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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. [ABSTRACT FROM AUTHOR]

Single crystalline α- and γ-MnS thin films have been deposited on Si and ITO substrates by reactive DC sputtering (Ar:H2S 2:1) of a manganese target for electrochemical energy storage application. We found that working pressure was one of the major parameters while optimizing the crystallinity of thin films, whereas the phase tuning (γ to α) was primarily controlled by temperature variations. The temperature was varied from RT to 450 °C, keeping the gas pressure constant at 10 mTorr optimized value, resulting in a transition between two different polymorphs of MnS as confirmed by XRD results. AFM and contact angle measurements were also performed to study the surface roughness, wetting properties, and surface energy calculations of prepared thin films. α-MnS films prepared at 400 °C were found to have a maximum contact angle of 118° and a minimum free surface energy (γSV) of 8.38 mN/m. Moreover, we have also studied the phase dependent electrochemical properties and found that γ-MnS thin films prepared at ambient substrate temperature displayed the highest specific capacitance of 178.3 F/g at a scan rate of 5 mV/s with superior charge-discharge rates in neutral electrolytes. As the substrate temperature was increased to 300 °C, we observed a continuous decrease in the respective specific capacitance values, and α-MnS electrodes were found to have a minimum specific capacitance of 120 F/g. The enhanced electrochemical performance of γ-MnS thin films can be attributed to the superior water interacting properties (θw = 90.4°) and its wurtzite structure, which enables easy penetration of electrolytes into the active materials. [ABSTRACT FROM AUTHOR]