Rubezhanska M. Influence of elastic deformation in Sі-Gе epitaxial heterojunction with Gе quantum dots on quantum size effect

The subject of study: quantum size effect in Ge quantum dot systems on Si. The goal of the study:investigation of processes on the surface of epitaxial heterosystems with essential lattice misfit and influence of elastic strain arising in the nanoisland film on the growth mode and size parameters of Ge quantum dots forming on Si(100) and Si(111) substrates. Methods of investigation: molecular-beam epitaxy, reflection high energy electron diffraction, Auger-spectroscopy, low energy electron diffraction, atomic force microscopy, field electron emission, photofield electron emission. The procedure of heteroepitaxial formation using intermediate Si(1-x)Ge(x) layers of thickness below critical with gradual increase of Ge mole fraction made it possible to obtain Ge quantum dot structures on Si(100) and Si(111) substrates with different form and size of Ge nanoclusters, as well as their size distribution. The irregular behaviour of Ge and Si lattice parameters in plane during formation of intermediate layerswas fixed corresponding to hydrostatic pressure 8 GPа and bond length decrease in Si-Ge heterojunction from 0.235 nm (for pure Si in the first intermediate layer) to 0.226 nm. A possibility of deformation phase change was regarded. On investigation of electron field emission from Ge nanoclusters on Si(100) and Si(111) substrates, the quantum size effect was revealed in such structures for the first time. Simulation of the nanoisland-surface elastic deformation showed that elastic deformation e in the island film does not depend on the nanocluster height and increases proportionally to reverse square root of nanoisland lateral size.