Investigation the phase transformation of sputtered molybdenum oxide thin films and their correlation with the film thickness

Polycrystalline of as-deposited molybdenum oxide thin films were synthesized using Radio-Frequency sputtering technique. X-ray diffraction technique showed the formation of hexagonal MoO3 beside the β-MoO3 phase for thin films of thickness 39 nm. The higher film thickness at about 132 nm showed the new tetragonal phase of molybdenum oxide MoO2 beside the β- phase. The film morphology and roughness were observed by Atomic Force Microscopy which approved that the roughness was observed to decrease as the film thickness increase. Optical properties of the sputtered films were examined by UV-visible spectral measurements. The optical band gap values are varied from 3.74 eV for lower film thickness to 3.8 eV for higher film thickness. Photoluminescence spectra were recorded for the studied films showing the spectral broadness in the range 350-600 nm related to near band edge emission and a red emission is observed at 725 nm.