Open Loop Z Calibration

1. Set up the microscope for TappingMode imaging.
2. Select Engage under the Microscope drop-down menu or click the Engage icon in the Main panel.
3. Find a square pit and center the pit in the image using a Scan size of approximately 10 mm.
4. Verify that the Z Center Position value shown next to the image display is close to 0 V (±5 V):

5. If the Z Center Position value is not close to zero, use the Microscope > Step Motor > Tip Up and Tip Down buttons to adjust:

	Set Channel 1 Data Type to Height and Channel 2 Data Type to Height Sensor.
	Capture an image by selecting Capture from the NanoScope tool bar, or click the Capture icon.
	When the image is captured, load the image by double clicking it in the browser bar.
	Click the height image (Channel 1) to select it.
	Remove all tilt and scan line errata from the image by selecting Modify > Flatten or click the Flatten icon on the NanoScope tool bar.
	Set the Flatten Order parameter in the input box to 1. Go to the display window and draw a stopband over the pit:

(Hover over the image to view larger)

With the image corrected, its vertical features may now be measured. This is performed using Depth analysis to utilize more data points.

Select the Analysis > Depth command or click the Depth icon on the NanoScope tool bar. This loads the Depth analysis screen:

(Hover over the image to view larger)

If the depth of the pit on the 10 μm silicon calibration reference deviates significantly from the actual depth, correct the ZScan Sens. parameter in the Z Calibration dialog box.

1. Open the Z Calibration dialog box by selecting Calibrate > Scanner > Z.
2. Divide the actual depth of features (200 nm for the 10 μm calibration reference) by the measured depth (indicated in Depth analysis by the Peak To Peak Distance):

3. Multiply this quotient by the ZScan Sens value in the Z Calibration dialog box, and replace the former ZScan Sens value with the new result.
4. Click OK to enter the new ZScan Sens value.

After executing the steps above, recheck the Z-axis measuring accuracy of the SPM by repeating the steps outlined above until you obtain accuracy of 1 to 2%.

Repeat Capture and Correct an Image, Measure Vertical Features, and Correct Z Sensitivity using Channel 2. This time you will adjust Z sensor sens rather than Z scan sens.

Piezoelectric materials exhibit greater sensitivity at higher voltages. In the steps outlined above, the Z-axis was calibrated while scanning near the middle of the piezo voltage range (i.e., Z Center Position ~ 0 V). In this section, you will calibrate the Z-axis piezo while extended and retracted to determine how much the Z sensitivity varies with Z Center Position.

1. If you are not already Engaged, select Engage under the Microscope drop-down menu or click the Engage icon in the Main panel (see Engage).
2. Use the Microscope > Step Motor > Tip Up button until the Z Center Position reads 50 V (±5 V).

3. Refer to the steps above (Capture and Correct an Image through Measure Vertical Features) to determine the measured depth of the calibration standard with a +50 V Z Center Position.
4. Record the measured depth. If the depth measured by the extended piezo is correct within two percent, skip to Step 9.
5. Select Calibrate > Z... to display the Z Calibration dialog:

6. Click the Extended offset der parameter.
7. Perform the following calculation:

For example, if the current offset equals 4% and the measured depth equals 185 nm, then:

8. Enter the new percent value from above (the answer for the example is 12%) for the Extended offset derparameter in the Z Calibration panel.
9. The procedure for calculating and setting the Retracted offset der is exactly the same as for the Extended offset der; however, the piezo must be retracted to –50 V. To calculate the Retracted offset der:
   1. Use the Tip Down button in the Motor Control panel to retract the piezo.
   2. Retract the Z Center Position to –50 V.
   3. Repeat steps 3–8 above.