On the specifics of the electrical conductivity anomalies in PVC nanocomposites

TL;DR

This paper presents a qualitative model explaining the anomalous electrical conductivity switching in PVC nanocomposites, attributing it to a cascade of soft breakdowns in insulating gaps that lead to a conducting state, influenced by external fields and pressure.

Contribution

The paper introduces a novel cascade breakdown model that accounts for conductivity anomalies in PVC nanocomposites, incorporating correlations between insulating gaps and explaining various experimental observations.

Findings

Switching to high conductivity involves soft breakdown of insulating gaps.

Conductivity anomalies can be explained by cascade breakdown mechanisms.

Model accounts for exponential resistance dependence on thickness and pressure.

Abstract

A qualitative model describing the "anomalous" features of the conductivity of polymer nanocomposites, in particular, switching to the conducting state in relatively thick (tens of microns or more) of flexible PVC films is considered. In previously published experimental results, change of conductivity by 10 or more orders of magnitude occurred both in the absence of external influences (spontaneously), and under the influence of an applied electric field, as well as other initiating factors (such as uniaxial pressure) . In a model of hopping conduction mechanism it is shown, that switching in the conduction states under the action of external field significantly (by orders of magnitude) below threshold can be associated with a high-resistance state instability that results from the sequence of "shorting" (reversible soft breakdown) of narrow insulating gaps between regions with relatively high conductivity. Increasing the field strength in the remaining insulating gaps ultimately leads to the formation of a conducting channel between the external electrodes and switching conductivity of the composite film sample in a state of high conductivity. This cascade model is essentially based on the transition from the usual description of the charge tunneling through single independent insulating gap to take into account correlations between adjacent gaps. In the frame of developed model other "anomalies" such as exponential dependence of the resistance on the sample thickness, pressure, and other influences can be qualitative explained. An analogy of the model with a cascading breakdown of avalanche transistors is also considered.