Acoustic wave monitoring of the excimer laser ablation of YBCO high-Tc superconductor

Abstract.

Monitoring the amplitude and the delay of arrival of the pressure waves generated during the interaction of laser pulses with YBCO in air, we can determine the vaporization and the ablation thresholds, the etching rate, the change of the acoustic wave velocity and the effect of plasma shielding on the etching rate. The steep increase of the amplitude and the order-of-magnitude increase of the etching rate above the ablation threshold, suggest that the laser–target coupling mechanism changes from (thermal) vaporization below threshold to a rapid solid-to-gas phase transition. The dumping of the acoustic waves following the ablation with successive laser pulses correlates with the evolution of the YBCO high-T_c superconductor surface morphology, which is known to relate to the deposition rate and the surface morphology of pulsed-laser-deposited high-T_c thin films.