Electronic structure of crystalline binary and ternary Cd-Te-O compounds

TL;DR

This study uses first principles calculations to analyze the electronic structures of various crystalline Cd-Te-O compounds, revealing their band gaps, density of states, and charge densities, and predicting properties of new materials.

Contribution

It provides detailed electronic structure data for several Cd-Te-O compounds and predicts the optical bandgap of Cd3TeO6, highlighting its semiconducting properties.

Findings

LDA accurately describes insulating behavior of some compounds

LDA underestimates optical bandgap by ~1 eV in certain compounds

Predicted bandgap of 1.7 eV for Cd3TeO6

Abstract

The electronic structure of crystalline CdTe, CdO, $\alpha$-TeO$_2$, CdTeO$_3$ and Cd$_3$TeO$_6$ is studied by means of first principles calculations. The band structure, total and partial density of states, and charge densities are presented. For $\alpha$-TeO$_2$ and CdTeO$_3$, Density Functional Theory within the Local Density Approximation (LDA) correctly describes the insulating character of these compounds. In the first four compounds, LDA underestimates the optical bandgap by roughly 1 eV. Based on this trend, we predict an optical bandgap of 1.7 eV for Cd$_3$TeO$_6$. This material shows an isolated conduction band with a low effective mass, thus explaining its semiconducting character observed recently. In all these oxides, the top valence bands are formed mainly from the O 2p electrons. On the other hand, the binding energy of the Cd 4d band, relative to the valence band maximum, in the ternary compounds is smaller than in CdTe and CdO.