弯曲应变对低维人工微结构（纳米线/石墨烯）的电子结构、光学和电学性质的调制作用

With the rapid progress of miniaturization of electronics devices, in particular the quick rising of flexible nanodevices, 1-D nanowire and 2-D grapheme nanomaterials are exceptional candidates of flexible devices, and play an more and more important role due to their peculiar physical properties arising from the giant surface effects, and quantum confinement effects, together with their superb mechanical properties of the strongest materials of man-made materials. Unlike in the strain-engineering in conventional micro-electronic industry, in which the uniform strain, such as monoaxial tensile and compressive strains dominate. In the flexible electronic devices like bendable TV and watches, the non-uniform strain, such as the bending strain plays a central role in the device performance. However, a systematic and profound research on the effect bending strain on the physical properties of the 1-D nanowire and 2-D grapheme materials are still missing. In this project, we intend to focus on the bending strain effect on the opto-electronic properties of the semiconductor nanowires and graphene: .1).How bending strain modify the electronic band-gap structures of semiconductor nanowires? According the band-gap theory, the band gap of the semiconductor materials such as ZnO, and GaN nanowire materials, decreases under tensile strain, and increases under compressive strain. However, we found recently, that a unique red shift occurs which increases with the increase of the strain gradient instead of the strain regardless of the tensile or compressive strain in a pure 4-point bending deformation configuration, and this finding is inconsistent with the prediction from the band-gap theory. Therefore, strain or strain gradient becomes the focus of the project. The bending deformation potential, its effects on the symmetry broken of the crystal field, the orbital coupling should be addressed as well..2).Our next efforts will be concentrated on the layer-layer interaction between multi-layer graphene stacks. Layer effects on the bending strain modulus, and elasticity, and the strength, and electronic properties such as carrier and spin transport of the graphene materials will be evaluated in great details. Comparison experiments both under uniaxial strain and bending strain effects will be elucidated in details..3). A protocol flexible device, say flexible solar cell based on flexible ZnO nanowires arrays grown on a stainless-still grids on PDMS flexible substrate using graphene both as transparent top electrode, and conducting bottom electrode will be fabricated, and the device performance will be studied regarding the strain modification of the physical properties of the ZnO nanowires/graphene..4). Theoretical calculations based on first-principle method will be used combing other simulation software to fit and support the experimental data and discovers.

低维人工微结构为物理学研究提供了全新的理想研究对象，是挑战尺度极限、发现新物理现象、制备新观念应用器件的重要课题。纳米线涵盖了非常丰富的1-维尺度区间和物理现象，石墨烯则是理想的二维分子体系，是跨越宏观牛顿世界与微观量子世界的奇妙桥梁。应变是自然中的普遍现象，在纳米尺度，应变对材料与器件性质的影响尤其显著。随着对纳米材料的深入研究，尤其是基于弯曲应变的纳米发动机等柔性电子学纳米器件的迅猛发展，开展低维纳米材料在非均匀应变下的物理性质的演化规律的研究显得越来越重要和紧迫。但人们对非均匀应变如弯曲应变下材料性质演化的规律则认知甚少。基于我们在低维人工微结构研究领域取得的成果，本项目拟针对柔性电子学器件中的若干低维人工微纳结构材料包括半导体纳米线、石墨烯等在弯曲应变作用下，电子结构与发光、输运、柔性光伏器件效应等性质随应变的演化规律开展系统深入的研究，为柔性电子学器件的发展提供科学依据。

揭示以基于柔性电子学应用的功能一维纳米线、二维石墨烯材料在非均匀弯曲应变作用下物理性质的演化规律，通过弯曲应变调制 1-D 半导体纳米线、2-D石墨烯的晶体场对称性、轨道耦合、带隙能量、发光性质、载流子复合机理、电子输运性质，对于纳米线、石墨烯在柔性电子学器件应用方面具有非常重要的意义。本项目深入系统地揭示了弯曲形变势中应变梯度对半导体纳米线材料电子精细结构、发光、电荷输运等性质的调制规律，结合时间分辨的阴极荧光光谱揭示了弯曲应变下纳米线中激子扩散的动力学机制；系统研究了石墨烯叠层垂直结构的杨氏弯曲性质，揭示了石墨烯垂直结构中层与层之间的耦合对载流子输运的影响规律；进一步设计并制备了新一代可弯折、可穿戴、可植入式的发电/储能一体化柔性电子学器件。发表标注项目号的SCI论文86篇，包括NATURE NANOTECHNOLOGY 1篇; NATURE COMMUNICATIONS 5篇; NANO LETTERS 3篇; ADVANCED MATERIALS 2篇; ACS NANO 11篇; SMALL 5篇; NANOSCALE 12篇; APPLIED PHYSICS LETTERS 10篇; PHYSICAL REVIEW B 10篇; 等。