Novel Correlated Energy-Loss and Cathodoluminescence Spectroscopy in the Transmission Electron Microscope

许多现代半导体器件都是基于多层结构或平面层的横向结构来定位载流子在特定位置。这些所谓的量子域结构可以具有独特的（光电）电子特性，这取决于用于载流子约束的设计（量子阱、量子线或量子点分别用于二维、一维或零维空间的约束）。各种形式的光谱学可以用来研究这些材料，然而，大多数都缺乏研究单个纳米结构所需的空间分辨率。透射电子显微镜（TEM）中的光谱学具有独特的优势，能够以纳米尺度的空间分辨率在二维上研究嵌入在样品表面以下的单个纳米结构。本课题拟将电子能谱分析（ELSP）、基于电子能量损失谱（EELS）的透射电子显微镜成像能谱混合方法与阴极发光（CL）光谱学相结合。EELS提供化学和电子信息，CL提供光学信息。因此，两种方法在同一仪器中的结合为发光量子域结构的局部光电特性提供了独特的探测。本文的目的是研究在一维或三维空间尺寸仅为几纳米的化合物半导体的量子阱和量子点结构，这些结构只有使用现代分析TEM才能真正访问。为了将CL检测整合到高质量场发射（扫描）TEM的窄高分辨率极片中，将对现有的标本支架进行修改，以适应新设计的高效光收集光学腔和光纤电缆。光纤将允许用户将样品架连接到两个外部光谱仪，一个小型的Czerny-Turner型光谱仪，带有硅二极管阵列探测器，用于紫外-可见（UV-VIS）波长范围，对于宽带隙氮化半导体很重要，或者安装在另一个实验室的高分辨率光栅衍射仪，带有冷却锗探测器，用于红外（IR）范围，与砷化半导体的研究相关。

Many modern semiconductor devices are based on multiple layer structures or the lateral structuring of planar layers to locate charge carriers in specific positions. These so-called quantum domain structures can have unique (opto)electronic properties, depending on the design used for carrier confinement (quantum wells, quantum wires or quantum dots for confinement in two, one or zero dimensions of space, respectively). Various forms of spectroscopy can be used to investigate such materials, however, most lack the spatial resolution necessary to study individual nanostructures. Spectroscopy in a transmission electron microscope (TEM) has the unique advantage of being able to investigate such individual nanostructures embedded below the specimen surface at nanometre-scale spatial resolution in two dimensions. This project proposes to combine the rather new method of electron spectroscopic profiling (ELSP), a hybrid imaging-spectroscopy method based on electron energy-loss spectroscopy (EELS) in a transmission electron microscope equipped with imaging energy filter, and cathodoluminescence (CL) spectroscopy. While EELS provides chemical and electronic information, CL yields optical information. Hence, the combination of both methods in the same instrument provides a unique probe of the local optoelectronic properties of light-emitting quantum domain structures. It is intended to investigate in particular quantum well and quantum dot structures of compound semiconductors with spatial dimensions of only a few nanometres in one or three dimensions, respectively, which are only really accessible using a modern analytical TEM. In order to incorporate CL detection into the narrow high-resolution pole-piece of a high-quality field-emission (scanning) TEM an existing specimen holder will be modified in order to accommodate both a newly designed highly-efficient light collecting optical cavity and a fibre optic cable. The fibre optics will allow the user to connect the specimen holder to two external spectrometers, a small Czerny-Turner type spectrometer with silicon diode array detector for the ultraviolet-visible (UV-VIS) wavelength range important for wide-bandgap nitride semiconductors or a high-resolution optical grating diffractometer installed in another laboratory with cooled germanium detector for the infrared (IR) range, relevant for the study of arsenide based semiconductors.