Optoelectronic properties of sprayed MnxZn1−xO optical waveguide thin films: Refractive index and birefringence tailoring

Abstract

This study investigated the properties of MnxZn1−xO thin films with varying Mn concentrations (x = 0, 0.03, 0.05, 0.07, and 0.09) fabricated via spray pyrolysis on glass substrates. The films exhibited a wurtzite structure with (002) orientation and decreasing crystal size. By utilizing the first derivative technique, it was found that the optical gap energy increased linearly by 0.06 eV, starting at 3.24 eV. Photoluminescence spectra deconvolution revealed the presence of multiple point defects, particularly VO, which correlated with the increase in optical gap energy. The Hall effect-based electric measurements indicated a decline in charge carriers and mobility accompanied by an increase in magnetoresistance and resistivity. The SEM observations revealed a morphological transition from flaky to dome-shaped grains with a reduction in size. The waveguiding properties of the films were studied using the m-lines technique, which showed that all films were dual-mode waveguides. The ordinary and extraordinary refractive indices increased to 2.0019 and 2.0005, respectively with Mn doping, while the birefringence inversion began at Mn0.05Zn0.95O and remained constant at Mn content of 7 and 9 at.%. Overall, these findings provide valuable insights into the structural, optical, electrical, and waveguiding properties of MnxZn1−xO thin films, which could be useful for the development of new optoelectronic devices.