THIN-FILM MATERIALS EXPOSURE TO LOW-EARTH-ORBIT ABOARD SPACE-SHUTTLE

To study the effects of Atomic Oxygen on various thin film materials, fourteen thin film samples were exposed to the corrosive environment of low Earth orbit. Total exposure was 42 hours, resulting in a nominal atomic oxygen fluence of 2.2, x 10(20) atoms/cm(2). The films included aluminum, diamondlike carbon, diamond, and multilayer stacks. Included are experimental details of sample preparation, exposure, and post-flight results. Pre-flight characterization techniques included Variable Angle Spectroscopic Ellipsometry, optical reflectance and transmittance, Atomic Force Microscopy, and Raman scattering. Post-night analysis repeated pre-flight characterization. Aluminum films resisted degradation, Surface contaminants were identified using Auger Electron Spectroscopy, Contaminants were SiO2, fluorine, and sulfur which most likely result from degradation of cargo bay lining, waste water dumps, and outgassing. Diamondlike carbon films were completely etched away during exposure. Polycrystalline diamond films were extremely resistant to atomic oxygen degradation, showing no post-flight structural, compositional, or mass changes. Aluminum films 23.5 nm thick simultaneously protect silver reflecting layers from oxidation and increase the ultraviolet reflectance of the stack. Decreasing the aluminum thickness to 7.5 nm resulted in complete oxidation during exposure and failure as a protective coating.