Three-dimensional Si islands on Si(001) surfaces

Abstract

Three-dimensional Si islands with a number density from ${10}^{12}$ to ${10}^{13} {\mathrm{cm}}^{\ensuremath{-}2}$ and size of 3--10 nm were grown on Si(001) substrates covered with 0.3-nm-thick ${\mathrm{SiO}}_{2}$ layers. The islands were epitaxial to the Si(001) substrate at growth temperatures above 460 \ifmmode^\circ\else\textdegree\fi{}C. They had a hemispherical shape at temperatures between 400 and $570\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ and a pyramidal shape at temperatures from 570 to 640 \ifmmode^\circ\else\textdegree\fi{}C. The ${\mathrm{SiO}}_{2}$ layer was completely desorbed during the pyramidal island formation. Competition between ${\mathrm{SiO}}_{2}$ decomposition through the reaction of Si adatoms with ${\mathrm{SiO}}_{2}$ and attachment of Si adatoms to nucleating islands determines this growth picture. The potential energy barriers for adatom diffusion between areas of ${\mathrm{SiO}}_{2}$ and bare Si and at step edges on Si surfaces are also responsible for the hemispherical and pyramidal shapes of the islands, respectively. Estimates showed that island nucleation occurred through the reaction between individual Si adatoms and ${\mathrm{SiO}}_{2}.$ A dot modification of \ensuremath{\delta}-doped Si layers in Si and also Si dots in a ${\mathrm{SiO}}_{2}$ matrix can be created by the present method.