Influence of Aluminium Contents on the Structure and Hardness of Chromium Aluminium Nitride Thin Films

Abstract

This research aims to study the influence of aluminum content in film on the structure and hardness of chromium aluminum nitride thin films, which are deposited on silicon by reactive DC unbalanced magnetron sputtering method from the Cr-Al alloy target (50:50 at%). The structure, chemical composition, morphology, and hardness were characterized by XRD, EDS, FE-SEM, and nano-indentation techniques, respectively. The results showed that the as-deposited films were formed as a (Cr, Al)N solid solution with fcc structure in the (111), (200), and (220) planes. The as-deposited film had lattice parameters in the range of 4.088-4.138 Å. The as-deposited film had nano-structure whereas the average crystallite size was in the range of 3.1-16.8 nm. The chemical composition from the EDS technique showed that the as-deposited film had chromium (Cr), aluminum (Al), and nitrogen (N) as the main component in different ratios. The FE-SEM micrograph presented that the Al content affected the surface morphology and cross-sectional of the as-deposited film. The hardness, of the as-deposited films measured by the nano-indentation technique, increased from 12.47 GPa to 67.29 GPa with the Al content while decreasing with the crystallite size. The highest hardness found in the CrAlN film with the Al content was 30.93 at% and the crystallite size was 3.1 nm.