Silicon–germanium interdiffusion and interfaces in self-assembled quantum dots

Abstract

A scanning transmission electron microscope (STEM) study of silicon–germanium alloying using annular dark field (ADF) or Z-contrast imaging and electron energy loss spectroscopy (EELS) is presented. Results and techniques are discussed. Growth of 11 equivalent monolayers of germanium on silicon at 650 °C results in dome-shaped islands or quantum dots that contain up to ∼40% silicon. The interface between the as-grown island and substrate shows a highly disordered or amorphous zone ∼1.5-nm wide directly under the island. Annealing for 60 min at 650 °C gives larger pyramidal islands with diffuse crystalline interfaces and an equilibrium distribution of up to ∼70% silicon in the islands.