| Summary: | 博士 === 淡江大學 === 物理學系 === 87 === This thesis consisted of three parts, first one was concerning about the x-ray-absorption spectra of a crystalline c-Si-C-N thin film at the C and Si K-edge using the sample drain current mode and at the N K-edge using the fluorescence mode. Second one was x-ray absorption spectra of a series of nano-diamond thin films with grain diameters ranging from 3.5 nm to 5 mm at the C K-edge using the sample drain current mode at room temperature. Latter, we study the x-ray absorption near edge structure (XANES) measurements for a variety of boron-doped and undoped diamond films at the C K-edge using the sample drain current mode.
For the first part, a resonance peak resembling the C 1s core exciton in the chemical-vapor-deposition-diamond/Si was observed. In addition, a broad feature was found in the energy range between ~290 and 305 eV, which can be assigned to the antibonding C 2p-Si 3sp hybridized states and the C 2p-N 2sp hybridized states as well. The fact that the resonance peak is located ~1.5 eV below the C 1s ionization energy suggests that the tightly bond Frenkel-type exciton model can appropriately describe the core exciton of carbon atoms in c-SiC-N. Closely examining the N K-edge near edge absorption spectra of c-Si-C-N and a-Si3N4 indicated that nitrogen atoms generally have a similar local environment in these two materials. Moreover, results obtained from Si K-edge absorption spectra of c-Si-C-N demonstrate a proportional combination of local Si-N and Si-C bonds associated with the local tetrahedral C-Si-N3 arrangement as well as the long-range ordered atomic structure around Si atoms. Theoretical calculations using the first-principles pseudofunction method are presented and compared with experimental data.
For the second part, the resonance peaks resembling the C 1s core exciton in the diamond nanocrystals also was observed. The exciton state and conduction band edge was found to shift to higher energies with the decrease of the grain size indicative of the presence of the quantum confinement effect.
Finally, for x-ray-absorption studies of boron-doped diamond films, the C K-edge XANES spectra of B-doped diamonds resemble that of the undoped diamond regardless of the B concentration, which suggest that the overall bonding configuration of the C atom is unaltered. B-impurities are found to enhance both the sp2- and sp2-bonds derived resonance features in the XANES spectra.
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