文摘
Phase-change nanowires (NWs) have emerged as critical materials for fast-switching nonvolatile memory devices. In this study, we synthesized a series of mGeTe路Bi2Te3 (GBT) pseudobinary alloy NWs鈥擥e3Bi2Te6 (m = 3), Ge4Bi2Te7 (m = 4), Ge5Bi2Te8 (m = 5), Ge6Bi2Te9 (m = 6), and Ge8Bi2Te11 (m = 8)鈥攁nd investigated their composition-dependent thermal stabilities and electrical properties. As m decreases, the phase of the NWs evolves from the cubic (C) to the hexagonal (H) phase, which produces unique superlattice structures that consist of periodic 2.2鈥?.8 nm slabs for m = 3鈥?. In situ temperature-dependent transmission electron microscopy reveals the higher thermal stability of the compositions with lower m values, and a phase transition from the H phase into the single-crystalline C phase at high temperatures (400 掳C). First-principles calculations, performed for the superlattice structures (m = 1鈥?) of GBT and mGeTe路Sb2Te3 (GST), show an increasing stability of the H phase (versus the C phase) with decreasing m; the difference in stability being more marked for GBT than for GST. The calculations explain remarkably the phase evolution of the GBT and GST NWs as well as the composition-dependent thermal stabilities. Measurement of the current鈥搗oltage curves for individual GBT NWs shows that the resistivity is in the range 3鈥?5 m惟路cm, and the resistivity of the H phase is lower than that of the C phase, which has been supported by the calculations.