Controlled Vapor–Liquid–Solid Growth of Long and Remarkably Thin Pb_1–<i>x</i>Sn_<i>x</i>Te Nanowires with Strain-Tunable Ferroelectric Phase Transition

The Pb_1-<i>x</i>Sn_<i>x</i>Te family of compounds possess a wide range of intriguing and useful physical properties, including topologically protected surface states, robust ferroelectricity, remarkable thermoelectric properties, and potential topological superconductivity. Compared to bulk crystals, one-dimensional (1D) nanowires (NWs) offer a unique platform to enhance the functional properties and enable new capabilities, e.g., to realize 1D Majorana zero modes for quantum computations. However, it has been challenging to achieve controlled synthesis of ultrathin Pb_1-<i>x</i>Sn_<i>x</i>Te (0 ≤ <i>x</i> ≤ 1) nanowires in the truly 1D region. In this work, we report on a Au-catalyzed vapor-liquid-solid (VLS) growth of remarkably thin (20-30 nm) and sufficiently long (several to tens of micrometers) Pb_1-<i>x</i>Sn_<i>x</i>Te nanowires of high single-crystalline quality in a controlled fashion. This controlled growth was achieved by enhancing the incorporation of Te into the Au catalyst particle to facilitate the precipitation of the Sn/Pb species and suppress the enlargement of the particle, which we identified as a major challenge for the growth of ultrathin nanowires. Our growth strategy can be easily extended to other compound and alloy nanowires, where the constituent elements have different incorporation rates into the catalyst particle. Furthermore, the growth of thin Pb_1-<i>x</i>Sn_<i>x</i>Te nanowires enabled strain-dependent electrical transport measurements, which shows an enhancement of electrical resistance and ferroelectric transition temperature induced by uniaxial tensile strain along the nanowire axial direction, consistent with density functional theory calculations of the structural phase stability.