Single crystals of the undoped Cs 2 HfCl 6 were grown using the vertical Bridgman method. Photoluminescence spectra and decays were measured in the extended temperature range of 8−500 K and approximated by a phenomenological model. Self-trapped exciton and defect-related emissions were clearly distinguished with the onset of thermal quenching above the room temperature. Electron paramagnetic resonance experiment revealed the formation of two configurations of V k center (Cl 2 − molecular ion) at low temperatures. One of the V k centers is created by a hole self-trapping at two neighboring Cl ions. In the temperature range 70−80 K, this state is thermally disintegrated and reappears in another configuration formed most probably by an interstitial Cl ion (an analog of the H-type center in alkali halides).

No abstract

No abstract

Charge trapping phenomena and recombination centers were studied in three Cs 2 HfCl 6 single crystals of slightly different stoichiometry grown by the vertical Bridgeman method. Electron paramagnetic resonance (EPR) spectra measured both before and after X-ray irradiation show creation of two distinct V k centers. One of them was V k (a) already known from a recent work by "R.