Fabrication of array of mesas on superconducting Bi2Sr 2CaCu2O8+? single crystals

Abstract

The superconducting properties of multi-layered high temperature superconductors (HTS) result mainly from the CuO2 planes, while the other structural components behave simply as charge reservoirs. Using these perfect-layered structures of HTS, arrays of mesas have been fabricated on the surfaces of Bi2Sr2CaCu2O8+δ (Bi2212) single crystals using hotolithography and argon ion beam etching techniques. These arrays have current-voltage (I-V) characteristics that consist of some branches corresponding to different intrinsic Josephson junctions in the mesas, The surface topography and heights of the mesas were examined with atomic force microscopy. Due to the small mesa area, conventional wire bonding techniques are not applicable. A novel method, point contact tunneling apparatus with a sharp Au tip, was used to obtain the I-V characteristics of the fabricated intrinsic Josephson junctions, below the critical temperature of Bi2212. Since the ultimate goal was to obtain an ordered group of mesas with small lateral dimensions, to eliminate heating effects during I-V measurements, we showed that submicron-sized mesas could be characterized by the new technique.