The latest research by the team of Professor Shan Zhiwei from the Micro-nano-scale Material Behavior Research Center of the School of Materials Science and Engineering in Xi'an Jiaotong University found that amorphous silicon nanowires have abnormal selectivity and adjustable hysteretic behavior at room temperature. Recently, the top nanotechnology journal "Nano Letters" (impact factor 12.279) published this research.
Hysteresis elasticity refers to the phenomenon that the deformation of the material does not recover immediately after the external force is removed, and it takes a long time to gradually recover. Since the process will generate energy dissipation, the damping performance of the hysteresis elastic material is good and can be used to reduce vibration , Noise reduction, etc. However, the hysteresis of macroblock materials is generally relatively small, especially at room temperature. When the feature size of the material is reduced to the nanometer scale, taking nanowires as an example, the hysteresis elasticity will be significantly improved. At this stage, the research on the hysterelasticity of nanowires is mainly aimed at crystalline materials, and the hysteretic properties of amorphous nanowires are rarely reported, mainly because of the difficulty in their synthesis and structural characterization.
Professor Shan Zhiwei's team took amorphous silicon nanowires as the research object and conducted a systematic study on the hysteresis behavior of them using advanced in-situ mechanical testing and electron microscopy characterization methods. For the first time, it was discovered and reported that one-dimensional nanomaterials have options The hysteretic behavior of elasticity and adjustability: The hysteretic elastic deformation of amorphous silicon nanowires is closely related to its morphology and loading direction: straight nanowires show pure elastic deformation, that is, the deformation will be restored immediately after the external force is removed; Nanowires can exhibit more pronounced hysteretic behavior, but only if the external force must be loaded along the original bending direction. With the help of ion beam irradiation, straight amorphous silicon nanowires can also be bent to regain hysteresis elasticity, and the magnitude of hysteresis elasticity can be adjusted by changing the irradiation dose. Based on the above-mentioned abnormal phenomena and the results of electron energy loss spectrum test analysis, the researchers proposed a new mechanism of hysterelastic deformation different from crystalline materials and bulk amorphous materials, that is, a valence bond exchange mechanism induced by uneven stress fields.
Amorphous silicon nanowires are selected as the research object because amorphous silicon is one of the most important amorphous semiconductor materials and has a wide range of applications in photovoltaic cells, flexible electronic devices, micro-electromechanical systems and other fields. In addition, amorphous silicon, because of its single element and simple structure, is often used as an important model material for studying the structure and performance of amorphous solids. The newly discovered amorphous silicon nanowires, which can be adjusted by changing the morphology, loading direction and ion irradiation dose to adjust the unique hysteresis behavior makes it expected to be an advanced nano-damping material, playing an important role in the semiconductor and electronics industries effect. At the same time, this work also provides a reference for the research and mechanism explanation of the hysterelasticity of other amorphous nanomaterials.
Explanation of the mechanism of hysteretic behavior of amorphous silicon nanowires
Dr. Wang Yuecun, a young teacher of Xi'an Jiaotong University, is the first author of the paper, and Professor Shan Zhiwei of Xi'an Jiaotong University and Dr. Tian Lin of Göttingen University are the corresponding authors of the paper. Also participating in this work are Professor Andrew Minor of the University of California, Berkeley, Dr. Shuigang Xu of the City University of Hong Kong, and Liang Beiming, a graduate student of Xi'an Jiaotong University. The research was jointly funded by the National Natural Science Foundation of China, the National Key R & D Program, and the 111 Project.