Microscopic parameters of heterostructures containing nanoclusters and thin layers of Ge in Si matrix

GeK XAFS measurements have been performed using the total electron yield de tection mode for pseudomorphous Ge films deposited on Si(001) substrate via molecular beam epitaxy at 300 degreesC. The samples have been produced by thrice repeating the growing procedure separated by deposition of blocking Si layers at 500 degreesC. The local microstructure parameters (interatomic distances, Ge coordination numbers) are linked to nanostructure morphology and adequate models are suggested and discussed. It was established that p seudomorphous 4-monolayer Ge films contain 50% of Si atoms on the average. Pyramid-like, pure Ge islands formed in the Stranski-Krastanov growth are c haracterized by the interatomic Ge-Ge distances of 2.41 Angstrom (by 0.04 A ngstrom less than in bulk Ge) and the Ge-Si distances of 2.37 Angstrom. It was revealed that the pure Ge nanoclusters are covered by a 1-2-monolayer f ilm with admixture on the average of a 50% Si atom impurity from blocking S i layers. (C) 2001 Elsevier Science B.V. All rights reserved.