Investigation of plasma ion composition generated by high-power impulse magnetron sputtering (HiPIMS) of graphite

• Published in: Journal of physics. Conference series 2019-11, Vol.1393 (1), p.12018
• Main Authors: Oskomov, K V, Vizir, A V
• Format: Article
• Language: English
• Subjects: Argon; Carbon; Cathode sputtering; Composition; Diamond films; Diamonds; Discharge; Graphite; Ion bombardment; Magnetron sputtering; Physics; Plasma; Pulse duration; Substrates; Vacuum chambers
• ISSN: 1742-6588; 1742-6596
• DOI: 10.1088/1742-6596/1393/1/012018

High-power impulse magnetron sputtering (HiPIMS) of graphite is used to increase the density of the plasma (up to 1013 cm−3) and the fraction of ionization of carbon (up to 70 %). It makes possible to increase the ion bombardment of the growing film by applying a negative high-frequency (HF) bias potential to the substrate, which allows deposition of diamond-like (DLC) coatings obtained by subplantation mechanism. The purpose of this research was to measure the ion composition of plasma during HiPIMS of graphite by time-of-flight spectrometer depending on discharge parameters (current, pressure, pulse-width). For any pulse-width (up to 250 μs) increase of discharge current leaded to growth of C+ fraction (up to 60 % for 70 A) that results from more intense sputtering of the graphite cathode. Decrease of argon pressure down to 3×10−4 Torr leaded to reduction of C+ fraction down to 13 %, which is related to less intense sputtering. It can be seen that as the argon pressure in the vacuum chamber increases, the percentage of carbon ions in the flow increases (up to 75 %), which may due to the "cooling" of electrons with increasing pressure - they no longer have enough energy to ionize argon (15 eV), but enough energy to ionize carbon (3.6 eV). Thus, using of time-of-flight analyzing of plasma ion composition generated by HiPIMS of graphite one can choose optimum discharge pressure and current - both of them should be maximized.