Raman Scattering from Ultrathin Multilayer Structures

In spite of the large lattice mismatch between Ge and Si, high quality layers of Ge1-xSix covering the entire range of alloy compositions have been grown utilizing strained-layer epitaxy methods. Such work has led to the study of artificial crystals containing GemSin structures with m and n less than seven,1 of quasiperiodic Fibonacci superlattices,2 and of multiple layers of Ge grown on Si substrates.3 The study of such materials is of much interest both from a basic physics point of view and for designing devices with unusual electro-optic properties.