Nanoscale x-ray investigation of composition fluctuations in AlGaN nanowires
Nanoscale x-ray investigation of composition fluctuations in AlGaN nanowires
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DOI：
10.1088/1361-6528/ab94e1
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发表时间：
2020-09-11
期刊：
影响因子：
3.5
通讯作者：
Daudin, B.
中科院分区：
文献类型：
--
作者：
Belloeil, M.;Proietti, M. G.;Daudin, B.
在本研究中，我们结合，在相同的同步加速器X射线实验，倒易空间映射，多波长异常衍射和衍射异常精细结构，以确定应变，晶体极性，合金成分和有序在原子尺度上的[0001]取向的AlGaN纳米线生长的GaN纳米线基地的分子束外延。我们获得的信息是平均超过一个宏观系综的纳米线。我们发现，从衍射异常精细结构，有一个各向同性增加的Ga-Ga对的数量在Ga下一个最近的配位壳（阳离子亚晶格）相对于预期的AlGaN合金组合物确定的异常衍射。无论AlN的摩尔分数和生长条件如何，都存在这种与随机合金原子分布的显著偏离。我们的研究结果是一致的纳米级的组成波动预期从合金无序或运动驱动的自发有序，这两种效应被怀疑占AlGaN三元合金的物理性质。
In the present study we combined, in the same synchrotron x-ray experiment, reciprocal space mapping, multiwavelength anomalous diffraction and diffraction anomalous fine structure, to determine the strain, crystallographic polarity, alloy composition and ordering at the atomic scale in [0001]-oriented AlGaN nanowires grown by molecular beam epitaxy on GaN nanowire bases. The information that we obtained was averaged over a macroscopic ensemble of NWs. We found from the diffraction anomalous fine structure that there were an isotropic increased number of Ga-Ga pairs in the Ga next nearest coordination shell (cation sublattice) with respect to what is expected for the AlGaN alloy composition determined by anomalous diffraction. This significant deviation from random alloy atomic distribution is present whatever the AlN molar fraction and growth conditions. Our results are consistent with nanoscale composition fluctuations expected from both alloy disorder or kinematically driven spontaneous ordering, both effects being suspected to account for the physical properties of AlGaN ternary alloys.