Vibrational properties of Ge nanocrystals determined by EXAFS
- Department of Electronic Materials Engineering, Research School of Physical Sciences and Engineering, Australian National University, Canberra (Australia)
Extended x-ray absorption fine structure (EXAFS) spectroscopy was applied to probe the vibrational properties of bulk crystalline Ge (c-Ge) and Ge nanocrystals (Ge NCs) of 4.4 nm mean diameter produced by ion implantation in SiO{sub 2} followed by thermal annealing. EXAFS measurements around the Ge K edge were carried out in the temperature range from 8 to 300 K at beam line 10-2 of the Stanford Synchrotron Radiation Laboratory (SSRL). Original information about thermal and static disorder, thermal expansion, and anharmonicity effects have been obtained for c-Ge and Ge NCs from temperature dependent EXAFS measurements using a correlated anharmonic Einstein model and thermodynamic perturbation theory. It was observed that the Ge NCs were stiffer (showed a stronger bond force constant) than both amorphous Ge (a-Ge) and c-Ge. Also, the values of the linear thermal expansion (thermal evolution of the mean interatomic distance) obtained for the Ge NCs were smaller than the ones obtained for c-Ge. These results were compared to the ones obtained for other nanocrystalline systems. They suggest that the increased surface to volume ratio of the nanocrystalline form and the presence of the surrounding SiO{sub 2} matrix might be responsible for the different vibrational properties of c-Ge and Ge NCs.
- OSTI ID:
- 20853867
- Journal Information:
- Physical Review. B, Condensed Matter and Materials Physics, Vol. 74, Issue 18; Other Information: DOI: 10.1103/PhysRevB.74.184102; (c) 2006 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1098-0121
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ABSORPTION SPECTROSCOPY
ANNEALING
CRYSTALS
FINE STRUCTURE
GERMANIUM
INTERATOMIC DISTANCES
ION IMPLANTATION
NANOSTRUCTURES
PERTURBATION THEORY
SEMICONDUCTOR MATERIALS
SILICON OXIDES
SURFACES
SYNCHROTRON RADIATION
TEMPERATURE DEPENDENCE
THERMAL EXPANSION
X-RAY SPECTROSCOPY