毫米级厚度碘化铅(PbI2)膜是制造下一代阵列高能辐射探测器的关键材料。 采用近空间升华法制备了PbI2厚膜, 研究升华源温度对制备样品晶体结构、 表面形貌及光谱性质的影响。 结果表明, 随着源温度的升高, 样品厚度由1 000 μm下降到220 μm。 X射线衍射测试表明, 厚膜为沿(002)晶面择优取向生长的六方相多晶结构, 其晶粒尺寸、 位错密度及生长应力与源温度密切相关。 扫描电子显微镜测试显示, 样品由六方片状颗粒堆积而成, 其颗粒直径约为248 μｍ, 厚约32.7 μｍ, 有明显的层状结构。 解谱拟合发现, 样品的拉曼光谱有147, 169, 217和210 cm-1等4个散射峰, 前三个峰对应于4H晶型PbI2晶体的纵光学波振动模式, 210 cm-1来源于衬底SnO2的相关振动模式。 随源温度的升高, 147 cm-1拉曼峰有明显变化, 其峰强高于225 ℃时出现大幅度的下降, 峰形展宽。 在340 nm光激发下, 样品的室温光致发光谱在2.25, 2.57和2.64 eV附近出现弱的发光峰, 来源于与缺陷和激子相关的复合。 综合结构表征与光谱测试结果, 200 ℃时沉积的PbI2厚膜具有最佳的结晶质量, 其厚度约为659 μｍ。

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 ℃ 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 ℃ achieves the best crystalline quality.