Ultraviolet luminescence of single crystals and single-crystal films of YAlO3

Abstract

The nature of intrinsic emission bands of yttrium orthoaluminate in the UV spectral region at max=220 nm (5.63 eV) and 330 nm (4.13 eV) is studied on the basis of the luminescence of single crystals and single-crystal films of YAlO3 and Ce: YAlO3 excited by synchrotron radiation sources with an energy of 3–25 eV at 9 and 300 K. The single crystals and single-crystal films were obtained, respectively, from solution and solution-melt by liquid-phase epitaxy and are characterized by considerably different concentrations of substitutional and vacancy defects. It is found that only the luminescence band at 300 nm, which has the decay time τ=4.1 ns and is excited in a band shifted from the range of interband transitions by 0.25 eV, has exciton-like character. The luminescence band at 220 nm with τ=0.1 µs at 9K, which is observed only for YAlO3 single crystals and is absent in the luminescence of single-crystal films, is associated with antisite defects of the YAl3+ type, which are a specific type of cationic isoelectronic impurities. It is shown that the phosphors based on single-crystal films of YAlO3 have a simpler scintillation decay kinetics than their bulk analogues due to the absence of channels of excitation energy dissipation associated with the antisite defects of YAl3+ type and vacancy defects.