Mono-crystalline SnTe with micro-octahedroncharacteristic: One-pot facile synthesis and comprehensive crystallographic evidence

In recent years, topological crystalline insulators have attracted increased attention due to practical demands of tunable electronic, spin electronic and thermoelectric devices. As an important topological crystalline insulator, mono-crystalline SnTe octahedra with {111} dominated surfaces, were successfully synthesized on a large scale via a surfactant-free hydrothermal synthesis route in this work. Important controlling factors for phase and morphology, i.e. reaction temperature, reactant concentration and stoichiometric ratio, are discussed in detail. The results indicated that high temperature is favorable for forming pure phase, and excessive Sn suppresses the appearance of SnTe with octahedral morphology. Lower reactant concentration is beneficial to preparing uniform SnTe octahedra via the selective growth mechanism. Crystallographic characteristics of the SnTe octahedra were investigated using focused ion beam, electron backscattered diffraction and transmission electron microscopy analysis. The hexagonal-like micro-plate (cut from an octahedron) was confirmed as mono-crystalline by the corresponding three Euler angle maps, the Kikuchi diffraction pattern and selected-area diffraction. It can be further deduced from the multiple experimental results that surfaces of octahedral SnTe are dominated by {111} crystallographic planes and the average size is 1–3 μm. Controllable mono-crystalline octahedra would effectively promote the development of topological crystalline insulators and their micro devices.