| Silicon has become the most important semiconductor material in the electronics industry for its excellent performance and mature technology, and is widely used in various fields. Devices based on Silicon improve people’s lives. The observation of visible photoluminescence in porous silicon has stimulated researcher to explore effective silicon-based light-emitting materials. As a great potential for development in electronic and optoelectronic devices, the silicon nitride showed excellent chemical stability, thermal stability, thermal shock resistance, electrical insulation and quality rigid. In addition, the silicon nitride have a wide range of applications in surface passivation and anti-reflection materials of solar cells.Silicon nitride has a potential and wide range application due to its excellent characteristics. Up to now, quite a few researchers have devoted efforts to investigate it. Most of the research results have been concerned on the fabrication of SiNx films and their optical properties. At present, the physical properties and mechanisms of SiNx still need further exploring. This thesis includes two parts of work as following:1. Photoluminescent properties of SiNx films with different N content annealed at high temperature were investigated. First, we deposited SiNx films with different nitrogen flow ratio by using ultrahigh vacuum multifunctional magnetron sputtering system, under conditions of high purity silicon as the target, and high-purity nitrogen and argon for the reactive sputtering gas. A SO2buffer layer has been grown on Si (100) substrates prior to deposit SiNx. In order to improve their optical properties, annealing is undertaken in N2ambient800°C for20min by tube type annealing furnace. Photoluminescence spectroscopy (PL), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) are employed to characterize the nature of SiNx films. It is found that the PL from SiNx films can be attributed to photo-generated excitons in the silicon-rich SiNx, which further move into the Si oxide to emit light. The particles size is found to be smallest in SiNx film in the case of N=3.2, in which the strongest PL is observed. This means that the quantum size effects contribute to the enhanced PL. The composition and structure indicated that the strong PL is related to the content of the Si-N and Si-O bonds. The moderate nitridation and oxidation can effectively enhance the photoluminscence of SiNx film.2. By means of the K-P model, we have established the Si/SiNx superlattices band model, and calculated its band structure. In combination with the experimental results, we discussed the relationship between the layers of film thickness, effective mass and the energy band structure. The results show that thin film bandgap tends to decrease along with the appropriate increased as the sublayer is thickened. In Si/SiNx superlattice system, photoluminescence can be controlled by changing the sublayer thickness. Our results prove that the K-P model applied to the Si/SiN superlattice structure is effective. |
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