Modeling the cobalt deposit on the AlN (0001)-(2 × 2) surface: Density functional theory studies

Abstract

Structural, electronic and magnetic properties of the cobalt (Co) adsorption and incorporation on the AlN (0001)-(2 × 2) surface have been investigated using spin-polarized first-principle total-energy calculations. The exchange–correlation energies are treated within the generalized gradient approximation. Provided that Co is a transition metal with highly correlated electrons, the Hubbard correction is considered with U = 1 eV. The magnetic properties have been investigated considering different magnetic configurations and different coverages. In the Co adsorption, a ferromagnetic (FM) behavior is obtained for coverages from ¼ monolayer (ML) to 1 ML. Concerning the Co incorporation, we observed: FM, antiferromagnetic (AFM) and non-magnetic (NM) behavior at low, intermediate and high coverages, respectively. In the Co substitution, the ¼ an ¾ ML of coverage are FM and the ¼ and ¾ ML of coverage are AFM. We employed the surface formation energy formalism to investigate the thermodynamic stability of the different surfaces. According to the formalism, Co deposit takes place at Co-rich and Al-poor conditions. The DOS and PDOS indicate that the 1st ML of the surfaces is metallic and the lower layers are semiconductor.