Light-Sensing Properties of Amorphous Vanadium Oxide Films Prepared by RF Sputtering.

In this study we analyzed the structure and light-sensing properties of as-deposited vanadium oxide thin films, prepared by RF sputtering in different Ar:O 2 flow rate conditions, at low temperature (e.g., 65 °C). X-ray diffraction (XRD), Scanning Electron Microscopy (SEM-EDX), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) were employed to analyze the film microstructure, composition and the oxidation states of vanadium ions. The SEM micrographs evidence V x O y films with smooth surfaces, whereas the XRD patterns show their amorphous structure. Raman spectra indicate an increased structural disorder in the films deposited in Ar:O 2 flow comparatively with those deposited solely in Ar flow. The XPS data suggest the modification of the oxidation state from V 4+ to V 5+ , thus proving the formation of the V 2 O 5 phase when increasing the oxygen content, which further affects the films' optical properties. We observed a good stability of the photogenerated current in Si/SiO 2 /V x O y /TiN heterostructures upon excitation with pulses of UV (360 nm), VIS (white light) and NIR (860 nm) light. The responsivity, detectivity and linear dynamic range parameters increase with the O/V ratio in the V x O y films, reaching comparable values with photodetectors based on crystalline V 2 O 5 or VO 2 .