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The Research of Low-carbon Hygrogenate Amorphous Silicon Carbide

Author: GanWuLin
Tutor: LuoYiLin
School: Shantou University
Course: Materials Physics and Chemistry
Keywords: low-carbon hydrogenate amorphous silicon carbide infrared structure optical band-gap photoluminescence surface topography
CLC: TB34
Type: Master's thesis
Year: 2011
Downloads: 64
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Abstract


Traditional energy will face oil consumed and environmental pollution problems, all countries in the world in efforts to develop new energy, including solar is a mine of clean energy, so widely attention. Hydrogenated amorphous silicon carbide (a -SiC: H) because of its bandgap wider and bandgap adjustable and become a kind of ideal window materials. On the other hand, hydrogenated amorphous silicon carbide is a kind of ideal short-wave luminescence materials, people for the light to shine effect research has maintained a keen interest.In order to further understand hydrogenated amorphous silicon carbide structure and optical properties, we adopt plasma enhanced chemical vapor deposition technology (PECVD), changing sedimentary parameters carbon source flow ratio R, deposition temperature T and hydrogen dilution ratio R conditions of the low hydrocarbon preparation of amorphous silicon carbide (a - SiC: H) films. Therefore, we mainly do the following several aspects of the research work:1. After the IR analysis, we found that when R is lesser than 7/15, the main structure of films is amorphous silicon, but there are still amorphous silicon carbide in amorphous silicon matrix. On the other side, when R is larger than 7/15, the main structure of films is began transform to amorphous silicon carbide. We also discussed the variation of deposit velocity with different carbon source gas flow ratio R. When R is lesser than 7/15, the deposit velocity is dramatically decreased with the increasing R, however, when R is larger than 7/15, the deposit velocity still decreased with increasing R, but the variation become much more slowly.2. By use of visible light absorption analysis, We concluded that when R is lesser than 7/15, the band-gap of films are consisted with the value of amorphous silicon about 1.7～1.8eV. While, the band-gap of films are approximate 2.2～2.36eV,this is biger than amorphous silicon. That is say we have proofed the conclusion that the films’structure transform from amorphous silicon to amorphous silicon carbide when R equate 7/15 we derived by IR analysis. At the same time, we discussed the variation of deposit velocity with changing hydrogen dilution r. Increasing the hydrogen dilution r, the band-gap of films will increase. This is because of increasing hydrogen can enhance the adjustment of the films’microstructures by etching week bonds, passivating and terminating dangling bonds.3. As for the photoluminescence of films, we found that when R is very small (less than 1), there is almost no apparently PL peaks. But when R becomes 1, there is a peak at 505nm, we think this is origin from the located band tail state’s defect. On the other hand, when we increase the hydrogen dilution r, the photoluminescence of films are dramatically enhanced, and the PL peak is overlay by two peaks located at 442 and 485, respectively. They are origin from sp2 carbon clusters and oxygen defect states, respectively. It indicates that high hydrogen dilution is better for films’photoluminescence.4. When we analyze the surface topography, the roughness of film increased by increasing carbon source gas flow R, and films began growth grains in amorphous matrix. While, increase the hydrogen dilution r, films become more uniform and densify, the roughness decreased. This indicates that high hydrogen dilution can improve film’s surface topography.

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