AlHassan Ali, Lähnemann J, Leake S, Küpers H, Niehle M, Bahrami D, Bertram F, Lewis R B, Davtyan A, Schülli T U, Geelhaar L, Pietsch U
Naturwissenschaftlich-Technische Fakultät der Universität Siegen, D-57068 Siegen, Germany.
Nanotechnology. 2020 May 22;31(21):214002. doi: 10.1088/1361-6528/ab7590. Epub 2020 Feb 12.
We report on the direct correlation between the structural and optical properties of single, as-grown core-multi-shell GaAs/InGaAs/GaAs/AlAs/GaAs nanowires. Fabricated by molecular beam epitaxy on a pre-patterned Si(111) substrate, on a row of well separated nucleation sites, it was possible to access individual nanowires in the as-grown geometry. The polytype distribution along the growth axis of the nanowires was revealed by synchrotron-based nanoprobe x-ray diffraction techniques monitoring the axial 111 Bragg reflection. For the same nanowires, the spatially-resolved emission properties were obtained by cathodoluminescence hyperspectral linescans in a scanning electron microscope. Correlating both measurements, we reveal a blueshift of the shell quantum well emission energy combined with an increased emission intensity for segments exhibiting a mixed structure of alternating wurtzite and zincblende stacking compared with the pure crystal polytypes. The presence of this mixed structure was independently confirmed by cross-sectional transmission electron microscopy.
我们报道了单根生长态的核-多壳层GaAs/InGaAs/GaAs/AlAs/GaAs纳米线的结构与光学性质之间的直接相关性。通过分子束外延在预先图案化的Si(111)衬底上、一排间隔良好的成核位点上制备，得以研究生长态几何结构中的单根纳米线。通过基于同步加速器的纳米探针X射线衍射技术监测轴向111布拉格反射，揭示了纳米线生长轴上的多型分布。对于同一批纳米线，通过扫描电子显微镜中的阴极发光高光谱线扫描获得了空间分辨的发射特性。将这两种测量结果相关联，我们发现，与纯晶体多型相比，对于呈现纤锌矿和闪锌矿交替堆叠混合结构的段，壳量子阱发射能量发生蓝移，同时发射强度增加。这种混合结构的存在通过横截面透射电子显微镜得到了独立证实。
