Simulation within a DFT framework and experimental study of the valence-band electronic structure and optical properties of quaternary selenide Cu2HgSnSe4

Abstract

We report data of simulation within a density functional theory (DFT) framework, employing different approaches for exchange correlation (XC) potential, of the electronic structure and experimental verification of these band-structure calculations using X-ray photoelectron spectroscopy (XPS) of Cu2HgSnSe4 crystal. The present studies indicate that fair good agreement of total density of states (DOS) with the valence band XPS spectrum of the Cu2HgSnSe4 crystal is derived when DFT simulation is performed within modified Becke-Johnson (mBJ) potential and taking into consideration Hubbard correction parameter U and spin-orbit (SO) coupling (mBJ–U–SO approach). The mBJ–U–SO calculation reveals the best fit of total DOS to the experimental valence band XPS spectrum as well as a fairly good energy gap value for this compound. The present theoretical data indicate that the principal contributors to the Cu2HgSnSe4 valence band are Se 4p states with their main input in upper and central portions of the band, while Sn 5 s and Hg 6 s states make prevailed contributions in its lower portion and the bottom is formed by Hg 5d states. The quaternary Cu2HgSnSe4 selenide is a direct gap semiconductor. Based on the present mBJ–U–SO band-structure data, the main optical constants are calculated indicating that the compound under consideration is a very promising optoelectronic material.