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 α-Al2O3(0 0 1) 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 5.45–5.55 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.

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► Ca-doped boron nitride was prepared by pulsed laser deposition.
► The films do not have long range order structure in terms of XRD.
► But the films had short-range order structure of h-BN sheets.
► Ca-free films had the same optical band gap as crystalline bulk h-BN (5.8 eV.)
► Ca-doping brought about decreases of the optical band gap by ca. 0.4 eV.