Crystal Shape Engineering of Topological Crystalline Insulator SnTe Microcrystals and Nanowires with Huge Thermal Activation Energy Gap

Since different high-symmetrical crystal planes of topological crystalline insulator possess their own topological electronic structure, manipulating crystal shapes with distinct facets of SnTe nanostructures is crucial for the realization of desired topological surface properties. Here, we developed crystal shapes engineering for the controllable synthesis of SnTe microcrystals and nanowires with specific exposed surfaces by optimizing experimental parameters in the chemical vapor deposition process. Crystal shapes of SnTe microcrystals are tailored from {100} surface-covered cubes, {100} and {111} surface-coated truncated octahedron, to a {111} surface-terminated octahedron. Significantly, with gold nanoparticles as the catalyst, two novel SnTe nanowires, octahedron-attached SnTe nanowires, and truncated octahedron-assisted SnTe nanowires, are achieved. The requirement of minimizing the overall surface energy drives the formation of various crystal shapes of SnTe microcrystals and nanowires. In addition, SnTe nanowires possess a huge thermal activation energy gap (350 ± 17 meV), 14 times larger than the energy scale of room temperature. This huge thermal activation energy gap can protect topological surface states of SnTe nanowires against the disturbance of thermal excitation. Our work provides the building block for the realization of unique topological surface effects on specific facets and novel spintronic devices.