A model for the ordering mechanism in SiGe films was developed in order to explain the appearance of 2 types of ordered structure. The stability of ordered structures was investigated by performing strain energy calculations. A rhombohedral (RH2) structure was stabilized by a surface with a 2 x 1 reconstruction. However, the RH2 structure became unstable, and another rhombohedral structure (RH1) became the preferred one in the film. The decision, as to which structure formed, depended upon atomic diffusion which was enhanced by the strains in the film. It was proposed that atomic exchange processes at the reconstructed surface were involved in the formation of the RH2 structure.

T.Araki, N.Fujimura, T.Ito: Applied Physics Letters, 1997, 71[9], 1174-6