The amorphous boron-carbon-nitrogen (BCN) thin films were prepared by RF magnetron sputtering from a B4C target in argon and nitrogen gas ambient. The substrate temperature was varied from room temperature to 500 degrees C. The structural and bonding characteristics were studied by X-ray photoelectron spectroscopy (XPS) and the optical properties were characterized by UV-Visible spectrophotometer. For different substrate temperatures, the optical band gaps (E-opt) ranged from 3.5-4.8 eV and refractive index were in the range of 2.66-1.5. The reported band gap values are significantly higher than the band gap values usually reported elsewhere in the literature for sputter deposited BCN thin films. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3610430] All rights reserved.