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TappingMode AFM

Advanced TappingMode AFM Operation

146 Dimension 3100 Manual Rev. D

9.4.4 Optimization of Scanning Parameters

The user is encouraged to review Section 8.3 which discusses parameter optimization for Contact

AFM.

9.4.5 Data Type

Data type is the ﬁrst parameter to set because the values of other parameters depend on it. The

Data type parameter in the Channel 1, Channel 2 and Channel 3 panels selects the type of data

collected by the system. Height data corresponds to the change in piezo height needed to keep the

amplitude of the cantilever constant. Amplitude data measures the change in amplitude relative to

the amplitude setpoint.

The scan parameters required to collect good Height data are different than the optimal parameters

for Amplitude data. To collect Height data while tracking the sample surface with minimal

change in the tip’s oscillation amplitude, the feedback gains must be high.

Amplitude data collected with high feedback gains is the derivative of the height. Amplitude

mode provides a sensitive edge detection technique. With the dual screen mode it is possible to

capture both Height and Amplitude data simultaneously.

9.4.6 Gain Settings

The Integral and Proportional gains on the Feedback Controls panel must be high enough to

force the feedback system to track the sample surface. When scanning in TappingMode, set the

Integral and Proportional gains to lower values than those values used in Contact mode. The

Proportional gain can usually be set 30%-100% higher than the Integral gain. To optimize the

gains, increase the Integral gain until the piezo begins to oscillate (feedback oscillation usually

occurs with Integral gains of 1-2), then eliminate the oscillations by reducing the gain with two or

three clicks of the left arrow key. Repeat the process for the Proportional gain.

9.4.7 Scan Size, Scan Rate, and Setpoint

The Scan size, Scan rate, and Setpoint values effect data output differently. As in Contact mode,

decrease the Scan rate as the Scan size is increased. Use Scan rates of 0.5-1.0 Hz for large scans

on samples with tall features. High scan rates help reduce drift, but only use them on ﬂat samples

with small scan sizes.

CAUTION: Do not conduct TappingMode microscopy with low feedback gain

values, as this will cause damage to both the tip and sample. The

maximum amplitude of the cantilever oscillation is not sufficient to

track tall features.

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