Preferential amorphisation of Ge nanocrystals in a silica matrix
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Date
2005-01-31
Journal Title
Journal ISSN
Volume Title
Publisher
Australian Institute of Physics
Abstract
Relative to bulk crystalline material, Ge nanocrystals in a silica matrix exhibit subtle structural perturbations including a non-Gaussian inter-atomic distance distribution. We now demonstrate such nanocrystals are extremely sensitive to ion irradiation. Using transmission electron microscopy, Raman spectroscopy and extended x-ray absorption fine structure spectroscopy, the crystalline-to-amorphous phase transformation in -8 nm diameter nanocrystals and bulk crystalline material has been compared. Amorphisation of Ge nanocrytals in a silica matrix was achieved at an ion dose -100 times less than that required for bulk crystalline standards. This rapid amorphisation of Ge nanocrystals is attributed to the preferential nucleation of the amorphous phase at the nanocrystal/matrix interface, the pre-irradiation, higher-energy structural state of the nanocrystals themselves and an enhanced nanocrystal vacancy concentration due to the more effective trapping of irradiation-induced interstitials at the nanocrystal/matrix interface and inhibited Frenkel pair recombination when Ge interstitials are recoiled into the matrix. To demonstrate the significance of the latter, we show ion irradiation of -2 nm diameter nanocrystals yields their dissolution when the range of recoiled Ge atoms exceeds the nanocrystal bounds.
Description
Keywords
Charged particles, Crystal defects, Crystal structure, Electron microscopy, Elements, Laser spectroscopy, Metals, Microscopy, Minerals, Oxide minerals, Point defects, Spectroscopy
Citation
Ridgway, M. C., Azevedo, G. M., Elliman, R. G., Wesch, W., Glover, C. J., Miller, R., Llewellyn, D. J., Foran, D. J., Hansen, J. L. & Nylandsted Larsen, A. (2005). Preferential amorphisation of Ge nanocrystals in a silica matrix. Paper presented to the 29th Condensed Matter and Materials Meeting, "Australian Institute of Physics Sixteenth Biennial Congress", Canberra, 2005, 31 January - 4 February 2005, 149-150.