5.2.3 Light Shading

Both 2-D and 3-D images can be viewed with light shading, as illustrated in Figure 5-5. By simulating a light shining on an image, the image looks photorealistic. The position and intensity of the light shining on the AFM image can be changed. Light shading often helps visualize the smallest, high frequency, structure on a surface.

FIGURE 5-5 Light shaded (Left) and color scale (Right) image of carbon nanotubes. The light shaded image typically looks more photo realistic than the color scale image.

5.2.4 Contrast / Brightness

Contrast and brightness functions in an AFM image are the same as used in a video monitor.

5.3 Analysis

AFM images are visual representations of a three dimensional array of numbers, thus it is possible to make quantitative analysis of AFM images. Of course, the quantitative measurements derived from AFM images are only as good as the quality of the measurements. For example, if the images have errors due to poor scanner quality or dull probes, the analysis will reflect these problems.

5.3.1 Line Profile

A line profile is a two dimensional profile, or cross section extracted from an AFM image. The line profile may be taken horizontally, vertically or at an obtuse angle. Line profiles are the most common type of analysis made on AFM images. From a line profile, the distances between two points, as well as angle, may be calculated, (see Figure 5-6).