SGER: Spin Injection from Ferromagnetic Nanodot Electrode to Organic Semiconducting Conjugated Polymers

目的：该SGER项目旨在了解最近观察到的Co/聚合物纳米异质结的自旋注入机制。具体来说，我们将利用氙缓冲层辅助MBE（分子束外延）生长，在共轭聚合物薄膜上制备具有精确可调尺寸和密度的Co/纳米点。然后，利用扫描隧道显微镜研究Co/聚合物纳米异质结的自旋相关输运随温度的变化。此外，将利用聚合物发光二极管（led）作为工具，研究自旋注入如何影响共轭聚合物中基于稳态和瞬态电致发光和光致发光的单、三重态激子形成和单、三重态系统间交叉。目的是增加对自旋注入机制的批判性理解，并开发一种利用铁磁性纳米自旋注入器控制激子形成的新方法。知识价值：提出的Co/聚合物纳米异质结自旋输运的研究有望阐明铁磁纳米电极与有机半导体聚合物薄膜之间界面的自旋输运过程。了解自旋注入机制对于在有机半导体器件中制造高效的自旋注入器至关重要。特别是，有效的自旋注入将为磁控制共轭聚合物中单线态和三重态激子的形成和相关光电性能提供新的途径。因此，该项目将影响易于加工和性能可调的聚合物半导体器件的发光、激光和光伏性能。广泛影响：该研究包括跨领域调查，因此将为参与的研究生和本科生提供光学，电子和磁学方面的多学科培训。为了进一步提高其教育影响，将为田纳西大学（UT）的聚合物物理（MSE 543）和聚合物材料与器件的光电过程（MSE 674）开发新的自旋输运课程。该项目还将继续通过由UT材料科学与工程系共同主办的材料营向高中生展示聚合物光电器件的概念和原理。

Objective: This SGER project seeks to understand the mechanism of recently observed spin injection across the Co/polymer nanoscale heterojunction. Specifically, we will use Xenon buffer layer assisted MBE (molecular beam epitaxy) growth to prepare Co/ nanodots with precisely tunable size and density on conjugated polymer thin films. Then, the spin-dependent transport across Co/polymer nano-heterojunction will be studied as a function of temperature by using four-tip STM (scanning tunneling microscope). In addition, polymer light-emitting diodes (LEDs) will be used as a tool to study how spin injection affects the singlet and triplet exciton formation and singlettriplet intersystem crossing in conjugated polymers based on steady and transient electroluminescence and photoluminescence. The goal is to increase the critical understanding of spin injection mechanism and to develop a new methodology of controlling exciton formation by using ferromagnetic nanoscale spin injector.Intellectual merit: The proposed studies of spin transport across the Co/polymer nano-heterojunction expects to elucidate the spin transport processes at the interface between ferromagnetic nanosize electrode and organic semiconductor polymer thin film. The understanding of the spin injection mechanism is critically important for the fabrication of efficient spin injectors in organic semiconductor devices. Especially, efficient spin injection will create a new pathway to magnetically control the singlet and triplet exciton formation and relevant optoelectronic properties in conjugated polymers. Therefore, the project will impact the light-emitting, lasing, and photovoltaic properties in easy-processing and property-tunable polymer semiconductor devices. Broad impact: The research consists of cross-field investigations and thus will provide multi-disciplinary training in optics, electronics, and magnetism to the involved graduate and undergraduate students. To further enhance its educational impact, new course work of spin transport will be developed for Polymer Physics (MSE 543) and Optoelectronic Processes in Polymeric Materials and Devices (MSE 674) at the University of Tennessee (UT). The project will also continue to demonstrate the concepts and principles of polymer optoelectronic devices to high school students through the Materials Camp co-sponsored by UT Department of Materials Science and Engineering.