Chapter_3_ - CHAPTER 3 Measuring AFM Images Learning to...

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CHAPTER 3 Measuring AFM Images 61 Learning to operate an AFM well enough to get an image usually takes a few hours of instruction and practice. It takes 5 to 10 minutes to measure an image if the sample is properly prepared. However, if it is an unknown sample that has never been scanned with an AFM before, it can take substantially more time to acquire meaningful images. Te following sections discuss the steps required for measuring an AFM image, illustrated in Figure 3-1. FIGURE 3-1 Sequential steps required for measuring an AFM image. Probe Approach – 3.3 Align Laser – 3.2 Replace Probe (optional) Place Sample in Stage Prepare Sample – 3.1 Tip Retract Zoom on Feature – 3.5 Scan Sample – 3.5 Optimize Feedback – 3.4
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Chapter 3 • Measuring AFM Images 62 Tis chapter assumes that contact mode is being used for scanning. If a vibrating mode is being used, Section 3.2 will change to include measuring the resonant curve of the cantilever. 3.1 Sample Preparation Sample preparation for an AFM is reasonably simple. Tere are a few basic rules that must be followed to adequately prepare a sample for AFM scanning. Te rules are: a) Sample must be adhered to the surface: If the sample has material adhered to the surface, the material must be rigidly mounted to the surface. If the material is not rigidly adhered two problems can occur. First, the probe can push the material to the edge of the scan range. When this occurs, the image appears as though there is nothing on the surface and only the substrate is observed. Second, the probe can pick up material from the surface because the material has a greater affinity for the probe than the surface. In this case the images often have streaks in them. Te streaks are created by material moving on and o± the probe, i.e. the probe geometry is changed by the material from the surface. b) Sample must be clean: AFM imaging requires that the probe move directly across the sample’s surface topography. If the surface is dirty with a thick contamination layer, the probe needs to penetrate through the contamination layer to reach the surface. Te contamination layer then causes severe distortion in the image (see Section 6.5.1).
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This note was uploaded on 04/09/2009 for the course MSE 111 taught by Professor Giannelis during the Fall '07 term at Cornell.

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Chapter_3_ - CHAPTER 3 Measuring AFM Images Learning to...

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