Análise teórica dos espectros de pendências e fases de um sistema de dois terminais baseados no modelo de circuito equivalente Rₛ - (R||C)

Abstract

This work presents a theoretical approach to electrical impedance spectroscopy, a technique widely employed in the analysis of materials and electronic devices. By applying a sinusoidal alternating voltage and analyzing the resulting current response, it is possible to obtain information regarding resistive and capacitive processes within the system. The study focuses on the application of a simple equivalent circuit model, consisting of a series resistance (Rs) connected to a parallel RC circuit, which represents devices with a metal/active layer/metal structure. In particular, the active layer consists of solid-state materials. Based on this model, impedance spectra were analyzed, and parameters such as contact resistance, as well as the resistance and capacitance related to the active layer, were extracted. For simulation purposes, a value of 50 Ω was assigned to Rs, representing the electrical contacts, while the resistance associated with the active layer (R) was varied among 1×10³ Ω, 1×10⁴ Ω, and 1×10⁵ Ω. For simplification purposes, the capacitance (C) associated with the active layer was fixed at 1×10⁻⁹ F. Based on these values, theoretical plots of the impedance and phase spectra were generated. The results provided a didactic visualization of the behavior of such devices, thus enabling further studies of more complex systems that often exhibit deviations from the model considered in this work.