Coupled Electronic and Lattice Structures in Thin Crystalline Films

University Of Illinois At Urbana-Champaign, Urbana IL

Investigators

Abstract

Non-Technical Abstract: Electronic effects and phenomena in materials underlie many applications; notable examples include the wide variety of semiconductors and metals employed in modern electronics, where ultrathin films and micro/nano crystals are often used as the basic building blocks. This research project focuses on experimentation at modifying, improving, and creating novel properties of these basic device building blocks by subjecting them to strain realized by controlled stretching or compression. The aim is to establish a basic understanding of strain effects and thereby to establish the guiding principles needed for building superior devices and new classes of systems for applications. The experimental work utilizes cutting-edge instruments at national facilities and offers rigorous training to graduate students and postdoctoral research associates in the science and art of materials preparation, fabrication, characterization, and optimization. Technical Abstract: Ultrathin films and micro/nano crystals are key building blocks for modern devices; their advantages include minimal usage of material resources, ease of fabrication and integration, reduction of electronic scattering and dissipation, and tailorable and emergent properties amenable to functionalization through layering and quantum coherence and confinement. This project examines the electronic structure and atomistic behavior of selected model systems, with a focus on the effects of stress/strain upon these systems that may alter the detailed electronic structure near the Fermi surface and transform the overall symmetry of the lattice with important consequences. Cases of special interest include nontrivial electronic states in films of topological insulators, Dirac/Weyl semimetals, etc., transition temperatures of superconductors and charge density wave materials, and surface chemical and catalytic properties of metallic microcrystals. Strain is introduced experimentally by mechanical means. Experimental techniques for the measurements of the electronic structure and atomic displacements include angle-resolved photoemission spectroscopy and x-ray diffraction both in the home laboratories and at synchrotron radiation facilities.