Enhanced optoelectrical properties of Mn-doped ZnS films deposited by spray pyrolysis for ultraviolet detection applications

Abstract

In the present study, chalcogenide manganese-doped zinc sulfide (Mn-doped ZnS) films were deposited by spray pyrolysis method at various concentration of Mn2+ ions (0 ≤ Mn2+ ≤ 15 mol%) and the effect of Mn-doping concentration on the photodetection characteristics of the films was investigated. The phase structure, chemical composition and surface morphology of the films were characterized by grazing incidence X-ray diffraction, energy dispersive spectroscopy, and field emission scanning electron microscopy. The results confirmed the stable zinc blende phase, nanocrystalline structure and the nearly stoichiometric ratio of elements, as well as uniform and well adherent of the films to the substrates. The Mn2+ concentration-dependent optical and electrical properties of the films were investigated using ultraviolet-visible spectroscopy, photoluminescence, and current-voltage measurements. The photoluminescence spectra exhibited two emission peaks located at ultraviolet (UV) and orange regions. The optical density, optical band gap energy, and Urbach energy were also evaluated. By increasing Mn2+ content, a slight decrease in the optical band gap energy was observed, while the Urbach energy broadened, gradually. Therefore, a linear relationship between the band gap energy and Urbach energy was found. Moreover, the relevance of the steepness parameter and electron-phonon interaction was studied. The optoelectrical analysis in the dark and under light irradiation with different wavelengths revealed the visible-blind nature of the samples. The electrical characteristics of the fabricated UV detectors featured tremendous photocurrent gain and photo-response switching behavior to UV-A irradiation.