Yang Ding-Yu, Zhu Xing-hua, Sun Hui, Hao Dong, Li Xu-ying
Guang Pu Xue Yu Guang Pu Fen Xi. 2014 Nov;34(11):2892-6.
In the present paper, the structural, morphological and optical properties of PbI2 thick films prepared by close-spaced sublimation technique were investigated. It was found that the thickness of PbI2 films decreased from 1 000 μm to 220 μm with the increase in the sublimation source temperature. X-ray diffraction (XRD) pattern shows that the thick films are polycrystalline hexagonal structure with preferred growth orientation of (002) plane, and their grain size, dislocation density and growth stress are closely related to the source temperature. Images of scanning electron microscopy (SEM) reveal the accumulation of hexagonal plate-like particles which constitute the samples, and the particles with a diameter of 248 μm and a thickness of 32.7 μm, exhibit clearly layered structure. By spectrum fitting using Gauss function, the Raman spectra show a shift of about 147, 169, 217 and 210 cm(-1) respectively, the first three peaks correspond to the longitudinal optical vibrations (LO) mode in 4H-PbI2 crystal, while the last peak originate from a vibration pattern associated with SnO2 in substrate. Raman peak of 147 cm(-1) changes significantly with the increases in source temperature, and a dramatic decrease in peak intensity with broadening peak width occurred when the source temperature increased up to 225 degrees C or more. Under 340 nm excitation at room temperature, several weak photoluminescence peaks of PbI2 samples which associated with defects and exciton recombination near 2.25, 2.57 and 2.64 eV were observed. Given a comprehensive consideration of structural and spectral characterization results, PbI2 thick films with a thickness of about 659 μm deposited at a source temperature of 200 degrees C achieves the best crystalline quality.
在本文中，对采用近距离升华技术制备的PbI₂厚膜的结构、形态和光学性质进行了研究。结果发现，随着升华源温度的升高，PbI₂薄膜的厚度从1000μm减小到220μm。X射线衍射（XRD）图谱表明，厚膜为多晶六方结构，具有（002）面的择优生长取向，其晶粒尺寸、位错密度和生长应力与源温度密切相关。扫描电子显微镜（SEM）图像揭示了构成样品的六方板状颗粒的堆积情况，直径为248μm、厚度为32.7μm的颗粒呈现出明显的层状结构。通过使用高斯函数进行光谱拟合，拉曼光谱分别显示出约147、169、217和210 cm⁻¹的位移，前三个峰对应于4H-PbI₂晶体中的纵向光学振动（LO）模式，而最后一个峰源自与衬底中SnO₂相关的振动模式。147 cm⁻¹的拉曼峰随源温度的升高而发生显著变化，当源温度升高到225℃或更高时，出现峰强度急剧下降且峰宽变宽的情况。在室温下340nm激发下，观察到PbI₂样品在2.25、2.57和2.64 eV附近与缺陷和激子复合相关的几个弱光致发光峰。综合考虑结构和光谱表征结果，在200℃源温度下沉积的厚度约为659μm的PbI₂厚膜具有最佳的晶体质量。
