Wallentin Jesper, Wilke Robin N, Osterhoff Markus, Salditt Tim
Institute for X-Ray Physics, University of Göttingen , Friedrich-Hund-Platz 1, Göttingen, 37077, Germany.
J Appl Crystallogr. 2015 Nov 10;48(Pt 6):1818-1826. doi: 10.1107/S1600576715017975. eCollection 2015 Dec 1.
Simultaneous scanning Bragg contrast and small-angle ptychographic imaging of a single solar cell nanowire are demonstrated, using a nanofocused hard X-ray beam and two detectors. The 2.5 µm-long nanowire consists of a single-crystal InP core of 190 nm diameter, coated with amorphous SiO and polycrystalline indium tin oxide. The nanowire was selected and aligned in real space using the small-angle scattering of the 140 × 210 nm X-ray beam. The orientation of the nanowire, as observed in small-angle scattering, was used to find the correct rotation for the Bragg condition. After alignment in real space and rotation, high-resolution (50 nm step) raster scans were performed to simultaneously measure the distribution of small-angle scattering and Bragg diffraction in the nanowire. Ptychographic reconstruction of the coherent small-angle scattering was used to achieve sub-beam spatial resolution. The small-angle scattering images, which are sensitive to the shape and the electron density of all parts of the nanowire, showed a homogeneous profile along the nanowire axis except at the thicker head region. In contrast, the scanning Bragg diffraction microscopy, which probes only the single-crystal InP core, revealed bending and crystalline inhomogeneity. Both systematic and non-systematic real-space movement of the nanowire were observed as it was rotated, which would have been difficult to reveal only from the Bragg scattering. These results demonstrate the advantages of simultaneously collecting and analyzing the small-angle scattering in Bragg diffraction experiments.
利用纳米聚焦硬X射线束和两个探测器，对单个太阳能电池纳米线进行了同步扫描布拉格对比度和小角度叠层成像。这条2.5μm长的纳米线由直径为190nm的单晶InP芯组成，表面涂有无定形SiO和多晶铟锡氧化物。利用140×210nm X射线束的小角散射在实空间中选择并排列纳米线。在小角散射中观察到的纳米线取向用于确定布拉格条件的正确旋转。在实空间中对齐并旋转后，进行了高分辨率（50nm步长）光栅扫描，以同时测量纳米线中小角散射和布拉格衍射的分布。相干小角散射的叠层重建用于实现亚束空间分辨率。对纳米线所有部分的形状和电子密度敏感的小角散射图像显示，除了较粗的头部区域外，沿纳米线轴的轮廓是均匀的。相比之下，仅探测单晶InP芯的扫描布拉格衍射显微镜揭示了弯曲和晶体不均匀性。在纳米线旋转时观察到了系统和非系统的实空间移动，仅从布拉格散射很难揭示这些移动。这些结果证明了在布拉格衍射实验中同时收集和分析小角散射的优势。
