Metrological properties of thin and ultra-thin coating thickness measurement by nanoindentation

Coatings enable the engineering of surface properties, and thickness is one of the most important design parameters to control function and integration within the application environment. Ultra-thin coatings, i.e., those with thicknesses smaller than 100 nm, find applications in the electronics and biomedical fields. However, measurement of the thickness is often challenging. Innovatively, this work demonstrates the applicability of a recent nanoindentation-based approach in measuring the thickness of hard, ultra-thin coatings. Additionally, the work innovatively discusses the traceability of the thickness measurement, highlighting its metrological properties in terms of accuracy and measurement uncertainty. Additionally, a comparison with other primary traceable techniques is provided, complemented by a sensitivity analysis of measurement accuracy to coating thickness. Results show a relative expanded uncertainty of about 15% of the measurement, and an excellent accuracy with a bias with respect to directly traceable measurements that is not statistically significant. This work contributes to demonstrate the applicability of nanoindentation for coating thickness measurement on a wide range of thickness and composition.