Tuning the band gap of ZnO thin films by Mg doping

Abstract

© 2016 Trans Tech Publications, Switzerland. Structural, morphological, optical and electrical properties of magnesium (Mg) doped zinc oxide (ZnO) films were prepared by the ultrasonic spray pyrolysis technique on a microscope glass substrate, and have been studied in terms of the Mg doping content. The precursor solutions of Mg doped ZnO films were prepared from zinc acetate dihydrate (Zn(CH3OO)2·2H2O) and magnesium acetate tetrahydrate (CH3COO)2Mg·4H2O) as dopant. The compositions of these solutions were fixed at 0.02 M of Zn(CH3OO)2.2H2O and the atomic percentage ratio of Mg/Zn varied from 0 to 20 atomic %. The XRD patterns of all films showed ZnO hexagonal wurtzite structure and the morphology showed homogeneous structure/texture being pinhole-free with added Mg content. It was found that Mg2+ ions did not change conductivity of ZnO films due to the partial substitution of Zn2+ ion with the same valence Mg2+ ion. For optical properties, all films showed high transmittance over 80% and absorbance around 0.01 in the visible and near infrared regions. Moreover, the Mg dopant affects the shift of the absorption edge in the transmittance spectra of the films to a lower wavelength in the ultraviolet region and increases the band gap of the samples.