Transition from antiferromagnetic metal to room-temperature ferromagnetic semiconductor in monolayer CrTe2 via Li adsorption

The lacking of two-dimensional intrinsic room-temperature ferromagnetic semiconductors severely restricts the development of future low-dimensional semiconductor spintronic devices. Is it possible to indirectly obtain ferromagnetic semiconductors that work at room temperature from the available antiferromagnetic metal through quantum state regulation? Here we employ the density functional theory to systematically investigate the electronic and magnetic properties of the 1T-${\mathrm{CrTe}}_2$ monolayer under Li atomic adsorption. The 1T-${\mathrm{CrTe}}_2$ monolayer is an antiferromagnetic metal, which is not suitable for semiconductor spintronic device applications. Interestingly, a desired room-temperature ferromagnetic semiconductor with a large out-of-plane piezoelectricity, i.e., the ${\mathrm{LiCrTe}}_2$ monolayer, is achieved successfully after one Li atomic layer is adsorbed at the 1T-${\mathrm{CrTe}}_2$ surface. The Curie temperature is above room temperature and reaches 392 K, which remains above room temperature and increases with the increase of in-plane biaxial tensile strain. A semiconductor-to-metal conversion and a change of the orientation of the easy magnetization axis can be realized with robust room-temperature ferromagnetism through electrostatic doping. Our results indicate that the atomic adsorption is an effective strategy to achieve van der Waals room-temperature ferromagnetic semiconductors.