Search for new materials in sputtered V 1− xC x films

Abstract

In this work, the vanadium–carbon system has been explored in a wide range of atomic carbon content x (0.01< x<0.69) with the aim of obtaining films of new materials. V 1− x C x films were prepared by reactive dc diode magnetron sputtering and Electron Probe Micro-Analysis (EPMA) was used to determine their composition. The structures of as-sputtered films were identified by X-ray and Transmission Electron Microscopy (TEM). It is shown that they strongly depend on the carbon content x and several interesting facts can be underlined. If most of the films are crystalline and contain phases related to the phase diagram, a glass forming ability (GFA), located around x=0.32, permits to obtain a mainly amorphous film. This value is in the carbon content range of the hemicarbide V 2C. Below x=0.32, films are composed of the bcc vanadium solid solution which can be considerably extended (up to 0.17) inducing a lattice parameter expansion. Above x=0.32, films are first wholly made up of the substoichiometric VC monocarbide and then contain additional amorphous carbon. For x=0.32, TEM images and associated diffraction patterns suggest a nanocomposite material with numerous little crystals of carbide embedded in an amorphous matrix. A special attention has been devoted to this composition and a crystallization study has been undertaken. All these results show the capability of the binary V–C system combined with a sputtering process to generate promising films and coatings.