Three-dimensional Si islands on Si(001) surfaces

Three-dimensional Si islands with a number density from 10¹² to 10¹³ cm^-2 and size of 3--10 nm were grown on Si(001) substrates covered with 0.3-nm-thick SiO₂ layers. The islands were epitaxial to the Si(001) substrate at growth temperatures above 460 ^∘{}C. They had a hemispherical shape at temperatures between 400 and 570^∘C and a pyramidal shape at temperatures from 570 to 640 ^∘{}C. The SiO₂ layer was completely desorbed during the pyramidal island formation. Competition between SiO₂ decomposition through the reaction of Si adatoms with SiO₂ and attachment of Si adatoms to nucleating islands determines this growth picture. The potential energy barriers for adatom diffusion between areas of SiO₂ 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 SiO₂. A dot modification of {δ}-doped Si layers in Si and also Si dots in a SiO₂ matrix can be created by the present method.