Correlation-free reflection diagnostics of biaxially anisotropic nanoscale films on transparent isotropic materials

The possibilities of determining the parameters of biaxially anisotropic ultrathin dielectric films on transparent isotropic substrates by differential reflectance and ellipsometric measurements are analyzed. The analysis is based on analytical reflection formulas obtained in the framework of a long-wavelength approximation. It is shown that it is possible to simultaneously determine the thickness and all six parameters of anisotropy for such films. The accuracy of the obtained analytical formulas for determining the parameters of anisotropic ultrathin films is estimated by computer simulations where the reflection problem was solved numerically on the basis of the rigorous electromagnetic theory for anisotropic layered systems.