Annealing effects in tunnel junctions (voltage annealing with alternating polarity)

This paper describes the time-dependent changes which occur in Al-Al oxide-Pb tunnel junctions as a result of voltage annealing with alternating polarity (AP). 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 some charge within the barrier is fairly mobile under the influence of AP voltage annealing while another portion appears to become trapped. Also, the IET intensity of the 118-meV Al--O stretching peak of the Al oxide was found to increase with decreasing barrier height