Growth of carbon-induced Ge quantum dots

C-induced Ge quantum dots grown by solid source molecular beam epitaxy was investigated as functions of pre-deposited C coverage, overgrown Ge layer, and substrate temperature using atomic force microscopy. It is observed tha t the quantum dots grows with increasing pre-deposited C contents and they also exhibit a bimodal size distribution. The smallest quantum dots with a 300 Angstrom mean diameter, a 50 Angstrom mean height, and an areal density of 3.0x10(10) cm(-2) are obtained with 0.1 monolayer C pre-deposition and a 3 monolayer thick Ge layer. We observed that an abrupt change in dot dens ity and size occur near 500 degrees C, which is attributed to the differenc e in the temperature-dependent surface diffusivities of Ge and C adatoms on Si(100). These results suggest that C would be useful in obtaining achieve much smaller quantum dots than Ge and SiGe dots on Si prepared using Stran ski-Krastanov growth mode.