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Morphology of three-dimensional Ge nanoclusters growing on SiOх (х<2) film

Yuriy N. Kozyrev 1Vasilij K. Sklyar 1Marija Y. Rubezhanska 1Andrii V. Sushyi 1Christian Teichert 2Christian Hofer 2

1. Institute of Surface Chemistry NAS of Ukraine, 17 General Naumov, Kyiv 03164, Ukraine
2. Montanuniversitaet Leoben, Franz Josef Str 18, Leoben 8700, Austria

Abstract

       Since newly elaborated optoelectronic and nanoelectronic devices require more and more small sizes of their structural components, the thickness of investigated silicon oxide layers was reduced to several nanometers. Three-dimensional Ge nanoclusters about 20 nm in height and 30 nm in the basis were prepared by molecular-beam epitaxy on initially amorphous SiOх (х<2) film of the thickness varying from 2 to 8 nm. Their distribution density over the substrate surface exceeded 1011 cm-2. In contrast to traditional heteroepitaxial formation of Ge quantum dots on Si(100) or growth of Si nanoclusters on SiOх, when the correlation between the nanocluster height and lateral size is usually about b~8-10 and pronounced facets {113} are formed, in our case the nanoclusters were almost hemispherical with  b~1-2.

       Formation mode of three-dimensional Ge nanoclusters on initially amorphous SiOх film is a question under discussion. Taking into consideration the fact that adhesion of Ge adatoms may be rather essential, the mechanism of 2D®3D transformation corresponds to the conditions of Stranski-Krastanov epitaxial growth realized in the presence of a lattice mismatch between the growing surface and Ge. We suppose that a large number of randomly aligned compound nanocrystallites, for example Si1-xGexOy, can be formed on the surface in our case. The presence of oxygen in these nanocrystallites even at a low concentration may essentially enlarge the strain relaxation. That is why the forming Ge nanoclusters take a shape of hemispheres with a low b coefficient and high distribution density over the surface that is more typical to Volmer-Weber epitaxial growth.

 

The work has been performed in the framework of Austra-Ukrainian joint scientific and technical collaboration supported by the Austrian Academic Exchange service under project #UA05/2007. Also this work is supported by the program of fundamental investigations “Nanosystems, nanomaterials and nanotechnologies”.

 

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Related papers

Presentation: Poster at E-MRS Fall Meeting 2008, Symposium G, by Andrii V. Sushyi
See On-line Journal of E-MRS Fall Meeting 2008

Submitted: 2008-05-12 15:11
Revised:   2009-06-07 00:48