Optical absorption of boron nitride nanomaterials

Optical absorption spectra have been measured for hexagonal boron nitride (h-BN), rhombohedral BN(rh-BN), and material obtained by laser vaporization of BN target under a nitrogen atmosphere and contained single-wall BN-nanotubes. Band gap of the BN materials was found to have a value of 6.0-6.3 eV. The spectra of h -BN and vaporized material exhibited a peak at ∝5.5 eV, moreover, the latter sample showed an absorption band around 4.5 eV. The vaporized material has been fractionated to the BN-platelets and single-wall BN-nanotubes. Absorption peaks, located bellow the bottom of the conductance band, were found to be characteristics of thin BN-platelets and they could be attributed to defects in BN network. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)