MTL Annual Research Report 2011

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.