Electronic structure of the CdTe(111)A-(2 x 2) surface

Based on data of scanning tunneling microscopy, ab initio calculations of the electronic structure were performed for the first time for four variants of Cd-terminated polar CdTe(111)A-(2 x 2) surfaces, namely, ideal, relaxed, reconstructed with a Cd vacancy, and reconstructed with the subsequent relaxation. In the approximation of a layered superlattice, the surfaces were simulated by a film with a thickness of 12 atomic layers and a vacuum gap of similar to 16 . Dangling bonds of Te atoms were closed by adding, on the opposite side of the film, four fictive hydrogen atoms, each having a charge of 0.5 electrons. Ab initio calculations were performed with the QUANTUM ESPRESSO program based on the density functional theory. In each of the variants, the equilibrium coordinates of 16 (15) atoms of cadmium and tellurium of the upper four freestanding layers were determined. It was shown that the relaxation leads to a splitting of layers of both the unreconstructed and reconstructed surfaces. For four variants of the surfaces, the band structures were calculated and analyzed, as well as the total densities of states of the surfaces and densities of states of individual layers. After the relaxation of the reconstructed surface, the upper two atomic layers 11 and 12 changed their places, which can be responsible for the specific features of the surface structure of these layers.