Local ordering in Ge/Ge–Sn semiconductor alloy core/shell nanowires revealed by extended x-ray absorption fine structure (EXAFS)
Local ordering in Ge/Ge–Sn semiconductor alloy core/shell nanowires revealed by extended x-ray absorption fine structure (EXAFS)
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DOI：
10.1063/5.0136746
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发表时间：
2023-02
影响因子：
4
通讯作者：
J. Lentz;J. Woicik;Matthew Bergschneider;Ryan C. Davis;Aranyak Mehta;Kyeongjae Cho;P. McIntyre
中科院分区：
文献类型：
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作者：
J. Lentz;J. Woicik;Matthew Bergschneider;Ryan C. Davis;Aranyak Mehta;Kyeongjae Cho;P. McIntyre
半导体合金中的短程原子有序是一个相对未探索的主题，可能会促进具有意想不到性能的新材料的设计。在这里，当地的原子有序的Ge-Sn合金，IV族系统，是有吸引力的，其增强的光电性能，通过直接的差距，锡浓度超过10000原子。%.在体Si或Ge衬底上生长期间施加在Ge-Sn薄膜上的大量失配应变可以诱导缺陷形成;然而，失配应变可以通过在Ge纳米线上生长Ge-Sn合金膜来调节，Ge纳米线有效地充当弹性顺应衬底。在这项工作中，Ge核/Ge 1 −xSnx（x <$0.1）壳纳米线的特征在于扩展的X射线吸收精细结构（EXAFS），以阐明其局部原子环境。同时拟合的高质量EXAFS数据收集在Ge K-边缘和Sn K-边缘揭示了一个大的（约40%）不足的Sn在第一配位壳周围的Sn原子相对于随机合金，从而提供了第一个直接的实验证据显着的短程有序的半导体合金系统。从EXAFS测量与密度泛函理论模拟的路径长度数据的比较提供合金原子结构与这一结论一致。
Short-range atomic order in semiconductor alloys is a relatively unexplored topic that may promote design of new materials with unexpected properties. Here, local atomic ordering is investigated in Ge–Sn alloys, a group-IV system that is attractive for its enhanced optoelectronic properties achievable via a direct gap for Sn concentrations exceeding ≈10 at. %. The substantial misfit strain imposed on Ge–Sn thin films during growth on bulk Si or Ge substrates can induce defect formation; however, misfit strain can be accommodated by growing Ge–Sn alloy films on Ge nanowires, which effectively act as elastically compliant substrates. In this work, Ge core/Ge1−xSnx ( x ≈ 0.1) shell nanowires were characterized with extended x-ray absorption fine structure (EXAFS) to elucidate their local atomic environment. Simultaneous fitting of high-quality EXAFS data collected at both the Ge K-edge and the Sn K-edge reveals a large (≈ 40%) deficiency of Sn in the first coordination shell around a Sn atom relative to a random alloy, thereby providing the first direct experimental evidence of significant short-range order in this semiconductor alloy system. Comparison of path length data from the EXAFS measurements with density functional theory simulations provides alloy atomic structures consistent with this conclusion.