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Proceedings Paper

Mechanisms of droplet formation in pulsed laser growth of thin oxide films
Author(s): Valentin Craciun; Doina Craciun; M. C. Bunescu; Eugen Vasile; A. Ioncea; Razvan V. Dabu; Ian W. Boyd
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Paper Abstract

The role of the sub-surface explosive boiling mechanism for droplet formation during the pulsed laser deposition of thin films has been examined. For photons with an energy lower than the target optical band-gap, hv<Eg, a highly perturbed target surface morphology exhibiting micrometer sized round- shaped cavities always formed, whereas for hv>Eg the surface was much less perturbed. Depth-profile estimations of the temperature profiles inside the laser irradiated targets were also quite different for these two cases. For low optical absorption coefficient (OAC) values, (alpha) < 5 X 104 cm-1, a thick layer of liquid formed whose maximum temperature was located at some point below the surface. Simultaneous to the cavity formation, the droplet density on the surface of the grown films was found to increase by orders of magnitude, indicating a clear connection between the target OAC, the temperature profile, the presence of the cavities and a high droplet density. The decrease of the OAC value during prolonged laser ablation could also explain the gradual increase of the droplet density observed when growing La0.5Sr0.5CoO3 films. Based on these results, we suggest that an important fraction of the droplets on the surface of films grown under laser irradiation conditions where the OAC is smaller than 5 X 104 cm-1 is caused by an explosive sub-surface boiling mechanism.

Paper Details

Date Published: 2 July 1998
PDF: 8 pages
Proc. SPIE 3405, ROMOPTO '97: Fifth Conference on Optics, (2 July 1998);
Show Author Affiliations
Valentin Craciun, National Institute for Laser, Plasma, and Radiation Physics (Romania)
Doina Craciun, National Institute for Laser, Plasma, and Radiation Physics (Romania)
M. C. Bunescu, METAV SA (Romania)
Eugen Vasile, METAV SA (Romania)
A. Ioncea, METAV SA (Romania)
Razvan V. Dabu, National Institute for Laser, Plasma, and Radiation Physics (Romania)
Ian W. Boyd, Univ. College London (United Kingdom)

Published in SPIE Proceedings Vol. 3405:
ROMOPTO '97: Fifth Conference on Optics
Valentin I. Vlad; Dan C. Dumitras, Editor(s)

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