Preparation Of Ga ₂ 3 Thin Films By Magnetron Sputtering And Its Properties

Transparent conductive oxide thin films (TCOTFs) have attracted intensive investigations due to its wide applications in white light emitting diodes (LEDs), lasers, flat panel displays and thin-film solar cells, etc. To date, the pursuit of higher performance requirements on TCOTFs for deep ultraviolet (DUV) detection and related applications inspiredstuides on TCOTFs with wider band gap, wherein Ga2O3thin films received most attentions.In this thesis, the magnetron sputtering method was adopted for the preparation of β-Ga2O3thin films with/without gold particles. The crystalline phases, microstructure, optical properties, and electric properties of as-prepared thin films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV absorption spectroscopy, fluorescence spectroscopy, and electrical characterizations, respectively. Besides, the effects of growthconditions (e.g., deposition pressure, substrate temperature, deposition atmosphere, heat treatment temperature, etc.) on the structuraland properties of β-Ga2O3thin films were discussed.After systematically investigations, the following main conclusions are attained:(1) The parameters for the growth of β-Ga2O3thin films by magnetron sputtering method were investigated, and their effects on the structuraland optical properties of thin films were discussed. The optimal parameters for its preparation were:using sapphire (α-Al2O3(0001)) as substrate, gas pressure of1Pa, substrate temperature of700℃, operation power of80W. The as-prepared thin films were transparent and smooth, withdense grains on the surface. The light absorption coefficients of the thin films decreased gradually from the wavelength of200nm to260nm, and almost no absorption to the lights with wavelength of>260nm. It illustrates that the as-prepared thin films have good solar-blind UV transmission properties.(2) The β-Ga2O3thin films were annealed at600℃,700℃and800℃, respectively. From the SEM observation, it is found that the annealing process increased the crystallinity of the thin films and the mean grain size. From the UV absorption spectra, the band gap of thin films increased with the increasing annealing temperature. Moreover, fluorescence spectra showed that with excitation wavelength of202nm, the strongest emission peak of thin films was at around467nm, and the emission intensity increased after annealing and reached maximum at600℃.(3) The Au/Ti differential electrodes were connected on the β-Ga2O3thin films, and the electric properties of thin film samples grown at different atmosphere were tested on an electric test platform. When using Ar atmosphere for the growth of thin films, the electric current measured at dark,365nm and254nm were2.4,7.5and76.5μA, respectively. While at O2atmosphere, both the dark current and light current of the thin films were relatively small.(4) The direct sputtering method was adopted for the gold plating on the surface of thin films. The gold particle size can be tuned by controlling the sputtering time. The absorption spectrum measurements suggested that, the gold plated thin films have similar spectra at deep UV range with the thin films without plating, that is, an obvious absorption peak emerged at red light of～550nm. It is believed that it can be ascribed to the surface plasmon polariton (SPP) phenomenon of gold particles. The peak intensity of the red light absorption increased with increasing the plating time of gold on the thin films.The relevant studies reported in this thesis can provide technique basis for the fundamental research in the deep UV detection and related applications. They can also enrich the methods for the preparation of β-Ga2O3thin films and the growth of gold particles on the thin films.