Chapter 6
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6.3.5 Image Looks Too Good |
If an AFM image looks too good to be true it probably is. All measurement techniques have some noise associated with them. Because AFM data is completely electronic, it is possible to take an image and alter it with image enhancement techniques to create a beautiful picture that does not represent the structure of the surface. |
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FIGURE 6-24 This 850 × 850 nm image of a nanotube had substantial noise when originally measured. Filtering added the "nodules" to the image making it seem like a much higher resolution image. |
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6.4 Vibrations |
Environmental vibrations in the room where the AFM is located can cause the probe in the microscope to vibrate and make artifacts in an image. Typically, the artifacts appear as oscillations in the image. Both acoustic and floor vibrations can excite vibrational modes in an AFM and cause artifacts. |
6.4.1 Floor Vibrations |
Often, the floor in a building can vibrate up and down several microns at
frequencies below 5 Hz. The floor vibrations, if not properly filtered, can cause periodic structure in an image. This type of artifact is most often noticed when imaging very flat samples. Sometimes the vibrations can be started by an external event such as an elevator in motion, a train going by, or even people walking in a hallway. |
6.4.2 Acoustic Vibrations |
Sound waves can cause artifacts in AFM images. The source of the sound
can be from an airplane going over a building or from the tones in a person's voice. Below is an image that shows the noise derived from a person talking in the same room as the microscope. |
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