Effect of Cu1+/2+ and C co-doping on the magnetic and optical properties of ZnS with point defects (VZn,Hi): A first-principles study

Abstract

In this paper, the generalized gradient approximation method within the density functional theory was employed to conduct an in-depth investigation into the electronic structure, magnetic coupling mechanism, and optical properties of the ZnS system in the presence of coexisting Cu, C, and H dopants as well as Zn vacancies. The research findings reveal that such coexistence can modulate the band gap of the ZnS system over a wide range. Among them, the system with the coexistence of Cu²⁺, C, and Zn vacancies exhibits unique advantages. This type of system possesses a suitable band gap, and its magnetic ground state demonstrates a significant red shift phenomenon and strong absorption characteristics in the visible light region. Moreover, the relative ratio of the effective mass of holes to that of electrons in this system is at a relatively high level,and the separation of electrons and holes is relatively ideal. As the C doping concentration increases, C-sp³ forms a shallow acceptor level, which can enhance the hole concentration in the valence band and strengthen the p-type conductive property. Furthermore, the system as a whole demonstrates good stability. In terms of the magnetic coupling mechanism, Cu doping with different valence states will induce different magnetic coupling mechanisms in the matrix. The sp³ hybridization of C atoms and Zn vacancies will introduce bound magnetic polarons, thereby exerting an impact on the magnetism of the system. When interstitial H atoms exist in the system, H is easily attracted by S²⁻. Under such circumstances, the Cu²⁺ doped system has a large net magnetic moment, while the Cu¹⁺ doped system is non-magnetic.