In Situ Temperature-Dependent Transmission Electron Microscopy Studies of Pseudobinary mGeTe路Bi2Te3 (m = 3鈥?) Nanowires and First-Principles Calculations

详细信息    查看全文

• 作者：Chan Su Jung ; Han Sung Kim ; Hyung Soon Im ; Kidong Park ; Jeunghee Park ; Jae-Pyoung Ahn ; Seung Jo Yoo ; Jin-Gyu Kim ; Jae Nyeong Kim ; Ji Hoon Shim
• 刊名：Nano Letters
• 出版年：2015
• 出版时间：June 10, 2015
• 年：2015
• 卷：15
• 期：6
• 页码：3923-3930
• 全文大小：519K
• ISSN：1530-6992

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.