Thin SnTe Nanoplates with Low Carrier Density

Two-dimensional (2D) nonlayered materials usually show structural and physical properties similar to those of their bulk counterparts. Therefore, the physical dimensions of a 2D nonlayered semiconductor are typically regarded as aspects of device architecture rather than intrinsic material properties. SnTe, a prototypical topological crystalline insulator, invariably exhibits substantial p-type bulk conduction with high hole density due to a high concentration of Sn vacancies, regardless of thickness. In this study, we investigate the structural and electronic properties of SnTe nanoplates with varying thicknesses, synthesized in the ambient of chemical vapor deposition experiment. We observe a clear dependence of the extra diffraction spots on nanoplate thickness, revealing a 2D distribution of point vacancies within thin nanoplates. Detailed diffraction analyses combined with thickness simulations reveal a pronounced decrease in Sn vacancy concentration with decreasing nanoplate thickness. Variations in gate modulation efficiency across a series of nanoplate thicknesses further indicate a lower carrier density in thinner nanoplates. Detailed modeling of low-temperature magnetotransport measurements demonstrates the coexistence of metallic bulk and topological surface states with distinct mobilities and densities in thin SnTe nanoplates. These findings imply that, as the thickness of nonlayered semiconductors decreases, their intrinsic physical properties may also evolve─analogous to what is commonly observed in layered semiconductors.