Effects of substrate temperature and substrate holder rotation speed on the characterization of (TiZrHfCr)Bx films

Abstract

(TiZrHfCr)Bx thin films were fabricated using HfB2, ZrB2, CrB2, and Ti targets in a magnetron cosputtering system onto Si wafers and SUS304 substrates. A Ti interlayer was employed to enhance the adhesion between the film and the substrate. The first batch (T batch) of (TiZrHfCr)Bx films was fabricated at substrate temperatures of 60, 200, 300, and 400 degrees C, with the substrate holder rotation speed fixed at 30 rpm. The second batch (R batch) of films was deposited at substrate holder rotation speeds of 5, 10, 15, and 30 rpm, with a substrate temperature of 400 degrees C. In the T batch, the B/(Ti + Zr + Hf + Cr) ratio of the (TiZrHfCr)Bx films varied from 1.47 to 1.39, the hardness values increased from 21.1 to 26.7 GPa, and the elastic modulus increased from 263 to 286 GPa as the substrate temperature was increased from 60 to 400 degrees C. The mechanical properties increased with increasing substrate temperature, attributed to film densification; however, the films' low stoichiometry limited the enhancement in mechanical properties. In the R batch, the hardness increased from 26.7 to 29.1 GPa, and the elastic modulus increased from 286 to 313 GPa, as the substrate holder rotation speed decreased from 30 to 5 rpm. The formation of nanoscale cyclic gradient concentrations raised the mechanical properties. The XRD analysis revealed that all the films exhibited a near-amorphous structure ascribed to under-stoichiometric compositions. Scratch test results indicated that the R5 sample, prepared at 400 degrees C with a substrate holder rotation speed of 5 rpm, exhibited the highest LC3 critical load of 41.3 N. In the wear tests, the R15 film exhibited the highest wear resistance, whereas the R10 film, under tensile stress, showed reduced wear resistance.