Engage and Adjust Scan Parameters

Engage

Select Microscope > Engage or click the Engage icon on the toolbar.

A pre-engage check begins, followed by Z-stage motor motion.

To move to another area of the sample, execute a Withdraw command to avoid damaging the tip and scanner.

Adjust Scan Parameters

Once engaged, the scan parameters should be adjusted to obtain the best image.

1. In the Scan panel, set Slow Scan Axis to Disabled (this function is available in the Expanded Mode).
2. Observe the agreement between the trace and retrace lines and adjust the setpointOperator-selected threshold used as the target of the feedback control loop., gainsThe gains are scaling factors for the error signal to determine how quickly corrections should be applied in the feedback loop. There are two important gain factors: the proportional gain scales to the current value of the error signal, and the integral gain scales the aggregate of the past values of the error signal (the "area under the curve"). and scan rate to bring the trace and retrace lines into coincidence. This procedure will be similar to operation in air, with the following exceptions:
   • Samples are generally softer in fluids. Adjusting the applied forces becomes more critical.
   • Optimal scan rates tend to be slower in fluid.

Adjusting Setpoint

Contact Mode

1. Adjust the Setpoint to as low a value as possible using the cursor keys until the cantilever pulls off the surface (and the Z-center voltage jumps to –220 V).
2. Increase the Setpoint slightly until the cantilever begins to touch the surface again and an image appears.

TappingMode

Usually the best images are obtained at setpoints 5–10 percent less than the cantilever RMS amplitude before engaging. To optimize the setpoint in TappingMode:

1. Select a Scan Size of 500 nm.
2. Increase the setpoint in small increments until the cantilever pulls off the surface and the Z center voltage is at –220 V.
3. Reduce the setpoint in small increments until an image appears. Continue reducing the setpoint until the image is optimized. Usually the best images are obtained at setpoints just below where an image appears.

When operating in TappingMode, it may be necessary to check the cantilever tuning after the system is engaged. To check the cantilever tuning:

1. Select Microscope > Cantilever Tune.
2. Set the Tip Offset to 200 nm and click OK.
3. Once in the cantilever tuning window, adjust drive frequency and drive amplitude if necessary.

Previous Steps:

1. Fluid Set Up
2. Align the Laser
3. Load the Sample and Adjust the SPM Scanner
4. Locate the Tip
5. Tune the Cantilever (TappingMode Only)
6. Focus on the Sample Surface
7. Check Initial Scan Parameters

Next Step:

9. Withdraw and Clean Up

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