Deposition of binary CrZr thin-film metallic glass using Cr/Zr dual-cathode high-power impulse magnetron sputtering

Abstract

Closed-field magnetron Cr/Zr dual-cathode unipolar high-power impulse magnetron sputtering (HiPIMS) is used to deposit binary CrZr alloy films of various compositions. The discharge voltage pulses of the Cr and Zr cathodes (targets) were synchronized with equal pulse widths, and the effects of the average discharge power of the target materials and substrate bias voltage on the composition, microstructure, mechanical strength, and electrical resistance of the deposited alloy films were determined. Varying the average power ratio of the targets provided a degree of control over the film composition. The deviation in the compositional Cr/Zr ratio in the films changed with the average discharge powers of the two targets owing to the contrasting dependence of the fractional deposition rate on the average discharge power ratio of the two elements. Most of deposited CrZr films were primarily amorphous, and coatings with Cr contents >82 %, <32 %, or close to 67 % possibly are nanocrystalline or contained minor crystalline domains. Enhancing the negative substrate smoothened the film surface and reduced the columnar structure of the films, thereby increasing the hardness of the Cr-rich films. The film hardness and elastic modulus increased with the Cr fraction. All obtained CrZr films exhibited relatively low electrical sheet resistances owing to the Cr fraction and substrate-bias-induced microstructure. The Cr₄₂Zr₅₈ thin films exhibited a thin-film metallic glass feature with a glass transition temperature of approximately 580 °C. The mechanical, structural, and electrical properties of the HiPIMS-deposited CrZr alloy films are advantageous for applications requiring high corrosion resistance, wear resistances and low electrical conductivity, such as in biomedical and wearable devices.