FAR-ULTRAVIOLET ABSOLUTE REFLECTOMETER FOR OPTICAL CONSTANT DETERMINATION OF ULTRAHIGH VACUUM PREPARED THIN FILMS

An absolute reflectometer is described, which can determine the optical constants of thin films prepared and maintained in ultrahigh vacuum (UHV) in the 30–200 nm far‐ultraviolet (FUV) region. The optical constants are calculated with Fresnel equations from reflectance measurements as a function of the incidence angle, which can be continuously varied from near‐normal to grazing incidence. Corrections for the surface roughness effects of both the deposited film and the substrate on the reflectance in the calculation of optical constants were incorporated. The surface roughness was determined by atomic force microscopy. An innovative feature of the instrument is an oxidation chamber containing an atomic oxygen source attached to the reflectometer. Inside this chamber the FUV reflectance degradation of materials, caused by oxidation processes in low earth orbits, can be simulated on freshly prepared UHV samples. Another improvement of the reflectometer is the capability of performing the reflectance measure...

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