Preparation And Optical Properties Of Si And Si/ZnO Nanowire Arrays

Silicon is a wonderful material for modern electronic devices. As a fundamental material used in micro-electronics, it speeds up the development of information technology. The continuously shrinking size of silicon devices has raised interest in the properties of silicon at the nanoscale, especially one-dimensional structures such as nanowires. Silicon nanowires are under active investigation because of their unique electrical, optical properties and good compatible properties with integrated circuits. Besides, the discovery of the photoluminescence (PL) properties of porous silicon also intrigues numerous studies to understand the origin of PL, and a vast variety of applications emerged.In this thesis, we prepared wafer-scale silicon nanowire arrays with low costs; investigated the luminescence mechanism of porous silicon nanowire arrays; and obtained the enhancement luminescence of porous silicon nanowire arrays by coupling with localized surface plasmons. In addition, ZnO nanorod arrays and nanowires were grown by hydrothermal and vapor phase deposition methods, respectively. Si/ZnO core-shell nanowire array were prepared by combination of metal-assisted chemical etching and MOCVD. The main results are as follow:1. Silicon nanowire arrays were synthesized by metal-assisted chemical etching. The reaction parameters were optimized by controlling the reaction substrate, solution concentration and reaction time. We also obtained the porous silicon nanowire arrays by changing the reaction condition.2. TEM, SEM and PL characterization techniques are employed to investigate the origin and the luminescence mechanism. We proposed a schematic model to explain the luminescence mechanism.3. Au nanoparticles were synthesized by reducing sodium citrate. The luminescence intensity of nanowire arrays was enhanced ten times coupling with localized surface plasmons of Au.4. ZnO nanorod arrays and nanowires were grown by hydrothermal and vapor phase deposition methods, respectively. At low temperature, the photoluminescence (PL) spectra of both samples are dominated by a broad peak around 3.34 eV. Combined with excitation density-dependent PL spectra and surface passivation process, it is indicated that the 3.34 eV emission could be attributed to free electron-to neutral acceptor transitions. In addition, Si/ZnO core-shell nanowire array were prepared by combination of metal-assisted chemical etching and MOCVD methods.