Oxygen Partial Pressure Effect on Nano-Structure and NO Gas Detection Sensitivity of Sputtered MoO3 Thin Films

This paper explains the influence of oxygen partial pressure on crystallographic structure, surface morphology and sensing properties of sputtered MoO3 thin films. The MoO3 thin films were deposited by DC reactive magnetron sputtering technique on glass substrate at different oxygen partial pressures in the range of 5×10-5-4×10-4 mbar. X-ray diffraction (XRD) results showed that all prepared films were polycrystalline of α-MoO3 stable orthorhombic phase. Atomic force microscopy (AFM) images depicted a needle-like structure for deposited film at lowest oxygen partial pressure (5×10-5 mbar) and a granular structure for formed samples at higher oxygen partial pressures (1×10-4 and 2×10-4 mbar). These results also showed that increasing of oxygen partial pressure up to 2×10-4 mbar caused increasing of grains size and surface roughness, while an increase in oxygen partial pressure to the highest pressure (4×10-4 mbar) had an inverse effect. The electrical response of samples was measured in vacuum and NO environments in the temperature range of 150-350 K. This study showed that the NO gas detection sensitivity of MoO3 thin films improved with increasing of oxygen partial pressure up to 2×10-4 mbar, and then decreased.