Deposition of diamond-like carbon thin films by the high power impulse magnetron sputtering method

The goal of the conducted experiments was to evaluate if the increased density of the plasma in High Power Impulse Magnetron Sputtering (HiPIMS) argon discharge would give the possibility of obtaining diamond-like films with high sp3 fraction content at room temperature. The magnetron cathode was driven by the self-designed supply. It consisted of high voltage supply, tank capacitors and a set of switches. The tank capacitors and the inductances of connecting wires formed an LC resonant circuit. As a result, each sputtering pulse (duration of 20μs, peak current of 1500–2200A) was followed by the inverse pulse (duration of 25μs, peak current of 400–700A), both having a sinusoidal shape. The repetition time was 3s. The silicon substrates were placed 8cm above the target surface. The sputtering processes of 99.99% pure graphite target were conducted in argon atmosphere at a pressure of 6–8×10−3hPa. The carbon films obtained after 400 deposition pulses had a thickness of 35nm. The surface RMS roughness, measured using an optical profiler, was about 2nm. The refractive index was estimated by means of ellipsometric studies to be 2.45 and 2.3 at 400 and 800nm, respectively. The sp3 hybridization fraction content of about 70–80% was calculated based on the analysis of Raman Scattering spectra.