Optical properties and surface morphology of Li-doped ZnO thin films deposited on different substrates by DC magnetron sputtering method

Thin films of zinc oxide doped with Zn1-xLixO with x = 0.2 (ZnO : Li), have been prepared on sapphire, MgO and quartz substrates by DC magnetron sputtering method at 5 mTorr. The substrate temperatures were fixed to about 573 K. We have measured the transmission and reflection spectra and determined the absorption coefficient, optical band-gap (E-gd(opt)), the high frequency dielectric constant epsilon'(proportional to) and the carrier concentration N for the as-prepared films at room temperature. The films show direct allowed optical transitions withE dp values of 3.38, 3.43 and 3.29 eV for films deposited on sapphire, MgO and quartz substrates, respectively. The dependence of the obtained results on the substrate type are discussed. (C) 2001 Elsevier Science B.V. All rights reserved.