Structure and optical properties of boron nitride thin films prepared by PECVD

Boron nitride (BN) thin films were deposited from borane dimethylamine and nitrogen using a plasma enhanced CVD technique at low temperature. The deposited films were characterized by X-ray diffraction, XPS spectroscopy, infrared absorption spectroscopy, and scanning electron microscopy. All the films crystallized in the hexagonal form of BN, and consisted of microcrystals with about 50 nm grain size. Optical reflectance and transmittance measurements of the films were recorded in the wavelength range 220–2500 nm. The optical constants, refractive index n and extinction coefficient k, of the films were calculated from these experimental data, by a numerical method based on the use of Fresnelʹs formalism via an iterative process. An optical gap Eg of about 3.6 eV has been deduced.