Introduction to Atomic Force Microscopy:Theory,practice,applications

AFM University Introduction to Atomic Force Microscopy by Paul West

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

Chapter 6

FIGURE 6-13 A: An 85 × 85 micron image of a flat piece of silicon. The bow introduced into the image is seen at the edges. B: A line profile across this image shows the magnitude of the bow.

6.2.5 Z Edge Overshoot

Hysteresis in the piezoelectric ceramic that moves the cantilever in the perpendicular motion to the surface can cause edge overshoot. This problem is most often observed when imaging micro-fabricated structures such as patterned Si wafers or compact discs. The effect can cause the images to be visually better because the edges appear sharper. However, a line profile of the structure shows errors.

FIGURE 6-14
A: The probe is scanned from left to right across a feature on a surface. B: Overshoot may be observed in the line profile at the leading and trailing edge of the structure.

FIGURE 6-15A: The AFM image of a test pattern appears to have no artifacts. B: However, a line profile of the test pattern shows overshoot at the top of each of the lines.

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