Glassy behavior of interface states in Al-AlOx-Al tunnel junctions

Abstract

We present results of a study of tunnel junction aging in which the early time dynamics are captured by in situ monitoring of electrical properties of Al-AlOx-Al planar tunnel junctions beginning when the deposition of the counterelectrode is complete. The observed stretched exponential dependences of the conductance and the capacitance manifest hierarchically constrained dynamics imposed by correlated relaxations of interface traps. Bias voltage is used as a control parameter to create bias-dependent aging trajectories that exhibit memory and age-dependent relaxations. Simple tunnel barrier and equivalent circuit modeling provide a comprehensive understanding of this novel and unexpected glassy behavior that appears to be unique to tunnel junctions and has important implications for technical applications.