Photoluminescence spectra of undoped and Sm~3+ -doped BaAl_2S_4 and BaAl_2Se_4 single crystals

摘要

Undoped and Sm~3+ -doped BaAl_2S_4 and BaAl_2Se_4 single crystals were grown by the chemical transport reaction method. The optical energy band gaps of the BaAl_2S_4 and BaAl_2Se_4 were found to be 4.10 and 3.47 eV, respectively, at 5 K. In their photoluminescence spectra measured at 5 K, broad emission peaks at 459 and 601 nm appeared in the BaAl_2S_4 and at 486 and 652 nm in the BaAl_2Se_4. These emissions are assigned to donor-acceptor pair recombinations. Sharp emission peaks were observed in the Sm~3+ -doped BaAl_2S_4 and BaAl_2Se_4 single crystals at 5 K. Taking into account the ionic radii of the cations and Sm~3+, these sharp emission peaks are attributed to the electron transitions between the energy levels of Sm~3+ substituting with the Ba site.