Controlling the density distribution of SiC nanocrystals for the ion beam synthesis of buried SiC layers in silicon

The depth distribution of SiC nanocrystals formed during high-dose implanta tion of carbon ions into silicon at conditions suitable for the ion beam sy nthesis of buried SiC layers in silicon is studied in this paper. For impla ntation temperatures of 400-600 degrees C and dose rates of 10(12) - 10(13) C+/cm(2)s, SiC precipitates in crystalline silicon are observed to be of a pproximately equal size, independent of the depth position beneath the surf ace. Ballistic destruction of small precipitates and difficulties in precip itate growth are thought to be responsible for the observed narrow size dis tribution. The destruction of precipitates may lead to the simultaneous rel ease of a superthreshold concentration of carbon atoms resulting in a carbo n-induced amorphization of the silicon host lattice. The local reduction of the number density of SiC nanocrystals involved with this amorphization ca n be used to tailor discontinuous depth distributions of oriented SIC preci pitates providing ideal starting conditions for the synthesis of well-defin ed single-crystalline SiC layers in silicon. (C) 1999 Elsevier Science B.V. All rights reserved.