Elastic energy mapping of epitaxial nanocrystals

Self-assembled nanocrystals grown by epitaxy represent a viable way to mass produce quantum structures exhibiting novel electronic properties. In order to infer the electronic properties of such systems, knowledge of both composition and strain is necessary. Here, detailed maps of these quantities were obtained by anomalous X-ray diffraction for samples grown at 600 °C and 700 °C by chemical vapor deposition and molecular beam epitaxy, respectively – two different temperatures and growth techniques. From these maps, the elastic energies stored in the islands were evaluated. It was found that the elastic energy is concentrated at the island borders, regardless of the growth temperature or method. In contrast, the regions with the lowest elastic energy were the island core and top. These results provide insight into the mechanisms that govern the growth and evolution of strained nanocrystals. PACS 71.35.Ji; 78.67.Hc; 73.22.Dj