Preparation of PbI_2 Polycrystalline Films by Vacuum Evaporation

The core note: Pbl2 is a direct wide bandgap compound semiconductor with a hexagonal close-packed structure 4 = 1, 6 = Pb). Its symmetry belongs to the pure PbI2*2H crystal form of the p3ml point group, in addition to 12R. And 4H two crystal forms. The hexagonal cell constant of the 2H crystal form is a=0.45

Pbl2 is a direct wide bandgap compound semiconductor, and its crystal structure is a hexagonal close-packed structure 4=1, 6=Pb), and its symmetry belongs to the PbI2*2H crystal form of the p3ml point group, in addition to both 12R and 4H. Seed crystal form. The hexagonal cell constants of the 2H crystal form are a = 0.4557 nm and c = 0.6979 nm. The Pbl2 is considered to be one of the most promising materials for the preparation of room temperature radiation detectors and radiation imaging devices, due in part to the constituent elements Pb of Pbl2. And I have a larger atomic number (1>=82,=53), have higher stopping power for X-ray and 7-ray, on the other hand, Pbl2 has a larger band gap of 0*=2.32.6 eV) 6, 'Used for room temperature radiation detector device leakage current.

Although people have conducted extensive research on the growth process and electrical and room temperature radiation detection properties of Pbl2 single crystals, it is difficult to grow high-purity and high-resistivity, 1)12 single crystals, which greatly limits the detection of Pbll2. Preparation. So far, people have proposed a variety of techniques for the growth of single crystal Pbl2, such as regional melting method 81, vapor transport method 7,91, gel method UQ1, Bridgeman method 11,121 and so on. These methods have complicated processes, and the prepared Pbl2 single crystal has a small volume and is not suitable for a radiation imaging device requiring a large area. Compared with growing monolithic crystals, preparing a large-area polycrystalline film is more economical and practical. Interesting results have been obtained in the preparation of Hgl2g crystal thin films and their application in radiation detectors. 131. For Pbl2, currently developed polycrystalline thin film growth methods mainly include solution growth methods 12, 14, 151 and melt purification methods. Compared with the solution growth method and the melt purification method, the vacuum evaporation film has the advantages of high purity, compactness and good uniformity, and the method itself is simple and easy to realize large area, so the vacuum evaporation method is widely used to prepare thin film materials. However, only Shah et al.81 reported the preparation of Pbl2 polycrystalline films by vacuum evaporation.

In this paper, Pbl2 crystal thin film was prepared by vacuum evaporation method, and its microstructure, surface morphology, chemical composition, etc. were studied in order to provide material parameters for the preparation of 112 room temperature radiation detectors. It is the relationship between the dark conductivity and the temperature of the sample. It can be seen that the dependence of the conductivity on the temperature above room temperature accords with the Arrhenius relation. The activation energy obtained in the temperature range of 333415 K is è‰® = .78 eV. 4 Conclusions The vacuum evaporation method can be used. Growth of dense, uniform and well-preferred Pbl2g crystal films on glass substrates at room temperature with low conductivity of 3.0910-(0111)4 and good photosensitivity, dark-conducting activation energy is private = 0.78 eV is expected to be used in room temperature radiation detectors and imaging devices.

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