Stark broadening diagnostics of the electron density in the laser ablation plume of YBa2Cu3O7−x and PbZrxTi1−xO3

Abstract

Diagnostics of pulsed laser ablation and deposition of superconductive YBCO (YBa2Cu3O7−x) and ferroelectric PZT (PbZrxTi1−xO3) thin films has been accomplished by measuring the Stark broadening of the laser produced plume. Fluorescence emission has been collected from regions along the axis of the plume at different distances from the target surface. The line shape of some selected transitions has been analyzed and the electron density ne determined from the observed linewidth. The measured values of ne are in the range 0.4–30×1017 cm−3 for YBCO and 0.1–6×1017 cm−3 for PZT. A scaling law of ne as a function of the distance from the target has been found, which indicates a one-dimensional behavior in the early stage of the electron cloud expansion. The dependence of ne on the presence of the ambient oxygen gas and on the laser fluence has been also investigated. The results of the diagnostics are compared with theoretical predictions and correlated with the deposition parameters.

Resonant Laser Ablation Mass Spectrometry of Barium Compounds: Enhanced Ionization at the 455.4 nm Ba+ Absorption

“…The measured Ba+ emission linesz3 are 0.1-0.2 nm below (i.e.. transition energy due to the high electron density in the ablation plume. 25 The approximate Ba' absorption linewidth of e0.2nm estimated from the present results is somewhat narrower than has been reported for other atomic species in ablation plumes. For example, linewidths of 1-2 nm have been observed for Ca' emissionz6 and for CU and Na absorption.'…”

Resonant Laser Ablation of Lanthanides: Eu and Lu Resonances in the 450−470 nm Region

“…A high-resolution laser-induced fluorescence study of the Eu atomic transitions corresponding to the major Eu + resonances evident here determined their natural line widths as ∼10 -3 cm -1 . 26 The extreme atomic line broadening typically evident in laser ablation plumes is generally attributed to Stark interactions 27 and other collisional processes in the materially and optically dense plume environment. 28 Saturation and power broadening may also be significant in RLA: based upon the measured saturation power densities for atomic transitions 29 with comparable oscillator strengths, 25 the Eu 8 S 7/2 0 f 8 P 5/2,7/2,9/2 transitions should saturate at a spectral irradiance of ∼10 -7 W cm -2 Hz -1 , several orders of magnitude below the ∼10 -3 W cm -2 Hz -1 applied here.…”

Wavelength dependent refractive effects and Stark broadening in laser-induced YBa2Cu3Ox plasma plumes

“…It should be stressed that the data in Fig. 5͑a͒ correspond to a temporal regime where the electron density is falling rapidly due to plasma expansion and that the maximum electron density ͑and ion density͒ at 1.0 mm will occur at a shorter delay of ϳ0.05-0.1 s. Fuso et al 13 report values of ϳ1ϫ10 18 cm Ϫ3 at comparable distances from target following 308 nm laser ablation of YBCO at a higher laser fluence of 2.6 J cm Ϫ2 . Their values, although of comparable magnitude to our values, were estimated from line shapes of temporally integrated Ba͑II͒ emission so exact comparison of values is not possible.…”

“…The line shapes of absorption and emission lines are also sensitive to local plasma conditions ͑such as temperature, pressure and electron den-sity͒, so line shape measurement has considerable diagnostic potential in this fluence regime and, in particular, provides a spectroscopic method for determination of local electron densities from the magnitude of the corresponding Stark broadening. [12][13][14][15] Both emission and absorption spectroscopy measurements on plasma plumes yield spectral linewidths [11][12][13] which are markedly wider than the corresponding natural linewidths ͑ϳ10 Ϫ4 Å͒. Three broadening mechanisms are likely to contribute significantly to UV/visible linewidths observed in plasmas produced during pulsed laser deposition 16 viz.…”