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

随着电子技术被驱动在更小的设备上产生更大的存储器和处理能力，研究越来越专注于将分子作为电子电路的构建块。由金属和半导体材料制成的较大的传统电路元件不仅必须传导和存储电荷，还必须传导和存储磁信息。电子带有负电荷，这使它们在运动时能够导电。电子的行为也像磁铁，因为它们拥有一种叫做“自旋”的性质。如果革命性的基于分子的电子学成为现实，我们必须能够理解和控制电荷和自旋如何不仅在单个分子中流动，而且在分子和其他材料(电路的其他部分)之间流动。在这个由化学系化学结构、动力学和机理A(CSDM-A)项目资助的项目中，亚利桑那大学的Oliver Monti教授和他的学生正在研究接触点上的电荷和自旋是如何与其他材料流动的。他们正在研究金属表面上的分子，以及用其他分子修饰的金属表面上的分子，以改变接触条件。蒙蒂研究小组使用了基于激光的技术和扫描隧道显微镜(STM)的组合，扫描隧道显微镜可以对单个原子和分子成像。这项研究试图发现决定基于分子的电子元件中电荷和自旋流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。预计这次培训将为他们为量子信息科学革命做好准备。除了博士生的正式培训外，蒙蒂教授还为亚利桑那州的本科生退伍军人开发了一个项目，以获得研究经验和个性化指导，以便在科学和工程领域取得成功。该项目专注于定制有机半导体/金属界面的界面电子结构和电荷转移动力学。这项研究需要通过在铜(111)上外延Ag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。利用低温扫描隧道显微镜和稳态和时间分辨光电子能谱相结合的方法，研究了这些系统性变化对表面过程的影响。因此，在不改变界面化学性质的情况下，分子自组装、界面电子结构和电荷转移动力学等过程可以在广泛的表面电子性质上得到表征。还在开发表面改性以促进Rashba分裂，而不需要外部磁场。这项研究涉及有机半导体的吸附，这些有机半导体支撑着大的电偶极子或可以在界面上诱导轨道混合。如果这种类型的Rashba分裂被实现，它可能会对控制和操纵有机/金属界面的自旋态产生重大影响。这项研究的更广泛影响包括开发新型高效电子设备的技术进步，这些设备还可能利用自旋自由度，而自旋自由度在量子处理中又是重要的。该项目为亚利桑那大学注册的科学和工程学位项目的退伍军人提供了一种培训研究生和本科生以及指导和研究机会的工具。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.