Surface and Optical Properties of Silicon-based Materials
Date Issued
2007
Date
2007
Author(s)
Cheng, Li-Chi
DOI
en-US
Abstract
Because of great motivation to develop the light amplifiers and emitters from Si or Si-based materials, we have promoted two different kinds of light-emitting mechanisms to achieve the goal.
One of them is to implant terbium ion into silicon oxides thin film which is grown on Si(111) substrates. Trivalent terbium (the preferred bonding state) has an incomplete 4f electronic shell (54[Xe]4f95d06s2) that is shielded from the outer world by inner 5s and 5p shells. As a result, the intra-4f transitions can be achieved from terbium doped materials. The structure of samples are studied by X-ray diffraction (XRD), and then show that the lattice planes of SiO2(211) and SiO2(301) disappeared if the plasma treated processes are added. The disappearance of SiO2(211) and SiO2(301) would not influence the results of photoluminescence (PL). In contrast, the PL intensity decreases since Tb2O3(600) disappears after annealing. The results of Fourier transform infrared (FT-IR) spectroscopy reveal that there are obvious dropping peaks at 1090 cm-1 which denote the asymmetric stretching vibration mode of Si-O bonding. The vibrational direction of Si-O bonding is parallel to the Si-Si bonding. The results of FT-IR and Raman spectroscopy lead us to the conclusion that the films are rich in Si-O-Si bonds and have an orderly silica network. Consequently, they are in good chemical stability. The result of X-ray photoelectron spectroscopy (XPS) exhibits the excess oxidation at the surface for the samples annealed in the furnace. The surface excess oxygen atoms come from the dangling Si-O- bonding which are damaged in the place under the surface, and incline to assembling towards the surface. The oxygen vacancies also play a role of radiative recombination center which enhance the recombination rate between electrons and holes. On the other hand, the phenomenon of “cross-relaxation” (between 5D3-5D4 and 7F0-7F6) arises since high Tb concentrations. It causes the increase of green lines at the expense of blue lines.
Another is chemical vapor deposition (CVD)-grown 3C-SiC on Si(100) substrates. The results of Raman spectroscopy indicate that the intensity from 3C-SiC LO phonon increases gradually compared with that from Si substrates with the thickness of 3C-SiC increasing. Besides, it can be seen that forbidden TO modes decrease in intensity with respect to the allowed LO modes with increasing growth times. The XPS results showed that the surfaces of the samples consist of Si oxides and unreacted CH (2nm), in addition to the stoichiometric SiC compound. The elemental Si which is attributed to unreacted Si atoms is absent in this work. The CH species on the surface of the 3C-SiC films are a result of unreacted SiH4 and C3H8 or their reaction intermediates.
Subjects
氧化矽
碳化矽
光致螢光光譜
傅氏光譜
拉曼光譜
silicon oxides
silicon carbides
photoluminescence
Fourier transform infrared spectroscopy
Raman spectroscopy
Type
thesis
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