Automated method for the determination of the band gap energy of pure and mixed powder samples using diffuse reflectance spectroscopy

Abstract

An automated method to determine the band gap energy (Eg) of pure and mixed powder compounds using diffuse reflectance spectroscopy is presented. This method is based on a five-step algorithm that mimics the judgment made by an expert analyst in identifying the linear segments in Tauc plots and subsequent estimation of the Eg value. It is demonstrated that the method to estimate Eg by intersecting the straight-line fit of the Tauc segment with the photon energy axis is not appropriate for those samples containing more than one optical absorbing phase because systematic underestimation of the Eg value results. The automated method accounts for such cases by introducing a base line function. The robustness of the implemented algorithm was tested using three model systems, ZnO-Al2O3, ZnO-CoO and ZnO-CdO. The estimated Eg's using the automated method differ in less than 1% than those obtained by its manual counterpart.