Abstract A series of single AlN and SiC thin films as well as SiC/AlN double layers were investigated by FTIR spectroscopy (reflection and transmission) and by Raman microscopy. The films (100–1200 nm thick) were prepared by laser ablation on Si(111) substrates at a relatively low temperature (800°C) to prevent thermal decomposition of the nitride. Raman spectra showed the formation of nanocrystalline AlN films characterized by broad scattering regions between 200 and 900 cm −1 and a weak, broad band at 665 cm −1. Furthermore they revealed amorphous SiC (scattering between 200 and 960 cm −1) with admixtures of amorphous carbon (scattering between 1300 and 1600 cm −1). The SiC films had a strong absorption and extinguished Raman scattering of the deeper layers. The IR spectra confirmed the presence of finely distributed SiC and AlN by intense bands at 795 and 665 cm −1, respectively. The optical models of these layers indicated free charge carriers in the SiC and SiC/AlN films. The AlN component of the SiC/AlN double layers showed a dielectric function containing free charge carriers in addition to that of a single film. Raman microscopy allowed the study of the boundary region between single and double layers on the same sample.