Thick UV-patternable hybrid sol-gel films prepared by spin coating

We report on the fabrication and characterization of thick UV-patternable hybrid sol-gel films by spin coating using a modified sol-gel process. Thick coatings of 25 microns with crack-free surfaces can be produced by one spin coating step. Characterization using different techniques including atomic force microscopy, scanning electron microscopy and profilometry show both a smooth surface of optical quality and precise patterning with sharp vertical walls. Refractive index measurements by prism coupling and using a spectroscopic ellipsometer indicate high reproducibility of coating optical properties prepared by this procedure. Large refractive differences can be obtained by varying the process conditions, allowing the preparation of channel waveguide structures.