X-ray diffraction analysis and x-ray photoelectron spectroscopy of α- and β-W thin films grown by ion beam assisted deposition

Abstract

Thin W films have been deposited by dual ion beam sputtering using a sputtering ion gun and an assisting ion gun. The crystal structure of the deposited films was strongly dependent on the energy of the assisting ions, substrate temperature, and the thickness of the film. All these variables were found to affect the oxygen concentration of the film which in turn, determines whether the film will have an A-2 body-centered-cubic α-W phase, an A-15 face-centered-cubic-like β-W phase, or a mixture of the two. Assisting ions and substrate temperature both increase the diffusivities of W and O resulting in a decreased oxygen concentration in the film which makes the α-W phase more stable. Films deposited at low substrate temperatures and without any ion bombardment show only the β-W phase.