Local structure of self-organized uniform Ge quantum dots on Si(001)

Pseudomorphous Ge films with pyramid-like Ge islands have been deposited on Si(001) substrate using molecular beam epitaxy at 300 degreesC. The islands revealing quantum dots (QD) properties are self-organized during the growth in uniform Ge nanostructures with lateral sizes similar to 15 nm and height similar to 1.5 nm. Ge K XAFS measurements have been performed using total electron yield detection mode. It was established that the presence of an appreciable exchange of atoms between the Si and Ge phases decreases the elastic strains in the system during the deposition of the blocking Si Layer at 500 degreesC. It has been found that the Ge QD's are characterized by interatomic Ge-Ge distances of 2.41 Angstrom, which is 0.04 Angstrom less than that in bulk Ge. (C) 2001 Elsevier Science B.V. All rights reserved.