In situ scanning tunneling microscopy study of C-induced Ge quantum dot formation on Si(100)

Deposition of submonolayer coverages of C on Si(100) prior to Ge growth lea ds to the formation of Ge quantum dots below the critical thickness for Ge islanding on bare Si(100). In situ scanning tunneling microscopy reveals a high density of irregularly shaped islands for Ge coverages from 2.5 to 4 M L. Island sizes are broadly distributed between 10 and 25 nm. Keeping the C coverage constant and increasing the Ge coverage from 2.5 to 4 ML, the isl ands increase in height but their density remains constant (10(11) cm(-2)). At a Ge coverage of 5.8 ML, formation of larger (105)-faceted islands is o bserved. Their density is reduced by a factor of 4 compared to smaller Ge c overages. Transmission electron microscopy shows that the nonfaceted island s are preserved after Si capping. (C) 1999 American Institute of Physics. [ S0003-6951(99)03107-1].