Characterization of as‐prepared and annealed W/C multilayer thin films Available to Purchase

Tungsten/carbon (W/C) multilayer thin films were prepared by dc magnetron sputtering. All samples consisted of 30 layer pairs with a nominal d spacing varying from 2.5 to 14 nm, the W layer thickness was kept at 2 nm in all samples. The W/C multilayers were subjected to isochronal anneals in a quartz tube furnace at the temperature range from 500 to 950 °C under a flow of high purity Ar gas. X‐ray diffraction, Raman scattering, and Auger depth profile were used to characterize the structure of the as‐prepared and annealed multilayer films. Both the W and C layers appear to be amorphous as‐prepared. An overcoat of 30 nm of plasma enhanced chemical vapor deposited silicon nitride was found to inhibit oxidation during annealing. For those multilayers containing thinner carbon layers (<1 nm), the formation of crystalline W₂C occurs at annealing temperature as low as 500 °C and a very small expansion (<2%) in the layer d spacing is observed. On the other hand, for all multilayers with carbon layer thickness equal or greater than 2 nm, crystallization occurs at much higher annealing temperatures and the crystalline phases observed were alpha‐W and WC. It is also observed that in the latter group the period increases monotonically with increasing annealing temperature, the total expansion is about 10% and affects both W and C layers approximately equally. The expansion stops at the crystallization temperature which occurs at 900 °C or higher. The expansion is under investigation but may be interpreted as due to the structural ordering processes in the amorphous W and C layers.