Broadly, our research focuses on the epitaxial growth of complex oxide thin films and heterostructures in the pursuit to uncover, understand, and engineer new electronic phenomena and to push the frontier of technology with next generation devices based on these materials. The complex oxides offer an extremely wide range of properties not observed in conventional compound semiconductors and, thus, are an exciting playground for investigating or tailoring exotic phenomena and exploiting the unusual behavior in devices. Particular interest resides in interface, spin, structure, and charge effects that occur in layered structures with ferroic (and antiferroic) materials, such as (anti)ferromagnets, (anti)ferroelectrics, and multiferroics.
Some specific topics:
Magnetoelectric Switching in Thin Film Multiferroic Heterostructures
Multiferroic heterostructures are on a trajectory to impact spintronics applications through the significantly reduced energy consumption per unit area for magnetization switching (1 – 500 μJ cm-2) when compared to of current-driven magnetization switching (0.2 – 10 mJ cm-2). Considering this potential impact, it becomes necessary to understand converse magnetoelectric switching (electric field control of magnetism) and demonstrate this performance at scale. We focus on two categories of magnetoelectric/multiferroic systems: single-phase materials in exchange coupled heterostructures and composite systems (Ferroelectric/Ferromagnet) where the magnetoelectricity is mediated by strain.
Our objective is to understand fundamental magnetoelectric switching in these systems and to demonstrate low energy consumption for next generation computational technologies. We use thin film epitaxy, interfaces, strain, and novel materials investigate magnetoelectric switching in magnetoelectric heterostructures for tailored application. We develop devices and transport techniques to investigate magnetoelectric switching in configuration compatible with nanoelectronics. Further, we employ and develop scanning probe microscopy techniques to understand the kinetics of magnetoelectric switching, influence of boundary effects, and domain correlations.
Harnessing disorder in high entropy oxides for new physical behavior and devices
Entropy and high entropy oxides are single phase materials that have a large configurational disorder stemming from the multi-cation composition. The entropy enables the synthesis of materials that have previously been unfeasible and ability to include cationic species in typically unfavorable or rare coordinations. Our objective is to explain how the fundamental disorder and frustration of species, charge, structure, and spin emerge in the electromagnetic properties to enable design of new extremes in functional behavior. We leverage high energy physical vapor deposition methods, epitaxial strain, and composition to elucidate fundamental disorder-property correlations in single crystal entropy-stabilized oxide thin films.
Design and testing of radio-frequency ferroic devices and circuits
Information and communication technologies require device operation to occur at the nanosecond (or faster) and in devices that are of the dimension of 10’s-100’s of nanometers. While ferroic materials have shown fantastic properties and performance at much larger scales than the domain length (typically ~ 1 micron), the physical behavior of these materials in this much smaller length scale is unknown and the underlying implications for devices may present significant deviations from bulk projections as the dominant physics shifts from an extrinsic multi-domain regime to an intrinsic single domain regime. We explore radio-frequency (rf) device engineering and precise nanofabrication expertise for ferroic material and device testing in the ranges of 1-20 GHz and 10’s-100’s of nanometers.