Micro‐contact impedance spectroscopy (MCIS) is potentially a powerful tool for the exploration of resistive surface layers on top of a conductive bulk or substrate material. MCIS employs micro‐contacts in contrast to conventional IS where macroscopic electrodes are used. To extract the conductivity of each region accurately using MCIS requires the data to be corrected for geometry. Using finite element modeling on a system where the resistivity of the surface layer is at least a factor of ten greater than the bulk/substrate, we show how current flows through the two layers using two typical micro‐contact configurations. This allows us to establish if and what is the most accurate and reliable method for extracting conductivity values for both regions. For a top circular micro‐contact and a full bottom counter electrode, the surface layer conductivity (σs) can be accurately extracted using a spreading resistance equation if the thickness is ~10 times the micro‐contact radius; however, bulk conductivity (σb) values can not be accurately determined. If the contact radius is 10 times the thickness of the resistive surface, a geometrical factor using the micro‐contact area provides accurate σs values. In this case, a spreading resistance equation also provides a good approximation for σb. For two top circular micro‐contacts on thin resistive surface layers, the MCIS response from the surface layer is independent of the contact separation; however, the bulk response is dependent on the contact separation and at small separations contact interference occurs. As a consequence, there is not a single ideal experimental setup that works; to obtain accurate σs and σb values the micro‐contact radius, surface layer thickness and the contact separation must all be considered together. Here we provide scenarios where accurate σs and σb values can be obtained that highlight the importance of experimental design and where appropriate equations can be employed for thin and thick resistive surface layers.

中文翻译：

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通过微接触阻抗光谱法对电阻表面层进行有限元建模

微接触阻抗谱 (MCIS) 是一种潜在的强大工具，可用于探索导电体或基板材料顶部的电阻表面层。与使用宏观电极的传统 IS 相比，MCIS 采用微接触。要使用 MCIS 准确提取每个区域的电导率，需要对数据进行几何校正。在表面层的电阻率至少比体/基板大十倍的系统上使用有限元建模，我们展示了电流如何使用两种典型的微接触配置流过两层。这使我们能够确定是否以及哪种方法是提取两个区域的电导率值的最准确和可靠的方法。对于顶部圆形微接触和完整底部对电极，如果厚度是微接触半径的 10 倍，则可以使用扩散电阻方程准确地提取表面层电导率 (σs)；然而，体电导率 (σb) 值无法准确确定。如果接触半径是电阻表面厚度的 10 倍，则使用微接触面积的几何因子可提供准确的 σs 值。在这种情况下，扩展阻力方程也为 σb 提供了一个很好的近似值。对于薄电阻表面层上的两个顶部圆形微接触，来自表面层的 MCIS 响应与接触分离无关；然而，整体响应取决于接触分离，并且在小分离时会发生接触干扰。因此，没有一种理想的实验装置是可行的。为了获得准确的 σs 和 σb 值，必须同时考虑微接触半径、表面层厚度和接触间隔。在这里，我们提供了可以获得准确的 σs 和 σb 值的场景，这些值强调了实验设计的重要性，并且可以对薄和厚的电阻表面层采用适当的方程。