Ion-irradiation-induced preferential amorphization of Ge nanocrystals in silica

Journal Article · Tue Mar 01 00:00:00 EST 2005 · Physical Review. B, Condensed Matter and Materials Physics

DOI:https://doi.org/10.1103/PhysRevB.71.094107· OSTI ID:20666285

Ridgway, M C; Azevedo, G de M; Elliman, R G; Glover, C J; Llewellyn, D J; Miller, R; Wesch, W; Foran, G J; Hansen, J; Nylandsted-Larsen, A ^[1]

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1. Department of Electronic Materials Engineering, Research School of Physical Sciences and Engineering, Australian National University, Canberra (Australia)

Extended x-ray absorption fine structure (EXAFS) measurements have been used to characterize the ion-irradiation-induced crystalline-to-amorphous phase transformation in Ge nanocrystals. The atomic-scale structure of Ge nanocrystals in a silica matrix is first shown to deviate from that of bulk crystalline material with an increase in both Gaussian and non-Gaussian forms of structural disorder. The magnitude of the disorder in the bond-length distribution is comparable to that of relaxed amorphous Ge. The amorphization of such nanocrystals is then demonstrated at an ion dose {approx}100 times less than that required for bulk crystalline material irradiated simultaneously. Specifically, Ge nanocrystals irradiated at -196 deg. C are rendered amorphous at {approx}0.01 displacements per atom. Finally, we show the atomic-scale structure of amorphized nanocrystals and bulk amorphous material is comparable. The rapid amorphization of Ge nanocrystals is potentially the result of several factors including (i) the preferential nucleation of the amorphous phase at the nanocrystal/matrix interface (ii) the preirradiation, higher-energy structural state of the nanocrystals themselves (iii) an enhanced vacancy concentration within the nanocrystals due to inhibited Frenkel pair recombination when Ge interstitials are recoiled into the matrix, and (iv) ion-beam mixing and the subsequent increase in nanocrystal impurity concentrations.

• OSTI ID: 20666285
• Journal Information: Physical Review. B, Condensed Matter and Materials Physics, Vol. 71, Issue 9; Other Information: DOI: 10.1103/PhysRevB.71.094107; (c) 2005 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1098-0121
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ABSORPTION
ABSORPTION SPECTROSCOPY
AMORPHOUS STATE
BOND LENGTHS
FINE STRUCTURE
FRENKEL DEFECTS
GERMANIUM
IMPURITIES
INTERFACES
INTERSTITIALS
ION BEAMS
IONS
IRRADIATION
NANOSTRUCTURES
ORDER-DISORDER TRANSFORMATIONS
RADIATION DOSES
RECOMBINATION
SEMICONDUCTOR MATERIALS
SILICA
SILICON COMPOUNDS
X RADIATION
X-RAY SPECTROSCOPY