Annealing effects in tunnel junctions (voltage annealing)

Abstract

This paper describes the time-dependent changes which occur in Al-oxide–Pb tunnel junctions as a result of voltage annealing (i.e., keeping a fixed bias across junction electrodes). By examining changes in junction resistance, barrier parameters (barrier thickness, average barrier height, and the separation between barrier heights at the two electrodes) and inelastic electron tunneling (IET) peak intensities, one finds that applying a voltage across the junction causes an accumulation or depletion of positive charge at the Al-oxide interface depending on the polarity of the applied bias. Along with charge redistribution, the voltage-induced electric field also enhances or retards other processes (such as reorientation of surface hydroxyl groups) which normally take place during thermal annealing.