Gate-Modulated Charge Density-Dependent Physics of Low-Dimensional Inorganic Semiconductors in Organic Multilayers

Technical Description: Topological insulators, such as bismuth selenides and bismuth tellurides, are materials with inherent conductive states near their surfaces. This research project utilizes multifunctional organic layers to control the surface chemical potentials and bonding interactions in these materials, introducing sufficient charge density to reveal atomic and structural features that determine the surface conductive states. The layered structures are used to encapsulate thin films of topological insulators to reach a high charge density at low applied voltages, maximize dielectric strength, and tune local band energies. Local electric fields are designed to be as large as those in ionic liquids presently employed, but in a much better defined geometry. Terahertz magneto-optical polarimetry will provide a powerful probe to determine scattering rates, charge densities, and band masses for several parallel transport channels simultaneously. The research offers opportunities to observe physical phenomena such as correlated electron transport, spin polarized conduction in topological insulators, and unconventional superconductivity and charge-density waves. It can lead to new ways of controlling chalcogenide-organic interfaces in general.

Non-technical Description: There is a great interest in materials that can manipulate electrical and magnetic signals with high energy efficiency, and that can store and process information more and more rapidly. This research project concerns the study of a new class of mineral-like materials that have a special ability to conduct electricity very effectively at certain locations. A new way to package and switch these materials using plastic-like media is developed. This method is expected to avoid some of the complications of previous methods and allow better understanding of the factors that control the electrical and magnetic behavior of the materials. The result of this work will help to create new possibilities for designing future computers and data management systems. Graduate and undergraduate students in this project synthesize materials and perform characterizations of materials and devices, acquiring a broad technical basis for diversified science and technology employment. These activities also form the basis of fabrication and characterization modules in undergraduate materials science and materials physics laboratory courses. Students from Western High School, a public, largely minority and low-income girl's school in Baltimore City, also participate in the research as part of an after-school program, and ultimately serve as ambassadors to feeder middle schools as well.