Structures and coalescence behavior of size-selected silicon nanoclusters studied by surface-plasmon-polariton enhanced Raman spectroscopy
- Lawrence Livermore National Laboratories, Livermore, California 94550 (United States)
- NEC, Silicon Systems Research Laboratories, Tsukuba (Japan)
- Lucent Technologies, Bell Laboratories, Murray Hill, New Jersey 07974-0636 (United States)
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208 (United States)
The structures and coalescence behavior of size-selected, matrix-isolated silicon clusters have been studied using surface-plasmon-polariton (SPP) enhanced Raman spectroscopy. The cluster ions were produced in a laser vaporization source, mass selected then deposited into a co-condensed matrix of Ar, Kr or N{sub 2} on a liquid He cooled substrate. Raman spectra from monodisperse samples of the smaller clusters studied, Si{sub 4}, Si{sub 6} and Si{sub 7}, show sharp, well-resolved, vibrations which are in good agreement with predictions based on {ital ab initio} calculations. From these comparisons we confirm that Si{sub 4} is a planar rhombus, and assign Si{sub 6} as a distorted octahedron and Si{sub 7} as a pentagonal bypyramid. Si{sub 5} depositions down to 5 eV did not reveal a measurable Raman spectrum under our experimental conditions. Evidence for cluster{endash}cluster aggregation (or fragmentation) was observed under some conditions, even for a {open_quotes}magic number{close_quotes} cluster such as Si{sub 6}. The spectra of the aggregated small clusters were identical to those observed for directly deposited larger cluster {open_quotes}bands,{close_quotes} such as Si{sub 25{endash}35}. The Raman spectra of the aggregated clusters bear some similarity to those of bulk amorphous silicon. Cluster-deposited thin films were prepared by sublimating the matrix material. Even under these {open_quotes}soft landing{close_quotes} conditions, changes in the Raman spectrum are observed with the thin films showing even greater similarity to amorphous silicon. {copyright} {ital 1999 American Institute of Physics.}
- OSTI ID:
- 345411
- Journal Information:
- Journal of Chemical Physics, Vol. 110, Issue 24; Other Information: PBD: Jun 1999
- Country of Publication:
- United States
- Language:
- English
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