ULTRASONIC SPRAY DEPOSITION OF METAL OXIDE THIN FILMS

Date

2023-8-22

Author

Tutel, Yusuf

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Thin films have a long history and have been present in various forms throughout human civilization. They play a significant role in shaping the modern technological landscape today. They serve as a crucial foundation for numerous advanced applications across various fields, including optical devices, environmental applications, micro/nanoelectronic devices, and energy storage devices. The key factor in determining the effectiveness of thin films in these applications is their morphology and environmental stability. The ultrasonic spray deposition method is known for its simplicity and cost-effectiveness. It differs from other deposition methods in that it does not require high-quality substrates or chemicals and does not rely on a vacuum environment during processing. It also enables the deposition of homogenous and high-quality thin films over large areas. Transition metal oxides are compounds in which oxygen atoms form bonds with transition metal elements found within the d block of the periodic table. They distinguish themselves from other materials through their valuable properties, including variable oxidation states, high melting/boiling points, catalytic activity, optical properties, and structural diversity. The nanostructured nature of these transition metal oxide thin films offers several advantages such as tailored optical and electronic properties, improved surface area and enhanced energy storage and conversion. In this thesis study, vanadium pentoxide, nickel oxide, and molybdenum trioxide were chosen as functional transition metal oxides because of their exceptional electrochromic and sensing properties, as well as their excellent physical and chemical stability. First, multi-electrochromic properties of vanadium pentoxide thin films deposited via ultrasonic spray deposition method over large areas (15 cm x 15 cm) were investigated. It was proved that ultrasonic spray deposition method is an extremely versatile technique for the reproducible deposition of uniform, high quality, multicolored and nanostructured vanadium pentoxide films over large areas using vanadium salt as a precursor solution. Moreover, the mass-production capability of the ultrasonic spray deposition method was exemplified through the fabrication of nickel oxide thin films. Approximately 300 sensor electrodes were obtained with a single deposition and this functional thin films were used as high performance non-enzymatic glucose and hydrogen peroxide biosensor electrodes. High sensitivity, a low detection limit, and a fast response time were obtained from nanometer-thick cobalt doped NiO film electrodes. To enhance the electrochemical activity of molybdenum trioxide, cobalt-doped molybdenum trioxide thin films, generated using the same deposition method, were employed in the fabrication of electrochromic smart windows and dual-band electrochromic devices. The specific capacitance of the cobalt-doped molybdenum trioxide electrodes showed great cyclic stability with a capacitance retention of 92 % over 5000 cycles. The dual-band electrochromic device demonstrated remarkable cyclic stability, exhibiting a capacitance retention of approximately 99% in a real-life application.

Subject Keywords

Ultrasonic Spray Deposition, Transition Metal Oxides, Thin Films, Electrochromism, Glucose Sensor

URI

https://hdl.handle.net/11511/105333

Collections

Graduate School of Natural and Applied Sciences, Thesis