Optical and mechanical properties of Cr and CrN x films by dc magnetron sputtering

Abstract

The optical, electrical and mechanical properties of chromium and chromium nitride films were investigated. Films of around 50 nm in thickness were deposited on glass substrates by dc sputtering of a Cr target with different levels of introduced argon and nitrogen flows. The real part of the refractive index of the film at 632.8 nm decreased from 3.6 at 0% N 2 to 2.9 at 100% N 2, while the imaginary part increased from 4.1 at 0% N 2 to 4.4 at 20% N 2 and then monotonically decreased to 2.3 at 100% N 2. The electrical resistivity of the film increased at around 60% N 2 and achieved a maximum of about 1 × 10 −2 Ω cm at 80% N 2, where the film had a Cr:N atomic ratio of 1.4:1.0 according to Auger electron spectroscopy (AES). In a Taber abrasion test, the area of the film peeled from the substrate was largest for the CrN x film at 60% N 2, whereas in a sand eraser abrasion test, the area was largest for the Cr film. The inconsistent results between the two abrasion tests are discussed from a viewpoint of the effects of friction, adhesion strength and internal stress.