The stability and durability of an active component material frequently governs the performance and reliability of electronic devices. Moreover, the device performance is often influenced by the presence of atomic-level structural defects or interfaces between dissimilar materials. While these defects and interfaces are in many instances unavoidable, our understanding of how to control and manipulate their effect on a material's properties still remains unclear. Accordingly, fundamental research of the atomic-scale impact of defects or interfaces on a material's macroscopic behavior is essential to continuing the development of next generation high-speed computer memory storage and energy-conversion devices. Ceramic materials that contain transition metals, such as cobalt or titanium, and oxygen have attracted increasing scientific attention due to their properties that can be used in innovative memory storage applications (e.g., hard-drives) and in reliable waste-heat recovery. In this research project, the PI combines atomic-resolution scanning transmission electron microscopy and computational materials modeling to establish control over defects in two specific ceramic oxide materials that can be used in such devices. One unique aspect of this research is that the effects of defects and interfaces on the functional properties of these ceramic oxide materials are tested inside the microscope column at atomic resolution using novel in situ experiments. This approach allows the PI to establish control over the effects that defects have on the overall performance and reliability of a novel device. The research activities involve education and training of science and engineering undergraduate and graduate students, including underrepresented minorities. In particular, the participation of undergraduate students in active research projects is fostered through the PI's Journal of Undergraduate Research at the University of Illinois at Chicago.
TECHNICAL DETAILS: The objective of this research project is to use a comprehensive research approach consisting of atomic-resolution scanning transmission electron microscopy, first principles density functional theory (DFT) materials modeling and molecular beam epitaxy, as well as pulsed laser thin film deposition to study two ceramic oxide thin film systems. The PI has assembled an interdisciplinary team of experts to develop a fundamental understanding of the role that defects and dopants play on the transport and ferroic properties of transition metal oxide thin films. More specifically, the effects of oxygen vacancies, dopants and interfaces on the ferroelectric properties of perovskite transition metal oxide thin films grown on GaAs and on the thermoelectric transport in incommensurately layered transition metal oxide thin films are studied. By combining state-of-the-art in situ electric-field biasing and sample heating experiments with atomic-resolution imaging and spectroscopy, and first-principles materials modeling, the defect chemistry in complex transition-metal oxide ceramics thin films is studied. An important feature of this program is the integration of research and education through the training of undergraduate and graduate students in state-of-the-art in situ scanning transmission electron microscopy and theoretical materials physics.
