Reactive DC magnetron sputter deposited Ti–Cu–N nano-composite thin films at nitrogen ambient

Abstract

Ti–Cu–N thin films have been grown on Si(111), KBr (potassium bromide), quartz and glass slide substrates using a TiCu (13:87 at. %) single multi-component target by reactive DC magnetron sputtering at nitrogen ambient. This study provides insight into the importance of nitrogen pressure on the characteristic of Ti–Cu–N thin films. Crystalline phases of these films are identified by X-ray diffraction (XRD) technique. The titanium atoms were inserted into the Cu 3N unit cell. The results from XRD show that the observed phases are nano-crystallite cubic anti-Rhenium oxide (anti-ReO 3) structure of Ti doped Cu 3N (Ti:Cu 3N) and nano-crystallite face centre cubic (fcc) structure of Cu. Formation of copper vacancies in Cu 3N cell substituted by titanium atoms and subsequent excess of interstitial nitrogen (N-rich) result in lattice constant expansion and optical energy gap widening. Surface morphology of the films studied by scanning electron microscope (SEM) indicates agglomeration of grains. Ti:Cu atomic ratio of Ti–Cu–N films, determined by energy dispersive X-ray (EDX) spectroscopy, is less than that of the original TiCu single multi-component target and nearly independent of nitrogen pressure. Optical study is performed by Vis-near IR transmittance spectroscopy. Film thickness, refractive index and extinction coefficient are extracted from the measured transmittance using a reverse engineering method. Absorption coefficient indicates that the nitrided films are direct semiconductor. The films electrically show quasi-metallic behavior. The effect of sputtering pressure on deposition rate is investigated. Compared with the Ti free Cu 3N film, the Ti:Cu 3N films possesses fine thermal stability in vacuum.