A novel surface design for preparing a Mo-10%Nb sputtering target with ultra-low oxygen content: Coating a NbC layer on Nb powder particles via chemical vapour reaction under CH4 atmosphere

Abstract

Mo-10%Nb sputtering target has broad application prospects in thin-film solar cells and displays. However, the absorption of oxygen by Nb powders during the sintering process leads to a high oxygen content and low density of the sintered Mo-Nb billet. In this study, Nb powder covered with a niobium carbide (NbC) layer was prepared via chemical vapour reaction under CH4 atmosphere for the first time. The NbC layer not only helps prevent oxygen absorption, but can also be completely consumed by reaction with oxygen at the desired temperature. The effects of the preparation method, reaction medium, and reaction parameters on the properties of the NbC layer were investigated, and optimised parameters were found to be a temperature of 600 °C, reaction time of 270 min, and gas pressure of 0.04 MPa. The surface morphology, chemical composition, and the distribution and uniformity of the layer were characterised by scanning electron microscopy, X-ray photoelectron spectroscopy, electron probe microanalysis, Raman spectroscopy, and atomic force microscopy. The oxygen and carbon contents were determined using ONH and CS analysers. The surface-modified Nb powder was mixed with a Mo powder and sintered under vacuum to obtain a sintered Mo-10%Nb billet with an oxygen content of 190 ppm, carbon content of 290 ppm, and relative density of 93%. The quality of this billet is significantly better than that of a billet prepared using a non-surface-modified Nb powder.