Preparation of calcium-doped boron nitride by pulsed laser deposition

Calcium-doped BN thin films CaxBNy (x = 0.05-0.1, y = 0.7-0.9) were grown on alpha-Al2O3(0 0 1) substrates by pulsed laser deposition (PLD) using h-BN and Ca3N2 disks as the targets under nitrogen radical irradiation. Infrared AIR spectra demonstrated the formation of short range ordered structure of BN hexagonal sheets, while X-ray diffraction gave no peak indicating the absence of long-range order structure in the films. It was notable that Ca-doped film had 5.45-5.55 eV of optical band gap, while the band gap of Ca-free films was 5.80-5.85 eV. This change in the band gap is ascribed to interaction of Ca with the BN sheets: first principle calculations on h-BN structure indicated that variation of inter-plane distance between the BN layers did not affect the band gap. This study highlights that PLD could prepare BN having short-range structure of h-BN sheets and being doped with electropositive cation which varies the optical band gap of the films. (c) 2012 Elsevier Ltd. All rights reserved.