Full-Field and Quantitative Analysis of a Thin Liquid Film at the Nanoscale by Combining Digital Holography and White Light Interferometry

Visualizing and measuring thin-film thickness at the nanoscale during dynamic evolution has been an open challenge for long term. Here, a joint-imaging method and the thereof innovative procedure are presented for merging digital holography (DH) and white light colorimetric interferometry (WLCI) measurement data in a single intelligent tool. This approach allows a complete quantitative study of the dynamic evolution of freestanding thin films under high spatial resolution and full-field modality over a large area. By merging interferometric and holographic fringes, it is possible to overcome the lack of DH in thickness measurements of ultrathin layers, providing a reliable reference for full-field quantitative mapping of the whole film with interferometric accuracy. Thanks to the proposed approach, the time-related and concentration-related evolution of surfactant film thickness can be studied. The thickness distribution curves reveal the small changes in the film thickness with time and concentration. The reported tool opens a route for comprehending deeply the physics behind the behavior of freestanding thin liquid films as it provides an in situ, continuous monitoring of film formation and dynamic evolution without limits of thickness range and in full-field mode. This can be of fundamental importance to many fields of applications, such as fluids, polymers, biotechnology, bottom-up fabrication, etc.