Role of ion beam etching in the fabrication of ramp-type junctions

The use of ramp-type junctions is not only limited to the fabrication of Josephson junctions for ultrafast high-temperature superconducting electronics but is also well suited for the controlled coupling of crystallographically compatible oxide materials such as ferromagnetic manganites and superconducting cuprates. Transport processes of ramp-type junctions strongly depend on the ramp interface generated in the fabrication process. With regard to the high potential of ramp-type junctions in the study and application of oxide materials, a detailed investigation of the process of ramp formation by modern surface analytical methods is highly desired. The enormous challenge in the fabrication of ramp-type junctions consists in the necessity of the engineering of the involved interfaces on a unit-cell length scale. We present a detailed study of the ramp formation by ion beam techniques. Special focus is put on the prevention of recrystallization of ion milled material which poses a major problem to the formation of atomically smooth ramp interfaces with desired stoichiometry.