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Title: Dynamics of confined plumes during short and ultrashort pulsed laser ablation of graphite

Abstract

The optical emission from electronically excited C species in the ablation plume following the short (ns) and ultrashort (fs) UV pulsed laser ablation of graphite is studied. Wavelength, time and spatially resolved imaging of the plume, in background pressures of inert gases such as argon and helium, is performed. Analysis of images of optical emission from C{sup +}* ions and C{sub 2}* radicals, yielded estimates of the apparent velocity of emitting species, which appear to arise both from the initial ablation event and, in the presence of background gas, mainly from impact excitation. At elevated background pressures of argon (P{sub Ar}), the formation and propagation of a shock wave is observed for ns pulses, whereas for fs pulses, the propagation of two shock waves is observed. During fs ablation, the first shock wave we associate with an initial burst of highly energetic/electronically excited ablated components, indicative of an enhanced fraction of non-thermal ejection mechanisms when compared with ns ablation. The second shock wave we associate with subsequently ejected, slower moving, material. Concurrent with the plume dynamics investigations, nanostructured amorphous carbon materials were deposited by collecting the ablated material. By varying P{sub Ar} from 5 to 340 mTorr, the film morphologymore » could be changed from mirror smooth, through a rough nanostructured phase and, at the highest background pressures for ns pulses, to a low density cluster-assembled material. The evident correlations between the film structure, the mean velocities of the emitting C species, and their respective dependences upon P{sub Ar} are discussed for both pulse durations. In addition, we comment on the effect of observed initial plume dynamics on the subsequent C cluster formation in the expanding plume.« less

Authors:
; ; ; ; ;  [1];  [2];  [3]
  1. Nano-Electronics Centre, Advanced Technology Institute, School of Electronics and Physical Sciences, University of Surrey, Guildford, GU2 7XH (United Kingdom)
  2. (United Kingdom)
  3. (Greece)
Publication Date:
OSTI Identifier:
20719842
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. B, Condensed Matter and Materials Physics; Journal Volume: 72; Journal Issue: 20; Other Information: DOI: 10.1103/PhysRevB.72.205413; (c) 2005 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ABLATION; ARGON; CARBON IONS; CORRELATIONS; EXCITATION; FILMS; GRAPHITE; HELIUM; LASER RADIATION; LUMINESCENCE; MORPHOLOGY; NANOSTRUCTURES; PULSES; SHOCK WAVES; SURFACES

Citation Formats

Henley, S.J., Carey, J.D., Silva, S.R.P., Fuge, G.M., Ashfold, M.N.R., Anglos, D., School of Chemistry, University of Bristol, Bristol, BS8 1TS, and Institute of Electronic Structure and Laser, Foundation for Research and Technology - Hellas, P.O. Box 1527, GR-711 10 Heraklion. Dynamics of confined plumes during short and ultrashort pulsed laser ablation of graphite. United States: N. p., 2005. Web. doi:10.1103/PhysRevB.72.205413.
Henley, S.J., Carey, J.D., Silva, S.R.P., Fuge, G.M., Ashfold, M.N.R., Anglos, D., School of Chemistry, University of Bristol, Bristol, BS8 1TS, & Institute of Electronic Structure and Laser, Foundation for Research and Technology - Hellas, P.O. Box 1527, GR-711 10 Heraklion. Dynamics of confined plumes during short and ultrashort pulsed laser ablation of graphite. United States. doi:10.1103/PhysRevB.72.205413.
Henley, S.J., Carey, J.D., Silva, S.R.P., Fuge, G.M., Ashfold, M.N.R., Anglos, D., School of Chemistry, University of Bristol, Bristol, BS8 1TS, and Institute of Electronic Structure and Laser, Foundation for Research and Technology - Hellas, P.O. Box 1527, GR-711 10 Heraklion. Tue . "Dynamics of confined plumes during short and ultrashort pulsed laser ablation of graphite". United States. doi:10.1103/PhysRevB.72.205413.
@article{osti_20719842,
title = {Dynamics of confined plumes during short and ultrashort pulsed laser ablation of graphite},
author = {Henley, S.J. and Carey, J.D. and Silva, S.R.P. and Fuge, G.M. and Ashfold, M.N.R. and Anglos, D. and School of Chemistry, University of Bristol, Bristol, BS8 1TS and Institute of Electronic Structure and Laser, Foundation for Research and Technology - Hellas, P.O. Box 1527, GR-711 10 Heraklion},
abstractNote = {The optical emission from electronically excited C species in the ablation plume following the short (ns) and ultrashort (fs) UV pulsed laser ablation of graphite is studied. Wavelength, time and spatially resolved imaging of the plume, in background pressures of inert gases such as argon and helium, is performed. Analysis of images of optical emission from C{sup +}* ions and C{sub 2}* radicals, yielded estimates of the apparent velocity of emitting species, which appear to arise both from the initial ablation event and, in the presence of background gas, mainly from impact excitation. At elevated background pressures of argon (P{sub Ar}), the formation and propagation of a shock wave is observed for ns pulses, whereas for fs pulses, the propagation of two shock waves is observed. During fs ablation, the first shock wave we associate with an initial burst of highly energetic/electronically excited ablated components, indicative of an enhanced fraction of non-thermal ejection mechanisms when compared with ns ablation. The second shock wave we associate with subsequently ejected, slower moving, material. Concurrent with the plume dynamics investigations, nanostructured amorphous carbon materials were deposited by collecting the ablated material. By varying P{sub Ar} from 5 to 340 mTorr, the film morphology could be changed from mirror smooth, through a rough nanostructured phase and, at the highest background pressures for ns pulses, to a low density cluster-assembled material. The evident correlations between the film structure, the mean velocities of the emitting C species, and their respective dependences upon P{sub Ar} are discussed for both pulse durations. In addition, we comment on the effect of observed initial plume dynamics on the subsequent C cluster formation in the expanding plume.},
doi = {10.1103/PhysRevB.72.205413},
journal = {Physical Review. B, Condensed Matter and Materials Physics},
number = 20,
volume = 72,
place = {United States},
year = {Tue Nov 15 00:00:00 EST 2005},
month = {Tue Nov 15 00:00:00 EST 2005}
}
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  • A modeling approach for calculating the expansion of a laser-generated plasma into a background gas has been developed. Although relatively simple in structure, the model gives excellent fits to various experimental data for Si in background gases of He and Ar, including the previously unexplained {open_quotes}splitting{close_quotes} of the ablated plume. The model is based on a combination of multiple-scattering and hydrodynamic approaches. It allows the plume to be broken up into components, or scattering orders, whose particles undergo 0, 1, 2,{hor_ellipsis} collisions with the background. Particles can only be transferred from one order to the next higher order by collisions.more » The densities in the individual orders propagate according to the usual conservation equations to give the overall plume expansion. When Ar is the background gas, there is a non-negligible probability that Si plume atoms will reach the detector without undergoing any collisions. This gives rise to a flux component that is undisplaced from that obtained when no background gas is present in addition to the delayed peak from the scattered flux. In Ar only a few orders are necessary for convergence. The behavior in the light gas He is more complex because of the relatively small effect of any one-scattering event and the calculations must be carried out in some cases to as high as the 12th scattering order to find agreement with the experiments. {copyright} {ital 1998} {ital The American Physical Society}« less
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