Optical and electrical properties of highly ordered α-, γ- and α + γ-MnS films deposited by reactive sputtering technique

Abstract

In this article, we have studied the detailed electrical and optical characteristics of crystalline α-, γ-, and α + γ-manganese sulfide (MnS) thin films. Highly ordered thin films of α-, γ-, and α + γ-MnS were prepared by direct current reactive sputtering on glass substrates at different substrate temperatures (room temperature to 400 °C) while maintaining other parameters at optimized values. The X-ray diffraction measurement revealed the synthesis of γ-, α + γ-, and α-phase of MnS thin films with preferred orientations (002), (002) + (200), and (200), respectively. The morphological and topographical results demonstrated that the particle size as well as the average roughness of MnS samples varied as a linear function of the substrate temperature. The x-ray photoelectron spectroscopy study revealed that the γ-MnS sample prepared at room temperature has the lowest oxygen related vacancy (12.7%). The optical characteristics such as refractive index n, extinction coefficient k, and optical bandgap Eg are determined in the broad wavelength range of 246–688 nm using spectroscopic ellipsometry. Moreover, the nonlinear refractive index n2 and the third-order nonlinear optical susceptibility χ(3) are determined using the Tichy–Ticha relation and Wemple–Didomenico parameters. The ratio of the carrier concentration to the effective mass N/m* has also been determined, indicating best electrical properties for γ-MnS films. The current research on the optical and electrical properties of highly ordered α-, γ-, and α + γ-MnS thin films is expected to have a significant impact on advanced optoelectronic, photonic, and energy applications.