A room temperature HSGFET ammonia sensor based on iridium oxide thin film

Gas-sensing properties of hybrid suspended gate FET (HSGFET) sensor containing iridium oxide as sensitive layer are reported in this paper. The sensor response to NH3 and H2 was measured. We obtained a non-amplified signal of 70 mV for 50 ppm of ammonia and no signal to hydrogen even for 10,000 ppm. Further, the gas-sensing properties of thin film of iridium oxide has been studied using Kelvin probe (KP) setup. Sensitivity of these films to gases like CO, H2, SO2, Cl2, NO2 under dry and humid conditions were examined by measuring contact potential difference (CPD) resulting from work function change of the film due to exposure to test gases. The results suggest that iridium oxide-based HSGFET is selectively sensitive to ammonia with negligible signal to all other gases. Iridium oxide films of 20 nm thickness used in this study were prepared by dc sputter deposition at 300 °C followed by sintering at 600 °C in oxygen. The films were characterized using Rutherford backscattering spectroscopy (RBS), X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), and atomic force microscopy (AFM) to determine their composition, phase and surface morphology.