Room temperature hydrogen gas sensitivity of nanocrystalline pure tin oxide.

Nanocrystalline (6-8 nm) tin oxide (SnO2) thin film (100-150 nm) sensor is synthesized via sol-gel dip-coating process. The thin film is characterized using focused ion-beam microscopy (FIB) and high-resolution transmission electron microscopy (HRTEM) techniques to determine the film thickness and the nanocrystallite size. The utilization of nanocrystalline pure-SnO2 thin film to sense a typical reducing gas such as hydrogen, at room temperature, is demonstrated in this investigation. The grain growth behavior of nanocrystalline pure-SnO2 is analyzed, which shows very low activation energy (9 kJ/mol) for the grain growth within the nanocrystallite size range of 3-20 nm. This low activation energy value is correlated, via excess oxygen-ion vacancy concentration, with the room temperature hydrogen gas sensitivity of the nanocrystalline pure-SnO2 thin film sensor.