In this letter, we present an atomic-force-microscopy investigation of the Stranski-Krastanov growth of Ge on Si(100). Upon increasing the base width of the islands, two morphology transitions are found. The first transition occurs at a base width of similar to 50-60 nm and marks the: evolution from few-monolayer-thick terraces to square-base pyramidal islands. In the second transition, which takes place when the base width exceeds similar to 300 nm, the island shape changes from square base pyramids to tetragonal truncated pyramids. Both transitions are brought about by the need for the system to minimize the elastic energy.
Capellini, G., Di Gaspare, L., Evangelisti, F., Palange, E. (1997). Atomic force microscopy study of self-organized Ge islands grown on Si(100) by low pressure chemical vapor deposition. APPLIED PHYSICS LETTERS, 70, 493-495 [10.1063/1.118191].