期刊
JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN
卷 79, 期 7, 页码 -出版社
PHYSICAL SOC JAPAN
DOI: 10.1143/JPSJ.79.074717
关键词
intrinsic luminescence; self-trapped exciton; decay kinetics; multiplication of electronic excitation; Auger decay; Bi4Ge3O12; Bi12GeO20; BGO; synchrotron radiation
资金
- Institute for Molecular Science
The intrinsic luminescence appearing at 500 nm in Bi4Ge3O12 (e-BGO) and that at 450 nm in Bi12GeO20 (s-BGO) have been studied over a wide range of temperature T = 5-300K by using a Nd:YAG laser and synchrotron radiation as excitation light sources. Luminescence decay curves in e-BGO depend dramatically on the laser power; they are composed of three decay components under high-density excitation, while they show a single exponential decay at low-density excitation. From temperature dependences of the decay time and emission intensity, it is clarified that the triplet state of a self-trapped exciton (STE) responsible for the e-BGO luminescence consists of a pair of closely spaced sublevels with separation energy of 5.7 meV. The decay curves of s-BGO luminescence are essentially nonexponential, irrespective of the excitation power. Time-resolved luminescence measurements of s-BGO suggest the existence of a singlet state lying higher than the triplet STE state. The excitation spectra for the intrinsic luminescence bands have been measured up to 35 eV (35 nm) at 5 K. From the obtained spectra, it is obvious that the multiplication of electronic excitations takes place efficiently in both BGOs. The production processes of multiple excitons are discussed by referring to a recent study on the electronic structures.
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