CAREER: Material Design and Research Oriented Multidisciplinary Education: Amorphous to Nanocrystalline Electronic Materials with Applications to Thermoelectrics

North Carolina State University, Raleigh NC

Investigators

Abstract

Amorphous based materials can possess fundamentally different electrical and thermal properties than crystalline or nanocrystalline forms of the same material. Although, amorphous materials have found applications and continue to show promise for modern technologies, charge carrier and phonon transport in these materials remain a point of dispute. The lack of long- and short-range order in amorphous materials leads to complicated interplay between structure and energy transport. In this project a novel class of electronic materials based on bulk amorphous structures in the form of amorphous-crystalline nanocomposites will be developed and their thermal and electrical properties will be tailored. The application will be focused on thermoelectric materials, but the results are expected to produce new science applicable to other functional materials including optical and magnetic materials. Parallel to the research endeavors, an educational plan will be implemented which incorporates and develops a new teaching initiative in the upper-division undergraduate curriculum, involves undergraduates in research, promotes student international collaborative research, exposes the field of energy materials to the general public, and provides a resource web-site for advanced thermoelectric material studies. The available resources in the Oklahoma Louis Stokes Alliance for Minority Participation (OK-LSAMP) and Multicultural Engineering Program (MEP) programs will be used for expanding the participation of minority students and the recruitment of high school students. This research plan addresses the essential need for a physical description of charge and phonon transport in amorphous based materials, characterization of their structural dependencies, and application of this understanding to enhance the thermoelectric performance of amorphous and the more complex structure of amorphous-crystalline nanocomposite materials. The focus will be especially in the regime where the carriers energy remains at non-equilibrium state due to the consecutive passage through material domains with different equilibrium energy distribution of carriers. The multi-mode transport of charge carriers in extended and localized states in disordered multi component amorphous-crystalline nanocomposite structures will be addressed. This is a new scientific problem with many unresolved scientific questions. Further understanding of charge carrier and phonon transport in such amorphous based materials will directly impact their material design and offer novel material structures for electronic applications. Parallel to theoretical studies, an efficient and scalable top-down approach for synthesizing such structures will be developed. The material is processed in a single transversal mode microwave cavity that provides an extraordinary route to create a new state of amorphous materials in a rather quick and convenient way. The decrystallization process happens by merely subjecting the solid material to a strong E or H field in the cavity. The method results in in-situ formation of such structures, which is not possible by conventional bulk processing methods. This unique capability opens a new landscape for engineering non-equilibrium structures.