Surface modification of laser ablated YBCO target

A modified surface layer of YBa ₂ Cu ₃ O _7-x (YBCO) target was systematically observed in the process of pulsed laser deposition (PLD) by scanning electron microscopy (SEM). We observed that the size of cones formed on the YBCO target by a pulsed laser became larger with increasing number of laser shots. The major effect of the surface modification like cone formation on PLD is a reduction of the deposition rate. To eliminate cones, we have used the method of rotating the target by 180° to shoot the same number of laser beams on the same spot from opposing angles. Experimental results of losing the directionality and changing the shape of cones formed on YBCO target surface by laser beams incident on the same spot from opposing angles are obtained. These results are mainly due to altering irradiation geometry because cones develop only under a unidirectional laser beam. Raman spectroscopy illustrates that the target phase is less degraded by the laser beams incident from opposing angles than the laser beams incident from only one direction.