Structure and lattice symmetry tailoring in monolayer SnTe epitaxially grown on Au(111)

Abstract

SnTe, as one type of topological crystal insulator (TCI), has crystal-symmetry-protected surface states, which is sensitive to its structure and lattice symmetry. Herein, the monolayer SnTe was well synthesized, presenting with tetragonal and hexagonal lattice symmetries, respectively. The lattice symmetry was found to be connected with precursors, as thermal evaporation of SnTe compounds led to a tetragonal type symmetry while co-deposition of Sn and Te elements can synthetize the hexagonal type. As a consequence of lattice mismatch with the underlying Au(111) substrate, SnTe with tetragonal lattice exhibits reconstructive stripe pattern, which would transform into hexagonal lattice symmetry with moiré pattern upon annealing at high temperature. Due to coupling with the substrate, SnTe exhibits metallicity in both symmetries, verified by corresponding differential conductance spectra (dI/dV). Comparative study on Cu(111) substrate was carried out and only copper telluride structures were formed, which may be related to the stronger surface decomposition of SnTe precursors on Cu(111) and direct copper tellurizing. Our work paves a practical way to control the surface structure and lattice symmetry of SnTe, providing a promising candidate for potential TCI applications.