Is. Hwang et al., EXCHANGE-BARRIER EFFECTS ON NUCLEATION AND GROWTH OF SURFACTANT-MEDIATED EPITAXY, Physical review letters, 80(19), 1998, pp. 4229-4232
The initial stage of nucleation and growth of two-dimensional (2D) Ge
islands on Pb covered Si(lll) surfaces at room temperature is studied
using scanning tunneling microscopy. The Pb overlayer is found to grea
tly enhance surface diffusion of deposited Ge adatoms. There is a crit
ical deposition time above which the observed island density increases
sharply while the average island size decreases. We believe nucleatio
n as well as growth is initially hindered by the high energy barriers
for Ge clusters to exchange with Pb atoms until Ce clusters reach a cr
itical size. A mechanism is proposed to explain the observed phenomena
.