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Matrix Density Effect on Morphology of Germanium Nanocrystals Embedded in Silicon Dioxide Thin Films

Published online by Cambridge University Press:  28 June 2011

Arif S. Alagoz
Affiliation:
Department of Applied Science, University of Arkansas at Little Rock, Little Rock, AR, U.S.A Department of Physics, Middle East Technical University, Ankara, Turkey.
Mustafa F. Genisel
Affiliation:
Department of Chemistry, Middle East Technical University, Ankara, Turkey. Department of Chemistry, Bilkent University, Ankara, Turkey.
Steinar Foss
Affiliation:
Department of Physics, University of Oslo, Oslo, Norway.
Terje G. Finstad
Affiliation:
Department of Physics, University of Oslo, Oslo, Norway.
Rasit Turan
Affiliation:
Department of Physics, Middle East Technical University, Ankara, Turkey.
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Abstract

Flash type electronic memories are the preferred format in code storage at complex programs running on fast processors and larger media files in portable electronics due to fast write/read operations, long rewrite life, high density and low cost of fabrication. Scaling limitations of top-down fabrication approaches can be overcome in next generation flash memories by replacing continuous floating gate with array of nanocrystals. Germanium (Ge) is a good candidate for nanocrystal based flash memories due its small band gap. In this work, we present effect of silicon dioxide (SiO2) host matrix density on Ge nanocrystals morphology. Low density Ge+SiO2 layers are deposited between high density SiO2 layers by using off-angle magnetron sputter deposition. After high temperature post-annealing, faceted and elongated Ge nanocrystals formation is observed in low density layers. Effects of Ge concentration and annealing temperature on nanocrystal morphology and mean size were investigated by using transmission electron microscopy. Positive correlation between stress development and nanocrystal size is observed at Raman spectroscopy measurements. We concluded that non-uniform stress distribution on nanocrystals during growth is responsible from faceted and elongated nanocrystal morphology.

Type
Research Article
Copyright
Copyright © Materials Research Society 2011

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References

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