Thin-Film Single-Crystal Growth of Layered Materials and Fabrication of The Layered Superlattices by a Hot Wall Technique, and Their Optical Properties

采用热壁法制备了以重金属卤化物为代表的复合层状材料PbI_2和BiI_3的极薄单晶。通过采用层状材料作为衬底，所谓的范德华外延成为可能。这种低温生长方法使生长高质量单晶成为可能。利用带边直接激子的低温吸收光谱作为薄膜质量的探测指标。透射电子衍射和x射线结构分析证实了这一点。结果表明，激子光谱对晶体质量非常敏感，特别是对层错和多型的影响。这样就有可能获得具有最佳厚度的薄膜，用于观察直接激子吸收光谱。对于PbI_2，激子的内部结构得到了澄清，从而解答了自1960年以来由于高脉冲磁场谱的磁光研究的成功而未解决的难题。同时，还了解了激子-声子相互作用的新特征。对于BiI_3，由于薄膜表面质量高，在吸收测量中首次观察到表面激子。对带边激子吸收光谱的详细分析成为可能，并发现了与激子-声子相互作用相关的激子动力学的新方面。利用该技术首次成功制备了PbI_2/BiI_3超晶格，并对其光学性质进行了研究，揭示了新超晶格中激子的有趣特征。利用BiI_3势垒势观察了PbI_2激子的量子尺寸效应。利用高场磁光和高压对该系统中激子的吸收和发光进行了研究。少

A hot wall technique was applied to grow very thin single-crystals of the compound layered materials, PbI_2 and BiI_3, which are the subject of the recent intensive investigations as the representative of the heavy metal halides. The so- called van der Waals epitaxy became possible by employing the layered material as a substrate. The low temperature growth by this method made it possible to grow high quality thin single-crystals. The low temperature absorption spectra of the band-edge direct exciton were used as a probe of the quality of the film. This is confirmed by the transmission electron diffraction and x-ray structural analysis.It was revealed that the exciton spectra was sensitive to the crystal quality especially for the layer stacking faults and polytypes. Thus it became possible to obtain the films with an optimized thickness for the observation of the direct exciton absorption spectra. As for PbI_2, the inner structure of the exciton were clarified to give the answer for t … More he puzzling problem unsolved since 1960 by the successful magneto-optical investigation of the high pulse-magnetic-field spectroscopy. At the same time, new features concerning the exciton-phonon interaction were understood. In the case of BiI_3, the surface exciton was observed for the first time in the absorption measurement due to the high quality of the film surface. The detailed analysis of the band-edge exciton absorption spectra became possible, and new aspects of the exciton dynamics were found correlated to the exciton-phonon interaction. The superlattice PbI_2/BiI_3 were successfully fabricated for the first time by this technique, and the optical properties were investigated, showing interesting features of the exciton in the new superlattice. The quantum size effect was observed on the exciton of PbI_2 by the BiI_3 barrier potential. The electrical energy structure are now under investigation using high-field magneto-optical and high-pressure investigation on the absorption and luminescence of the exciton in this system. Less