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

近几十年来，金属氧化物半导体薄膜在气体传感器中得到了广泛的应用。但是，对工业排放的环境影响进行全面监测的需求迅速增长，要求以百万分之几的水平检测污染物或工业气体。这一重大挑战必须通过合成新的传感器材料来解决。本研究项目的目的是通过实验和计算方法研究激光照射金属氧化物基薄膜与气体传感器性能相关的基本现象。以三氧化钨（WO3）和氧化锡（SnO2）为模型材料进行研究。传感器薄膜的载流子迁移率和电导率将作为功率水平、激光脉冲数和选择性掺杂的函数来测量。为了了解激光辐照对薄膜的影响，我们将对薄膜的表面和微观结构进行研究。通过对激光功率、脉冲数和薄膜生长参数的优化，制备出微气体传感器。将对从激光到薄膜的传热机制及其对微观结构的影响进行协调的实验和计算研究，从而对与传感器性能相关的电子特性进行研究。所提出的研究有望对脉冲激光与金属氧化物传感器膜相互作用的现象提供更基本的理解。由于激光照射增加了传感器膜的载流子迁移率和有效表面积，因此设想所提出的方法将产生更快和更灵敏的气体传感器。该研究还可能导致在较低温度下更好的传感器响应。这种加工技术可转移到工业规模的制造过程中。本文将对激光诱导金属氧化膜的加热和结晶进行理论和计算的协同研究。这种共同努力将加快工艺参数的优化。本研究提出了一种显著提高金属氧化物基气体传感器性能的新方法。从科学上讲，它将导致深入了解激光束和金属氧化物相互作用的潜在机制。在教育方面，它将让地区高中生参与前沿研究，教育和激励他们，激发他们从事科学和工程职业的兴趣。将强调扩大本科生研究经验和代表性不足的学生的机会。

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.