Bandgap energy of graphite-like hexagonal boron nitride

We have carried out laser-induced fluorescence measurements of hBN powder at room temperature under different environmental conditions (dry powder and suspensions in water or ethanol). From fluorescence excitation spectra, the absorption onset, related to the bandgap energy of this indirect gap semiconductor, has been precisely determined to be E-g = 4.02 +/- 0.01 eV. This result is of importance in view of large discrepancies in previously published data. (C) 2001 Elsevier Science Ltd. All rights reserved.