Time-resolved photoluminescence on samarium, nickel, and cesium ion doped scintillator CdWO4 (010) single crystal surfaces

Abstract

Photoluminescence (PL), cathode luminescence (CL), and x-ray excited luminescence (XL) are studied on Sm-, Ni-, and Cs-doped CdWO4 (010) single crystal surfaces. Luminescence spectra are deconvoluted to three constituent species at 2.77, 2.48, and 2.18 eV. Their intensities of the ion-doped CdWO4 crystals are compared with the undoped crystals. CL and XL intensities on Sm- and Ni-doped single crystals are suppressed to be about 20–40% of the undoped crystal. However, the luminescence component at 2.18 eV is dominant on the Sm-ion doped CdWO4 crystal. The x-ray diffraction peak at (020) face shifts to lower 2θ value on the Sm-ion doped CdWO4 single crystal, indicating that the crystal structure of CdWO4 is disturbed by Sm ions and the distance between (020) faces is enlarged. The distortion of the crystal structure will be induced by the exchange of W6+ ions into Sm3+ ions with larger ion diameter. Time-resolved PL decay analyses are studied on the doped and undoped crystals under excitation below the band gap. While only the slow decay component is detected with a lifetime of 14 μs on the undoped CdWO4 crystal, the fast and the slow PL decay components are detected with a lifetime of 0.7 and 10 μs on the three emission species in the doped CdWO4 crystals, respectively. The Cs-doped CdWO4 crystal has almost the same intensities for PL, CL, and XL as the undoped crystal.