Phase tuning of nebulized spray deposited manganese oxide thin films by the effect of annealing temperature and their linear and non-linear optical parameters

In this work, the annealing temperature induced effect on the formation of various forms of manganese oxide (Mn3O4, Mn3O4:Mn2O3 and Mn2O3) thin films were deposited on glass and quartz substrates by nebulized spray pyrolysis technique. The X-ray diffraction patterns confirm that the film exhibited a phase transition from tetragonal-Mn3O4 to cubic-Mn2O3 structure. From the micro-Raman spectra, the A1g, T2g and Eg modes of Mn3O4 and Mn-O stretching vibration of Mn2O3 are identified. The surface morphological study showed the formation of granular particles and nanorods on the surface. The observed peaks corresponding to Mn2+ and Mn3+ ions in the XPS study are confirmed the formation of Mn3O4 in the as-deposited film. The continuous reduction in optical transmittance of the prepared films was observed as a function of annealing temperature. The in-depth optical parameters like optical energy band gap, dielectric constant, skin depth, Urbach energy, steepness parameter and optical conductivity of the films were extracted from the optical data as a function of annealing temperature. The as-deposited Mn3O4 film has an excellent surface quality due to the lower extinction coefficient value. The Mn2O3 film is highly active in the near-infrared region, because of higher optical conductivity compared to the Mn3O4 films. The obtained optical parameters were further analyzed to determine the non-linear refractive index, linear and third order non-linear optical susceptibility of the films.