Bi trimers and self-limiting Bi-Sb interface formation upon Bi deposition on InSb(111)B surfaces

Investigating metal-semiconductor interfaces is crucial for enabling ultra-thin film growth and tuning the electronic properties. Here we have studied the atomic mechanism of Bi incorporation into the surface of InSb, the III-V semiconductor with the largest spin-orbit coupling, using surface science techniques and theoretical modeling. Bi deposition onto Sb-terminated InSb(111) surfaces at elevated sample temperature results in the formation of Bi monomers ( α -Bi) and Bi trimers ( β -Bi), in a (2 × 2) and (3 × 3) superstructure, respectively. Ab initio calculations for various possible Bi-integration models confirm the atomic arrangement of α -Bi and β -Bi superstructures and their energetically favorable formation. Both structures are based on strong covalent Bi-Sb bonds. This Bi-Sb compound is robust and has self-limiting thickness, which does not increase upon prolonged Bi deposition. On the contrary, Bi deposition at room temperature results in metallic Bi islands and layers of increasing thickness. However, the above-mentioned Bi-Sb compound is found unchanged in thickness after additional Bi deposition at room temperature and subsequent annealing, indicating the presence of a well-defined Bi-Sb interface even between InSb substrates and thicker metallic Bi surface layers. Tunable Bi surface structures and the self-limiting formation of a robust Bi-Sb interface offer a promising pathway towards developing Bi/InSb-based devices that combine a very large spin-orbit interaction with a technologically well-developed semiconductor platform, featuring superior electronic and optoelectronic properties.