Direct observation of intermixing at Ge/Si(001) interfaces by high-resolution Rutherford backscattering spectroscopy

The initial stage of Ge/Si(001) epitaxial growth is studied with high-resolution Rutherford backscattering spectroscopy. In contrast to the generally accepted picture, intermixing of Ge and Si begins before the first layer is completed at the growth temperature of 500 degrees C. If the layer is deposited at room temperature, intermixing takes place during annealing at 300-800 degrees C. These observations are in reasonable agreement with a recent theoretical study based on generalized gradient approximation density functional calculations [Y. Yoshimoto and M. Tsukada, Surf. Sci. 423, 32 (1999)].