User`s guide

AC Modes 6

Agilent 5500 SPM User’s Guide 109

In the Realtime Images window, make sure that Topography and

Deflection are displayed.

26 In the Scan and Motor window, click the Down blue arrow to

initiate a scan starting at the top of the grid. Click the Up blue arrow

to initiate the scan from the bottom up. The image maps will begin to

be rendered in the Realtime images window.

As the tip moves across the first scan line, the system will adjust the

voltage on the z-piezo to maintain constant amplitude (as specified by

the Setpoint voltage).

For each pixel, the system will record and plot the error signal (the

amount the oscillation amplitude would deviate from the Setpoint

voltage as the Amplitude Image (in volts).

The correction signal (the voltage that the system applies to the z piezo

to maintain the amplitude) is scaled by the system sensitivity and plotted

as topography (in nanometers).

At the end of each scan line the system will “retrace” the line to the

beginning of the scan. The scanner will advance one line width (based

on the resolution setting) and another line will be scanned.

Depending on the Frames setting in the Scan and Motor window, the

system will either scan once and stop, or it will scan infinitely,

overwriting the last scan each time. You can also specify a specific

number of scans to complete.

To stop the scan cycle, click the red STOP circle that will replace the Up

or Down arrow when you start a scan.

Constant Height Mode

AC Mode imaging can be completed using either Constant Amplitude

mode, as described above, or Constant Height mode. In Constant Height

mode the tip remains in the same horizontal plane throughout the scan

(it does oscillate, but the center of that oscillation stays in plane). The

servo gains are set very low so that the system effectively does not react

to changes in amplitude.

Constant Height Mode should only be used for very flat samples. To

image in Constant Height mode, in the Servo window set the I and P

gains to 0.1 %. This system will only very slowly adjust the z-piezo in