STRUCTURE AND STABILITY OF SPUTTER-DEPOSITED BETA-TUNGSTEN THIN-FILMS

The structure and stability of thin tungsten films prepared by radio frequency magnetron sputter deposition have been studied by x-ray diffraction and x-ray photoelectron spectroscopy. The structure of these films has been found to systematically evolve from the metastable A 15 beta-W phase to the equilibrium A2 alpha-W phase with decreasing oxygen impurity concentration. Within the beta-W phase a decrease in the concentration of incorporated oxygen results in a monotonic decrease in the lattice parameter of the unit cell until the beta-W phase eventually becomes unstable, and the alpha-W phase is formed.