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Title: Preferential amorphisation of Ge nanocrystals in a silica matrix
Authors: Ridgway, MC
Azevedo, GDM
Elliman, RG
Wesch, W
Glover, CJ
Miller, R
Llewellyn, DJ
Foran, GJ
Hansen, JL
Nylandsted Larsen, A
Keywords: Charged particles
Crystal defects
Crystal structure
Electron microscopy
Laser spectroscopy
Oxide minerals
Point defects
Issue Date: 31-Jan-2005
Publisher: Australian Institute of Physics
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. Retrieved from:
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.
ISBN: 0-9598064-8-2
Appears in Collections:Conference Publications

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