Effects of Mg Concentration of MgxZn1-XO Nanostructure Thin Films by PLD on Optical and Topographical Properties

Abstract

In this work, MgxZn1-xO thin films were synthesized by pulsed laser deposition technique, the morphology and optical properties of MgxZn1-xO films were characterized by Atomic force microscopy (AFM) and UV-VIS spectroscopy. The MgxZn1-xO films have been deposited on sapphire substrates with different Mg contents (x= 0, 0.1, 0.2, 0.3, 0.4, 0.6, 0.8, 1), using double frequency Q-switching Nd:YAG laser (532nm), repetition rate (6 Hz) and a pulse duration of (7 ns).The present of hexagonal and cubic structure of MgxZn1-xO thin films was shown from X-ray diffraction measurement. The optical transmission results show that the transparency of the MgxZn1-xO films are greater than 85% in the visible region which increases with the increasing of Mg content. The absorption can be extended to lower wavelength range with higher magnesium contents, which can improve the transparency in the ultraviolet wavelength range. The band gap energy was found to be changed to the higher energy side with the increasing of Mg concentration. By changing Mg content from x=0 to x=1, the optical band gap of MgxZn1-xO films can be tuned from 3.4 eV to 5.9 eV, while the refractive index decreases from (1.96 – 1.75) as Mg-content increases from (0 to 1) at constant wavelength 400nm. This provides an excellent opportunity for bandgap engineering for optoelectronic applications. It is found from the AFM studies that the surface roughness of the films decreases with increasing the Mg content and the smallest grain size (33.8nm) with Mg content (1).