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

AFM Image Artifacts

All measurement instrumentation used by scientists and engineers for research, development and quality control generates results that may have artifacts. This chapter serves as a guide to identifying common artifacts that occur in AFM images. This guide is organized in sections that are divided by the sources that generate the image artifacts.

There are four primary sources of artifacts in images measured with atomic force microscopes. They are:

Probes
Image Processing

Scanners
Vibrations

6.1 Probe Artifacts

Images measured with an atomic force microscope are always a convolution of the probe geometry and the shape of the features being imaged. If the probe is much smaller than the features of the images being measured, then the probe-generated artifacts will be minimal and the dimensional measurements derived from the images will be accurate.

Avoiding artifacts from probes is achieved by using the optimal probe for the application. For example, if the features that are being imaged have feature sizes of interest in the 100 nanometer range, a probe as large as 10 nanometers in diameter will be adequate for getting good images with no artifacts. In some cases, even if the probe is not as sharp as the object being imaged, it is still possible to get accurate information from the image.

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