Optical Nanomaterial Group, Institute for Quantum Electronics, Department of Physics, ETH Zurich , Auguste-Piccard Hof 1, 8093 Zurich, Switzerland.
ITMO University , Kronverkskiy 49, 197101 Saint Petersburg, Russia.
Nano Lett. 2016 Oct 12;16(10):6290-6297. doi: 10.1021/acs.nanolett.6b02592. Epub 2016 Sep 28.
In this work, we report an optical method for characterizing crystal phases along single-semiconductor III-V nanowires based on the measurement of polarization-dependent second-harmonic generation. This powerful imaging method is based on a per-pixel analysis of the second-harmonic-generated signal on the incoming excitation polarization. The dependence of the second-harmonic generation responses on the nonlinear second-order susceptibility tensor allows the distinguishing of areas of pure wurtzite, zinc blende, and mixed and rotational twins crystal structures in individual nanowires. With a far-field nonlinear optical microscope, we recorded the second-harmonic generation in GaAs nanowires and precisely determined their various crystal structures by analyzing the polar response for each pixel of the images. The predicted crystal phases in GaAs nanowire are confirmed with scanning transmission electron and high-resolution transmission electron measurements. The developed method of analyzing the nonlinear polar response of each pixel can be used for an investigation of nanowire crystal structure that is quick, sensitive to structural transitions, nondestructive, and on-the-spot. It can be applied for the crystal phase characterization of nanowires built into optoelectronic devices in which electron microscopy cannot be performed (for example, in lab-on-a-chip devices). Moreover, this method is not limited to GaAs nanowires but can be used for other nonlinear optical nanostructures.
在这项工作中，我们报告了一种基于测量偏振相关二次谐波产生来对单根半导体 III-V 纳米线的晶体相进行特征化的光学方法。这种强大的成像方法基于对入射激发偏振上产生的二次谐波信号进行逐像素分析。二次谐波产生响应对非线性二阶介电张量的依赖性允许在单个纳米线中区分纯纤锌矿、闪锌矿和混合及旋转孪晶晶体结构的区域。我们使用远场非线性光学显微镜记录了 GaAs 纳米线中的二次谐波产生，并通过分析图像中每个像素的极响应精确确定了它们的各种晶体结构。通过扫描透射电子显微镜和高分辨率透射电子显微镜测量，证实了 GaAs 纳米线中的预测晶体相。分析每个像素的非线性极响应的开发方法可用于快速、对结构转变敏感、非破坏性和现场的纳米线晶体结构研究。它可用于对电子显微镜无法进行的光电设备中构建的纳米线的晶体相特征化（例如，在片上实验室设备中）。此外，该方法不仅限于 GaAs 纳米线，还可用于其他非线性光学纳米结构。
