Spectrum Analyzer, Image Line display, cross section measurement tool, and Spectroscopy display
windows. The use of the common controls is described in Section 2, “XY Graph Windows”. Select the
Topography and Current channels to be displayed. As there is no input signal from a preamplifier, the
input signal will measure very close to zero nA. There should be less than 1 pA of noise on the displayed
signal.
As there is no input signal, the feedback loop will fully extend the tip since the measured signal is below
the feedback loop Setpoint. This can be seen in the Oscilloscope view with the tip at the -420 nm
position (the extended range of the UHV300 scan head). For these examples, it is best if the display
autoscale is turned off. Set the display range for the Current channel to autoscale and the display range
for the Topography to display from -500 nm to +500 nm. When this is entered, the display will change to
show the range as -0.5 um to + 0.5 um. The display range for the topography is set to more than the full
scale range of the Z piezo for ease of viewing. If autoscale is turned on, the Z signal will be difficult to
view as it will be sitting on top of the X axis of the display.
In the Z PI control panel, locate the drop down selector box labeled Tip Control. This control selects the
function of the feedback loop. When set to Unlimit, this feedback loop is active. This is the setting used
during normal operation. Select Center from the drop down menu. This setting forces the tip to move to
the center of its range. In this position the feedback loop is not active. The Oscilloscope trace for
Topography will now show the tip in the center of the range, or 0 nm. Now select Retract from the drop
down menu. The Oscilloscope will now show the tip to be fully retracted, or at the +430 nm position.
Return the drop down selection to the Unlimit position. The reactivates the feedback loop. This selection
box is used mostly for testing purposes and some specialized measurements. If the experiments to be
performed do not require this control, it can be easily hidden from display to prevent accidentally
changing it.
Important
RHK follows the convention that a positive value of the Z position means that the tip is
retracting away from the sample. A negative value means that the tip is moving closer to
the sample.
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