Thermal stability of Te nanowires and their crystallography-determined surface evolution at elevated temperatures

Nanowires are fantastic nanostructures for designing new functional devices because of their extraordinary properties. However, nanowires usually suffer pronounced size and surface effects with decreasing diameter size. Whether their structure and thermal stability can still fill the requirements of practical applications is a critical issue to be figured out. Herein, Te nanowires with diameters ranging from sub-10 to over 80 nm are used as samples to probe into this issue. In situ heating experiments are performed on these Te nanowires using an aberration-corrected transmission electron microscopy combined with a chip-based heating holder. It is found that Te nanowires suffer sublimation at elevated temperatures rather than melting, showing size-dependent sublimation scenarios. The Te nanowires with diameter smaller than 20 nm sublimate below 205 °C, while the larger ones with diameter around 85 nm require a higher temperature of around 225 °C. During sublimation-induced shape evolution, the interfacial wetting equilibrium and crystal orientations play critical roles, leading to the formation of spherical surfaces or featured facets at the free surfaces. A mean contact angle of 107.5° is determined at the C–Te interface when the crystalline Te nanowires stay in a quasi-liquid equilibrium state. However, once the crystalline feature is overwhelming, e.g., at moderate temperatures, the ( $10\overline{1}1$), ( $11\overline{\text{2}}0$), and ( $10\overline{\text{1}}0$) facets govern the free surface, despite the wetting condition at the interfaces.