Properties of pulsed laser deposited boron nitride films

Pulsed laser ablation using an excimer laser of 248 nm wavelength was applied to prepare boron nitride films, where the ablation from boron nitride as well as elemental boron targets was studied. The growing films were bombarded by a nitrogen or a nitrogen/argon ion beam to obtain stoichiometric films and to investigate ion induced modifications of structure and properties. Depending on deposition parameters the refractive index of the boron nitride films in the visible wavelength range varies between 2.5 and 1.7 and the optical energy band gap between 2.0 and 4.5 eV. Most films were found to be completely sp2-bonded and amorphous to nanocrystalline with a turbostratic microstructure. Only boron nitride films deposited from the boron target and bombarded with nitrogen/argon ions show also an absorption peak in the infrared spectrum that indicates the presence of the cubic phase.