Prolonged laser ablation effects of YBCO ceramic targets during thin film deposition: Influence of processing parameters
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Cumulative laser irradiation during high-Tc superconducting thin film pulsed laser deposition (PLD) may have a detrimental effect on film characteristics. Initial decrease of deposition rate and gradual shift of the center of the deposited material spot towards the incoming laser beam were registered on cold glass substrates. Their absorbance was used for evaluation of the film thickness distribution over the substrate area. At the initial stage, two components of the spot could be distinguished along its short axis: central (∼cosn θ, n≫1) and peripherial (∼cos θ), while with cumulative irradiation the thickness followed an overall cosm θ (m<n) angular distribution. Two stages of the laser-induced plasma optical emission evolution were observed, according to target surface morphology modification. Compositional and morphology changes of the ceramic YBCO target under prolonged XeCl laser irradiation were studied by EDAX and SEM for different processing parameters — laser fluence and oxygen environment. The results can be consistently explained suggesting the existence of an additional effective ablation threshold imposed by the modified surface relief.
PACS numbers74.76.−w 81.15.Fg
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