Far-infrared spectra of amorphous titanium dioxide films

Abstract The amorphous TiO 2 film structure on an aluminum substrate was studied by far infrared reflection–absorption spectroscopic (IRAS) analysis. The transverse (TO) and longitudinal (LO) optical modes of the amorphous oxide films were studied experimentally and through simulation. These optical modes were compared to those of the corresponding crystal. While TO modes of the films correspond to those of the crystal, the LO modes do not. The best agreement between the experimental and the simulated IRAS spectra is obtained when an appropriate dielectric function e film ( ν ) is chosen. e film ( ν ) must be related to the amorphous character of the films e.g. by averaging the anisotropic crystal properties. As a consequence of our findings, the Berreman effect does apply in amorphous films to absorption bands at frequencies of the peaks of the loss function Im[−1/ e film ( ν )], which does not correspond to frequencies of the LO modes of the crystal.