Crystal Growth and Spectroscopy of Yb2+-Doped CsI Single Crystal

The single crystals of CsI-Yb2+ were grown, and their spectroscopic studies were conducted. The observed luminescence in CsI-Yb2+ is due to 5d–4f transitions in Yb2+ ions. Using time-resolved spectroscopy, spin-allowed and spin-forbidden radiative transitions of ytterbium ions at room temperature were found. The excitation spectra of Yb2+ luminescence bands were obtained in the range of 3–45 eV. The mechanism of charge compensation of Yb2+ ions in a CsI crystal was also studied, the spectrum of the thermally stimulated depolarization current was measured, and the activation energies of the two observed peaks were calculated. These peaks belong to impurity–vacancy complexes in two different positions. The charge compensation of Yb2+ occurs via cation vacancies in the nearest-neighbor and next-nearest-neighbor positions.The Yb2+ ions are promising dopants for CsI scintillators and X-ray phosphors in combination with SiPM photodetectors.