A detailed analysis on optical parameters of spinel structured Mn3O4 thin films deposited by nebulized spray pyrolysis technique

Abstract

Abstract In this work, the role of precursor solution concentration on the diverse optical parameters of nebulized spray deposited spinel structured hausmannite manganese oxide (Mn3O4) thin films derived from the optical measurements are reported for the first time. X-ray diffraction study confirmed that the films belong to the tetragonal structure. This was further substantiated by the Raman measurement where we observe a major peak of single degenerate A1g (symmetry) mode corresponding to Mn–O breathing vibration of Mn2+ ions of spinel Mn3O4. The rod shaped morphology with honey comb pad like feature was identified from the surface morphological study. The strong broad photoluminescence emission peak at 484 nm is associated with the localized levels present near the band gap of Mn3O4. The wettability study indicated that the deposited Mn3O4 films are hydrophilic in nature. The highest optical transmittance of 65.9% was observed for the film and the red shift in transmittance threshold with increasing solution concentration indicated the systematic decrease in optical energy band gap (from 2.93 to 2.43 eV) of the films. The small value of extinction coefficient indicated the perfect surface homogeneity of Mn3O4 films. In addition, various optical parameters such as Urbach energy, plasma resonance frequency, high frequency dielectric constant, optical conductivity, dissipation factor, energy loss functions, lattice dielectric constant, first order linear and third order non-linear susceptibility and non-linear index of refraction of Mn3O4 thin films were calculated and reported for the first time due to variation in solution concentration during deposition. The attempts were made to explain and correlate these results with the help of underlying concepts. The present results will provide new physical insights for the design of any optical device using the spinel structured Mn3O4 films prepared by an amenable technique called nebulized spray pyrolysis.