ITO nanowires for gas-sensor applications

In this work we have realized ITO nanowires with typical dimensions of 700 nm width and 200 μm length. They were fabricated by using a novel approach of laser writing in a sputtered indium tin oxide (ITO) film by using a high-repetition rate near-infrared Ti:sapphire laser system based on a 85 MHz, sub-10 fs resonator. These nanowires were characterized electrically and tested as resistive gas sensors with self-heating capability. For this purpose they were exposed to NO₂ concentrations in the ppm range within synthetic air, showing a clear increase of resistance. At ambient temperature the sensor exhibits an integrating behavior with relatively long relaxation times. It was shown that the relaxation times can be shortened by exploiting the self-heating capability of this sensor. The self heating effect was studied by FEM simulations.