INFLUENCE OF SOLVENT CONCENTRATION ON THE MICROSTRUCTURE OF SIO2-TIO2SOL-GEL FILMS

Spin-coating is one of the possible methods for the fabrication of opt ical planar waveguides. These have several applications in integrated optical devices, provided that their optical losses are below similar to 1 dB/cm. The attenuation is caused in part by surface and bulk scat tering. The latter depends on the microstructure of the films and, mor e particularly, the porosity, which is studied here. A series of SiO2- TiO2 films were prepared from solutions containing different concentra tions of ethanol. The influence of the ethanol/(Si + Ti)alkoxides volu me ratio on the porosity was investigated by Ellipsometry, Infrared Sp ectroscopy, and Scanning Electron Microscopy. The porosity volume frac tion was found to reach a minimum when the ethanol volume ratio is nea r 4.