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The erosion plume resulting from ablation of copper and tantalum targets in vacuum with excimer laser irradiation (308 nm) was studied using Langmuir probe and optical emission spectroscopy. The ion and electron probe currents were obtained in the range of energy densities from 0.2 to 2.2 J/cm2 at the target with a probe-to-target distance from 10 to 133 mm. The ion velocity distribution calculated from the time-of-flight measurements has been revealed as a multimodal kind. Curves of the spatial and time dependence of electron probe current were obtained in real time. The electron temperature of different plume regions was determined from a series of I-U characteristics taken at different distances between the Langmuir probe and target. It was established that the plume electron temperature is nonuniform and it has a maximum in front of the plume. The optical emission spectra were used to study the plume composition qualitatively. In addition, the optical emission spectroscopy allowed us to measure both the ion and atom velocities by time-of-flight measurements. The electron temperature was calculated from the continuum part of the optical spectrum of the plume radiation. The results obtained were compared with probe measurements of electron temperature and ion velocity. An acceleration of tantalum ions has been performed successfully with CO[sub 2] laser irradiation perpendicular to the plume expansion. An increase of about 25 eV was observed in the middle ion energy. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

In thin tantalum films grown by pulsed laser deposition in a vacuum, the resistivity versus thickness dependence is found to oscillate. The oscillation periods equal 5.0 and 5.6 nm for α- and β-Ta films, respectively. This observation is interpreted as the quantum-size effect in thin tantalum films. © 2005 Pleiades Publishing, Inc. [ABSTRACT FROM AUTHOR]