Modification of evaporated chromium by concurrent ion bombardment

Bombardment of thermally evaporated chromium films with energetic inert gas ions during deposition (ion peening) causes marked changes in properties when the dose exceeds a minimum critical value. The property changes are characterized by a sharp reversal of intrinsic stress from high-tensile to high-compressive values, increases in the optical reflectance and optical density to levels approaching pure bulk chromium, and enhanced resistance to oxidation on heating. Observations of the shift in critical ion dose with accelerating voltage and ionic mass (argon and xenon) indicate that the ion peening transition may be controlled by the transfer of momentum to the depositing film. This observation is found to be consistent with results obtained in low-pressure, cylindrical post-magnetron sputtering, which ion peening was devised to simulate.