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

许多现代半导体器件基于多层结构或平面层的横向结构来在特定位置定位载流子。这些所谓的量子域结构可以具有独特的(光学)电子性质，这取决于用于载流子限制的设计(分别用于在二维、一维或零维空间中限制的量子井、量子线或量子点)。各种形式的光谱学可以用来研究这种材料，然而，大多数缺乏研究单个纳米结构所需的空间分辨率。透射式电子显微镜中的光谱学具有独特的优势，能够以纳米级的空间分辨率在两个维度上研究嵌入在样品表面下的这种单独的纳米结构。该项目提出将电子光谱轮廓(ELSP)方法、基于电子能量损失光谱(EELS)的混合成像光谱方法(在配备成像能量滤光片的透射电子显微镜中)和阴极发光(CL)光谱相结合。EELS提供化学和电子信息，而CL产生光学信息。因此，这两种方法在同一仪器中的结合为发光量子域结构的局域光电性质提供了一个独特的探针。它的目的是分别在一维和三维空间上研究空间尺寸只有几个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电子显微镜才能真正获得。为了将化学发光检测结合到高质量场发射(扫描)电子显微镜的窄的高分辨率极片中，将对现有的样品支架进行改造，以适应新设计的高效集光光腔和光纤电缆。光纤将允许用户将样品架连接到两个外部光谱仪，一个是小型Czerny-Turner光谱仪，带有硅二极管阵列探测器，用于宽禁带氮化物半导体的重要紫外-可见光(UV-Vis)波长范围，或者是安装在另一个实验室的高分辨率光栅衍射仪，其带有用于红外(IR)范围的制冷锗探测器，这与砷基半导体的研究相关。

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.