LARGE AREA, HIGH QUALITY, ELECTRON CYCLOTRON RESONANCE, CHEMICAL VAPOR DISPOSITION SIC THIN FILMS FOR ASTRONOMICAL MIRRORS

SILICON CARBIDE IS A LEADING NEW CANDIDATE FOR MIRROR BLANKS BECAUSE OF ITS HIGH STIFFNESS, RELATIVELY HIGH THERMAL CONDUCTIVITY, AND ABRASION RESISTANCE. THE BASE MATERIAL CONTAINS PORES OR LARGE GRAINS, WHICH MAKE IT DIFFICULT TO PROVIDE A SMOOTH FRONT SURFACE. RESEARCHERS HAVE DEVELOPED A PROCESS FOR USING ECR CHEMICAL VAPOR DEPOSITION TO DEPOSIT VERY SMOOTH AMORPHOUS SILICON CARBIDE (SIC) ON 100 MM SUBSTRATES. THE MATERIAL IS EASILY POLISHED TO OBTAIN A 10-20 A RMS SURFACE ROUGHNESS. RESEARCHERS ARE SCALING UP THIS PROCESS TO COAT LARGE DIAMETER OPTICS. THE MAIN PROBLEMS ASSOCIATED WITH SCALE-UP INVOLVE PLASMA GAS DYNAMICS AND FLUID FLOWS. RESEARCHERS ARE DEVELOPING A GENERAL COMPUTATIONAL MODEL TO BE USED FOR DESIGNING THE GAS DELIVERY SYSTEM. AN EXISTING SYSTEM TO COAT LARGE-AREA OPTICS WITH SMOOTH, AMORPHOUS SIC IS BEING MODIFIED.