Highly uniform wafer-scale synthesis of α-MoO3 by plasma enhanced chemical vapor deposition

Molybdenum oxide (MoO3) has gained immense attention because of its high electron mobility, wide band gap, and excellent optical and catalytic properties. However, the synthesis of uniform and large-area MoO3 is challenging. Here, we report the synthesis of wafer-scale alpha-MoO3 by plasma oxidation of Mo deposited on Si/SiO2. Mo was oxidized by O-2 plasma in a plasma enhanced chemical vapor deposition (PECVD) system at 150 degrees C. It was found that the synthesized alpha-MoO3 had a highly uniform crystalline structure. For the as-synthesized alpha-MoO3 sensor, we observed a current change when the relative humidity was increased from 11% to 95%. The sensor was exposed to different humidity levels with fast recovery time of about 8 s. Hence this feasibility study shows that MoO3 synthesized at low temperature can be utilized for gas sensing applications by adopting flexible device technology.