Effect of sputtering power on structural, morphological, chemical, optical and electrical properties of Ti:Cu₃N nano-crystalline thin films

¹ Department of Physics, Faculty of Science, Vali-e-Asr University of Rafsanjan, Rafsanjan, Iran
² Department of Solid State Physics and Electronics, Faculty of Physics, University of Tabriz, Tabriz, Iran
³ Materials and Energy Research Centre (MERC), P.O. Box 31787/316, Karaj, Iran

^a e-mail: alirahmati1980@gmail.com; a.rahmati@vru.ac.in

Received: 22 June 2012
Revised: 29 October 2012
Accepted: 15 November 2012
Published online: 12 December 2012

Abstract

A sintered Ti1₃Cu₈₇ bi-component target was sputtered by reactive DC magnetron sputtering in nitrogen ambient under various sputtering powers. Ti included Cu₃N (Ti:Cu₃N) thin films were deposited on Si (1 1 1), KBr (potassium bromide), quartz and glass slide substrates. Crystalline phases of the films were identified by X-ray diffraction (XRD) technique. Crystalline quality and phase stability are strongly dependent on sputtering power. Formation of copper vacancies in Cu₃N cell substituted by Ti atoms and subsequent excess of interstitial nitrogen (N-rich) result in lattice constant expansion. Bonding environment in these films was obtained from fourier transform infrared (FTIR) spectroscopy. Surface morphology of the films that were studied by a scanning electron microscope (SEM) indicates a granular structure. Atomic Ti:Cu ratio of Ti:Cu₃N films, determined by energy dispersive X-ray (EDX) spectroscopy, is less than that of original target. Optical study was performed by Vis-near IR transmittance spectroscopy. Film thickness, refractive index and extinction coefficient were extracted from the measured transmittance using pointwise unconstrained minimization approach. The TiCu₃N films are direct semiconductor with bandgap energy with the range of 2.79–3.34 eV. Ti incorporation and subsequent N-rich have a significant role in bandgap widening and lattice constant expansion. The films electrically show quasi-metallic behavior.