AVS 63rd International Symposium & Exhibition
    Thin Film Wednesday Sessions
       Session TF+MI-WeA

Paper TF+MI-WeA12
Watching Thin-film Aluminum Oxidize

Wednesday, November 9, 2016, 6:00 pm, Room 104E

Session: Thin Films for Magnetic and Optical Applications
Presenter: David Allred, Brigham Young University
Authors: D.D. Allred, Brigham Young University
M. Miles, Brigham Young University
S. Thomas, Brigham Young University
S. Willett, Brigham Young University
M.J. Greenburg, Brigham Young University
A. Vance, Brigham Young University
R.S. Turley, Brigham Young University
Correspondent: Click to Email
In three years NASA will be in the midst of its decadal review, establishing priorities for the 2020s. Very likely one of the chief astrophysical missions will contain a LUVOIR (large, UV-optical-IR) telescope. This space-based observatory will likely contain the largest mirrors ever flown and will probe the cosmos seeking to address key questions of the origin, current status and evolution of our universe. These investigations will profit from a truly broad-band mirrors. Thus, the reflective coating will almost certainly be aluminum. To be viable, the top surface of such a space mirror needs to be bare without the tarnish layers that naturally form in air. This could open up the 11-15eV band for space-based astrophysics without sacrificing IR, visible and UV reflectance. We report on two techniques aimed at clarifying the oxidation mechanism for Al. First, we have used VUV (>10 eV) reflectometry of bare, freshly deposited aluminum mirrors as they age in controlled atmospheres, and second, variable-angle, spectroscopic ellipsometry is shown to be capable of measuring changes at the angstrom level in multilayers consisting of aluminum, protected by various vacuum-applied barrier layers. These ultrathin barrier layers included polymers such as parylene and inorganic films, such as MgF2 and AlF3. For example, we saw that the growth in oxidation thickness of aluminum protected by a 7nm MgF2 film is logarithmic over a period of time of more than 1000 hrs.