Growth temperature dependence on the formation of carbon-induced Ge quantum dots

Carbon has been exploited to form Ge quantum dots since it can provide effe ctive nucleation sites. In this study, C-induced Ge quantum dots grown by s olid source molecular beam epitaxy are investigated as a function of pre-de posited C coverage, overgrown Ge coverage, and substrate temperature using atomic force microscopy. The smallest quantum dots with a 300 Angstrom mean lateral diameter, a 50 Angstrom mean height, and an areal density of 3.0 x 10(10) cm(-2) are obtained with 0.1 monolayer C pre-deposition and a 3 mon olayer thick Ge overlayer. Growth temperature dependence for the Ge dot gro wth reveals that the dot density and size are abruptly changed by two order s of magnitude near 500 degrees C. This is attributed to the difference in the temperature-dependent surface diffusivities of Ge and C adatoms on Si(1 00) substrate. The experimental results suggest that growth temperature pla ys a key role and should be kept below 500 degrees C. (C) 2000 Elsevier Sci ence S.A. All rights reserved.