| Summary: | 碩士 === 東海大學 === 物理學系 === 99 === Hot wire chemical vapor deposition (HW-CVD) is facing three major difficulties in nanorod growth even though it is successfully grown Si nanorods on amorphous substrates. (1) The reproducibility is highly affected by the aging of the hot filament. (2) Material quality of the nanorods grown on amorphous substrates using HW-CVD is always poor with rough surface and voids. (3) In the initial stage of nanorod growth, the nanorods cannot be regularly aligned along the growth direction that is perpendicular to the substrate surface.
To design a new plasma-enhanced chemical vapor deposition (PECVD) system, this study is aimed at producing high quality and vertically aligned Si nanorods on amorphous substrates. We also provide a solution to overcome the major problems for the Si nanorod growth that have been found in HW-CVD. In this work, I have optimized the growth conditions of the Si nanorods on SiO2 substrate using the newly designed home-made PECVD system.
Si nanorods are grown with gold metal catalyst in our newly designed home-made capacitively coupled PECVD system. In this home-made PECVD system, we have designed an extra quartz furnace as a reactor chamber and put it inside the PECVD system. For making parallel plate plasma CVD apparatus, we utilized the shower head as a top electrode, and the heater as a bottom electrode. This parallel plate plasma CVD apparatus is covered inside the quartz furnace in order to realize the unidirectional gas flow within the system. This design offers extra advantages that can be easily modulated and confined the plasma in the quartz furnace. Owing to this design, the ionization rate of the plasma is enhanced where the effectively plasma densities are also increased. Meanwhile, when the plasma is confined within the top- and bottom-electrodes, there is a plasma sheath generated in the edge of the apparatus. Because of the boundary effect, when the electric field induced by the plasma sheath is perpendicular to the top- and bottom-electrodes, this induced electric field is assisted to grow vertically aligned Si nanorods on amorphous SiO2 substrate. This is the most important reason why we are able to grow well-aligned Si nanorods on amorphous SiO2 substrate in our newly designed home-made capacitively coupled PECVD system.
By varying the power of the plasma, working distance, gas flow, and working pressure in our newly designed home-made PECVD system, I have fine-tuned the growth conditions and achieved the high quality and vertically aligned Si nanorods on SiO2 substrates.
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