Study of (Ti,Zr)C:H/a-C:H nanocomposite thin film formation by low temperature reactive high power impulse magnetron sputtering

Abstract

Single-phase nanocrystalline hydrogen-containing titanium zirconium carbide thin films and hydrogen-containing nanocomposite thin films consisting of a nanocrystalline hydrogen-containing titanium zirconium carbide phase in combination with an amorphous hydrogen-containing carbon network, (Ti1-xZrx)C1-δ:H/a-C:H, were deposited by low temperature reactive high power impulse magnetron sputtering (HiPIMS) in a methane-argon atmosphere. High power impulse magnetron sputtering offers a high degree of ionization of sputtered particles and therefore a precise control of the thin film growth. The thin film deposition in the Ti-Zr-C-H system was carried out by a combinatorial approach via the variation of both the titanium-to-zirconium ratio as well as the carbon and hydrogen content in the coatings. A single, metallic, segmented target consisting of two triangles of pure titanium and zirconium enabled the deposition of thin films with different titanium-to‑zirconium-ratio dependent of the substrate position in front of the target within one deposition process. By variation of the CH4 reactive gas flow at a constant Argon gas flow the carbon and hydrogen content of individual thin films was precisely adjusted. During the HiPIMS process a short pulse time of 50 μs was combined with a comparably low duty cycle of 3.3% in order to ensure a high ionization. In order to investigate the chemical composition of the thin films including hydrogen content electron probe microanalysis was combined in a self-consistent way with elastic recoil detection analysis. Structural analysis was done by a combination of different techniques: Raman spectroscopy suggests metal‑carbon bonds attributable to a nanocrystalline metal carbide phase as well as the formation of an amorphous hydrogen-containing carbon network. X-ray diffraction shows fcc (Ti1-xZrx)C1-δ:H grains with different sizes in all coatings. Transmission electron microscopy confirms the structure model of single phase nanocrystalline (Ti1-xZrx)C1-δ:H grains embedded in a hydrogen-containing amorphous carbon matrix. Scope of this work is the low temperature deposition of the (Ti,Zr)C1-δ:H thin films and the (Ti,Zr)C1-δ:H/a-C:H nanocomposites by HiPIMS with precise control of the resulting chemical composition and microstructure.