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

University Of Arizona, Tucson AZ

Investigators

Abstract

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.