Slow Conductance Relaxation in Insulating Granular Al: Evidence for Screening Effects

Abstract

It is shown that the conductance relaxations observed in electrical field effect measurements on granular Al films are the sum of two contributions. One is sensitive to gate voltage changes and gives the already reported anomalous electrical field effect. The other one is independent of the gate voltage history and starts when the films are cooled down to low temperature. Their relative amplitude is strongly thickness dependent which demonstrates the existence of a finite screening length in our insulating films and allows its quantitative estimate (about 10nm at 4K). This metallic-like screening should be taken into account in the electron glass models of disordered insulators.

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• Characterizing dielectric properties of ultra-thin films using superconducting coplanar microwave resonators
• Observation of thermally activated glassiness and memory dip in a-NbSi insulating thin films
• Electron glass effects in amorphous NbSi films
• Effect of nonlocal interactions on the disorder-induced zero-bias anomaly in the Anderson-Hubbard model
• Electron glass signatures up to room temperature in disordered insulators
• Screening and conductance relaxations in insulating granular aluminium thin films
• Anomalous thermal activation of the electron glass dynamics in a-InOx and granular aluminum