Resistive-nanoindentation on gold: Experiments and modeling of the electrical contact resistance

TL;DR

This study combines experiments, analytical models, and numerical simulations to understand electrical contact resistance during resistive-nanoindentation on gold, revealing transport regimes and validating a calibration method for complex samples.

Contribution

It provides a comprehensive analytical and numerical framework for interpreting resistive-nanoindentation data on gold, including transport regimes and calibration techniques.

Findings

Excellent agreement between analytical models and experimental data.

Validation of a calibration procedure for complex rheological samples.

Identification of transport regimes during nanoindentation contact resistance.

Abstract

This paper reports the experimental, analytical, and numerical study of resistive-nanoindentation tests performed on gold samples (bulk and thin film). First, the relevant contributions to electrical contact resistance are discussed and analytically described. A brief comparison of tests performed on gold and on natively oxidized metals highlights the high reproducibility and the voltage-independence of experiments on gold(thanks to its oxide-free surface). Then, the evolution of contact resistance during nanoindentation is fully explained in terms of electronic transport regimes: starting from tunneling, electronic transport is then driven by ballistic conduction before ending with pure diffusive conduction. The corresponding analytical expressions, as well as their validity domains, are determined and compared with experimental data,showing excellent agreement. From there, focus is made on the diffusive regime. Resistive-nanoindentation outputs are fully described by analytical and finite-element modeling. The developed numerical framework allows a better understanding of the main parameters: it first assesses the technique capabilities (validity domains, sensitivity to tip defect, sensitivity to rheology, effect of an oxide layer, and so on), butit also validates the different assumptions made on current line distribution. Finally, it is shown that a simple calibration procedure allows a well-resolved monitoring of the contact area during resistive-nanoindentation performed on samples with complex rheologies (ductile thin film on an elastic substrate). Comparison to analytical and numerical approaches highlights the strength of resistive-nanoindentation for continuous area monitoring.