Metal doping of dielectric thin layers by electric field assisted film dissolution

The incorporation of metal ions in dielectric layers by means of electric field assisted film dissolution is investigated. The samples consist of alkali-containing glass substrates coated first with SiO and then Ag thin films. The application of moderately elevated temperatures and DC voltages induces thermal poling in the glass matrix and metal film dissolution, resulting in the incorporation of metal ions in both dielectric layer and glass matrix. First, the process dynamics are simulated by modelling the migration of metal film ions and alkali species under an applied electric field. Numerical solution of the model indicates that metal ions progressively dope the dielectric layer until they reach the glass matrix. Then the dopant distribution in the layer becomes steady-state and further injection of ions contributes to increase the dopant concentration in glass. The influence on the process of alkali and dopant ion mobilities and alkali ion concentration is analysed. Additionally, Ag doping of SiO layers deposited on soda-lime and borosilicate glasses is experimentally carried out and characterized using spectroscopic ellipsometry. The evolution of refractive index profiles through both, SiO layer and glass substrate, is correlated with ion migration and confirms the model trends. Overall, this study shows that glass poling and film dissolution can be used to control metal doping of dielectric layers, with potential application in optical and photonic devices.