Optical investigations on the existence of phase transition in ZnO:Li thin films prepared by DC sputtering method

✍ Scribed by A. Abu EL-Fadl; E. M. EL-Maghraby; T. Yamazaki

• Publisher: John Wiley and Sons
• Year: 2008
• Tongue: English
• Weight: 223 KB
• Volume: 43
• Category: Article
• ISSN: 0232-1300
• DOI: 10.1002/crat.200710982

✦ Synopsis

Abstract

We investigated the effect of temperature on the absorption spectra of Zn~0.8~Li~0.2~O thin films (ZnO:Li), deposited at 573 K, in the wavelength range 190‐800 nm. The films were deposited on sapphire, MgO or quartz substrates by DC sputtering method. The results show a shift of the optical energy gap (E~g~), with direct allowed transition type near the fundamental edge, to lower wavelengths as the temperature increases. The temperature rate of E~g~ changes considerably showing an anomaly around 320 K depending on type of substrate. The founded results indicated that replacement of Zn ions with Li ions induces a ferroelectric phase in the ZnO wurtzite‐type semiconductor. The exponential dependence of the absorption coefficient on the incident photon energy suggests the validity of the Urbach rule. (© 2007 WILEY ‐VCH Verlag GmbH & Co. KGaA, Weinheim)