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A thin‐film sample of YBa2Cu3O7−δ on MgO was irradiated at room temperature with 50‐keV 2H+ (deuterium) to a dose of 1×1016 ions cm−2. The film was mainly c‐axis textured film, ∼360–420 nm thick, deposited by sputtering on 〈100〉 MgO substrate. The as‐implanted sample was divided into several pieces and annealed in a flowing oxygen ambient using (i) a rapid thermal annealing oven, at various temperatures between 450 and 940 °C, and (ii) a conventional annealing furnace, at various temperatures between 100 and 350 °C. Analysis by secondary‐ion mass spectroscopy shows that the implanted 2H is a fast diffuser in the 123 phase. The apparent activation temperature (energy) for 2H release from the initial traps within the YBCO film during the anneal is estimated to be ∼175 °C (∼0.97 eV), which is obviously lower than the apparent activation temperature (energy) for 2H release from the initial traps within the MgO substrate (∼550 °C, i.e., ∼1.78 eV). At 200 °C the diffusivity of 2H in the YBCO film is estimated t...

The domain structure of sputtered Co‐Pd multilayer films of varying thickness has been investigated by magnetic force microscopy. The domains appear as stripe domains, typical of perpendicularly oriented films. The size of the domains was strongly influenced by the thickness of the film. The domain repetition lengths give an additional experimental parameter which has been used to provide a stronger test of a theoretical model developed for ferromagnetic multilayer films [H. J. G. Draaisma and W. J. M. de Jonge, J. Appl. Phys. 62, 3318 (1987)]. It is found that the experiment and theory are broadly in agreement provided that the increased magnetization of the multilayer caused by polarization of the Pd is accounted for. There is a noticeable difference between the variation of the measured and theoretical domain repetition lengths with film thickness. This is attributed to the effects of domain‐wall pinning which is not considered in the model. It is estimated that the characteristic length of the films i...

Measurements on current‐biased Nb/AlOx/Al/AlOx/Nb double tunnel junction devices with very thin central Al layers show a novel double hysteretic structure in the subgap region. Similar junction structures have previously exhibited very large nonequilibrium effects; the effects reported here appear close to and above the equilibrium critical temperature of Al. A model is presented in which the hysteresis is shown to arise from a transition from finite to zero voltage across one barrier on increasing current, due to the nucleation of an inhomogeneous state in the ultrathin central Al layer in which normal and superconducting states coexist. This reverse switching effect is shown to arise from the self‐shunting effect of low‐gap regions. Predictions of this model are shown to agree with the experimental data.

The range data and migration of Au in YBa2Cu3O7−δ film were studied with implanted 197Au (1.5 MeV 5×1015 Au+/cm2) as a tracer. The film was a c‐axis oriented film, ∼750 nm thick, deposited by high‐pressure planar dc sputtering on 〈100〉 LaAlO3. Analysis by secondary ion mass spectroscopy shows that the as‐implanted Au concentration distribution is essentially Gaussian‐like and the depth (Rp) of maximum Au concentration (∼1.2 wt %) is 201 nm. The projected range (Rp) and (Rp) are found to be in very good agreement with the simulated data by TRIM−95, whereas the measured ‘‘straggle’’ (ΔRp*) is about 20% larger than that by TRIM−95 simulation. It has also been found that the implanted 197Au starts to migrate within the film at a temperature between 650 and 700 °C, which is much higher than that for the implanted 2H (∼175 °C) and the implanted 18O (between 250 and 300 °C) in c‐oriented YBa2Cu3O7−δ films.

We report results obtained from several hundred Nb/Al2O3/Nb tunnel junctions fabricated by the ‘‘whole‐wafer’’ process. These results indicate that one of the factors determining resistance and quality variations in such devices is the microstructure of the underlying base layer of niobium. We have further developed the technique of anodization spectroscopy to provide a quantitative measure of the variation in the thickness of the thin aluminum layers which contain the tunnel barrier and have related this to the temperature at which the niobium base layer is deposited. We show that at least two mechanisms are responsible for normal‐state resistance variations in such devices and that device quality is closely related to the integrity of the aluminum layer underlying the tunnel barrier.