| AVS 62nd International Symposium & Exhibition | |
| Plasma Science and Technology | Friday Sessions |
| Session PS+SE-FrM |
| Session: | Atmospheric Pressure Plasma Processing II |
| Presenter: | Michael Hovish, Stanford University |
| Authors: | M.Q. Hovish, Stanford University R.H. Dauskardt, Stanford University |
| Correspondent: | Click to Email |
For many modern energy and sensing applications, multilayer optical coatings are an effective way to dramatically improve light collection. Traditionally, such multilayer coatings are deposited on hard substrates using vacuum depositions. Furthermore, traditional vacuum techniques are not easily scalable, due to high costs and poor integration into the manufacturing scheme. Atmospheric plasma deposition has received attention in materials processing due to the ability to deposit functional coatings at room temperature and in open air. Room temperature operation allows for a dynamic range of substrates, both organic and inorganic. In addition to these qualities, atmospheric plasma deposition is a solvent free technique, making it a competitive alternative to sol-gel methods. In our research program, we have successfully shown several material systems which are amenable to atmospheric plasma deposition, including multifunctional organosilicate and metal oxide films. In particular, the solvent-free deposition of metal oxide films at atmospheric pressure and near room temperature provides an attractive platform for the design and fabrication of optical coatings.
We have employed atmospheric plasma to deposit thin, anti-reflection coatings on silicon. Both TaOx and TiOx films were investigated as candidates for single layer anti-reflection coatings. Films were optimized for low reflection within the visible wavelengths of light. High purity helium gas was used to transport either tantalum ethoxide or titanium ethoxide vapor into the afterglow of a helium-nitrogen plasma. A high temperature precursor delivery system was used to prevent the condensation of precursor vapors en route to the afterglow. Within the afterglow, the metal-organic compounds undergo molecular fragmentation and redistribution onto the substrate. Deposition rates, chemical compositions, optical properties, and adhesion energies to the substrate were investigated as a function of plasma power and gas composition. Spectral reflectance at 10° from normal was measured to determine the anti-reflection properties of the coatings. Atmospheric plasma deposited films on silicon show excellent anti-reflection properties, with less than 3% reflection loss near 550 nm.