Anharmonicity and local lattice distortion in strained Ge-dilute Si1-xGex alloy
Anharmonicity and local lattice distortion in strained Ge-dilute Si1-xGex alloy
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应变Ge稀Si1-xGex合金的非谐性和局部晶格畸变
DOI：
10.1016/j.jallcom.2015.08.253
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发表时间：
2016
影响因子：
6.2
通讯作者：
Dongliang Chen
中科院分区：
文献类型：
--
作者：
Juncai Dong;Zhiying Guo;Xiaoli Zhang;Pengfei An;Yu Gong;Hailiang Zhu;Pengshan Li;Dongliang Chen
利用Ge K边扩展X射线吸收精细结构测量结合从头算分子动力学模拟研究了应变稀Ge Si 1xGex合金的非谐性和局域晶格畸变.明显的不对称性是第一次揭示GeeSi的第一nearestneighbor（NN）的分布，即使在室温下，与理论模拟吻合得很好。与谐波近似相比，非谐性对GeeSi第一NN键距贡献了0.011 μ m的额外位移，进一步发现这对定性变化至关重要（即，收缩或拉伸）的GeeSi第二NN键距相对于体Si中相应的SieSi键距。由于更高NN壳的修改是由NN键距拉伸和四面体键角偏差之间的竞争引起的，因此这些结果表明，非谐性对于正确确定局部应变调节模式以及基底效应至关重要。更远的NN壳层表现出轻微的不对称性。我们的研究结果调和了长期存在的争议，占主导地位的局部应变弛豫机制在应变锗稀Si1xGex合金。
We have investigated the anharmonicity and local lattice distortion in strained Ge-dilute Si1xGex alloy using Ge K-edge extended x-ray absorption fine structure measurement coupled with ab initio molecular dynamics simulation. Pronounced asymmetry is for the first time revealed for the GeeSi first nearestneighbor (NN) distribution even at room temperature, in good agreement with theoretical simulations. In comparison with harmonic approximation, the anharmonicity contributes an additional shift of 0.011 Å to the GeeSi first NN bond distance, which is further found to be crucial to the qualitative change (i.e., contracting or stretching) of the GeeSi second NN bond distance relative to the corresponding SieSi bond distance in bulk Si. As the modifications of higher NN shells arise from the competition between the NN bond-distance stretching and the tetrahedral bond-angle deviation, those results indicate that the anharmonicity is critical in the proper determination of the local strain accommodation mode and thus the substrate effect. Farther NN shells exhibit slight asymmetry. Our findings reconcile the longstanding controversy regarding the dominant local strain relaxation mechanism in strained Ge-dilute Si1xGex alloys..