Atomic force microscopy characterization of a YBaCuO crystal surface patterned by proton irradiation

A YBaCuO single crystal and a c-axis grown epitaxial YBaCuO film were irradiated with 200 keV protons to study the changes of the transport and especially of the structural properties. The single crystal was covered with a special grid-mask with strips of 5-mu-m periodicity in the irradiation procedure. The changes of the structural properties of the film and of the single crystal were studied by X-ray diffraction and by interference contrast and atomic force microscopy, respectively. The main structural effect of irradiation with moderate fluences is a lattice expansion of 0.8% in the film. The expansion of the irradiated parts of the crystal was 15-20 nm which is a factor of about 2 higher than in the film. This discrepancy can be resolved by considering the different energy deposition processes in the crystal and in the film.