Temperature induced bandgap tuning and structural evolution in electrochemically deposited nanocrystalline mgs thin films

Abstract

This study presents the synthesis and characterization of nanocrystalline magnesium sulfide (MgS) thin films prepared via the electrochemical deposition technique at varying precursor temperatures. Structural analysis using X ray diffraction (XRD) confirms the polycrystalline nature of all deposited samples, with four distinct diffraction peaks indexed to the (011), (111), (200), and (211) planes. Although bulk MgS typically adopts a cubic rock salt structure, the observed indexing suggests possible variations in symmetry or phase composition influenced by the deposition conditions. Electrical characterization reveals a direct proportionality between resistivity and both temperature and film thickness, with resistivity values increasing from 74.97 × 107 Ω·cm to 79.88 × 107 Ω·cm as the deposition temperature was raised from room temperature to 45 °C. This trend is attributed to changes in grain size and structural defects that impede charge carrier mobility in thicker films. Optical analysis shows high transparency in the visible spectrum (400 to 700 nm), with absorbance values remaining low (0.1 to 0.4 a.u.). Notably, increasing the deposition temperature from room temperature to 45 °C resulted in a significant optical bandgap shift from 1.50 eV to 2.38 eV. These findings indicate that higher temperature MgS films are excellent candidates for UV photodetectors and window layers in photovoltaic cells due to their expanded transparency range.