Title Comparative study of titanium-doped and titanium–silver Co-doped diamond-like carbon films
Authors Platnieks, Oskars ; Marcinauskas, Liutauras ; Zhairabany, Hassan ; Sarakovskis, Anatolijs ; Vanags, Edgars ; Gaidukovs, Sergejs ; Khaksar, Hesam ; Gnecco, Enrico
DOI 10.1021/acsomega.5c10368
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Is Part of ACS omega.. Washington, DC : American Chemical Society. 2025, Early access, p. 1-12.. ISSN 2470-1343
Keywords [eng] Coating materials ; Friction ; Metals ; Oxygen ; Surface roughness
Abstract [eng] Hydrogen-free diamond-like carbon (DLC) films were deposited by magnetron sputtering and doped with titanium (Ti-DLC) and codoped with titanium and silver (Ti/Ag-DLC, 80/20 at. % TiAg target). Ti loadings of 0.3–1.8 at. % produced only modest roughness changes (Rq ≈ 1.8–2.3 nm) and a slight increase in ID/IG and sp2/sp3 ratios, though the D-band down-shifted markedly. Ti/Ag codoped DLC films contained 1.0–6.9 at. % total metal, while the surface was enriched in Ag according to X-ray photoelectron spectroscopy. Except for the highest doped film, Ti/Ag-DLC showed lower graphitization than the Ti-DLC films prepared under identical conditions. Rq increased to 3.9 nm for the Ti/Ag-DLC films, reaching the highest value at the lowest Ti/Ag content. The presence of Ag also diminished surface oxidation and reduced oxygen concentration at low doping levels. Ti doping and Ti/Ag codoping of DLC films reduced the coefficient of friction by up to 2-fold when normal loads of 1–10 nN were used. Nanoindentation tests revealed that both Ti-DLC and Ti/Ag-DLC films show their greatest hardness loss at the lowest dopant concentrations. Water contact angles for Ti-DLC films changed nonmonotonically but became slightly less hydrophilic (∼69°) compared to undoped DLC. Ti/Ag-DLC films first became more wettable (59.9°) and then recovered to 68.5° as metal content increased. OWRK calculations showed a dopant-induced decline in total surface free energy, which was driven by reductions in dispersive components. Collectively, these data indicate that the Ti/Ag codoping offers a tunable balance of hardness, roughness, and wettability, combining the benefits of Ti with the advantages of Ag when applied at low to moderate concentrations.
Published Washington, DC : American Chemical Society
Type Journal article
Language English
Publication date 2025
CC license CC license description