Robust ferromagnetism and half-metallicity in hydrogenated monolayer-CdS

We present our work on the structural, electronic and magnetic properties of monolayer-CdS which was subjected to bi-axial strain and hydrogenation at possible adsorption sites using the first-principles calculations. The results show that both bulk-CdS and monolayer-CdS are non-magnetic direct (Gamma-Gamma) band-gap semiconductors. By applying a compressive strain up to -10% the monolayer-CdS remain direct band-gap semiconductor with a maximum band gap value of 2.11 eV. In contrast, a semiconductor to metal transition occurred at 17% applied tensile strain. Moreover, hydrogenation on all possible adsorption sites induces ferro-magnetism and p-type conductivity in monolayer-CdS. Among all possible adsorption sites, H added on the Cd-top site is the most probable site showing strong ferromagnetism and half-metallicity. The strong ferromagnetism means 100% spin polarization is retained up to applied bi-axial strain of -5% to +15%. Also, half-metallicity is robust under the bi-axial strain in the range of -4% to +2%. To determine the strength of the exchange-coupling parameter, the FM (ferromagnetic) and AFM (anti-ferromagnetic) coupling between added atoms was investigated under the bi-axial strain of -5% to +5%. Our findings show that H added on the Cd-top site makes it ferromagnetic and half-metallic above room temperature. The maximum Curie temperature T-c = 651.41 K is achieved at a strain of epsilon = -2% of ferromagnetic state. This high Curie temperature has not been achieved for any 2D material to-date. The present work provides a route to harness the ferromagnetism and thermal stability of 2D monolayer-CdS for electronic and spintronic applications.