Optical and mechanical characteristics of nanocrystalline boron carbonitride films synthesized by plasma-assisted physical vapor deposition

Nanocrystalline boron carbonitride thin films were prepared using the electron-cyclotron- wave-resonance plasma-assisted deposition, whereby the energy for precursor ions was adjusted between 70 and 180 eV. Fourier-transform infrared spectroscopy confirmed the presence of ternary sp(3)-bonded structure and high-resolution transmission electron microscopy revealed a punctured lattice. The deposits unfold grains of about 200 nm in dimension under atomic force microscope, yet they exhibit extremely flat surfaces with a root-mean-square roughness less than 3 nm. For a 1.2 mum thick film, the transmittance in the visible light range is as high as 80%. The Vicker's hardness measures over 28 GPa. Therefore, this ternary material is competitive to nanocrystalline diamond in application as protective coatings for optical components. Remarkably, also very strong photoluminescence peaked at 430 nm was detected in the as-deposited films at room temperature. (C) 2003 American Institute of Physics.