Characterization of optical/physical properties of anisotropic thin films with rough surfaces by Stokes-Mueller ellipsometry

A decomposition model with depolarization matrix is proposed to characterize the optical and physical properties of anisotropic thin films with rough surfaces. In the proposed approach, the refractive index and thickness of the thin film are inversely extracted using a pure polarization matrix, and the surface roughness of the film is characterized using a depolarization matrix. The validity of the proposed method is demonstrated by comparing the experimental results for the refractive index and thickness of a thin film with the analytical results obtained using the effective ellipsometric parameters of the film. The results show that the proposed method provides a reliable means of obtaining the optical and physical properties of thin films with fine or coarse rough surfaces. Importantly, the proposed method not only enables the coarse surface roughness of thin-film samples to be determined in a non-contact optical manner, but also provides a more versatile approach than the well-known effective medium approximation (EMA) model, which is restricted to the characterization of samples with low surface roughness.