FIGURE 5-8 Three methods for measuring a step height:

1. Histogram Analysis
2. Single point at the top and bottom of a profile
3. A line fi t to the top and bottom of the profile.

5.3.4 Particle Analysis

An AFM is capable of measuring nanoparticle images, making analysis of the nanoparticles possible. After an image of nanoparticles is properly leveled, it is possible to identify the particles in the image and then analyze the nanoparticles.

Nanoparticle Recognition

Auto-Detect: This method has a software algorithm that searches for height transitions associated with particles in the AFM image. This technique is ideal if the nanoparticles in the AFM image are well defined. It is advantageous because it requires little or no expertise from the operator.

Threshold Method: In the threshold method, the particles are identified in an image by settings established by the person making the analysis. A "threshold" in the image is selected so that the nanoparticles are above the threshold. A color scale is used in the image to visually facilitate setting the threshold (see Figure 5-9).