Interferometric techniques for thickness measurement of 2D structures

In this study, we obtain the thickness of films deposited on a glass slide by an in-house built experimental setup based on speckle interferometry (SI) and Doppler-shifted optical coherence tomography (D-OCT) techniques. Three different film textures, a transparent, semi-transparent film (Graphene Oxide-Poly vinyl alcohol composite film) and a highly scattered film (Biofilm formed during wastewater treatment out of chemical and biological activity), were used to test the accuracy in the measurement process of our optical system. The thickness range compares favorably with those measured by SEM cross-sections. In addition to the thickness of the film, we can extract the thickness variation of the film within the illuminated area from the one-time measurement process. The novelty of the work stands in the successful extraction and comparison of the film parameters in a low-cost instrumental facility utilizing teaching lab equipment of films with varying textures viz transparent film to scattering films from the same setup.