Ab initio study of optoelectronic and magnetic properties of Mn-doped ZnS with and without vacancy defects

Abstract

The effect of vacancy defects on optoelectronic and magnetic properties of Mn-doped ZnS have been systematically investigated using first principle approaches. A single Mn substitution at Zn site induces a spin-polarized ground state in pure ZnS with total magnetization 5 . Our results for magnetic coupling show that the coupling between Mn spins in pure Mn doped ZnS is antiferromagnetic under the super-exchange mechanism. The existence of native defects has a great influence on the magnetic ground state of Mn-doped ZnS. In particular, a p -type defect such as Zn vacancy play a crucial role in stabilizing ferromagnetic ground state while n-type defect, such as S vacancy, has no effect on the magnetic ground state i.e. the interaction between two Mn spins with S-vacancy remain antiferromagnetic. Furthermore, optical properties such as dielectric functions, absorption coeffiecients, reflectivity and transmissitivity for Mn doped systems with and without vacancy defect were also studied, and we found that an absorption peak was obtained in the infrared region which is attributed to the defect states introduced by Zn vacancy in the system. In a S-vacancy defect system, the peaks in the near infrared and visible region are due to donor states introduced by S vacancy defect and these peaks are produced by electrons flipping from a spin up state to a spin down state. Finally, we also correlated the magnetic interactions with the d–d optical transition in pure Mn-doped ZnS and found that the d–d transitions during optical absorptions are red shifted and blue shifted in FM and AFM coupled Mn ions pair, which is in good agreement with the experimental observations. This study may help to understand the behavior of optical and magnetic properties of DMS under vacancy defects.

Realizing Red Mechanoluminescence of ZnS: Mn2+ Through Ferromagnetic Coupling

“…These experimental results agree well with those previously reported theoretical studies. [41,42] The temperature-dependent PL spectra of the ZnS:3.0%Mn 2+ @TCRA sample at the excitation wavelengths of 342 and 493 nm are presented in Figure 4a,b, respectively. The PL spectra comprise the yellow and red emission bands at all the testing temperatures (80-480 K).…”

Induced ferromagnetism in Ni(II) doped ZnO monolayers via Al co-doping and their optical characteristics: ab initio study

“…To shed light on the magnetic characteristics shown by ZnO nanostructures, many theoretical frameworks, such as super-exchange, double-exchange, Ruderman-Kittel-Kasuya-Yosida (RKKY), intrinsic exchange and bound magnetic polaron (BMP), have been put forward [19][20][21][22]. It has been discovered, both experimentally and theoretically, that certain defects, such as metal clustering, vacancies or metal or nonmetal co-doping, may alter the magnetic characteristics of diluted magnetic semiconductors (DMSs) [23][24][25]. Many DMSs, including Co-doped ZnS, Codoped ZnO, Co(II)-CdS nanowires, Ni-doped ZnO, and Mn(II)-doped ZnTe thin films were shown to have RT ferromagnetism induced by n-type co-dopants such as Al(III) [26][27][28][29][30][31][32].…”

Dopant Cluster Formation and Exchange Spin Coupling as Limiting Factors for the Magnetic Activity of Mn-Doped ZnS Quantum Dots

“…Our work follows upon earlier theoretical studies on the optical properties of Mn-doped ZnS nanostructures ,,,− but focuses on the magnetic properties in the ground state and on Mn cluster formation. We investigate a Zn 135 S 116 Cl 36 QD with a diameter of approximately 2 nm and introduce one, three, and five Mn atoms placed at high symmetry positions in the crystallographic (001) plane.…”