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Plasma Dynamics During Pulsed Laser Evaporation of High Tc Superconductors

Published online by Cambridge University Press:  26 February 2011

Rajiv K. Singh
Affiliation:
Materials Science and Engineering Department, University of Florida, Gainesville, FL 32611–2066
R. Neifeld
Affiliation:
US Army SLCET-ED LABCOM, ETDL, Fort Monmouth, NJ.
J. Narayan
Affiliation:
Department of Materials Science and Engineering, North Carolina State University, Raleigh NC 27695–7916
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Abstract

We have theoretically and experimentally investigated the dynamics of the evaporated material generated by nanosecond excimer laser irradiation of YBa2Cu3O7 targets in vacuum. The velocity distribution and the ionization of the plasma were determined by the ion time of flight measurements. The excimer laser ablated species possessed very high velocities (> 106 cm/sec) which increased non-linearly with energy density. The ionization/ volume of the evaporated material exhibited a weak dependence on energy density, thereby suggesting the role of nonthermal mechanisms in the ionization process. These experimental results have been correlated with the theoretical model analyzing the plasma dynamics during pulsed laser evaporation of materials. A new modification to the earlier theoretical model is developed which accurately predicts the terminal velocities and the effect of ionization on these velocities. Various factors including, evaporation rates, degree of ionization, and laser wavelength which affect the plasma velocities will also be discussed.

Type
Research Article
Copyright
Copyright © Materials Research Society 1991

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