Tunable electronic and magnetic properties of single layer CdS via Li substitutional doping: A first-principle study

Abstract

A first-principles theoretical study of the enhanced electronic and magnetic properties of a single-layer CdS (denoted as SL-CdS) was conducted via Li substitutional doping at possible sites. Previous work shows that SL-CdS is a non-magnetic and direct bandgap semiconductor. Our work demonstrated that electronic bandgap tuned to smaller and larger values, e.g., the calculated bandgap (pseudo bandgap) for LiCd (Lih) are 1.80 eV and 1.62 eV, respectively. Local magnetic moment induced via Li atomic doping at possible dopants sites except for Lih. The LiCd gives a maximum magnetic moment of 0.98 μB and shows the half-metallic character with a small dispersion for the spin-down channel at the Γ point. Among all the possible sites, the LiCd in SL-CdS is magnetic and being most favorable thermodynamically under both S-rich and Cd-rich conditions. The LiCd in SL-CdS indicates spin polarization with increased bandgap for spin-up and spin-down channels. In contrast, the LiS induces a magnetic moment of 0.86 μB with a reduced bandgap of 0.60 eV for both the spin-up and spin-down channels. The partial magnetic moment is due to the fact small concentration of the dopant. Interestingly, Lih in SL-CdS shows non-magnetic semiconducting nature with decreased bandgap. For further investigation, we considered the most favorable Cd-Site. For room-temperature ferromagnetism, we did ferromagnetic and anti-ferromagnetic calculations. We considered interactions between two Li atoms substituted at far positions (1, 2) and near positions (1, 3) in SL-CdS. It was found that 2LiCd in SL-CdS at near positions (1, 3) has FM order with Curie temperature (Tc) of 339.95 K at − 5% compressive biaxial strain. The effect of Li doping on electronic and magnetic properties of SL-CdS can help to utilize SL-CdS materials in electronics and spintronics devices applications.