有机半导体本征自旋注入和传输性能研究

Organic spintronics are of critical importance in the future quantum information technology and national security. The most studied organic thin-film spintronic devices contain high-density of crystal domains and trap states and result in shortened spin diffusion length and large fluctuation, hindering the obtainment of intrinsic spin transport properties and structure-property relationships. The present project will focus on organic single crystal spin valves which contain no crystal domains, aiming at fundamental issues such as intrinsic spin injection and transport in organic materials. The surface free energies of the substrates are tuned by chemical modification, thus the growth behavior of the single crystals of the semiconductors are controlled and single crystals with parallel and perpendicular orientation to the substrates can be obtained. Single crystal organic spin valves with both CIP and CPP configurations will be constructed by either the in-situ growth method or the crystal-transfer method and the intrinsic spin transport properties such as the diffusion length will be obtained. The model of the relationship between molecular structure, atomic number, energy level, energy gap, solid state packing motif, mobility etc. and spin transport properties will be established. This project is not only helpful for the confirmation of micrometer to millimeter sized spin diffusion length which is intrinsic to organic semiconductors, but is also critically important for the design and synthesis of high-performance organic spintronic materials and the further development of organic spintronic devices such as spin field-effect transistors.

有机自旋电子在未来量子信息技术、国防安全等领域有着十分重要的作用。广泛研究的有机薄膜自旋器件中存在高密度的晶界和大量的陷阱态，导致自旋扩散长度缩短且波动大、无法获得本征传输性能以及难以进行构效关系研究等问题。本项目以无晶界的有机单晶自旋阀为对象，研究有机半导体的本征自旋注入和传输等基本科学问题。通过化学修饰调控衬底表面能，控制有机单晶的生长模式，制备平贴衬底和垂直衬底生长的有机单晶。分别利用原位生长法和转移晶体法构筑CIP和CPP结构的单晶自旋阀，进而获得本征自旋扩散长度等本征自旋传输性能。在此基础上，分析有机半导体分子量、原子序数、能级、带隙、固态堆积模式、迁移率等因素与自旋传输性能的关系，建立分子结构与自旋传输性能关系的模型。本项目不仅有助于确定微米至毫米量级的有机半导体本征自旋扩散长度，而且对高性能有机自旋材料的设计合成和有机自旋晶体管等自旋器件的深入研究都具有重要的意义。

电荷与自旋是电子的两个内禀属性。传统微电子学只利用了电子的电荷属性，目前面临器件功耗大和制造成本高的挑战。自旋电子学进一步利用了电子的自旋属性，天生具有非易失、低功耗的特点，将成为下一轮信息产业革命的核心技术之一。而有机半导体具有弱的旋轨耦合，有望在自旋电子学中扮演重要角色。本项目在以往工作的基础上，针对有机半导体本征自旋注入和传输特性不清楚且难以探索的科学问题，以有机半导体单晶为研究对象，以有机自旋阀为工具，提出了有机半导体二维组装分子设计的方法，获得了易二维组装的有机半导体分子；发展了新型一维及二维有机半导体单晶制备的策略，通过掺杂提高了有机半导体的电学性能；基于大面积有机半导体单晶实现了第一例可工作的垂直有机单晶自旋阀，并探索了其自旋注入和传输特性。本项目获得的分子设计理论、单晶制备策略及单晶自旋阀探索成果可为有机自旋电子学发展过程面临的基本科学问题的解决提供理论和技术支持，促进有机自旋电子学的进一步发展和应用。