Dell 3100 Especificações descarregar pdf (Página 259)

Force Imaging

Force Modulation

Rev. D Dimension 3100 Manual 239

Note: You may also change the Drive Frequency by clicking on the Drive

Frequency parameter on the control monitor’s Feedback Controls panel, and

entering a new value.

Note: Bimorph resonance should be between 5 kHz and 30 kHz. If peaks are found at

a much higher frequency, these are cantilever resonances, not bimorph

resonances.

o. Record the Drive frequency. This is the resonant frequency of your force modulation

bimorph.

9. Select Stage > Locate Tip or click the Locate Tip icon.

10. Select Stage > Focus Surface or click the Focus Surface icon.

11. Check the scan parameters Scan speed, Scan size and Integral gain to verify they are

reasonable for Contact Mode AFM imaging. Also, it may be desirable to readjust the detector

mirror adjustment screws if the Vertical Difference signal has drifted from the value

originally set.

12. For the Channel 1 image, select Data Type > Height. Select Data Type > Amplitude for

the Channel 2 image. The multi-image capability views both the topography data and the

force modulation (elasticity) data at the same time.

13. Reduce the Drive Amplitude to 0 before engaging.

14. Select Motor > Engage.

Note: The motor moves the SPM head down towards the sample and stops once the

cantilever deﬂects to the chosen Setpoint. Under some conditions the system

may “false engage” before the cantilever actually reaches the surface. Increase

the Setpoint and engage again.

15. Adjust the Integral Gain, Proportional Gain, Setpoint, and Scan Speed to obtain a good

topography (Height) image. For force modulation operation, set the Integral Gain and

Proportional Gain to values of 1-10 and set the Setpoint as low as possible using the cursor

keys (or by typing in new Setpoint values) until the cantilever pulls off the surface and the Z-

center voltage jumps to -220V.

16. Record the Setpoint value where the cantilever pulls off the surface (the “pull-off value”).

17. Increase the Setpoint until the cantilever touches the surface, and an image appears. Then

decrease the setpoint to a value just above the value where the pull-off occurred.

Note: If you adjust the Setpoint very close to the pull-off value, imaging perform

with the smallest and least damaging force. However, in this condition imaging

may be more unstable, as the cantilever may pull off the surface unexpectedly.

The setpoint value affects the force modulation contrast. Examine the contrast

of the force modulation image.

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Dell 3100 Especificações Página 259