Study On Growth Characteristics Of CsPbBr₃ Single Crystal

As a promising material for fabricating room temperature nuclear detectors, cesium lead tri-bromine?CsPbBr₃? has many prominent features, such as high atom number?Cs:55,Pb:82, Br:35? which decides that the molecule has a great ability to stop high-energy ray.The electrical resistivity(about 10¹¹? · cm) of CsPbBr₃ is large enough to ensure that the detectors have low leakage current. A large band gap?Eg=2.26 ev? enables it to work at room temperature with low noise signal. All of these decide that CsPbBr₃ crystal is a prospective material for radiation detectors.Firstly, raw CsPbBr₃ was synthesized by solid synthetic method with CsBr?5N? and PbBr2?5N?. Compared with the XRD standard card, the XRD picture of raw CsPbBr₃ indicated that it had homogeneous composition. Then the influence of temperature filed,temperature gradient and growth rate on crystal properties was studied, and CsPbBr₃ crystals in 8 mm diameter were fabricated. A temperature gradient of 7-10°C/cm and a growth rate of 0.5 mm/h would be appreciated for perfect CsPbBr₃ crystal growth. Infrared?IR? transmittance spectrum indicated that the average IR transmittance was around 60%.And the UV transmittance spectrum with an absorption wavelength edge at 548 nm indicated that the band gap of the CsPbBr₃ crystal was 2.26 eV. The X-ray diffraction analysis showed that the crystals were preferentially oriented in different direction, two typically directions were respectively direction of?321? and direction of?220?. The I-V characteristics of wafers with gold electrode were studied and the resistivity of each wafer was above 109 ??cm.In addition, the influence of annealing on I-V characteristics of wafers was studied.The wafers were annealed in three different atmospheres?air, vacuum and N₂? and the annealing temperature ranged from 90 to 150°C. It was found that after annealing, the leakage current of wafers was decreased largely. It indicated that annealing can improve theresistivity of wafers. The resistivity of wafer annealing at 120°C increased 70 times. And other wafers' resistivity also improved different level.