Nb/Al-AlOx/Nb Junction Properties' Variations Due to Storage and Mounting (original) (raw)

The influence of aging and annealing on the properties of Nb/Al-AlO x /Nb tunnel junctions

Journal of Physics Conference Series, 2010

This paper presents results of our studies on aging and annealing properties of Nb/Al-AlOx/Nb junctions. We performed a long room temperature aging with subsequent annealing at different temperatures up to 250°C. A distinct change of the junctions' normal-state resistance has been observed. Aging at room temperature results in a slight decrease of the normal-state resistance combined with improved junction quality, characterised by a better subgap-to-normal resistance ratio. Annealing at moderate temperatures in air increases the normal-state resistance and leads to improvement of the junction quality followed by degradation at higher annealing temperatures. The increase in the junction quality after long-term aging at room temperature is attributed to relaxation of the internal junction structure and interfaces, thus, resulting in a lower density of interface traps. The deterioration at higher annealing temperatures could be a consequence of diffusion processes at the Al/Nb interface. We observe a sufficiently clear difference between the behaviour of preliminary aged and newly fabricated junctions after annealing: for the aged high-quality junction, the degradation was negligible up to temperatures of 200°C, while non-aged junctions show a much faster and abrupt degradation at lower annealing temperatures.

Dynamic conductance of Ni80Fe20/AlOx/Ni80Fe20 tunnel junctions

Journal of Applied Physics, 2000

The shape of the dynamic conductance versus voltage of NiFe/AlOx/NiFe tunnel junctions is correlated with the intensity and duration of oxidation. A shift of the conductance minimum towards positive voltage (up to 100 mV) indicates that the Al layer is only partially oxidized. In contrast, a shift of the conductance minimum towards negative voltage indicates oxidation of the bottom electrode and/or damage to the top surface of the barrier. Annealing of the junctions makes the tunnel barrier effectively thinner and taller, as implied by a fit to the parabolic conductance. These qualitative trends are observed for Al layers ranging from 10 to 35 Å in thickness. In conjunction with these effects, we observe the highest magnetoresistance (up to 26.6%) and the best bias dependence of the magnetoresistance when the conductance is symmetric.