Infrared reflection-absorption characterization of TiO2 films on ITO: detection of LO modes

By exploiting the high reflectivity of ITO substrates in the infrared and the detection of longitudinal optical (LO) modes provided by oblique incidence of radiation (Berreman effect), we showed that reflection-absorption experiments in the MID-IR can be successfully performed when thin inorganic oxide films deposited on ITO are used as samples. The samples we used were TiO₂ films deposited on ITO by a sol-gel method. After being annealed at different temperatures, the films presented different structures, which could be detected by the IR spectra. Cyclic voltammograms of the samples were also presented and correlated to the IR spectra. Since we expect that other inorganic oxides can yield similar results, this simple, non-destructive and inexpensive technique can be routinely used in an electrochemical laboratory.