Optoelectronic and birefringence properties of weakly Mg-doped ZnO thin films prepared by spray pyrolysis

Mg x Zn 1 −x O thin films were deposited on glass substrate with x varied between 0 . 01 and 0 . 05 by spray pyrolysis at a temperature of 450 °C. The structural investigation showed that all thin films had ZnO wurtzite structure with a preferred (002) orientation. The gap energy was calculated using Tauc’s plot, and it decreased over the Mg content by 0.07 eV. The charge carriers’ density dropped by an order of 10 5 as Mg content increased whereas the resistivity and the mobility increased. SEM observations revealed a significant difference between undoped and doped thin films. A 632.8 nm laser source prism coupler revealed 2 optical modes for every thin film in each Transverse Electric and Transverse Magnetic mode, and the birefringence of the Mg-doped films was positive. Both ordinary and extraordinary refractive indices were found to decrease as the Mg content increased. Great intention has been paid to the relation between the refractive, charge carriers’ density, and the optical band gap.