Grants and Contributions:

Grant or Award spanning more than one fiscal year. (2017-2018 to 2022-2023)

Many emerging or future technologies depend on the atomic level control of materials, and the optimization of such materials requires, in turn, an atomic level understanding of the materials properties. This is particularly true in applications related to microelectronics, where critical device performance depends on the detailed properties of materials, surfaces, and interfaces on length scales from individual atomic layers up to the sub micron scale. In this proposal, we will take advantage of a newly acquired low temperature scanning tunneling microscope (STM) to broaden the scope of our previous research on the atomic structure of surfaces and thin films to two areas of application.

The first is the study of molecular interfaces relevant to the performance of organic electronic devices such as organic light emitting diodes. The performance of these devices can depend on the exact manner in which individual layers of molecules are grown. Some of the differences have been attributed to the relative orientations of molecules at such boundaries, but evidence for this has been demonstrated in only a handful of systems. We will study a broad set of molecular interfaces, enabled in part by cryogenic STM which will restrict the motion of molecules on the surface while imaging, and will also enable more reliable spectroscopic measurements. We will also extend this work to molecular dopant systems, which are increasingly being used in the latest generation organic electronic devices. The insights provided by a detailed knowledge of the structure of these interfaces will lead to a better fundamental understanding, and will enable further improvements in this technology.

The second area is the study of surfaces and thin films that exhibit spin sensitive electronic structure due to the Rashba effect, with potential future applications in spintronics. The emphasis will be on probing the properties of grown thin films where periodic arrangements of heavy metal atoms can be created via surface reconstructions of semiconductor substrates. This will provide a wider variety of atomic structures than would be available by looking at either the bulk terminated surfaces of topological insulators, or the surfaces of heavy metal containing 2D layered compounds. We will also focus on the influence of defects on surfaces, which will be vital for the future applications of these materials.

What links the work in both areas is the structural and spectroscopic information provided at atomic resolution by STM. Through close collaboration with two other groups, this information will lead in one case to better organic electronic device performance, and in the other, development of new materials with spin dependent properties for future applications in spintronics.