Optical Absorption in Polymer‐Derived Amorphous Silicon Oxycarbonitrides

Three amorphous silicon oxycarbonitrides are prepared by thermal decomposition of a polymeric precursor at different temperatures. The optical absorption spectra of these materials are measured over a wide range of excitation energies from 0.4 to 5.0 eV. The spectra are analyzed using theoretical models. Two absorption transitions are identified between the deep defect energy level and the delocalized conduction band and between the two delocalized bands. It is found that the band gaps measured decrease with increasing pyrolysis temperature. The results obtained are discussed.