Three-dimensional Si islands on Si(001) surfaces

Three-dimensional Si islands with a number densitvy from 10(12) to 10(13) cm(-2) and size of 3-10 nm were grown oil Si(001) substrates covered with 0.3-nm-thick SiO2 layers. The islands were epitaxial to the Si(001) substrate at growth temperatures above 460degreesC. They had a hemispherical shape at temperatures between 400 and 570degreesC and a pyramidal shape at temperatures from 570 to 640degreesC. 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. Estimated showed that island nucleation occurred through the reaction between individual Si adatoms and SiO2. A dot modification of delta-doped Si layers in Si and also Si dots in a SiO2 matrix can be created by the present method.