Study on the Vertical Bridgman Method of Melt-Grown CsPbBr3 Single Crystals for Nuclear Radiation Detection.

As an excellent representative of all-inorganic perovskite materials, CsPbBr3 has been widely used in high-energy rays or high-energy particles detection for its outstanding high carrier mobility and long diffusion length. The great challenges and opportunities in these fields are crystal growth technology, especially the high-quality and large-sized CsPbBr3 single crystals. In this work, the influences of growth parameters (temperature gradient, growth rate, cooling rate) and thermal stress by the vertical Bridgman method on the quality and performance of CsPbBr3 crystals are systematically studied. The final results show that 10°C cm-1 is the optimized temperature gradient and 0.5 mm h-1 is the suitable growth rate for CsPbBr3 crystal growth. The study also shows that a cooling rate of 10°C h-1 for the general temperature interval and 1°C h-1 for the phase transition temperature interval is helpful to balance crystal growth efficiency as well as crystal quality. Crystal cracks caused by thermal stress as well as crystal adhesion on the ampoule can be effectively solved by depositing a uniform carbon film on the ampoule in advance. The optical, electrical and detection performance are also investigated. The optical characterization in the wavelength region ranging from ultraviolet to infrared indicates the crystal has a low density of deep-level defects and good crystal quality. The resistivity over 109 Ω cm and μτ of electrons over 10-2 cm-2 V-1 proves that the electrical performance of the crystal has met the basic requirement for nuclear radiation detection. The metal-semiconductor-metal structure Ti/Ni/CsPbBr3/Ni/Ti detector fabricated from the optimized CsPbBr3 single crystal has an energy resolution of 12.85% (137Cs, 662 keV). The purpose of this work is to provide a useful guide and reference for the future exploration of repeatable and improvable CsPbBr3 crystal growth technology.