Preparation of calcium-doped boron nitride by pulsed laser deposition

Abstract

Calcium-doped BN thin films CaxBNy (x=0.05–0.1, y=0.7–0.9) were grown on α-Al2O3(001) substrates by pulsed laser deposition (PLD) using h-BN and Ca3N2 disks as the targets under nitrogen radical irradiation. Infrared ATR 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 5.45–5.55eV of optical band gap, while the band gap of Ca-free films was 5.80–5.85eV. 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.