ORIGIN OF HOMOEPITAXIAL FAULTED ISLAND GROWTH ON THE SI(111) SURFACE

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.