OPTICAL AND STRUCTURAL CHARACTERIZATION OF BORON-NITRIDE THIN-FILMS

Thin films of baron nitride were prepared by three deposition methods: r.f. plasma deposition, pulsed laser deposition and r.f. magnetron sputtering. The films were characterized by Fourier transform IR spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, optical transmittance spectrophotometry and spectroscopic ellipsometry in the visible-near-UV range. The films are highly transparent with atomic B:N ratios from 2.5 to 1.1, and refractive index values between 1.6 and 1.9 depending on deposition conditions. IR and Raman spectra revealed a short-range atomic order with hexagonal BN bonds, which is more marked in r.f. plasma-deposited films. From the spectroscopic ellipsometric measurements, the optical response of the films was analysed using a two-layer model and applying the Bruggeman effective medium approximation far each layer.