Material Response to Dense Electronic Excitations: Nonlinear Defect Dynamics and Phase Transformations

University Of Tennessee Knoxville, Knoxville TN

Investigators

Abstract

Non-Technical Description: The response of materials to energy dissipation from energetic charged particles is important for defect engineering, ion-beam modification, ion-beam processing, ion-beam analysis, geologic age dating, space exploration, high-energy accelerators and nuclear applications. As a charged particle penetrates a solid, its energy is transferred to atomic nuclei and to electrons leading to complex energy dissipation processes in the solid that are coupled in time and space. The energy transferred to electrons results in highly-local, dense electronic excitations that often exceed those produced by intense pulsed lasers. These coupled processes bring materials to extreme and often transient regimes where unique defects, novel nanostructures, and material phases are formed, and where competitive self-healing can be induced. The goal of this project is to achieve critical understanding on these coupled phenomena on the response of materials and to identify new pathways to control the formation of defects, nanostructures and phases for advanced electro-optical systems, for tailoring materials functionality and performance, and for the design of better materials for advanced energy technologies. This project provides a unique set of integrated education, research, training and outreach activities to educate both undergraduate and graduate students in fundamental research on a new class of engineering materials, recruits students from under-represented groups in STEM areas, and provides training for the next-generation workforce in advanced electro-optical and energy technologies across academia, national laboratories and industry. Technical Description: This project applies experimental approaches to understand, model and ultimately control the far-from-equilibrium dynamic response of ceramic materials to extreme energy dissipation from energetic charged-particles at the level of electrons and atoms in order to guide materials discovery and tailor materials functionality and performance. The model ABO3 perovskites to be studied exhibit different bonding character, strong luminescence signatures for electronic and lattice defects, and distinctly different response to electronic and nuclear energy loss. The response of these model perovskite structures to single and multiple ion events is experimentally investigated over a range of conditions to vary the partitioning of energy transfer to electrons and atoms in both undamaged single crystals and in single crystals containing different pre-existing levels of damage. The investigations are designed to both separately and simultaneously probe high electronic excitation densities and the coupling of electronic and atomic processes under irradiation from cryogenic to elevated temperatures using in situ ion-beam analysis and optical spectroscopy techniques, as well as advanced microscopy and x-ray diffraction methods. This research provides transformative new understanding of the complex electronic and atomic correlations with extreme energy dissipation that enables the formation of unique defect states, the design and discovery of materials with novel functionalities for advanced technologies, and the development of self-healing and radiation tolerant materials for next generation high-energy accelerators, space environments and nuclear applications. This project provides a unique set of education, research and training activities on state-of-the-art ion-beam capabilities, materials characterization techniques and defect physics, as well as written and oral communication skills, that prepare students for the technological workforce. 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.