Investigation in Optical Properties of Magnesium Doped Nanostructure Zinc Oxide Films by Pulsed-Laser Deposition Method

Abstract

In the present work, films have been grown under various deposition conditions in order to understand the effect of processing on the film properties and to specify the optimum condition, namely substrate at temperatures of 400^°C, oxygen pressure (2×10^-1) mbar, laser fluence 0.4 J/cm², and with different Mg contents (x=0, 0.02, 0.04, 0.06), using double frequency Q-switching Nd:YAG laser beam (wavelength 532nm), repetition rate (1-6) Hz and the pulse duration of (10 ns), to deposit Mg_xZn_1-xO films glass substrates with thickness of about 200 nm for all Mg_xZn_1-xO films at different deposition condition and the number of laser pulses was 100 pulses. The optical properties were characterized by the transmittance and absorption spectroscopy at room temperature, measured in the range from 300 to 900 nm. For all the films, the average transmittance in the visible wavelength region λ = (400 - 800) nm is greater than 70%. The maximum value of the transmittance (greater than 95%) was obtained for these films. E_g values of Mg_xZn_1-xO thin films were (3.37, 3.59, 3.82, and 4.00) eV corresponding to the Mg-content (x = 0, 0.02, 0.04 and 0.06), respectively. In other word, the optical band gap of Mg_xZn_1-xO thin films become wider as Mg-content increases and can be precisely controlled between 3.37 and 4.00 eV. The refractive index of the films ranged from 2.1-2.8 between 350nm to 900nm. The extinction coefficient and the optical conductivity of the films increases with doped. The real dielectric constant and the imaginary part increases when the doped rate increasing.

Keywords: Optical properties, Pulsed-laser deposition, Mg_xZn_1-xO Nanostructures.