【作者】 陈成；

【导师】 郑志平；

【作者基本信息】 华中科技大学 ， 微电子学与固体电子学， 2019， 硕士

【摘要】 无机钙钛矿材料溴铅铯（CsPbBr₃）由于其独特的物理化学性质,受到了各个领域的广泛关注。其中最令人关注的是其作为高能射线探测器材料的应用前景,这里所说的高能射线一般是包含keV到MeV数量级能量的光子,而CsPbBr₃单晶拥有优异的光电特性,这些特性决定了CsPbBr₃适合用于制备高能射线探测器,本文的主要研究内容包括三个方面:一是使用两种熔体法生长高质量的CsPbBr₃单晶,并对单晶的质量作了详尽的测试表征和分析,在此基础之上对两种方法进行了对比研究;二是对CsPbBr₃单晶制备的高能射线探测器性能进行了表征和分析;三是对CsPbBr₃单晶的离子迁移特性进行了研究。首先,研究了水平移动区熔法和垂直布里奇曼法最适合的温度梯度和生长速率,水平移动区熔法优化的加热器温度应设置在640⁶50℃,优化的生长速率为0.48mm/h,垂直布里奇曼法优化的温度梯度为9℃/cm,优化的生长速率为0.48mm/h。对两种熔体法生长的CsPbBr₃单晶的结构、光学、载流子输运特性以及电学特性进行了研究,红外透过率最高达到75%,紫外透过率最高达到40%,根据紫外-可见光透过谱拟合得到的禁带宽度和PL光致发光谱得出的禁带宽度均接近理论值2.25eV,表明晶体没有出现明显的缺陷能级,用TRPL时间分辨光致发光谱得到的载流子辐射复合寿命最高达129.4ns,根据改进的Hetch方程拟合的载流子迁移率寿命积最高达到9.8×10^-4cm²/V,电阻率最高接近10GΩ·cm数量级。关于CsPbBr₃单晶的高能射线探测性能,分别研究了其对X射线（30keV）和对γ射线²⁴¹Am（59.54keV）的响应。CsPbBr₃单晶对X射线有明显的响应,并计算了响应灵敏度和增益因子,但是对γ射线的响应较弱,仅通过示波器观察到了信号的高斯波形。最后,还对CsPbBr₃单晶的离子迁移特性进行了详细的研究。众所周知,ABX₃型钙钛矿存在着离子迁移的现象,表现出明显的直流极化和I-V迟滞效应,这会对器件的稳定性造成不利的影响。实验上采用变温电流时间谱研究CsPbBr₃单晶的离子迁移激活能E_a,并和文献中理论计算的值进行了比对,结合课题组此前关于CsPbBr₃单晶本征缺陷的研究,确定了迁移的主要对象为V_Br,对V_Br的迁移路径进行了合理推测。同时,还测试了CsPbBr₃单晶的变温介频谱,从介电特性对其宏观极化现象进行了研究并结合理论模型分析了机理。更多还原

【Abstract】 The inorganic perovskite material bromine lead bismuth（CsPbBr₃）has received extensive attention in various fields due to its special physical and chemical properties.The most interesting of these is its application prospect as a material for high-energy ray detectors.The high-energy ray generally consists of photons containing energy of the order of keV to MeV,and the CsPbBr₃ single crystal has excellent optoelectronic properties.These characteristics determine that CsPbBr₃ is suitable for the preparation of high-energy ray detectors.The main research contents of this paper include three aspects:one is to use two melting methods to grow high-quality CsPbBr₃ single crystals,and the quality of single crystals is detailed.Based on the test characterization and analysis,the two methods were compared.The second is the characterization and analysis of the performance of CsPbBr₃ single crystal as a high-energy ray detector.The third is the research of ionic transport characteristics of CsPbBr₃ single crystal.We studied the temperature gradient and growth rate which are most suitable for horizontal moving melting zone method and vertical Bridgeman method.The optimized temperature for the horizontal moving melting zone method should be set to 640⁶50℃and the optimized growth rate is 0.48mm/h.The optimized temperature gradient for the vertical Bridgeman method is 9℃/cm,and the optimized growth rate is 0.48mm/h.Then the structure,optical,carrier transport characteristics and electrical properties of the two melt-grown CsPbBr₃ single crystals were studied.The results showed that high crystalline quality of CsPbBr₃ crystals was obtained.The infrared transmittance was up to 75%and the UV transmittance was up to 40%.The forbidden band width obtained by fitting the ultraviolet-visible light transmission spectrum and the forbidden band width obtained by the PL photoluminescence spectrum are close to the theoretical value of 2.25eV,indicating that the crystal has no obvious defect level.The radiation composite carrier lifetime of CsPbBr₃ single crystal is up to 129.4ns according to the results of TRPL time-resolved photoluminescence spectrum.The carrier mobility lifetime product is up to 9.8×10^-4cm²/V according to the improved Hetch equation.And the highest resistivity is close to the order of 10GΩ·cm.For the high-energy ray detection performance of CsPbBr₃ single crystal,we studied the response to X-ray（30keV）andγ-ray ²⁴¹Am（59.54keV）,respectively.CsPbBr₃ single crystal has obvious response to X-rays.We calculated the sensitivity and gain factors.But the response to gamma rays is weak,and the Gaussian waveform of the signal is observed only by the oscilloscope.Finally,the ionic transport of CsPbBr₃ single crystal grown by vertical Bridgeman method is studied in detail.It is well known that ABX₃ type perovskites have ionic migration phenomena,exhibiting obvious DC polarization and I-V hysteresis effects,which adversely affect the stability of the device.The ionic migration activation energy E_a of CsPbBr₃ single crystal was studied by the temperature-dependent I-t curve method,and it is compared with the theoretically calculated values in the literature.Combined with the previous research on the intrinsic defects of CsPbBr₃ single crystal,the main object of migration was determined to be V_Br.And we make a reasonable guess on the migration path of V_Br.At the same time,we studied the temperature-dependent dielectric-frequency spectrum of CsPbBr₃ single crystal.The macroscopic polarization phenomenon was studied from the dielectric properties and the mechanism was analyzed with theoretical models.更多还原