Investigations On Tungsten Trioxide Thin Films For Electrochromic Devices

Abstract

In this thesis, tungsten trioxide (WO3) thin films are prepared by electron beam deposition technique for developing the electrochromic devices. Electron beam evaporation technique has been revealed to be superior to other techniques for mounting extremely clean and crystalline transition metal oxide thin films for large area device applications. This technique gives control over the deposition rate, film thickness, grain size and purity of the films. newline newlineAmong the troupe of transition metal oxides, WO3 is one among the best n- type semiconductor materials, which exhibits multifunctional properties such as optical modulation, low power consumption, good cyclability, stability and durability. Due to these interesting properties, researchers have impressive enthusiasm to make use of these thin films in electrochromic devices, optical memories, display systems, flat panel displays, variable reflection mirrors, solar cells, gas sensors, humidity and temperature sensors and microelectronic devices. newlineThe deposition constraints such as substrate temperature, nature of substrate, oxygen partial pressure, source to substrate distance, vacuum annealing takes an imperative function in the thin film preparation. Besides that, the optimization of parameters is essential as they are directly related to growth, structure, stoichiometry and phase changes induced in tungsten trioxide. newlineIn the current study, WO3 thin films are primed by electron beam deposition method at various deposition conditions which are shown in the Table - I. WO3 films are coated onto ultrasonically well cleaned Corning 7059 glass and Indium Tin Oxide (ITO) coated glass and Si substrates. The fabricated films have thickness about 200 nm at a deposition rate of 0.2 nm/s approximately measured by quartz crystal thickness monitor, built in the vacuum coating unit. The source to substrate distance is fixed about 14 cm. newline