Chapter 10: Transmission Electron Microscopy Techniques for Imaging and Compositional Evaluation in Semiconductor Heterostructures and Nanostructures

Nowadays, the advanced discovery and development of nanometric-scale-structured materials with innovative properties require investigation techniques able to perform characterizations down to the atomic scale. The modern transmission electron microscopes are now able to accomplish this requirement, not only by imaging but also by obtaining chemical information with atomic resolution. This chapter is mainly devoted to a brief introduction to the transmission electron microscopy technique: the fundamentals of the diffraction and phase contrast are explained, with regard to the defect imaging, the chemical-sensitive imaging, the high-resolution electron microscopy with the lattice fringe analysis. The so-called Z-contrast technique for quantitative compositional analysis is concisely outlined as well. At the end, some examples are discussed, to approach the reader to the problems, this technique can solve in the case of quantum well (QW) structures. A typical example of the chemical-sensitive imaging and the interpretation of the strain- and defects-induced contrast is shown in InGaAs-based strain-balanced multi-QWs. A basic application of the lattice fringes analysis for the composition determination is described in the InGaN/GaN system, while it is shown that the In and N assessment in the InGaAsN alloy requires a combination of the diffraction contrast and the lattice fringes analysis. Then, the determination of the exact In content in InGaAs QWs.