Baladés N, Sales D L, Herrera M, Tan C H, Liu Y, Richards R D, Molina S I
Department of Material Science, Metallurgical Engineering and Inorganic Chemistry, University of Cádiz, Campus Río San Pedro, 11510, Puerto Real, Cádiz, Spain.
Instituto Universitario de Investigación en Microscopía Electrónica y Materiales (IMEYMAT). Facultad de Ciencias. Universidad de Cádiz, Campus Río San Pedro s/n. 11510 Puerto Real, Cádiz, Spain.
Nanoscale Res Lett. 2018 Apr 25;13(1):125. doi: 10.1186/s11671-018-2530-5.
The Bi content in GaAs/GaAsBi /GaAs heterostructures grown by molecular beam epitaxy at a substrate temperature close to 340 °C is investigated by aberration-corrected high-angle annular dark-field techniques. The analysis at low magnification of high-angle annular dark-field scanning transmission electron microscopy images, corroborated by EDX analysis, revealed planar defect-free layers and a non-homogeneous Bi distribution at the interfaces and within the GaAsBi layer. At high magnification, the qHAADF analysis confirmed the inhomogeneous distribution and Bi segregation at the GaAsBi/GaAs interface at low Bi flux and distorted dumbbell shape in areas with higher Bi content. At higher Bi flux, the size of the Bi gathering increases leading to roughly equiaxial Bi-rich particles faceted along zinc blende {111} and uniformly dispersed around the matrix and interfaces. FFT analysis checks the coexistence of two phases in some clusters: a rhombohedral pure Bi (rh-Bi) one surrounded by a zinc blende GaAsBi matrix. Clusters may be affecting to the local lattice relaxation and leading to a partially relaxed GaAsBi/GaAs system, in good agreement with XRD analysis.
利用像差校正高角度环形暗场技术研究了在接近340°C的衬底温度下通过分子束外延生长的GaAs/GaAsBi /GaAs异质结构中的Bi含量。高角度环形暗场扫描透射电子显微镜图像的低倍率分析，经能谱分析证实，揭示了平面无缺陷层以及界面处和GaAsBi层内Bi的非均匀分布。在高倍率下，定量高角度环形暗场分析证实了在低Bi通量下GaAsBi/GaAs界面处Bi的非均匀分布和Bi偏析，以及在Bi含量较高的区域中哑铃形状的畸变。在较高的Bi通量下，Bi聚集的尺寸增加，导致沿闪锌矿{111}面刻面的大致等轴富Bi颗粒，并均匀地分散在基体和界面周围。快速傅里叶变换分析检查了一些团簇中两相的共存：一个菱形纯Bi（rh-Bi）相被闪锌矿GaAsBi基体包围。团簇可能影响局部晶格弛豫，并导致GaAsBi/GaAs系统部分弛豫，这与X射线衍射分析结果高度一致。
