Fluid Operation
General Fluid Operation
132
MultiMode SPM Instruction Manual
Rev. B
8.2.7 Adjust the Detector Offsets and Setpoint (Contact Mode)
Adjust the detector mirror adjustment screws:
•
In Contact Mode (i.e.,
Other Controls
>
Microscope mode
set to
Contact
and
Feedback Controls
>
SPM Feedback
set to
De
fl
ection
), to achieve a vertical
de
fl
ection signal of roughly
-1.0V
. Set the
Feedback Controls
>
De
fl
ection Setpoint
to
0V
to begin.
•
The difference between the vertical de
fl
ection signal before engaging and the setpoint
determines the amount of force that the probe applies to the sample.
•
Typically, samples are softer in liquid than in air. Before engaging, verify that there is
not so large a difference between the setpoint and the vertical de
fl
ection signal as to
damage the sample.
•
Verify reasonable values for scan parameters (e.g.,
Scan rate
,
Scan size
,
Integral gain
and
Proportional gain
).
•
Once engaged, reduce the setpoint to minimize the tracking force.
8.2.8 Engage the Surface
1. Using the
Motor down
switch (and coarse adjustment screws if not using a vertical engage
scanner), lower the tip until it is just above the level of the sample surface.
•
The
Motor down
switch is located on the MultiMode base.
•
Watch the engagement closely through the 25
×
magni
fi
er or using the vertical optical
microscope.
2. In the
Real Time
>
Motor
menu, click
Engage
, or click the
Engage
icon.
•
The motor begins to move the AFM head and probe down to the sample.
•
When the tip reaches the surface, the system should automatically stop, beep, and begin
to image the sample.
•
In Contact Mode, if the system engages immediately or before the tip reaches the
surface, try increasing the
Setpoint
approximately
2.0V
, then repeat this step.
8.2.9 Adjust Scan Parameters (Contact Mode)
1. Once engaged, adjust the scan parameters to obtain the best image.
Note:
This procedure is similar to operation in air, except that samples are often softer
in
fl
uid. Adjusting the applied force can be critical.
