The voltage-biased current-voltage(I-V)characteristics of intrinsic Josephson junctions(IJJs),which are fabricated with misaligned high temperature superconducting Tl2Ba2Ca Cu2O8(Tl-2212)thin film,are investigated experimentally.Three characteristic regions in the I-V curve are observed at 47 K.In the low voltage part,the current firstly increases and then decreases slowly with increasing the biased voltage,which is shown as a bump.In the next region,the current slightly increases with increasing the biased voltage until a sudden decrease of the current appears.Thereafter,branch structure forms with increasing the voltage on the I-V characteristic.The influence of the self-heating on the I-V characteristics is investigated and the temperature dependence of the I-V characteristics is measured to explore these characteristics in detail.
WANG PeiXIE WeiHU LeiLIU XinJI LuHE MingZHANG XuZHAO XinJieYAN ShaoLin
For obtaining pure phase Tl2Ba2Ca2Cu3O10(Tl-2223) films with good superconducting properties, the growth technique is improved by dc magnetron sputtering and a triple post-annealing process. The triple post-annealing process comprises annealing twice in argon and once in oxygen at different temperatures. In the first low-temperature annealing phase in argon, Tl2Ba2CaCu2O8(Tl-2212) is obtained to effectively minimize evaporation in the next step. With the increase of temperature in the second annealing stage in argon, the previously prepared Tl-2212 inter-phase is converted into Tl-2223phase. An additional annealing in oxygen is also adopted to improve the properties of Tl-2223 films, each containing an optimal oxygen content value. The results of X-ray diffraction(XRD) θ–2θ scans, ω scans and rotational φ scans show that each of the Tl-2223 films has a high phase purity and an epitaxial structure. Smooth films are observed by scanning electron microscopy(SEM). The critical temperatures Tc of the films are measured to be about 120 K and the critical current densities Jc can reach 4.0 MA/cm2at 77 K at self field.
Intrinsic Josephson junctions in misaligned Tl2Ba2CaCu2O8 thin film were fabricated on LaAlO3 substrate. The temperature dependence of the critical current is investigated around liquid nitrogen temperature. In the current voltage characteristic, large voltage jump and lack of resistive branch are observed, which shows good consistency with the intrinsic Josephson junctions. By analyzing the large gap voltage in the curve, great suppression of the energy gap is found. Through discussing the temperature dependence of the gap voltage in liquid nitrogen temperature, it is shown that this phenomenon can be caused by the non-equilibrium quasiparticle injection. The temperature influence on the excess current also confirms the non-equilibrium effect.
Intrinsic Josephson junctions in misaligned Tl2Ba2CaCu2O8 thin film were fabricated on LaAlO3 substrate. The temperature dependence of the critical current is investigated around liquid nitrogen temperature. In the current voltage characteristic, large voltage jump and lack of resistive branch are observed, which shows good consistency with the intrinsic Josephson junctions. By analyzing the large gap voltage in the curve, great suppression of the energy gap is found. Through discussing the temperature dependence of the gap voltage in liquid nitrogen temperature, it is shown that this phenomenon can be caused by the non-equilibrium quasiparticle injection. The temperature influence on the excess current also confirms the non-equilibrium effect.
