Properties of junctions using a-axis oriented Y-Ba-Cu-O films.

采用射频磁控溅射和直流偏压衬底技术，在一定条件下，用a轴取向的YBCO薄膜制备了YBa&lt；@D22@&gt；D2Cu&lt；@D23@&gt；D2Ox(YBCO)/SrTiO&lt；@D23@&gt；D2(STO)/Au和YBCO/PrGaO&lt；@D23@&gt；D2(PgO)/Au的夹心型SiN结。研究了不同势垒厚度结的微分电导-电压(Di/DV-V)曲线。虽然有些结呈现针孔短路曲线，但结表现出类似隧道的行为。在(]sy.+-处，各结点的微分电导梯度发生了变化。[)20 mV，这种变化随着势垒厚度的减小而明显。另一方面，对于薄势垒结，也观察到了较小的零偏压反常。有PGO屏障的结与有STO屏障的结的曲线相似。认为隧道效应是通过非均匀势垒中的薄区发生的，并研究了Di/DV-V曲线对氧气气氛中热处理的影响。为了得到Di/dV-V曲线中Di/dV梯度的变化，最佳的退火时间为2-4h。随着退火时间的延长，结的本底电导斜率变得陡峭。

Sandwich type SIN junctions of YBa<@D22@>D2Cu<@D23@>D2Ox(YBCO)/SrTiO<@D23@>D2(STO)/Au and YBCO/PrGaO<@D23@>D2(PGO)/Au were fabricated using a-axis oriented YBCO films under the some conditions using a rf magnetron sputtering with dc voltage biased substrate holder. The differential conductance-voltage(dI/dV-V) curves of junctions with defferent barrier thickness were investigated. The junction showed the tunnel-like behavior, though some junctions showed the curves with pinhole-short-circuits. The junctions had the change in the gradient of differential conductance in the curves at about (]SY.+-。[) 20mV.This change was obviously observed with decreasing the barrier thickness. On the other hand, it was also observed the small zero bias anomalies for the junctions with thin barrier. The curves of junctions with PGO barrier were simillar to those with the STO barrier. It is considered that the tunneling occurs via thin region in the ununiform barrier.And then, the effects of dI/dV-V curves on the heat treatment in oxygen gas were also investigated. In order to obtain the change in the gradient of dI/dV in the dI/dV-V curve, the optimum annealing time was 2-4h. The slope of the background conductance of junctions becomes steep with increasing the annealing time.