Wegscheider, Werner and Eberl, Karl and Abstreiter, Gerhard and Cerva, Hans and Oppolzer, Helmut (1990) New relaxation mechanism in short period strained-layer superlattices. In: Sinclair, Robert, (ed.) High resolution electron microscopy of defects in materials: symposium held April 16.-18., 1990, San Francisco, California, USA. Materials Research Society symposium proceedings, 183. Materials Research Society, Pittsburgh, Pennsylvania, USA, p. 155. ISBN 1-558-99072-0.
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High quality Si/Ge strained-layer superlattices composed of a sequence of alternating 3 monolayers pure Si and 9 monolayers pure Ge have been grown by molecular beam epitaxy at 310 0 C on Ge(001) substrates. In order to investigate the transition from coherent to incoherent growth in these tensily strained structures a set of samples with varying number of superlattice periods has been studied by transmission electron microscopy. It is found that superlattices as thick as 33 nm at least show perfect and defect-free layer growth whereas for thicker superlattices strain accommodation occurs. For this strained heteroepitaxial system we observed, to our knowledge, for the first time the formation of microtwins as the only relaxation mechanism. High-resolution lattice imaging reveals that the twin lamellae result from successive glide of 900 (a/6)<112> Shockley partial dislocations on adjacent (111) planes from the surface towards the bulk. The activation barrier which has to be overcome in the case of 900 partial dislocations is compared with the energies required for the nucleation of 600 perfect and 300 partial misfit dislocation half-loops.
|Item Type:||Book Section|
|Institutions:||Physics > Institute of Experimental and Applied Physics > Retired Professors > Group Werner Wegscheider|
|Subjects:||500 Science > 530 Physics|
|Created at the University of Regensburg:||Unknown|
|Deposited On:||02 Mar 2010 13:34|
|Last Modified:||02 Mar 2010 13:34|