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tip DC voltage a direct mapping of the sample potential is possible. The
KPFM mode is performed in a constant sample to tip distance using the dual
pass technique. In the first line the sample topography is recorded and in
the second line the topography is retraced at a certain tip-sample distance
while the KPFM signal is recorded.
V.2.
Performing a Scan
The following sections describe the most important steps to be performed
before a scan is started. The AFM system must be in the following state
before you can go on:
-
all electrical and optical connections are correct (see chapter IV).
-
The tip-fiber system is well aligned.
-
The step function for the positioner axes of the ANC300 axes should be
activated in the hardware but disabled in the coarse menu of the
software.
-
For the non-contact mode, the BNC labeled
HF out
of the Lock-In
amplifier (on the ASC500) should be connected to the AC IN of the
AC/DC-coupler breakout panel and both the
HF in
input of the Lock-In
amplifier and ADC1 are connected in series to the output of the photo
detector.
With an o
pen system at ambient conditions, start to manually approach the
sample
to the tip using the z coarse positioner. This should be done under
eye inspection to a distance close enough for reasonable auto-approach
duration but still far enough away to avoid any crash of the tip. If the system
is going to be cooled down, the sample surface should be moved down 250-
500 steps from the contact position to (i) avoid the tip crashing into the
sample on cooling due to thermal contractions and (ii) assure a reasonable
approach time at low temperatures.
V.2.a.
Set the Actor Scaling
The voltage outputs of the ASC500 must be activated (check the ‘output
active’-button within the DAISY software)
However, before you start activating the outputs, check that the correct
temperature and the according scaling details are set correctly in the ‘Actor
Scaling’ box of the ‘Pref’ window.
Two sets of parameters for room temperature and low temperature may be
saved. The parameters for the low temperature scaling entered here by
attocube systems are the calibrated 4 K values.
Note that at room temperature 4 V is the upper limit for the ASC500 scanner
outputs and at 4 K this limit increases to 10 V (this limits are valid for an
amplifier with amplification factor 15, namely the ANC300). If the customer
wants to measure at temperatures in between he should not exceed the
