Temperature dependence of tunneling in intrinsic Josephson junctions of high temperature superconductors

Thesis (Master)--Izmir Institute of Technology, Physics, Izmir, 2008Includes bibliographical references (leaves: 73-79)Text in English; Abstract: Turkish and Englishxi, 79 leavesThe lack of coherent, continuous and tunable compact solid-state sources of electromagnetic radiations at terahertz (THz) frequency range (0.3-30 THz) can be solved by high temperature superconductors (HTS) which are better candidates for generation of THz radiation. THz sources have potential application areas in materials characterization, biology, communication, medicine and security. The HTSs have large energy gap intervals which are available for radiations at THz frequency range, so recently, they were used as better converters from DC-voltage to high frequency radiation in junction technologies. Bi2Sr2CaCu2O8+8 (Bi2212) HTS single crystals include natural superconductor-insulator-superconductor multi-junctions called intrinsic Josephson junctions. For generation of coherent continuous and powerful THz radiations, we have fabricated large and tall mesas on Ca rich Bi2212, although mesas with small planar and lateral dimensions were preferred in recent studies because of the heating effect. We have used under-doped Bi2212 to control the heating problem. The mesas with size of 100x300 .m2 have been fabricated by vacuum evaporation, photolithography analyzed by Atomic Force Microscopy. We have investigated temperature dependence of c-axis resistivity and current-voltage (I-V) tunneling characteristics of under-doped Bi2212 which exhibit exponentially increases in resistivity from 300 K to Tc. The influences of heating effect were analyzed at temperature evolution of I-V measurements. Finally, bolometric detections of emission from long edges of mesas were done

Progress in THz generation using Josephson fluxon dynamics in intrinsic junctions

Collective transverse plasma modes in Bi2Sr2CaCu2O8+x, intrinsic Josephson junctions (IJJs) can be excited by the moving fluxon lattices. Progressive transformation of the standing-wave-like fluxon-lattice configuration from a triangular lattice to a rectangular lattice takes place as the dynamic fluxon-lattice modes are in resonance with the collective transverse plasma modes. In this paper, we review the progress in terahertz-firequency-range electromagnetic wave generation from the IJJs using the resonance between moving fluxon lattice and the collective transverse plasma modes.open116sciescopu