An evaluation of chromium deposited by high rate sputtering

Abstract

The structure, chemical composition and hardness of 0.005 cm (0.002 in.) thick sputter-deposited chromium coatings produced at deposition rates of 2 to 5 nm/s (0.3 to 0.7 mils/h), substrate temperatures of 20‡C and 60‡C, and substrate potentials of -30 V (floating) and -50 V, with respect to ground, in a dc-triode sputtering system were examined. The chromium coatings were examined by X-ray diffraction, optical metallography, and scanning electron microscopy of fracture and growth surfaces. Trace element analysis and krypton analysis of powdered target and deposit material were performed by X-ray energy spectroscopy. Diamond pyramid and Knoop microhardness measurements were made on transverse sections. The chromium structure, krypton content and properties were influenced by substrate temperature and potential with little effect of target voltage and deposition rate. Both the deposit hardness and crystal lattice parameter decreased with increasing substrate temperature. A substrate bias of -50 V during deposition altered both the growth morphology and the krypton content of the chromium, but had little effect on the lattice parameter relative to a -30 V substrate potential (floating). A hardness increase of 150 KHN, a marked grain refinement and an increase in surface reflectivity accompanied the change in growth morphology.