STOICHIOMETRIC TRANSFER OF COMPLEX OXIDES BY PULSED-LASER DEPOSITION

The interaction of a spatially uniform 248 nm excimer laser beam with targets of various oxides (Ya(2)Cu(3)O(7-delta), Y2BaCuO5, Y2O3 and Sr TiO3) is investigated. We identify two different mechanisms for non-st oichiometric ablation. Evidence is found that in YBa2Cu3O7-delta and Y 2BaCuO5 the non-stoichiometric ablation at low fluences is due to a ph ase transformation of the target surface. This is a gradual process, o nly observable after prolonged irradiation of the target, For congruen tly melting SrTiO3 such a phase transformation is neither expected nor observed. We find, however, that at low fluences within 100 laser sho ts the target surface composition equilibrates to a stable, Ti-rich co mposition, In this case, the mechanism we propose is preferential abla tion, which is accompanied by bulk diffusion to compensate the induced surface depletion.