Low-Dimensional Semiconducting Materials in Developing Ultra-Fast Scintillators

An idea for developing scintillators having both a large light output and a quick response is presented. Usually, some direct-gap semiconductors exhibit sub-nanosecond decaying ultra-fast scintillation components only at a very low temperature. The authors found that the thermal quenching could be effectively prevented by a construction of a low-dimensional quantum confinement system, and practical light outputs were obtained even at room temperature. A comparative study in scintillation properties of two- and three-dimensional semiconducting materials having similar compositions was demonstrated in order to discuss physical effects of the quantum confinement systems. The authors believe that this achievement will play an important role when developing a time-of-flight (TOF)-PET. A crystals of (C6H13NH3)2PbI4 having a multiple quantum well structure exhibited three decay components of 390 ps, 3.8 ns and 16 ns with the ratios of 28%, 29% and 43%, respectively. And the total light output was 11% of that of NaI:Tl at 300K.The 4th Japan-Korea Joint Meeting on Medical Physics and The 5th Asia-Oceania Congress of Medical Physic