Optical and electronic properties of undoped La2Be2O5 single crystals in the far ultraviolet energy range

The optical and electronic properties of undoped La2Be2O5 single crystals were determined using low-temperature (T = 10 K) far ultraviolet (4.9-33 eV) synchrotron radiation spectroscopy, optical absorption spectroscopy (T = 80 and 320 K), and calculations for the dispersions of the optical functions. On the basis of the obtained data we determined the Urbach's formula parameters and the cut-off energy Ec = 5.49 eV at 80 K for the low-energy tail of the host absorption, the bandgap Eg = 6.78 eV at 10 K, the energy threshold for the creation of unrelaxed excitons Eex = 6.28 eV, and other electronic properties. © 2015 Optical Society of America