Microstructural, optical, photoluminescence and electrical studies of electrosynthesized S@MnO₂ composite film for photosensing and optoelectronic applications

In this report, we have prepared sulfurized MnO₂ thin film, Mn_xS_1-xO (0.0 ≤x≤0.1) with the aid of a simple electrodeposition process. A systematic study on their microstructure, optoelectronic and photoluminescence properties has been performed. X-ray diffractometery study unveiled the formation of tetragonal and cubic phases of α-MnO₂ and MnS, respectively with some traces of S-nanoparticles. Successful incorporation of S-atom and phase composition of the samples were also reaffirmed with the aid of energy dispersive x-ray and Raman spectroscopic measurements. Optical measurements of the samples revealed the sulfurization influences on the transparency and darkness of the deposited MnO₂ host film, confirming the dopant's modulation of the host's surface and internal microstructure. It also showcased its impacts on the modulation of the host films' band structure (band gap range: 3.5–4.3 eV) for optoelectronic response tailoring. Photoluminescence spectroscopy measurement of the samples revealed varying intrinsic defect states resulting into deep level photoemissions attributable to the display of a strong emission peak, each at the UV and the visible regions of the spectrum. It also unveiled the tailoring of oxygen vacancy concentration and optoelectronic state of MnO₂ with S-incorporation. The study on UV sensing reveals that the sulfurized MnO₂ thin film-based photodetector can possess values of photosensitivity (65 %), responsivity (2.85⨯10⁻² AW^{− 1}) external quantum efficiency (12 %), and detectivity (2.87⨯10⁸ Jones). Additionally, a potential mechanism for ultraviolet photodetector performance is unveiled in the work.