We study the dielectric function of CuBrxI1−x thin film alloys using spectroscopic ellipsometry in the spectral range between 0.7 eV to 6.4 eV, in combination with first-principles calculations based on density functional theory. Through the comparison of theory and experiment, we attribute features in the dielectric function to electronic transitions at specific k-points in the Brillouin zone. The observed bandgap bowing as a function of alloy composition is discussed in terms of different physical and chemical contributions. The band splitting at the top of the valence band due to spin-orbit coupling is found to decrease with increasing Br-concentration, from a value of 660 meV for CuI to 150 meV for CuBr. This result can be understood considering the contribution of copper d-orbitals to the valence band maximum as a function of the alloy composition.
@article{arxiv.2207.01344,
title = {Dielectric function of CuBr$_\mathrm{x}$I$_{1-\mathrm{x}}$ alloy thin films},
author = {Michael Seifert and Evgeny Krüger and Michael S. Bar and Stefan Merker and Holger von Wenckstern and Harald Krautscheid and Marius Grundmann and Chris Sturm and Silvana Botti},
journal= {arXiv preprint arXiv:2207.01344},
year = {2022}
}
Comments
Michael Seifert and Evgeny Kr\"{u}ger contributed equally. Some typos were corrected and references were added