User`s guide

AC Modes 6
Agilent 5500 SPM User’s Guide 108
Next, bring the tip into contact with the sample. In AAC mode,
“contact” occurs when the cantilever oscillation is dampened to a
specified percentage of the total oscillation.
18 In the Scan and Motor window, click the Motor tab (Figure 75).
Figure 75 Set the Stop At value in the Scan and Motor window
19 Set the Stop At% to specify the percentage of total oscillation that
represents “contact.” For example, if the total oscillation amplitude
(set in step 11) is 2 volts, and the Stop At value is set to 90 %, the
approach will stop when the oscillation is damped to 1.8 volts.
20 Click the Approach button in PicoView’s toolbar . The
system will raise the sample until the amplitude is damped to the
Stop At percentage. Because of air damping, oscillation typically
decreases as the tip nears the sample. The software monitors the rate
of change of amplitude as well as the absolute value, so the final
amplitude will not be exactly the Stop At percentage.
21 In the Servo window set the I Gain and P Gain to 5 %. These gains
dictate how quickly the system will react to changes in amplitude.
22 In the Scan and Motor window, select the Scan tab.
23 Enter a scan Speed of 1-2 ln/s and a Resolution of 256. More
information on fine tuning these settings can be found in Chapter 5.
24 Enter the Size (in microns) and X Offset and/or Y Offset values to
set the size and center of the scan. You can also click and drag the
Scan box in the graph on the Scan and Motor window to adjust the
scan size and location.