Wideband Gap Semiconductor Nanostructures Preparation And Optical Properties Of The Optical Microcavity Research

Self-assembled semiconductor nanostructure microcavities are attracting tremendous attention for their potential in precise control of the light-matter interaction. In these microcavities, the nanostructures themselves function as both the gain medium and the optical resonators, showing unique optical properties. So far, limited types of nanostructure microcavities such as one dimensional ZnO or GaN nanobelt/nanowire Fabry-Perot (FP) microcavities, and ZnO nanowire with hexagonal cross section whispering gallery (WG) microcavities are developed. In this thesis, we report our studies on the fabrication and optical properties of novel ZnO and In2O3 microcavities with different morphologies. The samples were fabricated by using simply chemical or physical vapor deposition method. For the optical properties, we investigated the photoluminescence (PL) of the microcavities by using microphotoluminescence spectroscopy. The detailed results are summarized as follows:In the first part of our work, we study the fabrication and optical properties of ZnO microtube and In2O3 microrod WG microcavities. The work includes:(1) single-crystalline ZnO microtubes with hexagonal cross section were fabricated through a simple oxidation-sublimation process. These microtubes were used as optical cavities for the first time. WG modes, FP modes and wave-guided modes with different polarization were directly observed in the visible spectral range at room temperature. The tube cavity diameter and wall thickness dependence of resonator properties were studied. In addition, UV lasing from the ZnO microtube WG microcavities was observed. (2) We report on the use of In2O3 nanowires with hexagonal cross section as optical WG resonators. The single-crystal In2O3 nanowires were fabricated by an in situ thermal oxidation method. WG modes in the visible spectral range were observed at room temperature. The experimental results were explained with a plane wave interference model and fitted well with Cauchy dispersion formula for refractive indices.In the second part of our work, we study the fabrication and optical properties of ZnO multilayer hexagonal microplate and In2O3 polyhedron FP microcavities. The details are as follows:(1) we present single crystalline ZnO multilayer hexagonal microplates prepared via a facile carbothermal reduction approach. FP modes were observed at room temperature from the microcavity. The lasing behaviors were investigated in details at low temperature. (2) We fabricated the In2O3 polyhedrons with high crystal quality, small perfect facets, and different morphologies by using a conventional chemical vapor deposition method. FP modes were observed at room temperature. The observed FP resonant energies are in perfect agreement with full-wave numerical simulations, and can be fitted with a plane wave interference model.In the third part of our work, nearly perfect In2O3 octahedra were fabricated by using a simple combustion method. A bow-tielike ray model is proposed. Bow-tielike modes in the visible spectral range were observed at room temperature. The resonator properties in relation to the cavity diameter were studied. The experimental observations are described and fitted well with the plane wave interference model and Cauchy dispersion formula for refractive indices.