Optically transparent dielectric films, when prepared by thermal evaporation or sputtering, have had limited use for many applications due to their permeability and lack of stability. We report on protective dielectric films produced by ion-beam-assisted deposition which demonstrate significant improvements over films produced by conventional deposition techniques. This result can be explained in terms of the increased packing density of ion-assisted films over the porous columnar microstructure usually associated with evaporated films. In addition, ion bombardment of the metal films produced the most stable structures and also substantially improved the adhesion of the films. The endurance under chemical attack of these films was found to be limited by the surface finish of the substrates.
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