Preparation and post-annealing effects on the optical properties of indium tin oxide thin films
Abstract of thesis entitled
PREPARATION AND POST-ANNEALING EFFECTS ON THE OPTICAL PROPERTIES OF INDIUM TIN OXIDE THIN FILMS
WANG Rong Xin
for the degree of Doctor of Philosophy
at The University of Hong Kong
in April 2005
Many opto-electronic devices, such as III-V compound devices, liquid crystal displays, solar cells, organic and inorganic light emitting devices, and ultraviolet photodetectors, demand transparent electrode materials simultaneously having high electrical conductance. To meet the requirements for particular applications, a great deal of basic research and studies have been carried out on the electrical and optical properties of these materials. As a most promising candidate for such materials, indium tin oxide (ITO) has attracted interest in recent years. Furthermore, ITO has many unique properties such as excellent adhesion on the substrate, thermal stability and ease of patterning. The deposition of high-quality ITO thin films is a key step for successful application of ITO thin films as transparent electrode materials. To obtain optimal electrical and optical properties of ITO films, the growth parameters and conditions must be determined. Moreover, the optical and electrical properties of ITO contact layers, which can either be on the top side or the bottom side of a device, are influenced by various post-deposition
treatments. For the present work, ITO thin films were deposited on glass and quartz substrates using e-beam evaporation with different deposition rates.
The influence of substrate material, deposition rate, deposition gas environment and post-deposition annealing on the optical properties of the films was investigated in detail. Atomic force microscopy, X-ray diffraction and X-ray photoemission spectroscopy was employed to obtain information on the chemical state and crystallization of the films. Analysis of these data suggests that the substrate material, deposition rate, deposition gas environment and post-deposition annealing conditions strongly affect the chemical composition and the microstructure of the ITO films and these in turn influence the optical properties of the film. Oxygen incorporation transfers the In2O3-x phase to the In2O3 phase and removes metallic In to form both indium oxide phases. Both of these reactions are beneficial for the optical transmittance of ITO thin films. Moreover, it was found that the incorporation and decomposition reactions of oxygen can be controlled so as to change the optical properties of the ITO thin films reversibly.
School:The University of Hong Kong
School Location:China - Hong Kong SAR
Source Type:Master's Thesis
Keywords:thin films optical properties indium compounds annealing of metals
Date of Publication:01/01/2005