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Figure 1: SEM, TEM, HR-TEM and SAED images of microsphere template InGaZnO3, illustrating a short range order of the spheres and amorphous phase of the sensor film.
Gas sensors are essential in the monitoring, control, and reduction of harmful emissions in the environment [1] . Conductometric gas sensors based on semiconducting metal oxides are advantageous in many applications due to high sensitivity, manufacturability, and small size. However, there are a number of drawbacks, including difficulty in control over the semiconductor/substrate interface, high power consumption, and reduced selectivity at high temperatures (300-400˚C) required for operation [2] [3] . To address these challenges, chemical sensors comprising a wide array of material composition and morphology have been fabricated and investigated via high-throughput combinatorial test procedures. A microsphere templating technique is employed in all device structures; it reduces the area of contact with underlying substrate and enhances interaction with the surrounding gases [4] . Sensor performance has been characterized and optimized through controlled variation in the volume fraction of Pt nanoparticles that are co-deposited on the surface of SnO2 and ZnO thin films. In addition, novel sensors based on amorphous InGaZnO4 have been investigated under a wide range of operating conditions and show promise for heightened sensitivity at reduced operating temperatures. With a combination of rapid testing procedures and physical models of chemical and electronic processes involved in gas sensing, further advancements are anticipated in device sensitivity, selectivity, and response time.
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