Download NanoWizard User Manual - Section for Nanostructure Physics

It is also possible to manually select a sensitivity using the Manual Sensitivity Selection button. This may be more helpful if the
curve is less "ideal" and does not have such
a clear linear region.
In this case, when the mouse is used to click
and drag on the plot area, a straight line is
plotted between the points (black line in left
panel). The slope of this line is used for the
sensitivity. Select a best fit straight line
through the steepest region of the repulsive
part of the curve.
When a line is drawn or fitted, the slope is used to calculate the sensitivity value
shown in the left hand part of the window (here, s = 34.1 nm/V). The value is not
used immediately, since the user may wish to redraw the line. When you are
happy with the straight line fit, click Accept Value to store and be able to use the
sensitivity value.
A sensitivity value can be stored with the scan or force data without actually being
used directly in the SPM software to display the deflection values in units of length
rather than Volts. When use it is ticked, then wherever the vertical deflection is
used in the software (contact mode setpoint, intermittent contact mode amplitude,
force spectroscopy axes etc.) the value is now displayed as nm rather than V.
When use it is unticked, these values are all displayed in Volts, but the sensitivity
value is still stored for use later, and saved with the files. Note: use it must be
ticked to proceed to the thermal noise measurement of the cantilever spring constant, as it is important to know the deflection in nm for this measurement.
If for some reason you want to discard the measurement (e.g. after changing the
cantilever), UNKNOWN can be reselected, and the values will be disregarded.
Typical sensitivity values are in the range 30-100 nm/V. If the value lies significantly outside this range, it may be
worth checking that everything is set up alright (see Section 4.2 for details of adjusting the optical detection path).
The Sensitivity measurement is the first stage in the thermal noise measurement of the cantilever Spring Constant.
7.3 Spring constant calibration (thermal noise measurement)
7.3.1 General information
Most suppliers of cantilevers deliver data sheets with their cantilevers that state the approximate spring constant.
Usually this has been calculated from the cantilever shape (length, width, thickness). The spring constant is very sensitive to the thickness of the cantilever, however, and these quoted values are usually not very reliable. The range of
values quoted by the supplier should give some idea of the variability, but generally the spring constant is not known
within a factor of 2 or 3.
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NanoWizard AFM User Manual
Version 4.2