Preparation, characterization, spectroscopic (FT-IR, FT-Raman, UV and visible) studies, optical properties and Kubo gap analysis of In2O3 thin films

Indium oxide (In2O3) thin films are successfully deposited on microscopic glass substrate at different temperatures by spray pyrolysis technique using Indium acetate as precursor solution. The physical properties of these films are characterized by XRD, SEM, AFM, UV–visible, PL and Photo acoustic measurements. XRD analysis revealed that the films are polycrystalline in nature having cubic crystal structure with a preferred grain orientation along (2 2 2) plane. The average transmittance in the visible region is found to vary from 60% to 93% depending upon the substrate temperature. The complete vibrational analysis has been carried out and the optimized parameters are calculated using HF and DFT (LSDA, B3LYP and B3PW91) methods with 3-21G(d,p) basis set for In2O3. The fundamental frequencies are calculated and assigned according to the experimental frequencies. Furthermore, 13C NMR and 1H NMR chemical shifts are calculated by using the gauge independent atomic orbital (GIAO) technique with HF/B3LYP/B3PW91 methods on same basis set. A study of the electronic properties; absorption wavelengths, excitation energy, dipole moment, Kubo gap (HOMO and LUMO) and frontier molecular orbital energies, are performed by HF and DFT methods. Besides frontier molecular orbitals (FMO), molecular electrostatic potential (MEP) is executed. The thermodynamic properties (heat capacity, entropy, and enthalpy) of the compound are calculated in gas phase.