Abstract
A study has been made of the optical properties of semi-transparent films of variable thickness produced by sputtering in hydrogen. The masses of the films have been computed from the assumed optical constants and densities of the metals, and from the locations of the interference fringes, when the films are viewed by reflected monochromatic light at approximately normal incidence. With few exceptions the computed masses are much greater than the masses determined directly by weighing. The differences between the computed and weighed masses can be accounted for by assuming higher refractive indices and lower densities of the films than those assumed for the bulk metals. Such would be the case if the films were composed of compounds, e.g., oxides of the metals. This has been verified by a colorimetric analysis of the iron films. Further confirmation is supplied by a study of the optical dispersion of the films, which seems to be characteristic of transparent insulators rather than of the metals. High refractive indices are also called for from a consideration of the aging of a platinum film. A mathematical analysis of the reflectivity of the films has been made, based upon the consideration of multiple reflections within the films. To account for the number of fringes observed, very low indices of absorption must be assumed, such as possessed by transparent insulators.
© 1939 Optical Society of America
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