Absence of Mn emission in MnxZn(1-x)S thin films grown by spray pyrolysis technique

Highlights: • Spray deposited MnZnS thin films have exhibited mixed phase. • From PL, enhanced blue emission from Mn doped ZnS films was observed. • Surface bound doping of manganese on ZnS is responsible for orange emission quenching. • XPS analysis revealed +2 oxidation state of Mn. In the present investigation, the effect of manganese (Mn) dopant on zinc sulfide (ZnS) thin films used for blue light emitting diode was studied. The basic studies on the structural and morphological properties showed good crystallinity up to 2 at % Mn concentration. Samples were studied for the presence of defects using models of Urbach energy and near-edge absorptivity ratio (NEAR). Upon manganese doping, enhancement in the blue emission (in the wavelength region ~ 400 nm) was observed, and interestingly, the Mn related orange emission was not observed. Here, we explained the possible reasons for the suppression of this signature orange emission. Present work is compared with various other reports on manganese doped zinc sulfide (Mn_xZn_(1-x)S). The properties of the MnZnS films were characterized using spectroscopic techniques like static and time resolved photoluminescence (TRPL) along with X-Ray photoelectron spectroscopy (XPS). Measured lifetime of defects was in several hundreds of pico-second. From the spectroscopic characterizations, anomalous behavior of Mn related defects in the MnZnS thin films were explained. An extensive study on XPS of the prepared Mn_xZn_(1-x)S thin film gave greater insight to the possible mechanism for this anomalous luminescence behavior.