Surface Reconstruction, Oxidation Mechanism, and Stability of Cd3As2

Cadmium arsenide (Cd3As2) has recently attracted considerable interest for the presence of 3D massless Dirac fermions with ultrahigh mobility and magnetoresistance. However, its surface properties are currently largely unexplored both theoretically and experimentally, due to the very large unit cell and the challenging growth of single-crystal samples, respectively. Here, by combining ab initio calculations with surface-science spectroscopic experiments, the presence of a surface reconstruction is unveiled in centimeter-scale (112)-oriented Cd3As2 single-crystal foils produced by the self-selecting vapor growth. Outermost Cd atoms descend into the As-sublayer with a subsequent self-passivation of the dangling bonds with As atoms, forming the triangle lattice previously imaged by scanning tunneling microscopy. Moreover, the oxidation mechanism of this reconstructed surface, dominated by the formation of As-O-Cd bonds, is revealed. Interestingly, it is found that the band structure of the reconstructed surface of Cd3As2 is quite robust against surface oxidation. Both computational and experimental findings point to a successful exploitation in technology of Cd3As2 single crystals.