Laser ablation of ceramic Al{sub 2}O{sub 3} at 193 nm and 248 nm: The importance of single-photon ionization processes

Journal Article · Fri Jun 14 00:00:00 EDT 2013 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.4809639· OSTI ID:22163022

Pelaez, R. J.; Afonso, C. N. ^[1]; Bator, M.; Lippert, T. ^[2]

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1. Laser Processing Group, Instituto de Optica, CSIC, Serrano 121, Madrid 28006 (Spain)
2. General Energy Research Department, Paul Scherrer Institut, CH-5232 Villigen PSI (Switzerland)

The aim of this work is to demonstrate that single-photon photoionization processes make a significant difference in the expansion and temperature of the plasma produced by laser ablation of ceramic Al{sub 2}O{sub 3} in vacuum as well as to show their consequences in the kinetic energy distribution of the species that eventually will impact on the film properties produced by pulsed laser deposition. This work compares results obtained by mass spectrometry and optical spectroscopy on the composition and features of the plasma produced by laser ablation at 193 nm and 248 nm, i.e., photon energies that are, respectively, above and below the ionization potential of Al, and for fluences between threshold for visible plasma and up to Almost-Equal-To 2 times higher. The results show that the ionic composition and excitation of the plasma as well as the ion kinetic energies are much higher at 193 nm than at 248 nm and, in the latter case, the population of excited ions is even negligible. The comparison of Maxwell-Boltzmann temperature, electron temperatures, and densities of the plasmas produced with the two laser wavelengths suggests that the expansion of the plasma produced at 248 nm is dominated by a single population. Instead, the one produced at 193 nm is consistent with the existence of two populations of cold and hot species, the latter associated to Al{sup +} ions that travel at the forefront and produced by single photon ionization as well as Al neutrals and double ionized ions produced by electron-ion impact. The results also show that the most energetic Al neutrals in the plasma produced at the two studied wavelengths are in the ground state.

• OSTI ID: 22163022
• Journal Information: Journal of Applied Physics, Vol. 113, Issue 22; Other Information: (c) 2013 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ABLATION
ALUMINIUM IONS
ALUMINIUM OXIDES
CERAMICS
DENSITY
DISTRIBUTION
ELECTRON TEMPERATURE
ENERGY BEAM DEPOSITION
EXCITATION
EXPANSION
FILMS
GROUND STATES
LASER RADIATION
MASS SPECTROSCOPY
PHOTOIONIZATION
PULSED IRRADIATION
STATISTICAL MECHANICS
WAVELENGTHS