Eur. Phys. J. B (2017) 90: 11
https://doi.org/10.1140/epjb/e2016-70061-3

Regular Article

Electronic and optical properties of CuGaS₂ nanowires: a study of first principle calculations

¹ Department of Physics, College of Technical and Engineering, Saveh Branch, Islamic Azad University, Saveh, Iran
² Plasma Physics Research Center, Science and Research Branch, Islamic Azad University, P.O. Box 14665-678, Tehran, Iran
³ Physics Group, Qazvin Branch, Islamic Azad University, Qazvin, Iran

^a e-mail: mrazavi@srbiau.ac.ir

Received: 27 January 2016
Received in final form: 20 July 2016
Published online: 18 January 2017

Abstract

In this work we study the electronic and optical properties of fully relaxed CuGaS₂ nanowires using the pseudo-potential density functional method. In our calculations we have investigated nanowires with two shapes of hexagonal and triangular with their corresponding diameters in the order of 8 to 15 Å in (1–10) growth direction. For CuGaS₂ bulk, the geometrical parameters such as anion displacement and equilibrium lattice constant agree well with other theoretical and experimental results. We have shown that for the CuGaS₂ nanowires, there is an important contraction of the Cu-S and Ga-S bond lengths in the wires of 2.1% and 1.24% of the bulk value. In addition, in this manuscript the electronic properties such as band structures and atom-projected density of states have been examined. Our results show that while the nanowire diameter increases, the band gap decreases. From partial density of states we found that the greatest valence bands involve atoms which are placed at the surface. The optical constants, the dielectric function, reflectivity, refractive index and absorption of the nanowires have been analyzed. The results show that compared to the CuGaS₂ bulk, the corresponding peaks of dielectric functions of CuGaS₂ nanowires are blue-shifted. The calculations reveal that the dielectric functions of the nanowires augment while the nanowires’ size increases. It is also found that the peaks related to optical parameters of nanowires are affected by the diameter of the nanowire.