Synthesis and surface-state transport of ultrathin topological crystalline insulator SnTe films

SnTe is a topological crystalline insulator that exhibits crystal symmetry protected surface states that may impact the development of novel electronic devices. With a practical implementation of these materials in view, we introduce a new way to synthesize ultrathin films of SnTe ($\sim$ 10 unit cell thick) for transport measurements on SrTiO$_{3}$ (001) substrates using molecular beam epitaxy. Commonly observed bulk conduction by Sn vacancies is greatly suppressed in these ultrathin films. We observe that the surface states near the SnTe/vacuum interface are depleted due to band bending. Importantly, we find that the surface-state carriers are buried and protected from depletion at the SnTe/SrTiO$_{3}$ interface and dominate the measured conductance at thicknesses smaller than 40 unit cells, and that these carriers have a high density and mobility.