SILICON DIOXIDE AS A HIGH TEMPERATURE STABILIZER FOR SILVER FILMS.

Silver films cannot at present be used as high temperature reflectors because of severe agglomeration in the presence of oxygen at temperatures in excess of 200 degree C. Cr//2O//3, Al//2O//3, SiO//2 and CrO//x were tested for their effectiveness as thin barrier layers, and SiO//2 is the best of those tested. The use of SiO//2 allows the process of hole healing to compete with the normal hole growth process. Hole healing does not last indefinitely but is superseded by a slower rate hole growth process with an activation energy of 49 kcal mol** minus **1. Because of this last mechanism, stabilized silver is less than 1% transmitting after 50 h at 650 degree C in air, whereas bare silver agglomerates to 66% transmittance after only 3 min under the same conditions. Therefore 500 A SiO//2 films can be used as long term stabilizers for silver films in oxygen atmospheres with temperatures of up to 650 degree C.