Atomic Force Microscopy (AFM) methods were used to characterize two samples in two different modes. Contact mode was used to characterize a zinc oxide sample and tapping mode was used to characterize a grating sample. The distance between the grating lines was calculated to be 1.173μm. The two samples characterized in the following report are zinc oxide and a grating sample. In order to examine the surface of the zinc oxide, our lab group used contact mode, a method of operation where the tip is in very close contact to the surface of the sample.
[...] The advantages of AFM over STM are that STM can be applied to both insulators and conductors while STM only applies to conducting materials the instrument voltage and the spacing between the tip and substrate can be controlled separately in the AFM, AFM is more versatile in that three different modes of operation exist and can be complemented to each other in one instrument The advantages of STM over AFM are that in some samples the resolution or STM is better than AFM and can even reach atomic levels, the surface of the sample is not altered in STM, while in AFM the surface can be damaged or even destroyed, 3)while both techniques have good horizontal or lateral resolution, STM has much better vertical resolution than AFM Summary and Conclusion Atomic Force Microscopy (AFM) methods were [...]
[...] The average width of the structures are 1.173 μm, as calculated from the AFM image analysis ( 3.520 x 10-6 1.173 x 10-6 m = 1.173 μm). What is the periodicity of the occurrence of these structures on the surface-- e.g. how many islands per unit area or how many steps per unit length? There are 6 lined structures that occur diagonally in a square region of 5 μm by 5 μm Estimate the random and systematic errors in length measurements (knowing the true distance between lines on the grating sample is 1.1 micron) x 10-6 1.173 x 10-6 m = 1.173 μm The error is ( 1.173 μm- 1.1 μm)/ 1.1 μm x 100%= The calculated distance between the grating has systematic error because the tip cannot fit into the troughs, not allowing the tip to fully scan the entire bottom of the trough. [...]
[...] This sharp tip, which is at the end of a cantilever, has a feedback mechanism that relays the information to a piezo-electric scanner to sustain a constant force over the surface or a constant height. As the instrument scans over the surface, a laser is shined of the cantilever, and a photo-detector can measure the difference in incoming and outgoing light intensities. This is then converted to a voltage, and the software is able to output an AFM image. While this is all going on, a bungee cord suspends the AFM to minimize vibrations, which minimizes any noise from the environment In what mode of operation did you use the AFM instrument--contact, non- contact, or wave mode? [...]
[...] Since the histogram shows the frequency of the heights of the ridges, we are able to see a higher frequency of heights around 160nm. A second peak in the histogram appears to be around 110nm. This can be correlated to the AFM image because the ridges are on average about 160nm in height, they appear as white surfaces on the black and white AFM image. On the other hand, the troughs are 110nm in height, which appear as the darker surfaces on the image. [...]
[...] Once this is accomplished, the experimenter needs to a set an amplitude for the tip by selecting the highest peak on the computer screen. After, it is possible to hit the scan button and allow the AFM to produce an image of the surface In contact and wave mode the tip has to make contact with the surface of the sample, which might alter the sample surface due to the minimal contact. The main difference between the two modes is that the wave mode oscillates the tip back and forth which does not create the constant surface contact with the sample, like the contact mode creates. [...]
APA Style reference
For your bibliographyOnline reading
with our online readerContent validated
by our reading committee
