AFM University Introduction to Atomic Force Microscopy by Paul West

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6.1 Probe Artifacts
6.1.1 Features on a Surface Appear Too Large
6.1.2 Features in an Image Appear Too Small
6.1.3 Strangely Shaped Objects
6.1.4 Repeating Strange Patterns in an Image
6.2 Scanner Artifacts
6.2.1 Probe / Sample Angle
6.2.2 X-Y Calibration / Linearity
6.2.3 Z Calibration / Linearity
6.2.4 Background Bow / Tilt
6.2.5 Z Edge Overshoot
6.2.6 Scanner Drift
6.2.7 X-Y Angle Measurements
6.2.8 Z Angle Measurements
6.3 Image Processing
6.3.1 Leveling
6.3.2 Low Pass Filter
6.3.3 Matrix Filter / Smoothing
6.3.4 Fourier Filtering
6.3.5 Image Looks Too Good
6.4 Vibrations
6.4.1 Floor Vibrations
6.4.2 Acoustic Vibrations
6.5 Other Sources
6.5.1 Surface Contamination
6.5.2 Electronics
6.5.3 Vacuum Leaks
6.5.4 PID Settings / Scan Rate
6.5.5 Laser Interference Patterns
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Chapter 6
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FIGURE 6-18 The blue lines drawn on this image show that the scanner has no measurable cross-talk between the X and the Y axis. The lines are orthogonal.
6.2.8 Z Angle Measurements
Mechanical coupling between the piezoelectric ceramics that move the probe in the X or Y directions and the Z direction can cause substantial errors when trying to measure side wall angles with the AFM. This error can best be measured with a sample that has repeating triangle structures.
FIGURE 6-19 A-B: Image A: This cross section is an ideal sample for demonstrating the ability of an AFM to measure angles. The sample has a series of repeating triangles at its surface. Image B: A line profile of the sample shows that the triangles do not appear symmetric.
FIGURE 6-20 The AFM image of a sample having a triangle pattern at its surface. B: A line profile extracted from the AFM image.
6.3 Image Processing
Image processing is required before viewing or analyzing almost all AFM images. Most AFM products are supplied with very powerful image display and analysis software. Properly used, the image processing software will typically not introduce artifacts into an image. This section presents some of the common artifacts that can be introduced into AFM images by the image processing software.

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