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In Situ Plasma Characterization of Laser-Ablated BaxSr1-xTiO3

Published online by Cambridge University Press:  10 February 2011

D. T. Venizelos ,
S. Sengupta  and
R. C. Sausa
D. T. Venizelos
Affiliation:
NRC/ARL Postdoctoral Research Associate
S. Sengupta
Affiliation:
U.S. Army Research Laboratory, AMSRL-WM-PC, Aberdeen Proving Ground, MD 21005
R. C. Sausa
Affiliation:
U.S. Army Research Laboratory, AMSRL-WM-PC, Aberdeen Proving Ground, MD 21005
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Abstract

High speed imaging and emission spectroscopy are used to characterize the plumes generated from the ablation of bulk barium strontium titanium oxide material in vacuum and 30–60 mTorr of O2 using a pulsed 248-nm laser with fluences ranging from 5–8 J/cm2. High speed imaging reveals that in vacuum the leading edge of the plume expands normal to the substrate surface with a velocity of 19.7 km/sec. The ratio of distance traveled to the plume's radius is ˜ 2 at the early stages of the expansion and 3.2 at the later stages near the substrate. Similar observations are observed when the plume expands in 30 mTorr of O2 for times less than 2.0 μsec. However, at times greater than 2.0 μsec the plume's expansion is retarded due to collisional momentum transfer and reactions with the background gas. This effect is more pronounced when the plume expands in 60 mTorr of O2. Blast wave theory is used to model these results. Time-resolved emission spectroscopy of Ba(I) lines in the 735–770 nm region reveals that the plume' electron temperatures, Te, in a vacuum expansion range from 18000±2000 K at 0.1 μsec to 15000±1500 K at 2.0 /μsec. In contrast, in 30 mTorr of O2 the values of Te range from 17000±2000 K at 0.1 μsec to 4000±500 K at 8.0 μsec. At 0.1 μsec the plume's electron density is estimated as 1.7±0.4 × 1017 cm−3 in both vacuum and 30 mTorr of O2. We also determine the Stark broadening of the Ba(I) line at 746 nm to be 0.5±0.1 Åat an electron temperature of 1 eV and an electron density of 1017 cm−3.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 502: Symposium II – In Situ Process Diagnostics & Intelligent Materials Processing , 1997 , 187
Copyright
Copyright © Materials Research Society 1998

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References

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