Fundamental Investigation of Pulsed Laser Irradiation on Metal Oxide Gas Sensor Performance

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Metal oxide semiconductor films have found extensive applications in gas sensors in the last few decades. However, rapidly growing need for comprehensive monitoring of the environmental impact of industrial emissions demands detection, at the few parts per million levels, of pollutant or industrial gases. This significant challenge has to be met by synthesis of new sensor materials.The objective of this research project is to investigate the fundamental phenomena of laser irradiation on metal oxide-based thin films relevant to gas sensor performance by employing experimental as well as computational approaches. The investigation will be conducted using tungsten trioxide (WO3) and tin oxide (SnO2) as the model materials. The carrier mobility and conductivity of sensor films will be measured as functions of the power level, the number of pulses of the laser and selective doping. The surface and microstructure will be examined to understand the effect of laser irradiation on these films. After optimizing for laser power, number of pulses and film growth parameters micro gas sensors will be fabricated. A coordinated experimental and computational study for the heat transfer mechanism from the laser to the film and its effect on microstructure and hence on electronic properties relevant to sensor performance will be undertaken. The proposed research is expected to provide greater fundamental understanding of the phenomena associated with the interaction of pulsed lasers and metal oxide sensor film. It is envisioned that the proposed method will create faster and more sensitive gas sensors because the carrier mobility and active surface area of sensor film are increased by laser irradiation. The research may also result in a better sensor response at lower temperatures. This processing technique is transferable to a manufacturing process of an industrial scale. A synergistic theoretical and computational investigation of the laser induced heating and crystallization of the metal oxide film will be carried out. This joint endeavor will speed the optimization of process parameters. This proposed research advances a novel method to significantly enhance the performance of metal oxide-based gas sensors. Scientifically, it will lead to insights into the underlying mechanism of interaction of laser beams and metal oxides. Educationally it will involve regional high school students in leading edge research, and educate and inspire them and pique their interest to pursue careers in science and engineering. Expansion of opportunities for undergraduate research experience and under-represented students will be emphasized.