Understanding Electronic and Spin Structure at Organic / Metal Interfaces: Surfaces and Symmetry

随着电子技术在更小的设备上产生更大的内存和处理能力，研究越来越多地关注分子作为电子电路的构建模块。较大的传统电路元件由金属和半导体材料制成，不仅要传导和存储电荷，还要传导和存储磁信息。电子带负电荷，这使得它们在运动时能够导电。电子也像磁铁一样，因为它们具有一种叫做“自旋”的特性。如果革命性的基于分子的电子学要成为现实，我们必须能够理解和控制电荷和自旋如何在单个分子中流动，而且在分子和其他材料（电路的其他部分）之间流动。在这个由化学部门化学结构、动力学和机理a （CSDM-A）项目资助的项目中，亚利桑那大学的奥利弗·蒙蒂教授和他的学生正在研究电荷和自旋如何在与其他材料接触点流动。他们正在研究金属表面上的分子，以及与其他分子修饰的金属表面上的分子，以改变接触条件。Monti的研究小组结合了激光技术和扫描隧道显微镜（STM），可以对单个原子和分子进行成像。本研究旨在发现决定分子基电子元件中电荷和自旋流动的重要分子结构因素。研究生接受高级化学、光学物理和原子显微镜方面的培训和经验。这种培训有望为量子信息科学革命做好准备。除了对博士生进行正式培训外，蒙蒂教授还为亚利桑那大学的本科生老兵制定了一个项目，以获得研究经验和个性化指导，帮助他们在科学和工程领域取得成功。该项目主要研究有机半导体/金属界面的界面电子结构和电荷转移动力学。该研究需要使用Ag on Cu（111）的外延层来调整表面电子结构，以改变表面电子波长，表面电子密度和表面对称性。这些系统变化对表面过程的影响是使用低温扫描隧道显微镜和稳态和时间分辨光谱学的组合来检查的。因此，诸如分子自组装、界面电子结构和电荷传递动力学等过程在不改变界面化学性质的情况下具有广泛的表面电子性质。也正在开发表面修饰，以促进Rashba分裂，而不需要外部磁场。本研究涉及支持大电偶极子或可以在界面处诱导轨道混合的有机半导体的吸附。如果这种类型的Rashba分裂能够实现，它将对有机/金属界面的自旋态的控制和操纵产生重大影响。这项研究的广泛影响包括开发新型高效电子设备的技术进步，这些设备也可以利用自旋自由度，而自旋自由度在量子处理中又很重要。该项目为研究生和本科生提供培训，并为在亚利桑那大学攻读科学和工程学位课程的退伍军人提供指导和研究机会。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

As electronics technology is driven to produce greater memory and processing power in smaller devices, research increasingly focuses on molecules as the building blocks for electronics circuitry. Larger traditional circuit elements made of metal and semiconductor materials must conduct and store not only electrical charge, but also magnetic information. Electrons hold a negative charge, which allows them to conduct electricity when they move. Electrons also act like magnets because they possess a property called “spin”. If revolutionary molecule-based electronics are to become a reality, we must be able to understand and control how charge and spin flow not only through individual molecules, but between molecules and other materials (other parts of the circuit). In this project, funded by the Chemical Structure, Dynamics, and Mechanism-A (CSDM-A) program of the Chemistry Division, Professor Oliver Monti and his students at the University of Arizona are investigating how charge and spin flow at contact points with other materials. They are studying molecules on metal surfaces, as well as molecules on metal surfaces that have been modified with other molecules, to modify the contact condition. The Monti research group uses a combination of laser-based techniques and scanning tunneling microscopy (STM) which can image individual atoms and molecules. The research seeks to discover the important molecular structural factors that determine charge- and spin-flow in molecule based electronic elements. The graduate students receive training and experience in advanced chemistry, optical physics and atomic microscopy. This training is expected to prepare them well for the quantum information science revolution. In addition to the formal training of doctoral students, Professor Monti is developing a program for undergraduate student veterans at Arizona to gain research experience and personalized mentoring toward a successful career in science and engineering.The project focuses on tailoring the interfacial electronic structure and charge-transfer dynamics at organic semiconductor / metal interfaces. The research entails tailoring the surface electronic structure using epitaxial layers of Ag on Cu(111) to change the surface electron wavelength, the surface electron density, and the surface symmetry. The effects of these systematic changes on surface processes are examined using a combination of low-temperature scanning tunneling microscopy and steady-state and time-resolved photoemission spectroscopy. Processes such as molecular self-assembly, interfacial electronic structure and charge-transfer dynamics are thus characterized over a wide range of surface electronic properties without varying the chemical nature of the interface. Surface modifications are also being developed to facilitate Rashba splitting without the need for an external magnetic field. This study involves the adsorption of organic semiconductors that support large electric dipoles or can induce orbital mixing at the interface. If this type of Rashba splitting is achieved, it could have significant implications for the control and manipulation of spin states at organic/metal interfaces. The broader impacts of this research include the advancement of technologies to develop novel highly efficient electronic devices that may also harness the spin degrees of freedom, which in turn are important in quantum processing. This project is providing a vehicle for training both graduate and undergraduate students as well as mentoring and research opportunities for veterans enrolled in science and engineering degree programs at the University of Arizona.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.