Operation of Interleave Scanning and LiftMode

These instructions apply to Scanning Tunneling Microscopy (STM), Contact AFM, or TappingMode AFM. You must be familiar with TappingMode or Contact AFM to obtain good images of surface topography. The interleave scanning procedure is described below; further detail is given for specific modes elsewhere: see Magnetic Force Microscopy (MFM) and Electric Force Microscopy (EFM).

1. Obtain a topography scan using the appropriate method (usually Contact or TappingMode).

When using LiftMode, it is important that the 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 setpointOperator-selected threshold used as the target of the feedback control loop. under Feedback controls be adjusted to give a faithful image of the surface. Because the height data is used in the lift pass to trace the topography, a poor measurement of surface height may give inaccurate measurement during the lift pass or cause the tip to strike the surface. Typically, the height data is displayed on Channel 1.

2. Choose the Interleave Mode (Interleave, Lift, or Linear) appropriate for the measurements to be performed.
3. Adjust the Interleave controls panel to the desired settings.

When using TappingMode, the Drive AmplitudeAmplitude of the signal used to oscillate a tip in TappingMode., Drive FrequencyFrequency of the signal used to oscillate a tip in TappingMode., gains, and Amplitude Setpoint can be set differently in the Interleave panel than in the main Feedback panel. However, it is often convenient to begin with the main and interleave controls set to the same values. Do this by toggling the parameters of the appropriate Interleave parameters to an “off” (grayed) condition. The values can be changed once the probe is engaged.

• If you are using LiftMode or Linear Lift Mode, set the Lift Scan height.
• If you are using Interleave mode, set the Gains and Amplitude Setpoint. For more information, refer to Use of LiftMode with TappingMode.

3. Choose the Interleave Data Type.

Depending on the type of microscope, Interleave mode allows the options of amplitude, phase, frequency, potential, input potential, or data types for doing far-field (MFM or EFM) imaging. Auxiliary channels are also available for some applications.

Once the Interleave Scan Line is chosen, Interleave mode is automatically enabled, triggering interleave scanning. Interleave data typically displays as the second image. Notice that the scan rate in the slow direction is halved.

4. Display the interleave data by switching Scan Line (in the Channel panels) to Interleave.

Final Considerations

• Lift Scan Height: The lateral and vertical resolutions of the Lift data depend on the distance between tip and sample: the lower the tip, the higher the resolution. However, the Lift Scan Height must be high enough that the tip does not contact the sample during the Lift trace and retrace.
• Tip Shape: As shown below, the tip separation in the LiftMode is defined in terms of the Z direction only. The Lift Scan Height is added to the height values taken from previous scan lines point-by-point. However, the tip may be closer to the sample than the Z separation indicates. On features with steep edges, the tip may get very close to the sample even though the Z separation is constant.

• Line Direction: The Line Direction should be set to Retrace for both the main and interleaved scans. If it is set instead to Trace, a band may appear along the left side of the images due to the ramp between the surface and the Lift Scan Height.

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