First-principles study of SiC and GeC monolayers with adsorbed non-metal atoms

Chemical adsorption of non-metal atoms may lead to the emergence of novel features in two-dimensional (2D) materials. In this work, the electronic and magnetic properties of graphene-like XC (X = Si and Ge) monolayers with adsorbed H, O, and F atoms are investigated using spin-polarized first-principles calculations. Deeply negative adsorption energies suggest strong chemical adsorption on XC monolayers. Despite the non-magnetic nature of both host monolayer and adatom, SiC is significantly magnetized by H adsorption inducing the magnetic semiconductor nature. Similar features are observed in GeC monolayers upon adsorbing H and F atoms. In all cases, an integer total magnetic moment of 1 mu(B) is obtained, originating mainly from adatoms and their neighbor X and C atoms. In contrast, O adsorption preserves the non-magnetic nature of SiC and GeC monolayers. However, the electronic band gaps exhibit significant reduction of the order of 26% and 18.84%, respectively. These reductions are consequences of the middle-gap energy branch generated by the unoccupied O-p(z) state. The results introduce an efficient approach to develop d(0) 2D magnetic materials to be applied in spintronic devices, as well as to widen the working region of XC monolayers in optoelectronic applications.