Download IMP Software Suite User Manual

IMP Software Suite User Manual, Release 1.2
• Use Correction will correct the measurement for an arbitrary linear, frequency-dependant transfer
function embedded between the output and the input points of the measurement chain.
• Set Correction stores the last-measured transfer function to an internal file which is used for the
correction.
2.2.2 Calibration
Quantitative AFM starts with a good calibration of the cantilever and ImAFM™ requires this calibration before
you start to scan a surface. The IMP Software Suite contains the latest methods for cantilever calibration based
on the measurement of the thermal Brownian motion of the cantilever and a theory of hydrodynamic damping of
the oscillating beam. By fitting a theoretical model to the noise data we determine all constants necessary to the
measure the cantilever deflection in meters, and convert this deflection to force in Newtons.
The calibration procedure applies to a particular cantilever eigenmode (resonance). Details and references to the
literature are given in the advanced section on Noise Calibration. Here we describe how to perform the calibration.
The tab at the very top selects between calibration of a Flexural or Torsional eigenmode. The procedure is
very much the same for either type of mode, but the underlying formulas and analysis are different. We begin by
describing calibration of flexural eigenmodes, and end with a discussion of torsional eigenmodes.
Choose Cantilever and Method
Calibration Parameters specifies the type of cantilever and calibration method.
• Temp [C] is the temperature of the damping medium in Celsius, used to determine the magnitude of the
thermal noise fluctuation force driving the cantilever.
• Fluid selects the density and viscosity of the medium surrounding the beam, needed for calculation of
hydrodynamic damping. Noise calibration methods have not been tested thoroughly beyond studies in Air,
but we include to option to apply the theory in Water 20 C.
• Cantilever selects from a list of pre-programed cantilevers for which calibration constants have been
published. If your cantilever is not on this list you can choose Arbitrary Rectangular and enter the
Length and Width , or plan-view dimensions of your rectangular beam cantilever. You can edit the length
and width fields for any chosen cantilever without changing the stored values for pre-programed cantilevers.
Alternatively, you can Add Edit Remove cantilevers as described below.
• Method selects between six methods of calibration:
– Hydrodynamic function uses an analytic expression for the hydrodynamic function to calculate
the damping. The calculation applies to a rectangular beam in the limit length >> width (see [Sader1998]). This method uses length and width given in the fields above.
– Sader constants uses a good approximation to the hydrodynamic function described with three
parameters 𝑎0 , 𝑎1 , 𝑎2 that are specific to a particular cantilever. These constants have been measured
and checked against other methods and according to theory they should apply to any cantilever of the
same shape (see [Sader-2012]). For this method, the length and width fields have no influence.
– Reference calibration brings up three fields. If you have one good calibration using another
means, such that you know all three constants: the quality factor, stiffness and resonant frequency, or
Q-ref, k-ref and f0-ref respectively, you can use this calibration as a reference for calibrating
other cantilevers of the same shape (see [Sader-2012]). For this method, the length and width fields
have no influence.
2.2. The Work Flow
7