The comprehensive science journal《Nano Energy》recently reported the current research results “Sublimation and related thermal stability of PbSe nanocrystals with effective size control evidenced by in situ transmission electron microscopy”, which were completed by Associate Prof. Luying Li, Prof. Yihua Gao (Wuhan National Laboratory for Optoelectronics) and Associate Prof. Jianbin Zhang (School of Optical and Electronic Information, Huazhong University of Science and Technology).
Sublimation is an important endothermic phase transition in which the atomic bonds of the solids break down leading to the formation of the gas phase. Investigating the mechanism of sublimation at atomic resolution is a direct approach to better understanding the reversed process of epitaxial growth. Moreover, sublimation is closely related to material stability, and the studies on sublimation process of NCs would reveal the factors affecting the stability of nanomaterials including facet reconstructions, dislocation movements, and surface ligand modifications. Up to now, most studies on sublimation focus on the different surface energies of the major crystal planes, which are considered as the most important factor in many thermodynamic processes. On the other hand, the discussions about the interfacial defects and size dependence are relatively limited. The NCs are easy to grow into larger crystals during the heating process, which precludes the accurate determination of the corresponding size dependence.
Here, the sublimation process of PbSe nanocrystals as a typical case is studied at atomic scale, and the related size, surface and interface effects are discussed. Due to the interaction of electron beam and surface organic ligands, the sizes of nanocrystals are effectively controlled via introduction of electron beam at different growth stages, which facilitates direct observation of the size dependence of sublimation process. The nanocrystals of less than 10 nm in size show directional sublimation, and those of larger size sublimate uniformly. At the contact interface of nanocrystals with slightly different orientations, the strain fields accelerate local sublimation, while the dislocation motions retard local sublimation, which lead to the deviation of fracture interface from original contact interface. The systematical study of size/surface/interface dependent sublimation behaviors of PbSe nanocrystals facilitates better understanding of the stability of related materials during sublimation as well as crystal growth as the reversed process.
This work was supported by the National Natural Science Foundation (51871104，11674113,11874025), Hubei Provincial Natural Science Foundation (2017CFB417) and Special Funds for Fundamental Scientific Research Business Expenses of Central Universities (No.2017KFYXJJ039). Associate Prof. Luying Li, Prof. Yihua Gao and Associate Prof. Jianbin Zhang are corresponding authors of this work, and Ph.D. students Feng Cheng is the first author, Linyuan Lian, Jiangyu Rao, Chen Li, Tianyu Qi, Yongfa Cheng, Associate Professor Zhi Zhang and Professor Jianbo Wang are also involved in final completion of this work.
Paper links: https://www.sciencedirect.com/science/article/pii/S2211285520303736?via%3Dihub#undfig1
