Ge_1–xSn_x nanorods (NRs) with a nominal Sn content of 28% have been prepared by a modified microwave-based approach at very low temperature (140 °C) with Sn as growth promoter. The observation of a Sn-enriched region at the nucleation site of NRs and the presence of the low-temperature α-Sn phase even at elevated temperatures support a template-assisted formation mechanism. The behavior of two distinct Ge_1–xSn_x compositions with a high Sn content of 17% and 28% upon thermal treatment has been studied and reveals segregation events occurring at elevated temperatures, but also demonstrates the temperature window of thermal stability. In situ transmission electron microscopy investigations revealed a diffusion of metallic Sn clusters through the Ge_1–xSn_x NRs at temperatures where the material composition changes drastically. These results are important for the explanation of distinct composition changes in Ge_1–xSn_x and the observation of solid diffusion combined with dissolution and redeposition of Ge_1–ySn_y (x > y) exhibiting a reduced Sn content. Absence of metallic Sn results in increased temperature stability by ∼70 °C for Ge_0.72Sn_0.28 NRs and ∼60 °C for Ge_0.83Sn_0.17 nanowires (NWs). In addition, a composition-dependent direct bandgap of the Ge_1–xSn_x NRs and NWs with different composition is illustrated using Tauc plots.

中文翻译：

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推动各向异性Ge _{1– x} Sn _x纳米结构的组成极限及其热稳定性的确定

通过改良的基于微波的方法在极低的温度（140°C）下使用Sn作为生长促进剂，制备了标称Sn含量为28％的Ge _{1- x} Sn _x纳米棒（NRs）。即使在升高的温度下，在NRs的成核位置观察到富Sn区域和存在低温α-Sn相也支持了模板辅助的形成机理。研究了两种不同的Ge _{1– x} Sn _x成分的行为，这些成分在热处理时具有17％和28％的高Sn含量，揭示了在高温下发生的偏析事件，但同时也显示了热稳定性的温度窗口。原位透射电子显微镜研究表明，在材料成分急剧变化的温度下，金属锡团簇通过Ge _{1– x} Sn _x NRs扩散。这些结果对于解释Ge _{1– x} Sn _x的明显成分变化以及观察固溶与Ge _{1– y} Sn _y（x > y）的溶解和再沉积相结合而显示出减少的Sn含量非常重要。不含金属锡会导致温度稳定性提高，Ge _0.72 Sn _0.28 NRs的温度稳定性约为70°C，Ge _0.83 Ge的温度稳定性约为60°CSn _0.17纳米线（NWs）。此外，使用Tauc图说明了具有不同成分的Ge _{1– x} Sn _x NR和NW的成分依赖的直接带隙。