Abstract

Gradient-index films up to 5-µm thickness have been produced by simultaneous deposition of electron beam evaporated silicon and of energetic nitrogen particles from a 500-eV Kaufman ion source. The relative fluxes of beam and evaporant atoms determine the ratio of nitrogen to silicon in the films and therefore control the index. The near infrared refractive index of amorphous silicon-nitrogen films decreases monotonically with composition from pure silicon to stoichiometric silicon nitride. Thin film devices were fabricated under computer control using Faraday cups to monitor the ion beam current and a quartz crystal oscillator to monitor the evaporation rate of Si. The utility of the method is demonstrated by devices including antireflection coatings, narrowband rejection filters of the rugate design, and broadband IR reflectors.

© 1989 Optical Society of America