IR‐Spectroscopic Data of Thin Insulating Films on Semiconductors. New Methods of Interpretation and Analysis

On the basis of the Fresnel theory special IR optical equations for the description of the transmission (T), reflection (R), and attenuated total reflection (ATR) of thin films on semiconductors are derived. It is shown that these relations (quadratic approximations of film thickness) lead to a theoretical explanation for the detection and identification of transverse and longitudinal phonon‐polaritons by means of oblique incidence of polarized light realized in different experimental modes (T, R, ATR). A comparison of calculated model spectra of SiO2 with corresponding experimental spectra shows good quantitative agreement. Furthermore, in this framework a very effective method of determination of the dielectric functions of thin films from their IR spectra is developed and applied to an Al2O3‐film on silicon.