We report the crystal structures of GaAs and GaAs/GaNAs/GaAs core-multishell nanowires (NWs). From statistical investigations by X-ray diffraction (XRD) and electron backscattered diffraction (EBSD) pattern analysis, we statistically and microscopically resolve the zinc-blende (ZB) and wurtzite (WZ) polytypism within the NWs. The XRD analysis shows a smaller fraction of WZ segments in the NWs with a larger concentration of nitrogen. With increasing nitrogen content in the GaNAs shell, the ZB peak position shifts toward higher angles and the WZ peak intensity decreases. The EBSD measurements also confirm the coexistence of ZB and WZ polytypes in all of the NWs. Their polytype switches along the length. Twin defects are observed in the ZB segments in all of the NWs. The unique grain map and grain size distribution show a decrease of the WZ segments in the GaAs/GaNAs/GaAs NW, in agreement with the XRD results. Microscopically, the local area where the polytype switches from WZ in the inner-core side to ZB toward the outer-shell surface is observed. Overall, we propose that the WZ polytype in the GaAs NWs decreases because of the strain induced by the growth of the GaNAs shell with a smaller lattice constant.

中文翻译：

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GaAs/GaNAs核壳纳米线的多型性

我们报告了 GaAs 和 GaAs/GaNAs/GaAs 核-多壳纳米线 (NW) 的晶体结构。通过 X 射线衍射 (XRD) 和电子背散射衍射 (EBSD) 图案分析的统计调查，我们在统计和微观上解析了 NW 内的闪锌矿 (ZB) 和纤锌矿 (WZ) 多型性。XRD 分析显示 NW 中 WZ 片段的较小部分具有较大的氮浓度。随着 GaNs 壳中氮含量的增加，ZB 峰位置向更高的角度移动，WZ 峰强度降低。EBSD 测量还证实了 ZB 和 WZ 多型在所有 NW 中的共存。它们的多型沿着长度切换。在所有 NW 的 ZB 段中都观察到双缺陷。独特的晶粒图和晶粒尺寸分布显示 GaAs/GaNAs/GaAs NW 中 WZ 段的减少，与 XRD 结果一致。在显微镜下，观察到多型体从内核侧的WZ向外壳表面的ZB切换的局部区域。总体而言，我们认为 GaAs NWs 中的 WZ 多型体由于晶格常数较小的 GaNAs 壳的生长引起的应变而降低。