Reactive Sputtering Process Study for Vanadium Oxynitride Films

Abstract

In this study, vanadium oxynitride thin films were deposited by reactive magnetron sputtering using pure vanadium targets, Ar as a plasma carrier, and a mix of N2 and O2 as reactive gases. Various ratios of mass flow rates between two reactive gases were maintained as a constant during the process. To obtain crystalline phases of oxynitrides, rapid thermal annealing in Ar atmosphere at 600 °C and 700 °C for 5 min was conducted after the deposition. This study aims to define the range of the process parameters of magnetron sputtering to deposit vanadium oxynitride thin films. The assessment for the characterization of films utilizes the surface profiler, scanning electron microscope, X-ray diffraction, X-ray photoelectron spectroscopy, four-point probe, Hall analyzer, and UV-visible-NIR spectrometer. Experimental results reveal that the annealed films can be oxynitrides when the oxygen flow rate is below 0.25 sccm, and the ratio of oxygen/nitrogen is no more than ~1/10. The annealed vanadium oxynitride films, in terms of their properties, are closer to vanadium nitrides than to oxides, due to the intended low supply of oxygen during deposition. For instance, the film is more metallic than semi-conductive with dark appurtenance and high optical absorbance across the spectrum between 200 and 900 nm. For practical purposes, the deposition conditions of O2:N2 = 1/20, O2 < 0.25 sccm, and 600 °C annealing are recommended to obtain vanadium oxynitride films with relatively lower resistivity (10−2 Ω cm) and optical transmittance (<15%) through films.

Mechanical Properties of V-O-N Coatings Synthesized by Cathodic Arc Evaporation

“…The literature indicates that it is difficult to accurately determine the crystalline phase in vanadium oxynitride films due to the possibility of the simultaneous presence of oxynitrides, nitrides, and various oxides [39,40]. The phase diagram of the V-O system is rich in numerous oxides because vanadium can exist in different valence states (from +2 to +5) [57].…”

“…The formation of amorphous phases has already been observed in ion-plasma coatings of the V-O-N system. In [39], thin amorphous films of vanadium oxynitride were deposited by reactive magnetron sputtering. To obtain the crystalline phases of the oxynitrides, rapid thermal annealing in an Ar atmosphere at 600 • C and 700 • C for 5 min after deposition was necessary.…”