Thermal annealing investigation of the optical properties of BxN1-x films by ion beam assisted deposition and application for an optical filter

The annealing behavior of the optical properties of boron nitride films (BxN1-x is described for films fabricated by ion beam assisted deposition. The data are needed for the precise manufacture of optical filters, where the index of refraction must be predicted from deposition parameters and film annealing history. The reflection of homogeneous samples deposited at room temperature on (100) silicon substrates was measured from 400 to 3125 nm to obtain the wavelength dependence of the index of refraction as a function of film nitrogen content. Nitrogen atom fraction was varied from 0.325 to 0.5 by variation of the incident of nitrogen ion beam current to evaporant boron flux ratio. The films were annealed in argon at 500 C and 700 C, and the optical measurements repeated after each anneal. The index of refraction obtained for the annealed films was used to design a narrow band optical reflection filter at 1060 nm. The filter, constructed by sinusoidally varying the index of refraction of the BxN1-x film by varying x, performed as designed