4-2
A
PPROACHING
THE
S
AMPLE
AND
T
AKING
A
S
CAN
Refer to Chapter 3, observing all Warning and Caution statements, when following this pro-
cedure.
Step 1
Locate the tip with the transmission and reflection objectives.
Step 2
Bring the tip into feedback, if it is not already, following the procedure under
“Moving the Tip into Feedback,” on pg. 3-3.
Step 3
The z piezo voltage should be around 0.
Step 4
Pull the z piezo back by typing in a set-point value that is more negative than the
internal sensor signal. E.g., if the internal sensor signal is -30 nA, type in -64 nA.
The piezo will retract. This is done so the tip doesn’t break when you flip the
mirror.
Step 5
Make any final necessary adjustments to the transmission objective. The image
should be in focus and in the middle of the monitor.
Step 6
Flip the camera path mirror down, to open the PMT path.
Step 7
Close the instrument enclosure and, if possible, dim or turn off the room lights.
Step 8
Turn off the Aurora-2 light.
CAUTION
The light on the Aurora-2 must be off to prevent damage to the PMT.
Step 9
Select S
ETUP
⇒
A
CQUIRE
, and from the Data Channels list check the F
WD
checkbox for the NSOM channel.
Step 10
Bring the tip back into “true feedback,” i.e., at the sample surface, as described in
Steps 7-16 under “Moving the Tip into Feedback,” on pg. 3-3. The P-I-D settings
should be low (the Integral gain in particular) so the tip doesn’t jump as it
approaches the sample. Be sure to observe all the Warning and Caution
statements!
Step 11
Increase the P-I-D settings to improve the topography response, following the
procedure under “Optimizing the P-I-D Settings,” on pg. 3-5.
Step 12
Click the S
COPE
option in the upper right of the Signal window, and choose
“NSOM” from the drop-down signal source list to the right of the upper
oscilloscope. The signal should read 0, both on the oscilloscope and the Aurora
Control Unit.
Step 13
Slowly turn up the PMT voltage on the Aurora Control Unit. The PMT will
typically “turn on” at around 230 V. Watch the PMT signal, and make sure there
is a signal response as the PMT voltage is increased. Aim for a signal of about
200mV. Increasing voltage increases the signal strength, but it also increases the
noise level within the signal.
Step 14
Perform a line scan by clicking the L
INE
option in the Signal window.
Step 15
Adjust the set point and the P-I-D settings until you get repeatable line scans, as
shown in Figure 4-1.
Summary of Contents for Aurora-2
Page 30: ...2 18 Figure 2 20 Reflection Tower Controls Swivel Tilt Focus Rotating mirror selector ...
Page 44: ...3 8 ...
Page 52: ...5 4 ...
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