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

摘要

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.