Chapter 3 Structure and Characterization of Strained-Layer Superlattices

Abstract

This chapter describes the structure and characterization of strained-layer superlattices. It discusses the techniques used to characterize strain and strain relief in strained-layer material structures. Two techniques, Rutherford backscattering spectrometry (RBS)/ion channeling and x-ray diffraction, are discussed in the chapter. The chapter presents a framework for understanding stability, metastability, and relaxation of strained-layer structures. The discussion in the chapter is conducted in terms of the concepts of the driving force, as characterized by the excess stress, and the materials response, as characterized by stability diagrams. The chapter presents the characterization techniques and the stability/metastability/ relaxation concepts for both single strained layers and strained-layer superlattices. The chapter presents the basic concept of the formation of a single strained layer. Under commensurate growth, the layer is biaxially strained, and the atom relaxation normal to the plane of the layer leads to a tetragonal distortion of the strained layer. The chapter also presents the schematic structure of a commensurate strained-layer superlattice.