Hard multifunctional Hf–B–Si–C films prepared by pulsed magnetron sputtering

Hf-B-Si-C films were deposited onto silicon and glass substrates using pulsed magnetron co-sputtering of a single B4C-Hf-Si target (at a fixed 15% Hf fraction and a varying 0–50% Si fraction in the target erosion area) in pure argon. We focus on the effect of the Si content in the films. The film structure changes from nanocolumnar (at 0–7 at.% of Si) to nanocomposite (at around 10 at.% of Si) to amorphous (at higher Si contents). Both nanocolumnar and nanocomposite HfB2-based films exhibit a hardness of up to 37 GPa and a high H/E* ratio of around 0.15. The Si incorporation leads to a significant reduction of the compressive stress of films and improvement of their oxidation resistance (unmeasurable mass change after annealing up to 800 °C at 35 at.% of Si). All films exhibit a high electrical conductivity and very smooth defect-free surfaces with an average roughness below 1 nm. Consequently, the films may be used as a new class of hard and electrically conductive protective coatings with a high oxidation resistance at elevated temperatures.