Dissociation of large silicon clusters: the approach to bulk behavior

Jarrold, Martin F.; Honea, Eric C.

doi:10.1021/j100176a028

Cited by 200 publications

(166 citation statements)

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“…22 As demonstrated in the cluster-surface collision experiments of St. John and Whetten, 49 fragmentation is even less likely for silicon clusters deposited at 25 eV, since they have higher dissociation energies and the larger clusters have correspondingly larger heat capacities. 3 In our experiments, evidence of fragmentation was only observed at the higher deposition energies. For example, Si 10 clusters show the Raman signature of Si 4 and Si 6 clusters at high deposition energies.…”

Section: Fragmentation And/or Aggregation Of Deposited Clusters Inmentioning

confidence: 42%

“…For instance, fusion of two Si 6 clusters to form Si 12 would release roughly 3 eV of energy. 3 A small fraction of this energy could melt a large volume of matrix, further increasing diffusion and subsequent aggregation of clusters.…”

Section: E Matrix Aggregation Of Clusters and Clusterdeposited Thin mentioning

confidence: 99%

“…1 Silicon clusters, in particular, have demonstrated many fascinating properties. [2][3][4] While impressive progress has been made in the understanding of this range of matter between atoms and bulk materials, structural information has been more difficult to obtain. High level calculations [5][6][7] and studies using empirical potentials 8,9 predict that silicon clusters differ significantly from the bulk crystal lattice and surfaces, i.e., they are extensively reconstructed compared to microcrystal fragments.…”

Section: Introductionmentioning

confidence: 99%

“…Many of the observed properties of silicon clusters have been interpreted as evidence for three dimensional reconstruction, 2,3 even for clusters containing up to 70 atoms ͑ϳ10 Å diameter͒. Since small particles of silicon of 20-30 Å diameter have been observed to have crystalline bulklike lattices, 14,15 obtaining information about the structures of small clusters and the transition to bulklike crystalline or amorphous structure would be extremely important in the study of basic material properties and growth processes.…”

Section: Introductionmentioning

confidence: 99%

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Structures and coalescence behavior of size-selected silicon nanoclusters studied by surface-plasmon-polariton enhanced Raman spectroscopy

Honea

Ogura

Peale³

et al. 1999

The Journal of Chemical Physics

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The structures and coalescence behavior of size-selected, matrix-isolated silicon clusters have been studied using surface-plasmon-polariton ͑SPP͒ 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 2 on a liquid He cooled substrate. Raman spectra from monodisperse samples of the smaller clusters studied, Si 4 , Si 6 and Si 7 , show sharp, well-resolved, vibrations which are in good agreement with predictions based on ab initio calculations. From these comparisons we confirm that Si 4 is a planar rhombus, and assign Si 6 as a distorted octahedron and Si 7 as a pentagonal bypyramid. Si 5 depositions down to 5 eV did not reveal a measurable Raman spectrum under our experimental conditions. Evidence for cluster-cluster aggregation ͑or fragmentation͒ was observed under some conditions, even for a ''magic number'' cluster such as Si 6 . The spectra of the aggregated small clusters were identical to those observed for directly deposited larger cluster ''bands,'' such as Si [25][26][27][28][29][30][31][32][33][34][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 ''soft landing'' conditions, changes in the Raman spectrum are observed with the thin films showing even greater similarity to amorphous silicon.

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Section: Fragmentation And/or Aggregation Of Deposited Clusters Inmentioning

confidence: 42%

Section: E Matrix Aggregation Of Clusters and Clusterdeposited Thin mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Structures and coalescence behavior of size-selected silicon nanoclusters studied by surface-plasmon-polariton enhanced Raman spectroscopy

Honea

Ogura

Peale³

et al. 1999

The Journal of Chemical Physics

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“…The proportionality constant is the fraction of the cluster ions translational energy that is converted into internal energy. This quantity can be estimated from a simple impulsive collision model, [19,20] …”

Section: Methodsmentioning

confidence: 99%

Ion calorimetry: Using mass spectrometry to measure melting points

Neal

Starace

Jarrold

2007

J. Am. Soc. Mass Spectrom.

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Calorimetry measurements have been used to probe the melting of aluminum cluster cations with 63 to 83 atoms. Heat capacities were determined as a function of temperature (from 150 to 1050 K) for size-selected cluster ions using an approach based on multicollision-induced dissociation. The experimental method is described in detail and the assumptions are critically evaluated. Most of the aluminum clusters in the size range examined here show a distinct peak in their heat capacities that is attributed to a melting transition (the peak is due to the latent heat). The melting temperatures are below the bulk melting point and show enormous fluctuations as a function of cluster size. Some clusters (for example, n ϭ 64, 68, and 69) do not show peaks in their heat capacities. This behavior is probably due to the clusters having a disordered solid-like phase, so that melting occurs without a latent heat. (J Am Soc Mass Spectrom 2007, 18, 74 -81)

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Strukturübergänge in Clustern

Hartke

2002

Angew. Chem.

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Lagert man an einen Cluster aus einzelnen Teilchen weitere Teilchen an, so bleibt die energetisch günstigste Grundstruktur weder erhalten noch ändert sie sich kontinuierlich. Stattdessen findet man Größenbereiche mit jeweils einem stark dominierenden Bauprinzip und vergleichsweise schmale Grenzen zwischen diesen Bereichen. Die Struktur des Festkörpers wird in der Regel erst nach mehreren Strukturübergängen bei relativ großen Clustern erreicht. Für das Auftreten dieser Strukturübergänge scheint es keine Rolle zu spielen, ob die Teilchen Atome oder Moleküle sind und ob der Cluster homogen oder heterogen ist. Offenbar handelt es sich um ein kollektives Vielteilchenphänomen, das in rein reduktionistischer Sicht zwar prinzipiell berechnet, aber nicht einfach verstanden werden kann. Weil die tatsächliche Berechnung bei hinreichender Genauigkeit derzeit noch am viel zu hohen Rechenaufwand scheitert – auch beim Einsatz unkonventioneller evolutionärer Algorithmen zur globalen Geometrieoptimierung –, wären einfachere Strukturregeln sehr wertvoll. Denn bei diesen Strukturübergängen geht es nicht nur um die akademische Frage nach dem Zusammenhang zwischen Potentialenergiefläche und Clusterstruktur, sondern auch um wichtige Vorgänge in der Natur und in der technischen Chemie, vom Wachstum von Kristallkeimen bis zur Nanotechnologie. Hier wird eine exemplarische Übersicht über die Untersuchung von Strukturübergängen bei Clustern gegeben – von einfachen Modellsystemen, bei denen erste qualitative Erklärungsversuche bereits Erfolge zeigen, bis zu realistischeren, komplexen Systemen, die sich unserem Verständnis noch weitestgehend entziehen.

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Dissociation of large silicon clusters: the approach to bulk behavior

Cited by 200 publications

References 0 publications

Structures and coalescence behavior of size-selected silicon nanoclusters studied by surface-plasmon-polariton enhanced Raman spectroscopy

Structures and coalescence behavior of size-selected silicon nanoclusters studied by surface-plasmon-polariton enhanced Raman spectroscopy

Ion calorimetry: Using mass spectrometry to measure melting points

Strukturübergänge in Clustern

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