Effect of N_2-Gas Partial Pressure on the Structure and Properties of Copper Nitride Films by DC Reactive Magnetron Sputtering

Copper nitride thin films were deposited on glass substrates by reactive direct current （DC） magnetron sputtering at various N2-gas partial pressures and room temperature. Xray diffraction measurements showed that the films were composed of Cu3N crystallites and exhibited a preferential orientation of the [111] direction at a low nitrogen gas （N2） partial pressure. The film growth preferred the [111] and the [100] direction at a high N2 partial pressure. Such preferential film growth is interpreted as being due to the variation in the Copper （Cu） nitrification rate with the N2 pressure. The N2 partial pressure affects not only the crystal structure of the film but also the deposition rate and the resistivity of the Cu3N film. In our experiment, the deposition rate of Cu3N films was 18 nm/min to 30 nm/min and increased with the N2 partial pressure. The resistivity of the Cu3N films increased sharply with the increasing N2 partial pressure. At a low N2 partial pressure, the Cu3N films showed a metallic conduction mechanism through the Cu path, and at a high N2 partial pressure, the conductivity of the Cu3N films showed a semiconductor conduction mechanism.

Microstructure, mechanical properties, and milling performance of arc-PVD AlTiN–Cu and AlTiN/AlTiN–Cu coatings

AlTiN,AlTiN–Cu and AlTiN/AlTiN–Cu coatings were prepared on WC–6%Co substrates by cathode arc evaporation deposition technology.Two kinds of nitrogen pressures were used to deposit both AlTiN–Cu and AlTiN/AlTiN–Cu coatings.Surface and cross-sectional morphologies of films were observed by scanning electron microscopy(SEM).Crystal structure of films was analyzed by X-ray diffraction(XRD)and X-ray photoelectron spectroscopy(XPS).Hardness and adhesion of films were measured by nano-indentation and nano-scratch tester.Cutting tests were performed under milling conditions during wet machining of TC4 alloy.The results show that with addition of Cu,more droplets occur on AlTiN coating surface,but the grain size of it is refined,and the hardness decreases but the toughness is improved.Under higher N2 pressure,the defects on the surface of AlTiN–Cu and AlTiN/AlTiN–Cu coatings diminish,and the hardness of them is enhanced,while the adhesion is reduced.Compared to AlTiN coated cemented carbide tool,the lifetimes of AlTiN–Cu and AlTiN/AlTiN–Cu coated tools under the same N2 pressure are improved by 11%and 24%,respectively.