Single-step growth of MoO3 nanorods via magnetron sputtering

Uniformly distributed crystalline alpha-molybdenum oxide nanorods (NRs) were grown on c-plane sapphire substrates using a single-step radio frequency sputtering technique. The shape and size of the NRs can be controlled by regulating the composition of the sputtering gas (Ar : O-2 mixture). A pin-like nanowire structure was observed at an Ar : O-2 ratio of 20 : 0, which transformed to NRs at Ar : O-2 ratios of 20 : 2 and 20 : 4. Additionally, the length of the NRs increased with an increase in the deposition time. X-ray diffraction and transmission electron microscopy analyses indicated the highly crystalline nature of the NRs. X-ray photoelectron spectroscopy measurements revealed that the NRs were composed of nearly stoichiometric alpha-MoO3. Humidity sensing experiments indicated that the as-grown alpha-MoO3 NRs have good sensitivity to moisture.