Control of dopant adsorption from aqueous solution into nanoporous sol-gelfilms

The doping of porous sol-gel films by adsorption of cations onto silica fro m aqueous solutions is demonstrated. The films are fabricated using the sol -gel method, giving nanometer scale porosity, high surface area, and homoge neity on the scale of optical wavelengths. After deposition by spin coating and initial heat treatment, the films are soaked in a salt solution of the desired dopant, and then given a further consolidating heat treatment. Doping with lead, aluminum and calcium has been demonstrated, and consisten t and reproducible processes have been established. Results are presented s howing control of doping level through pre-doping temperature and surface t reatment, doping time and temperature, and doping solution pH. Potential ap plications in integrated optics are proposed.