Max Planck Institute for the Science of Light, Erlangen, Germany.
Nanotechnology. 2011 Sep 23;22(38):385201. doi: 10.1088/0957-4484/22/38/385201. Epub 2011 Aug 26.
Electrical and optical properties of semiconducting nanowires (NWs) strongly depend on their diameters. Therefore, a precise knowledge of their diameters is essential for any kind of device integration. Here, we present an optical method based on dark field optical microscopy to easily determine the diameters of individual NWs with an accuracy of a few nanometers and thus a relative error of less than 10%. The underlying physical principle of this method is that strong Mie resonances dominate the optical scattering spectra of most semiconducting NWs and can thus be exploited. The feasibility of this method is demonstrated using GaAs NWs but it should be applicable to most types of semiconducting NWs as well. Dark field optical microscopy shows that even slight tapering of the NWs, i.e. diameter variations of a few nanometers, can be detected by a visible color change. Abrupt diameter changes of a few nanometers, as they occur for example when growth conditions vary, can be determined as well. In addition a profound analysis of the elastic scattering properties of individual GaAs NWs is presented theoretically using Mie calculations as well as experimentally by dark field microscopy. This method has the advantage that no vacuum technique is needed, a fast and reliable analysis is possible based on cheap standard hardware.
半导体纳米线（NWs）的电学和光学性质强烈依赖于其直径。因此，对于任何类型的器件集成，精确了解它们的直径都是至关重要的。在这里，我们提出了一种基于暗场光学显微镜的光学方法，可以轻松地确定单个 NW 的直径，精度可达几纳米，相对误差小于 10%。该方法的基础物理原理是，强 Mie 共振主导了大多数半导体 NW 的光学散射谱，因此可以利用这一点。使用 GaAs NW 证明了该方法的可行性，但它应该也适用于大多数类型的半导体 NW。暗场光学显微镜显示，即使 NW 稍微变细，即直径变化几纳米，也可以通过可见的颜色变化检测到。当生长条件发生变化等情况时，直径发生几纳米的突然变化也可以确定。此外，还使用 Mie 计算从理论上以及通过暗场显微镜从实验上对单个 GaAs NW 的弹性散射特性进行了深入分析。该方法的优点是不需要真空技术，基于廉价的标准硬件可以快速可靠地进行分析。
