Electric-field-induced memory effects in granular films

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Abstract
We report on a study of memory effects in granular film systems. Experiments by Lambe and Jaklevic and by Adkins et al. are examined. In the former, a granular film is embedded in a capacitor, and the memory effect is an anomaly in the low-temperature capacitance-voltage plot centered at the bias in which the capacitor was cooled. In the latter, the granular film forms one plate of a capacitor, bias is applied between the capacitor plates, and the memory effect is an anomaly in the low-temperature plot of the granular film’s conductance versus bias, centered about the cooling bias. In reviewing these experiments, it is found that there is lacking a theoretical understanding which correctly addresses the roles of electrostatic and electrochemical potentials in establishing the memory. Experiments are carried out on a Lambe-Jaklevic device which provide insights into the effect and supplement the existing experimental results. Two theoretical models are proposed. One, based on the idea of the Coulomb glass, predicts results inconsistent with some aspects of the experimental results. The other is related to the ideas in the original Lambe-Jaklevic and Adkins et al. works but resolves issues raised in considering their models and is consistent with all experimental results.