Time-of-flight spectroscopy of the energy distribution of laser-ablated atoms and ions
- Institut fuer Allgemeine Physik, TU Wien, Wiedner Hauptstrasse 8-10, A-1040 Wien (Austria)
The growth of ultrathin films, deposited by laser ablation, crucially depends on the energy of the ablated species. Therefore, a time-of-flight (TOF) spectrometer has been constructed and measurements have been carried out in order to determine the energy distribution of laser-ablated Fe and Pt atoms and ions in the plasma created by nanosecond pulses of a frequency-doubled neodymium doped yttrium aluminum garnet laser. The experiments have been performed in ultrahigh vacuum at relatively low laser power. For measuring the spectra of the neutrals, a cross-beam electron source for postionization and electric as well as magnetic fields for repelling the ions are employed. Nevertheless, measurements of neutral particles are restricted to low plasma densities due to electrostatic shielding within the plasma, leading to an inefficient deflection of charged particles by electrostatic and magnetic fields. Test measurements have been performed by utilizing the TOF spectrometer as a pressure gauge and also by chopping the electron beam, running the TOF spectrometer as a residual gas mass spectrometer. The spectra of the laser-ablated plasmas have shown plasma conditions with a Debye length of approximately 10{sup -4} m, densities of 10{sup 15}-10{sup 16} m{sup -3} and ion energies up to 150 eV. Neutral spectra have shown an unexpectedly low fraction of neutrals (10{sup -3}-10{sup -4}) and hyperthermal energies up to several 10 eV, possibly contributed by recombination of ions and electrons in the plasma. Even though gas spectra had demonstrated the expected sensitivity of the TOF spectrometer for low-energy neutrals, no thermally evaporated neutral atoms could be found.
- OSTI ID:
- 21123885
- Journal Information:
- Review of Scientific Instruments, Vol. 79, Issue 4; Other Information: DOI: 10.1063/1.2901607; (c) 2008 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0034-6748
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ALUMINIUM
DOPED MATERIALS
ELECTRON BEAMS
ELECTRON SOURCES
ENERGY BEAM DEPOSITION
ENERGY SPECTRA
EV RANGE
IONS
LASER RADIATION
LASERS
MAGNETIC FIELDS
MASS SPECTROMETERS
PLASMA
PLASMA DENSITY
PLATINUM
PRESSURE GAGES
SPECTROSCOPY
TIME-OF-FLIGHT METHOD
TIME-OF-FLIGHT SPECTROMETERS