. When the distance between the plates changes the sensor capacitance, offset of the axis can be measured. «Nano Scan Technologies Ltd.» User manual 35 Operating principles 2.3. Probes 2.3.1. Basic probe parameters The main element of any scanning probe microscope is the probe. Based on the interaction of the probe and the surface, image of the surface is constructed and the distribution on the surface of local physical characteristics. In general, a scanning probe microscope is a conical needle or pyramidal shape. The most common material for the probes are metals (tungsten, platinum, and similar to scanning tunneling microscopy), silicon and silicon nitride Si 3N4 – for atomic force microscopy. Silica coated for magnetic and conducting techniques, silicon with a diamond coating for indentation, etc. General view of the probes is shown in Figure 2.7. A Probe body. B Coating. R Tip curvature. H Tip Height. Cone angle. Fig. 2.7 Probe drawing. Resolution and accuracy of surface elements mapping depends on the probe corner radius and the cone angle. Maximum height difference on the surface available for display depends on height of the probe. Coverage probes allow to use of various «Nano Scan Technologies Ltd.» User manual 36 Operating principles techniques of scanning probe microscopy. In addition to these parameters on the quality of the image, a set of techniques and the ability to study samples of different nature is influenced by two parameters. This is the probe stiffness or the force constant (N / m) and the probe resonant frequency (resonant frequency, kHz). 2.3.2. Probe drawings In general, probes for scanning probe microscopy can be a needle, but using industrial lithography and various coating methods, the probes cab be made with specialized forms (Fig. 2.8). A Chip B Bulk С Tip D Cantilever with rectangular bulk E Cantilever with triangular bulk F SEM tip image Fig. 2.8 Cantilever tip drawings and images. «Nano Scan Technologies Ltd.» User manual 37 Operating principles 2.4. Cantilever Z position detection system Different registration systems are using to register the movement of the probe and its position relative to the surface. For atomic force microscopy, two types of registration systems are using. 2.4.1. Deflector registration system. The most common registration system based on laser deflectometer. Schematic diagram of the system shown in Fig. 2.9. A Tip. A1 Deflection of cantilever bulk. B Laser. C PSD (Position Sensitive Diode) with 4 sensitive areas D Sample. E PSD image. Sections is marked A, B, C, D. F1 Laser spot position at PSD center. F2 Random laser spot position at PSD. Fig. 2.9 Deflectometer scheme. The laser beam is focused on the probe bulk. The reflected beam falls on the 4cell photodiode. By the ratio of the intensity in the photodiode sections, position of the «Nano Scan Technologies Ltd.» User manual 38 Operating principles reflecting probe part in space is determined. When the probe is moved along Z axis or beam is rotated, laser spot position is changed on the photodiode. As a result, the probe position relative to the surface according to predetermined relationships. In the scanning probe microscope Certus registration system based on laser deflectometer shown in Fig. 2.10. A PSD with 4 cells. B Probe (cantilever). С Laser beam. D Probe holder and scanner. Fig. 2.10 Deflectometer system in the SPM Certus head Fig. 2.11 PSD with laser spot. «Nano Scan Technologies Ltd.» User manual 39 Operating principles 2.4.2. “Shear-force” registration system The "shear-force" method is based on recording changes in the oscillation frequency of the probe caused by the tangential component of interaction forces between the probe and the surface. To determine changes in frequency are used tuning-fork resonators type (tuning-fork, Fig. 2.12). Resonators vibrations are detected by a direct piezoelectric effect of quartz crystals. A Probe tip. B Probe. C Electrodes that are used to measure voltage changes occurring on the sides of a quartz crystal (direct piezoelectric effect) due to changes in frequency during the interaction with the surface. D Quartz crystal (piezoelectric). E Piezoelectric Driver. Used to create a forced oscillation of the resonator (set the initial vibrations). Fig. 2.12 “Shear-force” registration system. This registration method is used where need to avoid interaction of the sample substance with a laser radiation, or in near-field microscopy systems. There is a special probe holder for tuning-fork type probes. For the near-field scanning optical microscopy special near-field tip is mounted on the tuning-fork instead of scanning tip (Figure 2.13). «Nano Scan Technologies Ltd.» User manual 40 Operating principles A «Tuning-fork» type probe B Probe holder C NSOM fiber. D Certus SPM head Fig. 2.13 “Shear-force” registration system. «Nano Scan Technologies Ltd.» User manual 41 Operating principles 2.5. Feedback To generate the control signal is commonly used proportional-integral-differential (PID) controller (see the scheme 2.14) in the feedback loop of a scanning probe microscopes. PID controller generates a control signal based on the components of the proportional signal, the integral of the input signal and the derivative of the input signal. P Proportional component of the signal is proportional to set point error. I Integral component is used to smooth out the statistical errors in the input signal. D Differential component needed to predict the controlled variable deviations. Setpoint Error Set value of the controlled variable. Difference between the actual and set value of the controlled variable. Process Controlled process. Output Output form the process sensor. +/- Sign of the term to calculate the difference between the actual and set value for actual value. Fig. 2.14 PID control. 2.6. Combining optical and scanning probe microscope The scanning probe microscopy has some drawbacks: accurate probe positioning to the sample surface point, selecting of field of a surface of interest from the scientific point of view, combining optical and topographical information about examinee surface. To overcome this lack combine a scanning probe microscope with an optical one. Optical microscopy techniques allow to select required surface field, to move the probe «Nano Scan Technologies Ltd.» User manual 42 Operating principles to this field and to perform scanning. A Optical image of the examinee and the cantilever. B SPM image of the examinee on the surface (topography). Fig. 2.15 Combination of the optical and scanning probe microscopes. «Nano Scan Technologies Ltd.» User manual 43 Start operation 3. Start operation 3.1. SPM Certus Standard installation The sequence of commissioning SPM Certus Standard includes following steps: 1 Installation of the vibrating protection 2 Installation of the SPM Certus Standard base and videomicroscope 3 Installation of the SPM Certus 4 Connection to the computer 3.2. Installation of vibration protection Depending on the chosen configuration can be installed both passive, and active vibrating protection. It should be installed on chosen SPM Certus Standard installation site before installation and microscope connection. In case of use of active vibrating protection it is necessary to use the installation instruction for the chosen model. «Nano Scan Technologies Ltd.» User manual 44 Start operation 3.3. Installation SPM Certus Standard base and videomicroscope A Installation of the base plate B Installation of the stand C Installation of the arm D Installation of the microscope mover E Installation of the videomicroscope Fig. 3.1 Microscope base installation steps. «Nano Scan Technologies Ltd.» User manual 45 Start operation 3.3.1. Installation of the stand A The slot for stand mounting B The holes for stand mounting screws Fig. 3.2 Installation of the stand on the base. 3.3.2. Installation of the arm A Arm fixation knob Fig. 3.3 Installation of the arm «Nano Scan Technologies Ltd.» User manual 46 Start operation 3.3.3. Installation of the microscope mover A Slots for the top screws B Slots for the top screws Fig. 3.4 Installation of the microscope mover. The microscope mover fastens to an arm on 4 screws. The top screws are established from mover face sheet. The bottom motions from the back party. For installation of the bottom screws it is necessary to transfer a mover in extreme bottom position. «Nano Scan Technologies Ltd.» User manual 47 Start operation 3.3.4. Installation of the videomicroscope A Installation of the holder ring B Installation of the cover C Installation of the microscope mover Fig. 3.5 Installing the microscope on the mover. At microscope installation it is necessary to fix the holder ring on a microscope, to put a cover on a holder ring and to install a microscope with a holder ring and a cover in a microscope mover. The cover is fixed on a mover by three screws. If necessary the illumination device is connected to a microscope. At connection of the illumination device it is necessary to use the instruction applied on this device. «Nano Scan Technologies Ltd.» User manual 48 Start operation 3.4. SPM Certus installation Installation of the SPM Certus requires scanning head Certus, SPM controller series EG-3000, the probes holder, cable kit and computer. 3.4.1. SPM Certus head description Initially, you must arrange scanning head on a hard flat surface (Fig. 3.1). A XYZ scanning system. B Stepping motors. C Stepping motors cables D Knobs for laser beam to cantilever bulk alignment. E Knobs for reflected laser beam to PSD diode alignment. Fig. 3.6 Certus scanning head. Stepping motors connectors from the SPM head side: «Nano Scan Technologies Ltd.» User manual 49 Start operation A Cable connector for two side-stepper motors. At one connector there are two cables. B Rear stepping motor cable connector. At one end is a single cable. C Appearance of the stepper motors cables and connectors Fig. 3.7 Stepping motors connectors. Additionally, the SPM head Certus needs to connect cables for high voltage signals and digital interface, analog signals cable and power (Fig. 3.8). Fig. 3.8 Scanning head signals cable. Additional cables are connected to the back side of the head (Fig. 3.9). «Nano Scan Technologies Ltd.» User manual 50 Start operation A High voltage cable and digital interface cable. B Analog signals cable and power. Fig. 3.9 Cable connections diagram. Fig. 3.10 Scanning head cables connection. Cable plugs are designed the way that allows them to join up just in one direction. For this purpose it's required to nest the plug into the socket and wheel smoothly turning it define the lay to enter it. «Nano Scan Technologies Ltd.» User manual 51 Start operation Fig. 3.11 Scanning head with connected cables. Probe holder connector is located at right head side (Fig. 3.7). Probe holder plug connects to a similar manner. Fig. 3.12 Connector for the probe holder. 3.4.2. Probe holder connection Probe holder must be connected to scanning head(Fig. 3.13). Regardless of the scanning probe microscope mode, the principle of holder connecting is the same. «Nano Scan Technologies Ltd.» User manual 52 Start operation Fig. 3.13 Probe holder. The holder is attached to SPM head with magnetic tablets. Appropriate mounting is located on the head bottom side. To fix the probes holder it is necessary to move to the corresponding fastening the SPM head and install the appropriate slot. To prevent damage of the probes after their installation it is recommended initially install the holder on the AFM head, and then connect the plug to the jack on the head (Fig. 3.9). Fig. 3.14 Probe holder mounting. «Nano Scan Technologies Ltd.» User manual 53 Start operation 3.4.3. Installation SPM Certus on the base Fig. 3.15 Installation SPM Certus on the base. Installation of the SPM head Certus on the base can be spent in two ways. In the first way, the optical microscope remains in working position. The SPM head needs to be got for an optical microscope and to establish on seats on the base. In the second way, the optical microscope is tilted back in non-working position, and SPM is put on seats then the optical microscope is came back in a working position. «Nano Scan Technologies Ltd.» User manual 54 Start operation 3.5. EG-3000 controller connection After connecting all cables and probe holder installation, scanning head must be connected to SPM controller EG-3000 series. Pin and connectors description are given in Figure 3.15. A complete description of the connectors on the controller front panel there is in the SPM controller EG-3000 User Guide. A Piezo stacks high voltage and displacement sensors digital interface. B Supply voltage and analog signals. C Back stepping motor connector. D Side stepping motors connector. Fig. 3.15 Сertus scanning head and EG-3000 controller correspondents. «Nano Scan Technologies Ltd.» User manual 55 Start operation 3.6. PC connection After scanning head connection to the controller, it is needed to connect the USB controller to your computer. Certus scanning head has no direct connection to the computer. In this case, the computer must have installed software to control SPM system, and USB driver. 3.7. Videocamera connection to the computer The microscope videocamera is connected to the computer with USB. For camera connection it is necessary to connect a cable to the camera and the computer, to install camera drivers. 3.8. Remote controller connection If the delivery complete set includes the additional remote control device for SPM Certus Standard manipulation – it is necessary to connect it to the computer with USB and to establish the necessary software. Fig. 3.16 Remote control device for SPM Certus Standard. «Nano Scan Technologies Ltd.» User manual 56 Start operation 3.9. NSpec software installation Before working with the program NSpec, an archive containing the program files, you need to unzip to a local or removable drive. Installation is not required. The program runs directly from the *. exe file. To work with the program is to start by double clicking the left mouse button or file nst. exe or NSpec_№. exe in the folder Soft_Package_ №. The example in Fig. 3.17. When you run nst. exe or NSpec_ №. exe will run the program (Figure 3.18). After performing the above action, main window NSpec displays. Following the withdrawal of the main window on the screen you can start working with the program and connected equipment. Fig. 3.17 NSpec starting. «Nano Scan Technologies Ltd.» User manual 57 Start operation Fig. 3.18 NSpec is starting. 3.10. SPM Certus Standard «on/off» regulation 3.10.1. «On» rules • Turn PC power «On»; • Run PC; • Run NSpec software; • Turn controller power «On»; • Check system functionality. In the case of correct connection of the controller, in the upper right corner of the main window NSpec SPM controller connection indicator appears as The indicators on the front of the SPM controller means: 1 PWR Power indicator 2 USB USB data transfer indicator 3 FNC Service indicator 4 RDY Stand By indicator 5 SCN Scan indicator 6 FB SPM Feedback status indicator «Nano Scan Technologies Ltd.» User manual 58 Start operation 3.10.2. • • • • • «Off» rules Stop scanning; Save data (if needed); Move up scanning head from sample to avoid tip damage. Close NSpec software; Turn controller power «Off». 3.11. NSpec basic options For program interface tuning is used Options unit, that is located on the basic instruments panel . After pressing this button program options window appears. Fig. 3.19 NSpec user interface options. «Nano Scan Technologies Ltd.» User manual 59 Start operation For SPM Certus Standard properly working required following options: Interface language Interface language combo box Buttons size Interface buttons size (px) Select font Calls “Select font” standard dialog Show data window Data unit on/off check box Show scan window Scan unit on/off check box Show SPM options window SPM unit on/off check box Show oscilloscope window Oscilloscope unit on/off check box Show lithography window Lithography unit on/off check box Show scan (Head) window Scanning by head tab in the Scan unit on/off check box Show scan (Stage) window Scanning by stage tab in the Scan unit on/off check box Show oscilloscope calibration Oscilloscope calibration window on/off check box Show head calibration window Scanning head calibration tab in the Oscilloscope unit on/off check box Show stage calibration window Scanning stage calibration tab in the Oscilloscope unit on/off check box Show video window Video unit on/off check box Enable auto-send to Data from Scan Auto-send obtained data to the Data unit on/off check box Enable Sensors autocalibration on start Sensors autocalibration with device start on/off check box Enable Optics initialization start Optics initialization with device start on/off check box Enable PID autocalibration on start PID autocalibration with device start on/off check box Data auto-save time, min Sets data auto-save interval in the Data unit. If 0 – auto-save disabled «Nano Scan Technologies Ltd.» User manual 60 Start operation Fig. 3.20 NSpec after adjustment for working with SPM Certus Standard. Below options determines by user choice Enable auto-send to Data from Scan Auto-send obtained data to the Data unit on/off check box Enable Sensors autocalibration on start Sensors autocalibration with device start on/off check box Enable PID autocalibration on start PID autocalibration with device start on/off check box Data auto-save time, min Sets data auto-save interval in the Data unit. If 0 – auto-save disabled «Nano Scan Technologies Ltd.» User manual 61 Working with SPM Certus Standard 4. Working with SPM Certus Standard In this section work with scanning probe microscope Certus Standard in a semi-contact atomic force microscope mode is described. For other AFM modes look the user manual additions. Before reading this section it is recommended to familiarize with the user's guide the software NSpec. To start work it is necessary to switch SPM Certus Standard on. 4.1. The list of base operating modes It is possible to allocate following basic modes: Обозначение Описание SPM modes Optical microscopy modes Superposed modes The full list of base operating modes: SPM modes — probe scanning + + - Optical microscopy modes - + + * The scanning stage is used only for positioning of samples 4.2. Basic SPM Certus Standard operations (atomic-force microscope techniques) For getting of SPM images it is necessary to adjust an atomic-force microscope. The general sequence of actions on SPM adjustment: Adjustment of range and bias of the capacity sensors «Nano Scan Technologies Ltd.» User manual Operation isn't obligatory, there is an automatic and manual mode of adjustment 62 Working with SPM Certus Standard Piezoscanner calibration Operation isn't obligatory, there is an automatic and manual mode of adjustment Capacity sensors calibration Operation isn't obligatory, there is an automatic and manual mode of adjustment Adjustment of PID control Operation isn't obligatory, there is an automatic and manual mode of adjustment Probe installation Required Adjustment of deflection system Required Adjustment of feedback system Required Adjustment of feedback setpoint Required Preliminary positioning of samples If necessary Probe landing Required Sample positioning If necessary Preliminary scanning Operation isn't obligatory. It is required for samples with unknown parameters Correcting of the scanning parameters Operation isn't obligatory. It is required for samples with unknown parameters Scanning If necessary Primary data treatment and saving If necessary Probe lifting Required 4.3. Adjustment of range and bias of the capacity sensors Each time the SPM Certus Standard switch on and software NSpec occurs automatic adjustment of range and bias of capacitor sensors. The automatic adjustment option is switched in window with Enable Sensors autocalibration on start check box. In case of automatic recalibration is needed or for manual mode calibration it is required to press Show/hide calibration window in the Oscilloscope unit. After pressing the button the calibration instruments arises. Press Run capacitance sensors auto adjustment button for automatic calibration executing. After pressing this button sensors auto adjustment will start. «Nano Scan Technologies Ltd.» User manual 63 Working with SPM Certus Standard Fig. 4.1 Oscilloscope unit in calibration mode drawing. 4.4. Adjustment of PID control Each time the SPM Certus Standard switch on and software NSpec occurs automatic tuning of PID control. The automatic adjustment option is switched in window with Enable PID autotuning on start check box. In case of automatic calibration needs iteratively or in manual mode it is required to press Show/hide calibration window in the Oscilloscope unit. After pressing the button the calibration instru- ments arises. For automatic tuning executing requires to press PID autotuning button. After pressing this button scanning head PID control auto adjustment will start. «Nano Scan Technologies Ltd.» User manual 64 Working with SPM Certus Standard 4.5. Probe installation Before you start, you must install the probe into the probe holder as shown in Figure 4.2. Fig. 4.2 Probe holder. Probes or cantilevers are stored either in the form of plates on which it to break off before the work of individual probes, or already prepared for work in special containers (Fig. 4.3). Usually, cantilevers tips directed toward the cover package. Fig. 4.3 Cantilevers in gel-pack boxes. «Nano Scan Technologies Ltd.» User manual 65 Working with SPM Certus Standard Fig. 4.4 Cantilever mounting to holder. Installation procedure: • use tweezers to capture probe for the side surfaces so that the bulk with the tip was directed toward the hand; • probe holders have to be turned over and pressed to the surface to reveal clip so that the button was pressed on the upper side of the probe holder (Fig.4.4); • Mount probe to holder; • Release the probe fix button; • Mount probe holder to scanning head with p.3.4.2. «Nano Scan Technologies Ltd.» User manual 66 Working with SPM Certus Standard A Probe. B Spring knob. Fig. 4.5 Probe mounting. 4.6. Sample mounting The SPM Certus Standard allows to operate with samples satisfying the following dimensions: min Any max without SPM Up to Ø 230 mm and 30 mm height. max with SPM Up to Ø 125 mm and 16 mm height. Samples should be fixed to special polycrystalline sapphire substrates, which are contained in the hardware set of the instrument. Dimensions of these substrates are 24х19х0.5 mm. Fastening of the sample to the substrate can be done by using doublesided scotch tape or glue. When mounting the substrate with samples on the sample stage, the substrate is put on the sample platform (see Fig. 1.9, point C) and pressed by spring clips (Fig 4.6). «Nano Scan Technologies Ltd.» User manual 67 Working with SPM Certus Standard Fig. 4.6 Sample fixed on the substrate, which is mounted on the stage. «Nano Scan Technologies Ltd.» User manual 68 Working with SPM Certus Standard 4.7. Information about NSpec software required for SPM Certus Standard adjustment To entry SPM window press the button , that is situated on the top panel of the NSpec window. Key parameters of adjustment a scanning probe microscope are located in the SPM window. In the SPM window feedback parameters are set, stepper motor are controlled, scanning mode are set and etc. Fig. 4.7 SPM window drawing. «Nano Scan Technologies Ltd.» User manual 69 Working with SPM Certus Standard 4.7.1. Plot mode control In the left part of a window there is a panel of Plot mode control. It is used for display resonant curve and others signals received by system from sensors and a digital microscope. Fig. 4.8 Plot mode control. Frequency curve mode A field of the probe amplitude-frequency curve is displayed in the right window part. Oscilloscope mode An oscilloscope field is displayed in the right window part. There are aver age and RMS of selected signal values fields under oscilloscope curve. Spectroscopy mode A land/lift curves, Z spectroscopy and spectroscopy parameters panel are displayed in the right window part. 4.7.2. Cantilever resonant frequency acquisition Fig. 4.9 Cantilever resonant frequency acquisition. «Nano Scan Technologies Ltd.» User manual 70 Working with SPM Certus Standard The signal for plotting the frequency curve is selected in the Channel combo box on the Frequency scan panel. In the near fields the frequencies range is completely set. By default, in the Channel combo box is selected signal Mag used for reception of resonant frequency of probes. Fig. 4.10 Signals available for the frequency curve. The button performs frequency scanning. The nearby progress bar shows scanning complete progress with percents. The current resonant frequency value is displayed on the Current frequency slider. It can be set in other value if necessary. The Drive intensity slider controls probe piezodrive output voltage. 4.7.3. Oscilloscope mode Fig. 4.11 Oscilloscope plot window. An average value of the signal magnitude is displayed in the Average, V field. A «Nano Scan Technologies Ltd.» User manual 71 Working with SPM Certus Standard root mean square of the signal is displayed in the RMS, V field. In the T, s field sets a time interval. 4.7.4. Land/lift curves Fig. 4.12 Z spectroscopy curve. The red strip displays current position of probe Z0, and two dark blue strips display limits of construction of a curve and correspond to positions Z0-Z1 and Z0+Z2. At construction the curve probe moves to point Z0+Z2 then moves downwards to point Z0Z1, further it makes movement in the opposite direction and comes back to an initial position. The slider <--ΔZ1, μm sets start position Z0-Z1. The slider ΔZ2-->, μm sets final position Z0+Z2. It is also possible to set start and final position value in the fields nearby the sliders. After typing-in the number value from the keyboard press the button Enter Key. In the Channel combo box it is necessary to selected signal for curve acquisition. The Points combo box sets a number of curve points. In the Speed, nm/sec field it is possible to set curve scanning speed. The button «Nano Scan Technologies Ltd.» User manual runs curve acquisition process. 72 Working with SPM Certus Standard 4.8. Deflectometer system adjustment Initially, you must configure the system of probe deflection. To do this: • Align laser beam to cantilever bulk; • Align reflected from bulk beam approximately to PSD center; • Find appropriate parameters for resonant mode; • Ger probe resonant curve. 4.8.1. Laser beam alignment to cantilever bulk Procedure: • Open SPM window in NSpec software; • Define current system configuration. Two different choices is shown at fig.4.5 • Align laser beam to cantilever bulk. a) b) Fig. 4.13 а) Not aligned system; b) Aligned system. In the case of fully disaligned registration system, laser beam may come out cantilever bulk or come to the probe holder «Nano Scan Technologies Ltd.» User manual 73 Working with SPM Certus Standard a) b) Fig. 4.14 а) out of cantilever chip; b) Laser spot located at holder. In this case, using the positioning screws, make coinsidience laser beam with cantilever bulk Fig. 4.15 Compliance of the direction of rotation with direction of laser spot travel. When the laser beam hit on the cantilever bulk, the diffraction pattern will be clearly visible. «Nano Scan Technologies Ltd.» User manual 74 Working with SPM Certus Standard Fig. 4.16 Laser beam aligned to bulk and diffraction pattern is clearly visible. 4.8.2. PSD (position sensor diode) alignment You have to align reflected laser beam from bulk with center PSD, to do this you can use PSD positioning screws. Fig. 4.17 Compliance of the direction of rotation with direction of PSD travel. SPM Feed Back window shows laser spot position at PSD and it's intensity. «Nano Scan Technologies Ltd.» User manual 75 Working with SPM Certus Standard б) a) Fig. 4.18 a) reflected beam is out of PSD; b) laser beam is within PSD area. 4.8.3. Search of the reflected beam Once the SPM Feed Back window will display the signal from the photodiode it is necessary to find the maximum reflection from the bulk. Red sphere size corresponds to laser spot position and its intensity, during alignment must be on a blue field (PSD area) Fig. 4.19 PSD signal. Using laser beam alignment screws, try to get signal maximum. «Nano Scan Technologies Ltd.» User manual 76 Working with SPM Certus Standard Fig. 4.20 Signal maximum. 4.8.4. Alignment the reflected beam with the PSD center After finding the maximum of the reflected signal it is necessary to combine the laser spot center to the photodiode center. To do this, use the photodiode positioning screws to move the laser spot in the center of the SPM Feed Back window and obtain close to zero values of indicators DFL and LFL as possible. (Figure 4.21). In the drop-down menu beneath the SPM Feed Back should be set OFF. Fig. 4.21 Laser Beam is in the PSD center. «Nano Scan Technologies Ltd.» User manual 77 Working with SPM Certus Standard 4.8.5. Probe resonant frequency acquisition After finding the maximum of the reflected signal and overlapping centers of the laser spot and the photodiode, in the case of contact mode, you can proceed to feedback parameters settings and approach of the probe to the surface. In the case of non-contact methods, you should find the resonant frequency of the cantilever. For non-contact methods in the field FB Input Signal (SPM Mode) must be set to Probe Magnitude – Tapping Mode. To do this: • choose the MAG in Channel combo box in the Scan window SPM (Fig. 4.22); • set the frequency search range from 0 to 500 kHz (or greater in the case of use cantilevers with a large resonant frequency); • set all multiplier Input Gains is equal to 1; • set Drive Intensity slider value is equal to 1; • press Run. Fig. 4.22 Probe resonant data. After that, Plot will show the current resonant curve of the cantilever (Figure 4.23). If you know roughly the resonance frequency value of the cantilever, search range can be narrowed (Figure 4.24). If necessary, resonant frequency can be set manually (Figure 4.25), using obtained resonant curve. «Nano Scan Technologies Ltd.» User manual 78 Working with SPM Certus Standard Fig. 4.23 Cantilever resonant frequency acquisition. Fig. 4.24 Cantilever resonant frequency acquisition. «Nano Scan Technologies Ltd.» User manual 79 Working with SPM Certus Standard Fig. 4.24 Manual chose of the cantilever driver frequency. You have to achieve the resonant magnitude of 1 V in the absence of information about the sample properties. Take this value as reference value. 4.9. Feedback parameters The Feedback panel contains a field of display of laser reflected from a cantilever beam signal strength, elements of management of the laser, and also elements of management of feedback system. On a blue field intensity of the laser reflected from a cantilever beam to the foursection photo diode is displayed by a red stain. Position of a stain in a midfield means that the stain from the laser is in the central part of the four-section photo diode, thus values of DFL and LFL signals have values zero or close to zero values. In the left bottom corner of the blue field the laser intensity signal INT is displayed. INT Value is comparable to the sizes of a red stain. FB Z means the device carrying out feedback (by scan stage or head). In the right bottom corner the Mag signal value is displayed. There is head scanner Z position bar in the right top corner. Green color corresponds to a safe approach of a probe, and red means that the probe is too close to the sample and there is a probe damage possibility. «Nano Scan Technologies Ltd.» User manual 80 Working with SPM Certus Standard Fig. 4.25 SPM Feedback panel. SPM laser on/off SPM laser on/off button. Show PID parameters The button causes displaying feedback Integral, Differential and Proportional components and Setpoint. Feedback sign The button changes feedback sign. Feedback on/off The feedback on/off switch button. Feedback by head/stage Switching head/stage Z scanner for caring out the feedback. «Nano Scan Technologies Ltd.» User manual 81 Working with SPM Certus Standard Set the feedback input signal and the relevant scan mode in the combo box. Fig. 4.27 Choosing feedback input signal. The automatic landing state indicators are shown in this window additionally. Landing complete The probe has landed to the surface. Move tip down/up Launches landing or lifting the probe to the sample. Lower/upper limiter Lower/upper limiter has reached. When choosing microscope type Snotra in a stepper motors options menu it will be running in a resonance microscopy mode using quartz resonators – Tuning-fork (TF mode). Fig. 4.28 Switching in a resonance microscopy mode using quartz resonators. «Nano Scan Technologies Ltd.» User manual 82 Working with SPM Certus Standard 4.9.1. Additional scan parameters Fig. 4.29 Additional scan parameters panel. Gain factors for the DFL, LFL, Int signals are established in the corresponding combo box. The frequency of the low-pass filter are established by corresponding slider and entry field. The phase shift for lock-in phase detector are established by corresponding slider and entry field. It is also possible to set the value in the fields nearby the sliders. After typing-in the number value from the keyboard press the button Enter Key. 4.9.2. General recommendations of feedback parameters If you have no information about surface properties it is recommended to set all gains equal to 1 by corresponding sliders. After prior image analysis adjust feedback parameters. Feedback maximum gains are determined by starting the feedback loop instability. It looks as a noise with high amplitude and high frequency in the feedback controlled signal. Instability can occurs under same parameters with others samples. For each sample feedback parameters have to be established individually. Than "more softly"sample surface and the high difference of heights, the feedback parameters should be larger. The same advice concerns the noise and influence of the outer vibrations. For this purpose require to regulate Proportional and Integral gains. Its optimal ratio is around 10:1. For “hard” material and low difference of heights (about some tens of nm) feedback gains may be established closer to zero, for example, 0,1-0,3. For high speed scanning it is recommended to establish gains equal-to-or-greater-than 1. Closer to value, when instability has started. 4.9.3. Setpoint tuning After setting the resonant frequency and amplitude, and tuning feedback parameters, set up the setpoint value in the relevant input field using MAG value. For the as- «Nano Scan Technologies Ltd.» User manual 83 Working with SPM Certus Standard sessment scan it is recommended to install feedback value to 50% of current MAG value. Normally, this value is depends on the surface sample characteristics. 4.9.4. Probe Z axes control There is a probe Z position slider in the left upper corner of the SPM window for setting up current probe Z position. To set up Z probe position using keyboard type value in the input field and press Enter key. Fig. 4.30 Probe Z control slider. 4.10. Sample stage positioning Firstly the sample should be placed on the stage and, if necessary, mounted. A Stage with sample holders B Sample X positioning screw С Sample Y positioning screw Fig. 4.31 Sample stage. «Nano Scan Technologies Ltd.» User manual 84 Working with SPM Certus Standard Two screws are designed to sample stage positioning. A Sample X positioning screw B Sample Y positioning screw Fig. 4.32 4.9. Sample stage positioning. 4.11. Probe approaching to the sample Stepper motors perform the probe approaching to the sample surface. The control of the stepper motors is carried out by the NSpec program or by the remote controller. 4.11.1. The control of the stepper motors There is a Motors control panel in the left part a window. Fig. 4.33 Motors control panel drawing. This instrument panel are used to control and operate with the stepper motors. The motors are utilized for automatic approaching the tip to the sample by moving down scanning head. «Nano Scan Technologies Ltd.» User manual 85 Working with SPM Certus Standard Move up By pressing this button movement of stepper motors upwards with the set speed on the set distance is carried out. Move down By pressing this button movement of stepper motors downwards with the set speed on the set distance is carried out. Fast movement By pressing this button movement of stepper motors upwards upwards to limit with the set speed to limit switch is carried out. switch Fast movement By pressing this button movement of stepper motors downdownwards to limit wards with the set speed to limit switch is carried out. switch Landing By pressing this button automatic approaching is carried out. Step up By pressing this button stepper motors perform one step up Step down By pressing this button stepper motors perform one step down. Motor options This button invokes motor options window Control for each Switching in the each motor control mode. motor Not available with Certus Light device. Shuttle options This button invokes remote control properties window. Fig. 4.34 Drawing of the motors control panel in the each motor control mode. «Nano Scan Technologies Ltd.» User manual 86 Working with SPM Certus Standard 4.11.2. Stepper motors settings By pressing the button additional Motors options window is opened. Fig. 5.11 Motor options window. In the Device type combo box you can choose «Nano Scan Technologies Ltd.» microscope configuration that you have. Fig. 4.35 Choosing microscope configuration. In the Up moving options the Speed (up 0 to 1000 μm/s) and the Distance (up 0 «Nano Scan Technologies Ltd.» User manual 87 Working with SPM Certus Standard to 1000 mm) for upward moving are set up. In a similar way set up options for downward moving. With One step options sets the values of the motors step in relevant directions for One Step Up and One Step Down button. In the Landing options parameters of automatic approach by button are set up. Landing mode means: Mode 1 – the approach is carried out by only one motor (rear motor, № 3); Mode 2 – the approach is carried out by three motors. The Speed (μм/сек, 0…1000) in the Motor level options means the motor speed when Fast movement upwards (downwards) to limit switch buttons pressed. On the Calibrations panel parameters of stepper motor calibration are set. In the field the Thread pitch (mm) is set a thread pitch. In the Step number field is set full quantity of steps. 4.11.3. Remote control adjustment The Remote control button calls remote control adjustment window. Fig. 4.36 Remote control GUI. «Nano Scan Technologies Ltd.» User manual 88 Working with SPM Certus Standard Mechanical Z-mover motion Shuttle controls lens mechanical mover. Piezo Z-mover motion Shuttle controls lens piezo mover. Control 3 motors together Shuttle controls stepper motors together. Control first motor Shuttle controls stepper motors number 1 Control second motor Shuttle controls stepper motors number 2. Control third motor Shuttle controls stepper motors number 3. Run approach Start/stop head soft approach. Other functions keys Keys for other device and functions controlling. Tabs All motors and Motor 1 ÷ 4 are contained control options by the joystick. Steps — number of steps on one turn of a wheel for stepper moving. Speed — number of steps in a second at turn of a shuttle for fast movement on the first position. Speed Multipliers for shuttle positions-multipliers on which speed increases at installation of a shuttle for fast moving by the chosen position. For control from the program devices operated the joystick it is necessary to guide the cursor at a wheel of management (it is shown on the figures more low) and to move to the necessary position. For a stop of movement it is required to return a wheel of management in former position. Fig. 4.37 Shuttle fast moving. «Nano Scan Technologies Ltd.» User manual 89 Working with SPM Certus Standard Fig. 4.38 Wheel for step-by-step moving. 4.11.4. • • • • Tip approaching The approach of a probe to a sample surface consists of following actions: head leveling; head tilting; coarse approaching; fine approaching. 4.11.5. Head leveling After probe installation it is necessary for leveling scanning head Certus. For this purpose press the button Fast movement upwards to limit switch . Thus three motors run together and a scanning head will be lifted in the maximum position and will accept horizontal position. The given operation needs to be repeated after probes replacement. After scanning there is no necessity to translate a scanning head in extreme top position. It is enough to take away SPM from a surface on convenient for work and safe for a probe distance. 4.11.6. Head tilting and coarse approaching In some cases it is recommended to scan with the probe tilted at a certain angle to the surface, or to compensate for the slope of the surface samples. It's allow to minimize contact spot area of the tip with the surface. To do this, use individual control of each stepper motor. The algorithm is: • Move down head on the 5-10 mm from the top position by button Fast «Nano Scan Technologies Ltd.» User manual 90 Working with SPM Certus Standard movement downwards to limit switch ; • For a stop of movement it is necessary to press this button repeatedly; • Go to the stepper each motors control mode ; • Move up to maximum rear motor; • Return to the option of all motors control ; • Start rough approach to sample by button Fast movement downwards to limit switch . Use rough approach till approximately 3-5 mm from the surface. Decrease approach speed for closer distance. 4.11.7. Fine approaching After a coarse approach has complete it is necessary to switch on feedback by Feedback on/off and to run landing by . Upon reaching the surface, and the magnitude of the probe oscillations equal to the specified by Setpoint value approach process will stop. Next, it is need to verify the absence of oscillations. Switch to Oscilloscope mode in the Plot Mode Control (Section 4.1 details. software NSpec manual). 4.11.8. Approaching by remote controller. All operations on control of stepper motors and feedback are duplicated on buttons of the remote controller. «Nano Scan Technologies Ltd.» User manual 91 Working with SPM Certus Standard 4.12. Sample positioning If after a head approach to a surface there is a necessity of sample positioning it is necessary to switch off feedback by the button Feedback on/off . After switching- off of feedback there will be an automatic lift of a probe from a surface on safe distance. After positioning of the sample it is necessary to switch on again feedback and to run fine approach if necessary. 4.13. Adjustment of scan parameters After tip landing to the surface, open Scan window. In the Scan tab scan key parameters, such as number of image points, its sizes, a scanning direction, scanning speed and others, are presented. Four fields for displaying of the received data are located in the central part of the Scan window. Fig. 4.39 Scan window drawing. «Nano Scan Technologies Ltd.» User manual 92 Working with SPM Certus Standard Fig. 4.40 Scan parameters. Nx size Points number of in X scan direction. Ny size Points number of in X scan direction Scan width, μm Scan width in μm. Scan width and height field are active only when the Area selection Scan height, μм button has pressed. Scan height in μm. Scan width and height field are active only when the Area selection button has pressed. Channel A and B The signals received in forward scan direction are selected in the combo box Channel C and D The signals received in backward scan direction are selected in the combo box Section The check box for cut section construction for relevant channel. The title color is relevant to the cut section color. Velocity, Hz The slider sets a scan velocity. A scan velocity value also can be set in the edit field near the slider (press Enter key after changing the value). Above the Velocity slider scan complete percents are displayed. Lift mode Enables double-pass scan techniques. «Nano Scan Technologies Ltd.» User manual 93 Working with SPM Certus Standard Disables double-pass scan techniques. Directions Combo box for scan direction choosing. The arrow means fast scan direction. Along X axes, from upper left corner. Along Y axes, from upper left corner. Along X axes, from upper right corner. Along Y axes, from upper right corner. Along X axes, from lower left corner. Along Y axes, from lower left corner. Along X axes, from lower right corner. Along Y axes, from lower right corner. Fig. 4.41 Changing scan size. By pressing the Feedback tab occurs feedback control panel opening. On it are displayed sliders of feedback Integral, Differential and Proportional component and Setpoint. «Nano Scan Technologies Ltd.» User manual 94 Working with SPM Certus Standard Fig. 4.42 Feedback page. 4.13.1. Signal description Height Sample surface topography. DFL Signal proportional to a probe deviation concerning a normal. Pays off as a difference between signals from the top and bottom half of four-section photodiode. (Fig. 4.43). DFL= (A+B)-(C+D). LFL Signal proportional to a probe deviation concerning a torsion. Pays off as a difference between signals from the left and right half of four-section photodiode. LFL= (B+D)-(A+C). MAG Magnitude of DFL signal… MAG Sin In-phase components of DFL signal MAG Cos Quadrature components of DFL signal Phase Phase of DFL signal. MAG, MAG Sin, MAG Cos, Phase signals are computational result of ADC1 with phase-lock detector. The direct digital synthesizer of frequency (DDS) which creates harmonious fluctuations with the set frequency and amplitude lies at the heart of the phase-lock detector. This signal is deduced for a probe excitation and is used for demodulation of the signals coming on the synchronous detector input. ADC1 input signal arrives on a preamplifier (PGA) where can amplify in 1…100 times. The amplified signal ar rives on an input high-speed ADC. The digital signal from ADC output arrives on a multiplier input where it is «Nano Scan Technologies Ltd.» User manual 95 Working with SPM Certus Standard multiplied with a basic signal, and also with the basic signal shifted on 90º. The received signals pass through low frequencies filters, thus on an output signals MAG Sin and MAG Cos are formed. Amplitude (MAG) and the Phase signals are calculated mathematically from these signals. DInt Total signal from all four sections of the photo diode. This signal is proportional to intensity of the laser beam reflected from a cantilever. Dint=A+B+C+D. ADC 01 ADC01 signal, DFL ADC 02 ADC02 signal, LF ADC 03 ADC03 signal, DInt. ADC 04 ADC04 signal. ADC 05 ADC05 signal. X sensor The signal from capacity sensor by X scan head axes. Y sensor The signal from capacity sensor by Y scan head axes. Z sensor The signal from capacity sensor by Z scan head axes. Ux High voltage output for X axes head piezostack. Uy High voltage output for Y axes head piezostack. Uz High voltage output for Z axes head piezostack. X2 sensor The signal from capacity sensor by X scan stage axes. Y2 sensor The signal from capacity sensor by Y scan stage axes. Z2 sensor The signal from capacity sensor by Z scan stage axes. Ux2 High voltage output for X axes stage piezostack. Uy2 High voltage output for Y axes stage piezostack. Uz2 High voltage output for Z axes stage piezostack. ADC HR 1 Auxiliary analog input. ADC HR 2 Auxiliary analog input. Fig. 4.43 Foursection photodiode drawing. «Nano Scan Technologies Ltd.» User manual 96 Working with SPM Certus Standard 4.13.2. Multi-pass technique By pressing the button the scanning two-through passage technique is activ- ated. On the Scan tab there is a field LM height, nм for distance value on axis Z on which the second pass of a probe will be carried out is established. Near to the fields of a signals choice (Channel A, Channel B, Channel C, Channel D) appear buttons Pressing such buttons . means the signal is chosen for obtaining on the second pass of a probe. Fig. 4.44 Scan tab in two-pass mode drawing. 4.13.3. Additional scan parameters The probe position is shown in the XY probe positioning panel, when the button Point selection has pressed. «Nano Scan Technologies Ltd.» User manual 97 Working with SPM Certus Standard Fig. 4.45 Probe positioning panel drawing. The Z Positioning slider is necessary for moving of a probe on axis Z. Position Z can be set from the keyboard in the field near to the slider. After typing-in the number value from the keyboard press the button Enter Key. Depending on a choice of a way of scanning slider control or position on Z in a scanning head, or position on Z in a scanning stage. Fig. 4.46 Z positioning. The Current Tip Position bar indicates Z scanner lever in percents. Green color of the indicator corresponds to a safe supply of a probe, and red means that the probe is too close to the sample and there is a possibility of probe damaging. Fig. 4.47 Z position. Fig. 4.48 Escaping high voltage amplifiers. Set high voltages HYZ to zero – by pressing the button an output of high-voltage amplifiers of the head scanner pressure is established to zero. / Fig. 4.49 Fast scanning button. By pressing the Fast scanning button enables algorithm allowing to carry out fast scanning by special algorithm. «Nano Scan Technologies Ltd.» User manual 98 Working with SPM Certus Standard 4.13.4. Selection of scanning parameters At set of scanning parameters choose values of following parameters: • number of points; • scan size area; • signals for acquisition; • signals for cut section displaying; • scanning speed; • If necessary to switch on a mode of program correction for fast scanning; And after this start the scan process. It is recommended to obtain overview scan, than to correct selection of feedback parameters, probe oscillation parameters. We recommend following parameters for data acquisition with maximum resolution: • Full scan area; • Points number 300х300 pixels; • Scanning speed 1 line/sec (Hz); • Signals Height and Phase for forward and backward directions. After getting test images, you may select desired scan settings and the interesting area on the surface. To select the number of pixels in the image should be guided by the following rules: • For non-contact techniques does not make sense to put the number of points, which is equal to resolution less than the probe curvature radius; • Scanning speed depends on size of the scanning field for the same number of points. It is recommended to reduce the number of points with decreasing scanning field to save the scanning speed in proportion to the size of the scanning field or increase the scanning speed; • For different sizes of the scanning field may need to change the parameters of the feedback. 4.13.5. Scanning conditions At work with microscope Certus Standard without vibrating and acoustic protection it is recommended not to subject the device to vibrating and acoustic influences. These influences can lead to occurrence of artifacts on the image and even to moving of the sample concerning a microscope and probe damage. «Nano Scan Technologies Ltd.» User manual 99 Working with SPM Certus Standard 4.14. Scanning For start scanning press the button Start again this button . For stop scanning press . Scanning is started only after a choice of signals on the Channel 1-4. For start enough one signal. Fig. 4.50 Start scanning. The check box for cut section construction for relevant channel. The title color is relevant to the cut section color. «Nano Scan Technologies Ltd.» User manual 100 Working with SPM Certus Standard Fig. 4.51 Start scanning with line cut section. 4.15. Primary image processing and saving For primary results processing and saving use built-in tools to work with images and graphics. A detailed description of the location and functions of these instruments is given in the software NSpec user manual in sections: Par. 2. Interface tools; Par. 3. DATA window. It is recommended to save data without filters processing and extra filters. «Nano Scan Technologies Ltd.» User manual 101 Working with SPM Certus Standard 4.16. Precise probe positioning For precise positioning of a probe in the range of 100х100 micron with step 0.1 nanometers is used a scanning head. Positioning is applied for indentation, to obtain of spectroscopy curves in SPM modes, and in aggregate with an optical microscope allows to precisely position the probe for prompting on a site of a research object surface. For precise probe positioning use the Point selection / button on the 3D panel. At pressing by the left mouse button in an active scan window the scanner moves the probe to the chosen point. «Nano Scan Technologies Ltd.» User manual 102 Working with SPM Certus Standard 4.17. Scanner calibration If a scanner have no calibration or a recalibration required, it is necessary to use calibration tools. Scanner calibration contains a set of factors for recalculation of voltage put to a piezostack in real displacement taking into account nonlinear effects and factors for recalculation of capacity of sensors in displacement. To implement the nonlinear correction, go to the option Oscilloscope , click- ing in the upper toolbar, the corresponding icon. In the right pane, find the section Scanner test /calibration (Fig. 4.52). Fig. 4.52 Scanner calibrations tables. «Nano Scan Technologies Ltd.» User manual 103 Working with SPM Certus Standard Close loop The button of on/off switching of scanner close loop. When close loop is on the button has blue color. Non-linear correction The button of on/off switching of scanner nonlinear correction. When close loop is on the button has green color. PC File Save calibrations in PC file. PC File Load calibrations from PC file. DSP Memory Save calibrations in DSP. DSP Memory Load calibrations from DSP (internal controller memory). Show/hide calibration window Show/hide calibration window Firmware upgrade Firmware upgrade from file function. Speed [μm/s] of probe or stage moving in an start scan point or new position from the previous position is in the field Free Positioning speed established. The PID panel is designed to set PID control coefficients of capacity sensors close loop. In fields Proportional, Integrated and Differential corresponding factors for each axis are set (X, Y, Z). On the panel Scanner Range in the field Range, μm scanning range for each axes are set. The fields Scale gain and shift are designed to service adjustment of sensors. On the Piezo calibrations panel for each axis (X, Y, Z) are set nonlinear calibration coefficients without sensors close loop. This panel contains the table of coefficients of program piezostack nonlinear correction. This table coefficients is necessary for non-linear conversion of the voltage U applied to piezostack to X movement. In the system EG-3000 4 3 2 U ( X )= A× X +B× X +C× X +D× X +E , U – voltage in DACs counts 0…65535, X – displacement in μm, 0… Xmax, this function is working at NLC is ON . If NLC button is off, voltage is calculates by linear relationship U ( X )=65535× X X max . On the Senors calibrations panel for each axis (X, Y, Z) are set sensor calibration coefficients for sensors close loop. This panel contains the table of coefficients of pro- «Nano Scan Technologies Ltd.» User manual 104 Working with SPM Certus Standard gram sensor nonlinear correction. This table coefficients is necessary for non-linear conversion of the capacity C of the sensor to piezostack to X movement. In the system EG-3000 4 3 2 C ( X )= A× X +B× X +C× X + D× X +E , С – sensor capacity in DACs counts 0…65535, X – displacement in μm, 0… Xmax. this function is working at close loop is ON . If close loop is off , capacity is cal- culates by linear relationship С ( X )=65535× «Nano Scan Technologies Ltd.» User manual X X max . 105 Working with SPM Certus Standard 4.18. Calibration procedure 4.18.1. Calibration mode For scanner calibration go to calibration mode by pressing Show/Hide calibration window . Then in a window there will be tools for carrying out of calibra- tions. Fig. 4.57 Oscilloscope window in the calibration mode drawing. 4.18.2. Piezostack calibration • Switch off nonlinear correction and sensors close loop ; • Scan test sample with the full amount of points (1000 x 1000) in the direction of the calibration, and the full range, the direction of the fast scan X (measurements should occur on the growth of the voltage from minimum to maximum) ; • Produce a horizontal section of the image; • Calculate calibration coefficients using Controls panel tools (Procedure of coefficients calculatiing is described below in point 4.17.5); • Store new coefficients in the related table; • Save data. «Nano Scan Technologies Ltd.» User manual 106 Working with SPM Certus Standard 4.18.3. Sensors calibration • Switch off nonlinear correction and switch on sensors close loop ; • Scan test sample with the full amount of points (1000 x 1000) in the direction of the calibration, and the full range, the direction of the fast scan X (measurements should occur on the growth of the voltage from minimum to maximum) ; • Produce a horizontal section of the image; • Calculate calibration coefficients using Controls panel tools (Procedure of coefficients calculatiing is described below in point 4.17.5); • Store new coefficients in the related table; • Save data. 4.18.4. Tool panel Settings Fig. 4.58 Controls panel. «Nano Scan Technologies Ltd.» User manual 107 Working with SPM Certus Standard Acquire data Get data from the selected source. Filters Standard filters for curves. Save to settings Store obtained coefficients in the related table. Sensors autoadjustment Run sensors automatic adjustment. Tools panel Settings: Output Combo box for device for calibration choise: head or stage Channel Combo box for calibration channel choice Voltage Ux X piezostack calibration Voltage Uy Y piezostack calibration Voltage Uz Z piezostack calibration Sensor Cx X sensor calibration Sensor Cy Y sensor calibration Sensor Cz Z sensor calibration Scan section For calibration the profile is used directly from the scanned image Section from 3D data For calibration the profile is used from the earlier saved one Section from Data Use for calibration the section stored in the file. Source Falling edge Installations of points of a binding on the falling edge of test structures: Level, 0…1 Point level, Period, μm Test structure period. «Nano Scan Technologies Ltd.» User manual 108 Working with SPM Certus Standard 4.18.5. Calibration coefficients obtaining Let's consider the example. For piezostack calibration of a scanning head on an axis X by the image saved in a file earlier it is necessary to go to the Data unit, to open earlier scanned image of a test grating and to construct its section. For constructing the section set up marker on the scan by the button Marker Section and the button Markers Horizontal mode , press the button Cross . Fig. 4.59 Profile for calibration. Then go to Oscilloscope unit, press Show/Hide calibration window , select Head in the Device combo box, select Voltage Ux in the Channel combo box, select 3D data Section in the Source, and type-in the gratings period. And then press the button Acquire data «Nano Scan Technologies Ltd.» . User manual 109 Working with SPM Certus Standard Fig. 4.60 Calibration curve. Apply filters for section nonlinear correction . Fig. 4.61 Calibration curve after filter applying. Markers on the curve can be moved manually in case of wrong automatic installation. «Nano Scan Technologies Ltd.» User manual 110 Working with SPM Certus Standard Fig. 4.62 Calibration curve. After loading calibration structure curve and carrying out all steps for calculation of polynomial coefficients, in the frame Coefficients it will be shown. Fig. 4.63 Polynomial coefficient. Then press the button Save to settings , to store polynomial coefficients on the chosen axis in the Piezo Calibration table. Similarly coefficients are defined for other axes and scanners, and for capacitor gauges. After getting all coefficients it is necessary to keep options by pressing the button PC File . «Nano Scan Technologies Ltd.» User manual 111 SPM Certus head application with external optical equipment 5. SPM Certus head application with external optical equipment 5.1. Basic principles of optical equipment application Scanning probe microscope Certus Standard is designed for use with optical equipment. The SPM head Certus design can combine it with both direct and inverted microscope, to inject additional sources of light, such as lasers, to use regular microscopes light sources, etc. One of the basic restrictions of a scanning probe microscope is difficulty in search of an interest site on a research object surface, and as probe positioning in the chosen point on a surface. To bypass this restriction use of techniques of optical microscopy and spectroscopy allows. The full range of positions of lenses concerning an axis passing through a tip makes 0-90 ° for a direct microscope and 0 ° for the inverted. The maximum diameter of used lenses in case of a direct microscope-40 mm, and for inverted lenses diameter is limited only by their design. The working distance of lenses (WD) is 12 mm for direct microscope, and for the inverted microscopes is limited only by thickness of a used substrate. For combination of techniques optical and scanning probe microscopy the field of vision of an optical microscope is necessary to combine with scanning area of a scanning probe microscope. Fig. 5.1. External objective application. «Nano Scan Technologies Ltd.» User manual 112 SPM Certus head application with external optical equipment 5.2. Example The combination of the upright optical microscope allows to study both transparent and opaque objects. In this case, you should align microscope field of view and tip position (Fig. 5.2). Furthermore, using optical microscopy techniques and sample movers you can to select interesting areas on the research surface and scan it. Fig. 5.2 Sample and cantilever tip image. 5.3. Video-videocam mode adjustment In the SPM Certus Standard built-in optical microscope with CCD sensor. The Video unit is used to work with and adjustment of camera. Fig. 5.3 Video unit drawing. «Nano Scan Technologies Ltd.» User manual 113 SPM Certus head application with external optical equipment 5.4. Video unit basic functions To entry Video window press , that is situated on the top panel of the NSpec window. Start/stop Start/stop CCD camera video imaging. Automatic white balance Enables automatic white balance adjustment. Repeated pressing of the button disables this. Automatic exposure Enables automatic exposure adjustment. Repeated pressing of the button disables this. Autoadjustment Enables automatic white balance and exposure adjustment. Repeated pressing of the button disables this. Autofocus by image Enables automatic focusing by image. Lens Z position is controlled by the slider Obj. Z. Autofocus by laser spot Automatic focusing by reflected laser. Enable with only Centaur device. Save image Saving current CCD image in the raster format file. Start recording Recording CCD video in *. avi file. Show tip scan area The scan areas by tip and by stage are shown on the video image. It corresponds to piezoscanner and may has various range. Show laser scan area The scan areas by stage are shown on the video image related to laser spot. (not available in Certus Standard) Settings Lenses settings. Measure distance Distance measurement by video image. It makes sense when only the lens has a calibration. Show axes Enables axes on the video image. It makes sense when only the lens has a calibration. Show grid Enables grin on the video image. «Nano Scan Technologies Ltd.» User manual 114 SPM Certus head application with external optical equipment Fig. 5.4 Scan area demonstration Fig. 5.5 Measuring tool . . Each scan area has its own color. Scan area by head has the blue. Fig. 5.6 Scan areas colors. «Nano Scan Technologies Ltd.» User manual 115 SPM Certus head application with external optical equipment To disable the axes press the button . Fig. 5.7 Video without axes. To disable the grid press the button . Fig. 5.8 Video without axes and grid. «Nano Scan Technologies Ltd.» User manual 116 SPM Certus head application with external optical equipment 5.5. Lenses calibration Work with devices and complexes form company «Nano Scan Technology» means possibility to use various lenses of various manufacturers. As lenses have various characteristics, such as the zoom, focal length and work distance, it is necessary to spend adjustment for each used lens. Lens adjustment includes calibration on the test sample and combination of scanning fields of SPM with the optical image. 5.5.1. Settings panel main functions For lens adjustment or configuration changing press the button Settings . The panel of options will be displayed. Fig. 5.9 Video with lens settings panel. Add new configuration Creates new lens configuration Remove current configura- Remove current lens configuration tion Measure reference «Nano Scan Technologies Ltd.» Tool for measuring reference length. The reference length is entering in the Line length field. User manual 117 SPM Certus head application with external optical equipment Tip scan area center align- The scan areas by tip and by stage are shown on the video image. ment. By mouse clicking scan area center moves to mouse point. Laser scan area center The scan areas by stage are shown on the video image related to alignment (not available in laser spot. By mouse clicking scan area center moves to mouse Certus Standard) point. 5.5.2. Tools panel Settings Fig.5.10 Tool panel Combo box with available configurations. The list of available configurations is enumerate in the combo box. Name: Current configuration name. Name of new configuration is entered here. Range X: X axes field of view size Range Y: Y axes field of view size Width Width of the image in percentage of width of a matrix Height Height of the image in percentage of height of a matrix Line length The field to enter the reference size of the test structure. Flip X. Horizontal image flip. Flip Y. Vertical image flip. «Nano Scan Technologies Ltd.» User manual 118 SPM Certus head application with external optical equipment 5.5.3. New lens calibration For new lens calibration it is necessary to focus on the test sample surface and produce following steps: • Press the button Add new configuration ; • Enter the configuration name; • Enter reference size of the test structure; • Using tool Measure reference select reference structure on the video im- age. Irrespective of a numerical ruler length on the image its length will make a preset value and all axes will be calibrated according to set the reference. See figure 5.11. Fig. 5.11 Creating new lens configuration. After input of the reference size and its choice on the image there will be a change of axes scale of the image according to the reference size. 5.5.4. Scan field selecting After lens calibration and creation of a new profile it is possible to spend combination and/or installation of fields of scanning. For this purpose it is necessary to press «Nano Scan Technologies Ltd.» User manual 119 SPM Certus head application with external optical equipment the button Tip scan area center alignment and having clicked on object on the video image to define a scanning field center. The sizes of scan fields are set according to the sizes stored in the file of options. Fig. 5.13 Scan fields select. «Nano Scan Technologies Ltd.» User manual 120 SPM Certus head application with external optical equipment 5.6. Microscope positioning For microscope focusing and positioning use the focusing and positioning knobs. A Microscope focusing knob B Microscope mover knob C Microscope mover knob «Nano Scan Technologies Ltd.» User manual 121
