| Summary: | 碩士 === 國立臺灣科技大學 === 機械工程系 === 92 === This article constructs a simulated measurement model of constant force mode in AFM contact mode, so as to simulate and analyze the outline scanning measurement of AFM. The simulation method is to calculate the force of the sample atoms towards the tip atoms of the probe by means of Morse potential calculation when the probe tip passes through the surface of the sample. From calculation, the equivalent force of the probe''s cantilever can be acquired. Through the development of this research and the induced rotation equation of probe''s cantilever, the rotation can be calculated. When the rotation reaches fixed rotation on the measurement point, the scanned height of this model can be acquired, and the scanned outline curve of the model can be simulated by scanning under an order sequence.
Based on this measurement model, the result of edge effect error in times of AFM measurement can be simulated and analyzed. Next, the ideal features of nano-scale standard sample can be simulated, and the result is being compared with the result of edge effect error of the practical AFM measurement, so as to confirm that the measurement model simulated by this study is reasonable. At the same time, with the application of the concept of sensitively analysis, AFM simulative and measurement experiment is underwent with the ideal nano-scale standard sample towards the round angle of probe tip of different probes, and the effect of the round angle of probe tip towards the edge effect during the measurement is also investigated.
Result shows that the scanned outline of simulation is mainly affected by the geometrical outline of the simulated probe. Besides, apart from the geometrical shape of the simulated probe, the main reason why error occurred between the simulated and practical scanned ladder outline is the scanned speed during the practical experiment, which can also induce errors. Finally, if the errors are taken into further analysis, it is found that all the errors are relatively trivial, proofing that the model established herein is both reasonable and accurate.
In the aspect of ladder outline in atomic-scale, it is found that the irregular rising and falling shape of the curve of the force is created by the phenomenon of discontinuity of the atoms. Also, the scanned ladder outline having smaller the round angle of tip is closer to the practical cross-section outline, which can thereby come up with a more practical ladder outline curve. As to the aspect of surface outline of the atomic scale, it is found that within the simulative range of this study, the best condition of eliminating the effect of single atom towards the AFM scanned outline curve is when the radius of round angle is larger than 12nm.
The result of this study helps to understand the measurement behavior of the AFM under nano-scale, contributing to an establishment of a new direction of nano-scale measurement.
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