Characterization Of Optical Coatings Deposited With A Large-Area Radio Frequency Plasma Ion Source

The present research is devoted to the characterization of thin film optical coatings deposited with a large-area radio frequency plasma ion source.  A new type of radio frequency plasma ion source was used to deposit a wide range of oxide materials with ion assisted electron beam evaporation.  These coatings were deposited in large production optical box coaters with planetary and dome fixtures.  The plasma ion source was characterized with Faraday cups and a Retarding Field Energy Analyzer (RFEA).  Faraday cups measured the ion current density and ion beam profile across the fixtures.  The RFEA was used to determine the average ion energies and ion energy distributions for different operating conditions.  Average ion energies were measured in the range of 30-500 eV.  Optical properties of these coatings were measured with a spectrophotometer to determine the index of refraction, absorption, and moisture stability.   Optical properties were correlated with plasma ion source parameters for each material.  For example, titanium dioxide films have been deposited with high refractive indices, n= 2.40-2.46, utilizing ion current densities of 300-350 mA/cm² and average ion energies of 50-200 eV.  The optical performance of multilayer high and low refractive index coatings will be presented as well.