Oxide Decomposition and Sn Surface Segregation on Core/Shell Ge/GeSn Nanowires
Oxide Decomposition and Sn Surface Segregation on Core/Shell Ge/GeSn Nanowires
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DOI：
10.1021/acsaelm.2c01061
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发表时间：
2022-11
影响因子：
4.7
通讯作者：
M. Braun;J. Lentz;Ishaa Bishnoi;A. Meng;L. Casalena;Huikai Cheng;P. McIntyre
中科院分区：
文献类型：
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作者：
M. Braun;J. Lentz;Ishaa Bishnoi;A. Meng;L. Casalena;Huikai Cheng;P. McIntyre
亚稳Ge_（1-x）Sn_x（x> 0.1）合金是一种具有直接带隙的IV族合金，是一种非常有意义的光电材料。锗芯/锗-锡同轴异质结构提供了一个机会，研究锡表面偏析从Ge 1-xSnx合金在技术上有趣的组成范围，超过了最大的固体溶解度的锡在金刚石立方结构锗。我们调查的退火特性的锗锡表面和原生氧化物的锡含量在2至12原子%的范围内的初始条件范围从故意的空气暴露到表面无氧化物的纳米线。对于暴露在空气中的样品，我们显示了存在的富锡氧化物，表现出一个组合物依赖的温度在沉积后退火的XPS室中的热分解。在研究的Sn组合物的范围内，氧化锡和氧化锗的分解温度被发现是相同的，表明单相氧化物，其中两个组件同时分解。利用名义上的空气自由转移的新鲜合成和快速热退火的Ge/GeSn纳米线，我们研究了氢和真空（150毫托）退火的影响，并显示抑制Sn偏析的GeSn壳表面时，表面氧化物的形成。退火过程中表面氧化物的形成进一步抑制了Sn表面偏析，并且与氢退火相比，允许在纳米线表面形态发生变化之前退火温度窗口增加约175 °C，从而提高了许多器件制造工艺所需的热稳定性。
As a direct bandgap Group IV alloy, metastable Ge1–xSnx(x> ∼0.1) is an extremely interesting optical and electronic material. Germanium core/germanium-tin coaxial heterostructures offer an opportunity to study Sn surface segregation from Ge1–xSnxalloys in the technologically interesting composition range that exceeds the maximum solid solubility of tin in diamond cubic structure germanium. We investigate the annealing characteristics of the germanium-tin surface and native oxide for tin contents in the range of 2 to 12 at% for initial conditions ranging from intentional air exposure to surface oxide-free nanowires. For air-exposed samples, we show the presence of a tin-rich oxide that exhibits a composition dependent temperature for thermal decomposition during postdeposition annealing in the XPS chamber. Across the range of Sn compositions investigated, the decomposition temperatures of tin oxide and germanium oxide were found to be the same, indicating a single-phase oxide in which both components decompose simultaneously. Utilizing nominally air-free transfer of freshly synthesized and rapid thermally annealed Ge/GeSn nanowires, we investigated the effects of hydrogen and vacuum (∼50 mTorr) annealing and show the inhibition of Sn segregation to the GeSn shell surface when a surface oxide forms. Formation of a surface oxide during an anneal inhibits further Sn surface segregation and, compared to hydrogen anneals, permits an approximately 175 °C increase in the annealing temperature window before changes occur in the nanowire surface morphology, thus promoting thermal stability needed for many device fabrication processes.