Sensors: High Selectivity Gas Sensing by Photostimulation of Semiconducting Metal Oxides

感知越来越多的化学物质的能力对于保护环境、保护工人免受有毒工业化学品的伤害、保护我们的国家免受化学武器的伤害、确保室内空气质量、通过闭环过程控制提高生产率以及改善医疗诊断至关重要。半导体金属氧化物气体传感器(MOGS)虽然对不同的气体种类具有很高的灵敏度，而且结构简单，但选择性相对有限，限制了其更广泛的应用。此外，与聚合物不同，MOGSS需要加热到200℃以上，以确保足够快的动力学，从而增加了复杂性和功率需求。在这个研究项目中，我们探索了一种新的方法来激活MOGSS的灵敏度和调节选择性，通过使用单色光来促进传感器和吸附气体分子之间的电荷转移相互作用，从而消除了对热激发的需要。为此，我们将考察由PLD制备的具有可控取向和微结构的照明n型SrTiO_3薄膜对多种还原和氧化气体的敏感性和选择性。直流和交流阻抗和光电流光谱测量将在一个独特的微探针系统中进行，以实现对传感机制的更好理解。将组装带有集成LED的小阵列MOGS，以展示在室温下以高选择性监测一些气体的能力。将准备类似的设备作为本科生和高中生的实验室实验的基础，以演示与照明下的半导体结相关的原理及其与气体传感的相关性。沿着这些路线的成功将成为固态气体传感器领域的重大突破，并将为选择性检测大量额外的气体创造可能性，提高设备的稳定性和寿命，并有助于更好地从根本上理解气体传感现象。

The ability to sense an ever larger number of chemical species is essential for safeguarding the environment, protecting workers against toxic industrial chemicals, securing our nation against chemical weapons, insuring indoor air quality, improving productivity via closed loop process control and improving medical diagnosis. Semiconducting Metal Oxide Gas Sensors (MOGSs), while exhibiting high sensitivity to different vapor species and simple construction do, however, suffer from relatively limited selectivity inhibiting wider use. Furthermore, unlike polymers, MOGSs require heating to above 200C to insure sufficiently rapid kinetics thereby increasing complexity and power demands. In this research program, we explore a novel approach for activating sensitivity and tuning selectivity of MOGSs by using monochromatic light to promote charge-transfer interactions between the sensor and adsorbed gas molecules thereby eliminating the need for thermal excitation. Towards these ends we will examine the sensitivity and selectivity of illuminated n-type SrTiO3 thin films, prepared by PLD with controlled orientation and microstructure, to a number of reducing and oxidizing gases. DC and AC impedance and photo-current spectroscopy measurements will be performed, in situ, in a unique microprobe system for achieving an improved understanding of the sensing mechanisms. Small arrays of MOGSs with integrated LEDs will be assembled to demonstrate the ability to monitor a number of gases with high selectivity at room temperature. Similar devices will be prepared to serve as the basis of a laboratory experiment for undergraduate and high school students for demonstrating principles relating to semiconductor junctions under illumination, and their relevance to gas sensingSuccess along these lines would serve as a major breakthrough in the field of solid-state gas sensors and would create possibilities for the selective detection of numerous additional gases, improve device stability and lifetime as well as contribute to an improved fundamental understanding of the gas sensing phenomenon.