Influence of adsorbates on UV-pulsed laser melting of Si in ultra-high vacuum |
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Authors: | B Dragnea J Boulmer D Débarre B Bourguignon |
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Institution: | (1) Laboratoire de Photophysique Moléculaire du CNRS, Batiment 210, Université de Paris-Sud, 91405 Orsay Cedex, France, FR;(2) Institut d’Electronique Fondamentale, Batiment 220, Université de Paris-Sud, 91405 Orsay Cedex, France, FR |
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Abstract: | The dynamics of laser melting of atomically clean Si is investigated in ultra-high-vacuum (UHV) by transient reflectivity
with single-pulse sensitivity in the presence of monitored amounts of chlorine, oxygen or propene. Adsorption of one monolayer
(1 ML) leads to measurable variations of the melting dynamics, which are strongly adsorbate-dependent. The variations differ
qualitatively and quantitatively from those observed with heavy exposures to gases. The melting dynamics returns to that of
clean Si upon subsequent irradiation by laser pulses without readsorption. The required number of pulses for return to clean
Si dynamics depends strongly on the type of adsorbate. Adsorbate-induced changes of absorption and reflectivity, and/or incorporation
of adsorbates into the substrate, do not explain the results. By contrast, the variations of the melting dynamics are correlated
to the photoemitted electron yield, suggesting that laser melting is sensitive to the presence of electrons in the conduction
band. These results show that accurate modelling of laser melting of Si interacting with gases should take into account the
presence of the gases.
Received: 12 September 2000 / Accepted: 9 January 2001 / Published online: 27 June 2001 |
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Keywords: | PACS: 61 82 Fk 79 20 Ds 81 40 Wx |
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