Surface coupling effects on the capacitance of thin insulating films

TL;DR

This paper investigates how surface roughness and coupling between surfaces affect the capacitance of thin insulating films, revealing that coupling can significantly alter capacitance depending on the nature of the interaction.

Contribution

It introduces a general model for surface roughness effects on capacitance, emphasizing the role of coupling between rough surfaces and its impact on capacitance modifications.

Findings

Coupling between rough surfaces can increase or decrease capacitance.

Uncoupled rough surfaces behave as two capacitors in series.

Coupling effects are significant when correlation length and roughness exponent are small.

Abstract

A general form for the surface roughness effects on the capacitance of a capacitor is proposed. We state that a capacitor with two uncoupled rough surfaces could be treated as two capacitors in series which have been divided from the mother capacitor by a slit. This is in contrast to the case where the two rough surfaces are coupled. When the rough surfaces are coupled, the type of coupling decides the modification of the capacitance in comparison to the uncoupled case. It is shown that if the coupling between the two surfaces of the capacitor is positive (negative), the capacitance is less (higher) than the case of two uncoupled rough plates. Also, we state that when the correlation length and the roughness exponent are small, the coupling effect is not negligible.