Optical properties and surface activities of thin metallic films deposited in ultra high vacua

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1965
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Virginia Polytechnic Institute
Abstract

Copper and silver films of various thicknesses were deposited at a rapid rate, from four to twenty-five seconds, on glass substrates in ultra high vacua at pressures of 10⁻⁸ torr or lower. Their optical properties, reflectivity, transmissivity and absorptivity, were determined in vacua and in air by direct measurement using photomultiplier tubes. All the measurements were made at nearly normal incidence with a monochromatic light beam of wavelength 4358 A.

It was found that the reflectivity of films of both copper and silver decreased as they were exposed to air. The change took place in equal steps. Under the same circumstances, transmissivity increased but in a less regular way. Absorption changed in a most irregular fashion; no pattern could be established.

From this study of optical properties, the layer formation on fresh, clean surfaces of copper and silver caused by the air molecules was quite evident. In the case of copper, there may be one or two layers depending on the thickness of the film. They are formed primarily by cuprous oxide. In the case of silver the layer was attributed to chemisorption. Even though there was some indication that more than one layer was formed, the evidence was not conclusive.

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