Determination of the refractive index and wavelength-dependent optical properties of few-layer CrCl3 within the Fresnel formalism

Based on previous reports on the optical microscopy contrast of mechanically exfoliated few layer CrCl (Formula presented.) transferred on 285 nm and 270 nm SiO (Formula presented.) on Si(100), we focus on the experimental determination of an effective mean complex refractive index via a fitting analysis based on the Fresnel equations formalism. Accordingly, the layer and wavelength-dependent absorbance and reflectance are calculated. Layer and wavelength-dependent optical contrast curves are then evaluated demonstrating that the contrast is significantly high only around well-defined wavelength bands. This is validated a posteriori, by experimental UV-Vis absorbance data. The present study aims to show the way towards the most reliable determination of thickness of the 2D material flakes during exfoliation.