PROMOTION OF EPITAXIAL-GROWTH OF GE BY AG AND PB DEPOSITED ON A CLEAN GE(111) SURFACE

Epitaxial growth of Ge on Ag and Pb covered Ge(lll) surfaces is investigated by reflection high-energy electron diffraction (RHEED) intensity oscillation, RHEED spot profile analysis and total reflection angle X-ray spectroscopy. The Ag and Pb atoms are segregated at the surface during the Ge growth even at room temperature. Furthermore, the optimum temperature for duration of strong RHEED oscillation is significantly lowered on the Ag covered Ge(111) surface. It was found that the spot width of RHEED changes periodically during the growth. Effective activation energies for surface diffusion estimated from the specular spot width of RHEED are 2.6 eV on clean Ge(111) and 0.95 eV on Ge(111)-Ag surfaces. It is considered that this energy difference effectively causes promotion of surface diffusion of a Ge atom leading to low temperature epitaxy.