Effect of substrate temperature on the structural and optical properties of ZnO and Al-doped ZnO thin films prepared by dc magnetron sputtering

• Published in: Optics communications Vol. 282; no. 2; pp. 247 - 252
• Main Authors: Li, Xue-Yong, Li, Hong-Jian, Wang, Zhi-Jun, Xia, Hui, Xiong, Zhi-Yong, Wang, Jun-Xi, Yang, Bing-Chu
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.01.2009; Elsevier
• Subjects: Al-doped ZnO; Condensed matter: electronic structure, electrical, magnetic, and optical properties; dc Magnetron sputtering; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Electronic transport in interface structures; Exact sciences and technology; Ii-vi semiconductors; Microstructure; Optical properties; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions; Photoluminescence; Physics; 71.55.Gs; 73.40.Lq; Optical properties; Al-doped ZnO; Microstructure; dc Magnetron sputtering; 61.72.Vv; Surface morphology; Photoluminescence; Doped materials; Measuring methods; Binary compounds; Zinc Oxides; Ceramics; XRD; Sensor materials; Transmittance; Al-doped; Thin films; Aluminium Oxides; II-VI semiconductors; Aluminium additions; Optical method; 71.55.Cs
• ISSN: 0030-4018; 1873-0310
• DOI: 10.1016/j.optcom.2008.10.003

ZnO and Al-doped ZnO(ZAO) thin films have been prepared on glass substrates by direct current (dc) magnetron sputtering from 99.99% pure Zn metallic and ZnO:3 wt%Al 2O 3 ceramic targets, the effects of substrate temperature on the crystallization behavior and optical properties of the films have been studied. It shows that the surface morphologies of ZAO films exhibit difference from that of ZnO films, while their preferential crystalline growth orientation revealed by X-ray diffraction remains always the (0 0 2). The optical transmittance and photoluminescence (PL) spectra of both ZnO and ZAO films are obviously influenced by the substrate temperature. All films exhibit a transmittance higher than 86% in the visible region, while the optical transmittance of ZAO films is slightly smaller than that of ZnO films. More significantly, Al-doping leads to a larger optical band gap ( E g) of the films. It is found from the PL measurement that near-band-edge (NBE) emission and deep-level (DL) emission are observed in pure ZnO thin films. However, when Al was doped into thin films, the DL emission of the thin films is depressed. As the substrate temperature increases, the peak of NBE emission has a blueshift to region of higher photon energy, which shows a trend similar to the E g in optical transmittance measurement.