Introduction

This script was made to make the calculation of the optical bang gap (Eg) a bit more streamlined and to make the visualizations uniform.

Simply put, the Eg is the energy difference between the valence band and conduction band of a material. In other words the Eg equates to the minimum amount of energy required for an electron to break free from its bound state. Knowing the value of Eg gives important insight into a materials properties. Depending on the size of the Eg we differentiate materials as conductors, semiconductors and insulators.

There are different approaches for calculating the Eg. In this project I chose the Tauc plot method using calculations for allowed transitions in direct and indirect types of Eg.

Data

For the example data I chose my own experimental data obtained by UV-VIS spectroscopy of transparent titanium dioxide thin films. In these two measurements, ultra-violet and visible light passes through the sample or is reflected off the surface of the sample and we track, using special sensors, how that light changes in intensity in respect to its wavelength. These measurements showed how much of the light dependent on its wavelength was absorbed (Absorbance), reflected (Reflectance) or passed through (Transmittance) the material. From these simple observations we can calculate the optical Eg using the Tauc method.

Tools

Python
Linear regression
Tauc plots
UV-Vis spectroscopy - optical properties of the thin film
Profilometry - thickness of the thin films