Optical properties of amorphous boron carbonitride thin films deposited by reactive radiofrequency sputtering
A. Essafti*, E. Ech-chamikh, M. Azizan, Y. Ijdiyaou
Laboratoire de Physique des Solides et des Couches Minces,
Département de Physique, Faculté des Sciences Semlalia, Université Cadi Ayyad, B.P. 2390,
* Corresponding author. E-mail: email@example.com
Received: 24 May 2007; revised version accepted:10 October 2008
Amorphous boron carbonitride (a-BCN) thin films were deposited, at room temperature, onto glass substrates, by reactive radio frequency (RF) sputtering from a boron carbide (B4C) target in a gas mixture of argon and nitrogen. The optical properties of these films were obtained from the optical transmission measurements in the ultraviolet-visible-near infrared (UV-Vis-NIR) wavelengths range. The influence of the RF power, from 150 to 350 W, on the optical properties of the a-BCN films was studied. In the explored RF power range, the films are characterized by a high transmission in the Vis-NIR wavelengths region, and the optical band gap varies from 3.8 to 3.6 eV. The refractive index n(l) was analyzed by the single – effective oscillator model. The single oscillator energy Eo and the dispersion energy Ed were determined. The values of the static refractive index n(0), calculated at the photon energy hn=0, increase form 1.60 to 1.68 with increasing the RF power from 150 to 350 W. The change observed in refractive index and optical band gap has been related to boron content and sp2 C=N bonds contribution.
Keywords: boron carbonitride; RF sputtering; amorphous thin films; optical band gap; refractive index; static dielectric constant.