(Digital Presentation) Fabrication and Characterization for Vanadium Oxynitride Thin Films By Magnetron Sputtering

Abstract

Vanadium oxynitride (VNxOy, x+y=1) is a metallic compound between vanadium oxides (VO, V2O3, V2O5) and vanadium nitride (VN) which would have interesting properties and functions that potentially can be supplied for different applications. In this study, vanadium nitride and oxynitride thin films were obtained by reactive magnetron sputtering using vanadium targets, Ar as plasma carrier, and a mix of N2 and O2 as reactive gas. The ratio of mass flow between the two gases is maintained around O2:N2=1:20 during the process. To obtain crystalline phases of oxynitrides a post rapid thermal annealing (RTP) in Ar atmosphere at 600ºC and 700ºC for 5 minutes was done. The purpose of the study is to define the effect of the magnetron sputtering parameters, such as reactive gas flow rates, and annealing temperature on the composition, microstructure, and optical properties of the obtained vanadium oxynitride thin films. The characterization of obtained films includes the examination of thickness and morphology by the surface profiler and SEM; identifying crystal structures and further microstructural vibration modes of molecular polarizability by X-ray diffraction and Raman spectroscopy, respectively; evaluation of the chemical composition of films by XPS analysis; assessing of optical transmittance, reflectance, and absorbance by the UV-visible- NIR spectrometer. Experimental data reveal that the annealed films can be oxynitrides when the oxygen flow rate is below 0.25 sccm and the ratio of oxygen/nitrogen ≤1/20. The annealed vanadium oxynitride films in terms of their properties are closer to vanadium nitrides than to oxides: more metallic than semi-conductive with dark appurtenance and high optical absorbance across the spectrum between 200 and 900 nm. The optical absorbance reaches almost 90% around 300 nm and then slowly reduces to 70% at 900 nm. Thus, these films could be good optical shields. For practical usage, the deposition of O2:N2=1/20, O2<0.25 sccm, and 600ºC annealing are recommended because of the truly low transmittance (<10%) through films.