Complex dielectric function, Cole-Cole, and optical properties evaluation in BiMnO3 thin-films by Valence Electron Energy Loss Spectrometry (VEELS) analysis

Valence Electron Energy Loss Spectrometry-Transmission Electron Microscopy (VEELS-TEM) analyses were found to provide important information on optical properties and the dielectric function of BiMnO3 thin films grown, via radio frequency (RF) magnetron sputter-deposition on SrTiO3 substrates. The research described in this article involved using Kramer's-Kronig analysis to determine bandgap, complex dielectric function, and static dielectric constant, epsilon* = 4.68 of the grown BiMnO3 thin films. The reflection coefficient Gamma l of the BiMnO3 thin films was used to elucidate the reflection loss in the BiMnO3 thin films. The bandgap energy of the films was determined using a polynomial fit in the energy loss function (ELF) plot with an Eg = 1.63 eV. The scope of the Cole-Cole plot demonstrates the bandgap and the plasmon region in the BiMnO3 films, which is reported here for the first time. A key contribution of this article relates to describing formulations used for transforming the experimentally obtained dielectric constant components of the BiMnO3 films to produce Cole-Cole plots and applying Kramers-Kronig analysis to transform a single scattering energy loss function, to enable determination of the complex dielectric function epsilon ' and epsilon '' and structure of BiMnO3 films.