Laser-induced modification in YBCO target surface

Surface modification of YBa2Cu3O7-x (YBCO) target in the process of pulsed laser deposition was systematically investigated by Scanning Electron Microscopy (SEM). We observed that the size of cones formed on YBCO target by pulsed laser became larger with increasing the laser energy density. The image of SEM shows the difference of cone formations at the boundary and at the center of the ablated area on the target surface. This nonuniform modification of the ablated area is supposed to be mainly due to Gaussian profile of the laser beam and the difference of thermal conductivities of the ablated area. To eliminate cones, we have used the method of rotating the target by 180 degree(s) to shot 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 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 one direction.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.