Optical conductivity of high- T c cuprate thin films deposited by multi-target laser ablation

Abstract : Superconducting cuprate thin films were grown upon MgO single crystals by alternating laser pulses in controlled sequences upon an insulating MCuO2 target (M = Ca, Sr) and a YBa2 Cu3 O7-delta (YBCO) target. The infrared conductivity of the series of films obtained by this multi-target laser ablation technique is deduced from the analysis of infrared reflectivity. The method of fitting by a `double-damping' Drude model is emphasized and applied to cuprate thin films in a situation in which current Kramers-Kronig analysis is hardly applicable. The agreement of experiment and model is found to be as good as for other conducting oxides investigated previously, including those without transition-metal elements. The concentration dependence of the infrared conductivity profile is discussed.