Silicon homoepitaxy on Si(111) substrates has been studied using a nov
el growth technique which allows new details of the growth mechanism t
o be investigated, In agreement with earlier studies the growth of fau
lted Si(111) islands is observed, Under low-temperature growth conditi
ons these faulted structures are the dominant growth nuclei on the sur
face, The preference for metastable structures is shown to be intimate
ly related to the manner in which the rest-layer structure of the Si(1
11)-(7 x 7) reconstruction is gradually transformed into a bulk (1 x 1
) structure - a transformation that is a prerequisite for Si(111) homo
epitaxial growth. Nucleation is seen to occur rapidly following transf
ormation of small triangular regions of rest-layer to a bulk (1 x 1) s
tructure, However, nucleation events are explicitly avoided for which
the island's edge runs along or closely parallel to the dimer rows tha
t border these (1 x 1) regions. This repulsive interaction is suggeste
d to result from excessive tensile stress due to rebonding along. the
island's step-edge, The repulsion is largest for the case of unfaulted
islands since these islands and the (1 x 1) regions in which they are
found always point in the same [11 (2) over bar] direction. Under the
se conditions, faulted-island nucleation is favored since these island
s point in the opposite [(1) over bar (1) over bar 2] direction which
largely avoids this repulsive interaction. (C) 1998 Elsevier Science B
.V. All rights reserved.