| Summary: | 碩士 === 國立成功大學 === 材料科學及工程學系碩博士班 === 96 === Hydrogenated Amorphous Carbon (a-C:H) films was deposited on the silicon substrate by unbalanced magnetron sputtering with the addition of methane (CH4) or acetylene (C2H2) and the variation of flowing rates from 2 to 10 sccm into argon plasma. The flowing rate of argon was constant at 25 sccm and the deposition time was fixed at 120 min. Optical Emission Spectrometer (OES) was employed in analyzing the excited species in methane or acetylene/argon plasma through a view port of the processing chamber. The quality of a-C:H films, including their chemical structure, nano-hardness, friction coefficient, and surface resistance, was examined. From OES spectra, the emission intensity of atomic hydrogen Hα and Hβ for methane/argon plasma was found higher than that for acetylene/argon plasma. In addition, by increasing the flowing rate of methane or acetylene, the intensity of Hα, Hβ, CH*, C2* significantly changed. The excitation of Hα and Hβ were relatively simple, in comparison with that of CH* and C2*. It is assumed that CH4 and C2H2 were firstly ionized into CH3 and C2H, respectively. From Raman and FTIR spectra, as increased the flowing rate of methane or acetylene, sp3 CH3 and sp3 CH2 structure increased on surface that caused sp3/sp2 ratio of a-C:H films increased; in addition, sp2 structure transformed from aromatic rings into olefinic chains. Owing to the varied lengths of pathway to ionize the hydrocarbon species, methane was more affected than acetylene by the formation of sp3 C-H on the a-C:H surface. Hydrogen in a-C:H films blocked carbon atoms to form the sp3 C-C (cross-linking) and formed sp3 C-H instead which caused nano-hardness of a-C:H films decreased with the increased flowing rate of methane or acetylene. Nano-hardness of a-C:H films decreased to 2.75 GPa and 5.86 GPa at the flowing rate 10 sccm of methane and acetylene. Due to sp3 C-H increased and sp2 structure transformed, the resistance of a-C:H films increased with the flowing rate of methane or acetylene. From the observations of the excited gaseous species and the quality of a-C:H films, the mechanical properties of a-C:H films were most probably affected by the formation of sp3 C-H structure, which was closely associated with the efficiency of ionization from methane/argon or acetylene/argon plasma.
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