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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6.2.6 Scanner Drift
Drift in AFM images can occur because of "creep" in the piezoelectric scanner and because an AFM can be susceptible to external temperature changes. The most common type of drift occurs at the beginning of a scan of a zoomed-in region of an image. This artifact causes the initial part of a scan range to appear distorted. Drift artifacts are most easily observed when imaging test patterns. Drift will cause lines that should appear straight to have curvature.
FIGURE 6-16 After a region of a sample is scanned with the AFM it is common to "zoom" into a small section of the image to get a higher magnification of an image. Scanner drift will cause the image to appear distorted at the beginning of the scan.
FIGURE 6-17 Zoomed image showing a distortion at the beginning of the scan. The scan angle is 45 degrees.
6.2.7 X-Y Angle Measurements
If the motion generated by the X-Y scanner is not orthogonal, then there can be errors in the horizontal measurements in an image. This error, or artifact, can best be seen when imaging a test pattern with squares. The error in orthogonality can be measured by using a straight edge to measure "orthogonal" lines in the images.

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