| Summary: | 碩士 === 逢甲大學 === 機械工程學所 === 97 === In this thesis, single crystal silicon micro-cantilever beam is fabricated by MEMS techniques on a 4 inch wafer. Three kinds of surface treatments were conducted on the beam including coating nickel by sputtering, annealing and CVD for growth of carbon nanotubes. With Si beams, there are four kinds of specimens. For bending test, a MTS micro-force testing machine with a probe is adopted. Besides, tested specimens is analyzed by Raman spectral analysis, SEM observation and EDX composition analysis.
Under bending test, properties of four kinds of beams are as follows: single crystal silicon has average strength of 920 MPa, failure strain of 7.93×10-2; Si coated with nickel has the highest strength among the four of 2.3 GPa, and the failure strain of 1.77×10-2; Si annealing in 700℃and 800℃ have following properties respectively: average strength 780 and 670 MPa, failure strain 1.54×10-2 and 1.30×10-2; Si coated carbon nanotubes has following properties: strength between 0.8 and 1.3 GPa, failure strain between 1.08×10-2 and 9.29×10-2. Comparing nanotube processes on Si, the stress-strain curves show that they are still brittle materials. The average strength is higher with the increase of the catalyst coating thickness, temperature and flow, but data of failure strain is unstable. The average strength and failure strain of the beams with scratches on surface are lower than those without scratches. Regarding reactant gases, the average strength and failure strain of coated beams by using methane are better than those by using acetylene.
In Raman spectral analysis for specimens with the nanotube processes, they are identical in the D-band and G-band spectrum. The peak of D-band is at 1336 cm-1, and G-band is nearby 1554 cm-1. It shows that the crystalline structures are similar even by different reactants. In observing picture of SEM of CVD specimens, the EDX composition analysis confirms that the coating is carbon. Observation of the coating on the surface shows that it may contain carbon films, carbon pellet and carbon nanotubes based on different processes. The bending fracture plane of cantilever beam occurs along the lattice plane (111) and the plane is approximately smooth. However, there are some variations due to distinct surface treatment and various degrees of carbonization.
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