Synthesis of orthorhombic-molybdenum trioxide (α-MoO3) thin films by hot wire-CVD and investigations of its humidity sensing properties

In present work, we report synthesis of orthorhombic-molybdenum trioxide (alpha-MoO3) thin films using home-build hot wire-CVD (HW-CVD) method simply by heating the Mo filament in a controlled O-2 atmosphere. The formation of alpha-MoO3 was confirmed by low angle-XRD and Raman spectroscopy. Low angle-XRD analysis revealed that alpha-MoO3 crystallites have orientations along (110), (101) and (111) directions while Raman spectroscopy analysis shows two prominent vibrational modes similar to 819 and similar to 994 cm(-1) associated with Mo-2-O and Mo=O respectively. SEM and TEM analysis show the formation of nano-sheets like morphology of alpha-MoO3 thin films. The SAED pattern shows highly crystalline nature of alpha-MoO3. The humidity-sensing properties were investigated at room temperature by fabricating the two probe device. The humidity sensing results showed n-type behavior of alpha-MoO3. The maximum humidity sensitivity of similar to 6957% along with response time of similar to 66 s and recovery time of similar to 5 s were observed for alpha-MoO3 thin film humidity sensor device. Our results have opened up a new avenue to grow alpha-MoO3 for humidity sensor applications.