CHARACTERIZATION OF RAMP-TYPE YBA2CU3O7 JUNCTIONS BY AFM

We studied the morphology of ramps in REBa2Cu3O7 (REBCO) epitaxial fil ms on SrTiO3 substrates, fabricated by RF magnetron sputter deposition and pulsed laser deposition (PLD), by Atomic Force Microscopy (AFM) a nd High Resolution Electron Microscopy (HREM), The ramps were fabricat ed by Ar ion beam etching using different masks of standard photoresis t and TiN, AFM-studies on ramps in sputter deposited Films show a stro ng dependence, i.e., formation of facets and ridges, on the angle of i ncidence of the ion beam with respect to the substrate surface as well as the rotation angle with respect to the crystal axes of the substra te, Ramps in pulsed laser deposited films did not show this dependence . Furthermore, we studied the effect of an anneal step prior to the de position of barrier layers (i.e., PrBa2Cu3-xGaxO7) on the ramp, First results show a crystallization of the ramp surface, resulting in terra ces and a non-homogeneous growth of the barrier material on top of it, The thickness variations, for thin layers of barrier material, can ev en become much larger than expected from the amount of deposited mater ial and are dependent on the deposition and anneal conditions, HREM st udies show a well-defined interface between barrier layer and electrod es, The angle of the ramp depends on the etch rate of the mask and REB CO and on the angle of incidence of the ion beam Hard masks, like TIN, have a much lower etch rate compared to photoresist, resulting in an angle of the ramp comparable to the angle of incidence and, subsequent ly, in a low etching rate on the ramp.