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ABSTRACT: The expansion dynamics of the plasma generated during pulsed laser deposition of gold in vacuum has been
investigated at the laser fluences of 2.5, 6.0, and 9.0 J cm−2. A severe distortion of the expansion is observed
in the presence of a substrate that is accompanied at 9.0 J cm−2 by the appearance of a secondary plasma front
expanding from the substrate surface. Langmuir probe analysis at 9.0 J cm−2 shows that the substrate surface
is bombarded by a high transient flux of energetic Au+ ions �3.0�1019 ions cm−2 s−1� having very large kinetic
energies ��400 eV�. Analysis of the plasma dynamics shows that these observations are consistent with
self-sputtering of Au neutrals from the substrate induced by incident Au ions while a fraction of them are
backscattered. Self-sputtering is found to be 2 orders of magnitude larger than backscattering. The comparison
with experimental data allows concluding that the apparent recoil of the plasma front is caused by collision
with self-sputtered neutrals, while the secondary emission is originated by backscattered ions.
Physical Review B 07/2007; · 3.69 Impact Factor
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ABSTRACT: We report a technique that is able to achieve high spatial resolution in the measurement of the temporal and spectral emission characteristics of laser-induced expanding plasmas. The plasma is imaged directly onto the slit of an imaging spectrograph coupled to a time-gated intensified camera, with the plasma expansion direction being parallel to the slit extension. In this way, a single hybrid detection system is used to acquire the spatial, spectral and temporal characteristics of the laser induced plasma. The parallel acquisition approach of this technique ensures a much better spatial resolution in the expansion direction, reproducibility and data acquisition speed than commonly obtained by sequential measurements at different distances from the target. We have applied this technique to study the laser-induced plasma in LiNbO 3 and Bi 12 Ge 1 O 20 , revealing phenomena not seen in such detail with standard instruments. These include extreme line broadening up to a few nanometers accompanied by self-absorption near the target surface, as well as different ablation and expansion dynamics for the different species ejected. Overall, the high precision and wealth of quantitative information accessible with this technique open up new possibilities for the study of fundamental plasma expansion processes during pulsed laser ablation. D 2005 Elsevier B.V. All rights reserved.
07/2005;
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ABSTRACT: Optical emission spectroscopy is used to investigate the spatial evolution of the electron temperature (T<sub>e</sub>) and electron density (N<sub>e</sub>) in the plasma generated by laser ablation in a vacuum of a wide-band-gap material, such as LiF, with a pulsed 193 nm excimer laser operating at a fluence of 1.5 J cm <sup>-2</sup> close to the threshold. It is found that, whereas N<sub>e</sub> (in the range of 10<sup>16</sup> cm <sup>-3</sup> ) decreases by a factor of 2 as the distance to the target increases, T<sub>e</sub> exhibits a sharp decrease (from 1.85 eV to 0.66 eV) between 1 and 2 mm from the target and it remains practically constant for longer distances from the target. These results provide direct measurements of the electron temperature and density during nanosecond laser ablation of LiF.
Applied Physics Letters 06/2005; · 3.84 Impact Factor
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ABSTRACT: Lead–niobium-germanate glass thin films have been produced by pulsed laser deposition in a broad O2 pressure range (10-6–10-1mbar). The cation composition in the films approaches that of the glass target for a pressure of 10-2mbar. The oxygen content is only close to or above that of the glass for a pressure close to 10-1mbar, for which a Pb enrichment is also observed. Films grown in vacuum are highly absorbing, whereas transparent films with an absorption edge shifted to the UV with respect to the bulk glass are produced for pressures higher than 10-2mbar. The evolution of the optical energy gap and the refractive index of the films with the oxygen pressure is correlated to the changes observed in the film composition and discussed in terms of the features of the deposition process, the role of oxygen in the formation of the glass network and the progressive increase of the oxidation state of the cations as the oxygen pressure is increased.
Applied Physics A 11/2004; 79(8):1907-1911. · 1.63 Impact Factor
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ABSTRACT: We report a hybrid imaging technique capable of performing measurements of the spatial, temporal, and spectral emission characteristics of laser-induced plasmas by use of a single detection system. We apply this technique to study the plasma produced by laser ablation of LiNbO3 and observe phenomena not seen in such detail with standard instruments. These include extreme line broadening up to a few nanometers accompanied by self-absorption near the target surface, and expansion dynamics that differ strongly between the different species. Overall, the wealth of quantitative information provided by this novel technique sheds new light on processes occurring during plasma expansion.
Optics Letters 11/2004; 29(19):2228-30. · 3.40 Impact Factor
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ABSTRACT: Heavy metal oxide thin films of the ternary system Nb2O5–GeO2–PbO have been prepared by pulsed laser deposition in an O2 environment from either glassy or crystalline bulk samples. The range of ([Pb]+[Nb]) content in which the films are optically
homogeneous and transparent is much broader (0.5–1.0) than that of the bulk samples considered in the present work (0.55–0.62).
The imaginary part of the refractive index is very low in all cases (k<10-3), whereas the real part increases linearly with the ([Pb]+[Nb]) content up to values as high as 2.35. The optical energy
gap has been found to be strongly dependent on [Pb], whereas it is almost independent of [Nb]. This dependence is discussed
in terms of the role of Pb and Nb as network modifiers or formers.
Applied Physics A 01/2003; 76(6):943-946. · 1.63 Impact Factor
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ABSTRACT: This paper focuses on the preparation and characterization of crystalline thin films of rare-earth-doped sesquioxides (Y2O3, Lu2O3,and Sc2O3) grown by pulsed laser deposition (PLD) on single-crystal (0001) sapphire substrates. X-ray diffraction (XRD) measurements show that the films with thicknesses between 1 and 500nm were highly textured along the [111] direction. Using Rutherford backscattering (RBS) analysis the correct stoichiometric composition of the films could be proved. The emission and excitation spectra of the europium-doped films down to a thickness of 100nm look similar to those of the corresponding crystalline bulk material, whereas films with 20nm thickness and below show a completely different emission behavior.
Materials Science and Engineering B-advanced Functional Solid-state Materials. 01/2003; 105(1):30-33.
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ABSTRACT: Optically active thin films on Si substrates have been produced by laser ablation of a Nd-doped potassium gadolinium tungstate
(Nd:KGW) single crystal. Films grown at low oxygen pressures (<0.6mbar) are potassium-deficient and appear to be mainly disordered.
They show a poor photoluminescence (PL) performance that improves upon annealing in air at temperatures in the range 700–1000°C.
Films grown at high oxygen pressure (1mbar) show instead good stoichiometry and the presence of a dominant textured gadolinium-tungstate
phase compared to KGW. These films have low absorption, a refractive index close to that of bulk KGW and good PL performance,
the emission lifetimes being longer (τ>150μs) under certain conditions than those measured in the single-crystal material.
Applied Physics A 12/2001; 74(1):109-113. · 1.63 Impact Factor
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ABSTRACT: Emission spectroscopy is used to determine the spatial and temporal evolution of the electronic temperature (Te) and density (Ne) of the plasma generated by laser ablation in vacuum of a LiNbO3 target. It is found that whereas Ne (in the range of 1016 cm−3) decreases by a factor of 2 as the distance to the target surface increases 10 mm, Te (in the range 0.7–0.8 eV) only decreases 10% between 2 and 4 mm from the target to remain nearly constant for longer distances. While Te is almost constant in time at the studied distances, Ne presents a maximum at a time delay that increases when increasing the distance to the target surface. The space–time constancy of Te is related to a collisional decoupling of the heavy species in the plasma for distances longer than 2–4 mm. © 2001 American Institute of Physics.
Applied Physics Letters 12/2000; 78(1):7-9. · 3.84 Impact Factor
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ABSTRACT: Fast photography of the plume produced by laser ablation of LiNbO3 in vacuum has been performed using an image intensified CCD (ICCD) camera in a time interval up to 2 7s after the laser pulse. Two differently oriented single crystalline LiNbO3 targets were used. The results show that although the emission intensity of the laser-generated plume initially depends on the crystalline orientation of the target, it reaches a stationary state after several minutes which is the same for both targets orientations. Under these stationary conditions, the angular distribution of the Li atoms is found to be broader than that of Nb atoms. The observed less forward directed expansion of the Li species may explain the poor Li content normally observed in films grown by laser ablation of LiNbO3 in vacuum.
Applied Physics A 11/1999; 69(7):S141-S144. · 1.63 Impact Factor
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ABSTRACT: Optically active Er3+:Yb3+ codoped Y2O3 films have been produced on c-cut sapphire substrates by pulsed laser deposition from ceramic Er:Yb:Y2O3 targets having different rare-earth concentrations. Stoichiometic films with very high rare-earth concentrations (up to 5.5 × 1021 at cm− 3) have been achieved by using a low oxygen pressure (1 Pa) during deposition whereas higher pressures lead to films having excess of oxygen. The crystalline structure of such stoichiometric films was found to worsen the thicker the films are. Their luminescence at 1.53 μm and up-conversion effects have been studied by pumping the Yb3+ at 0.974 μm. The highest lifetime value (up to 4.6 ms) is achieved in films having Er concentrations of ≈ 3.5 × 1020 at cm− 3 and total rare-earth concentration ≈ 1.8 × 1021 at cm− 3. All the stoichiometric films irrespective of their rare-earth concentration or crystalline quality have shown no significant up-conversion.
Thin Solid Films 500:336-340. · 1.89 Impact Factor
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ABSTRACT: Cited By (since 1996): 5, Export Date: 17 April 2012, Source: Scopus, Art. No.: 035435, CODEN: PRBMD, doi: 10.1103/PhysRevB.76.035435, Language of Original Document: English, Correspondence Address: Gonzalo, J.; Laser Processing Group, Instituto de Optica, CSIC, Serrano 121, 28006 Madrid, Spain; email: j.gonzalo@io.cfmac.csic.es, References: (1994) Pulsed Laser Deposition of Thin Films, , edited by D. B. Chrisey and G. K. Hubler (Wiley, New York;
Physical Review B - Condensed Matter and Materials Physics. 76(3).
