Thin film synthesis serves as the foundation of the group’s research activities on oxide heterostructures. We use molecular beam epitaxy to deposit films and superlattices with nominal unit cell precision. Our activities have focused on ABO3 perovskites, AMn7O12 quadruple perovskites, and A2B2O5 brownmillerites. We are also working on synthetic routes to stabilize mixed-anion perovskite films via post-growth topotactic processes. For example, we have synthesized oxyfluoride ferrite and nickelate films through reactions with fluorine containing polymers and have created lateral oxide/oxyfluoride heterostructures. Finally, we use reactive magnetron sputtering to deposition binary oxide thin films as coating for implantable electrodes.
We employ a wide range of characterization techniques to understand the structural, electronic, optical and magnetic properties of oxide films and interfaces. We make extensive use of synchrotron- and neutron-based scattering to provide elemental- and depth-resolved information in addition to conventional magnetometry and electronic transport measurements. We are particularly interested in magnetism at oxide interfaces, metal-insulator transitions, and dynamic control of functional properties through voltage-based manipulation of anionic vacancies.
We are currently synthesizing and characterizing topological semimetals for applications in spintronic devices. Recent work has highlighted the potential for Weyl semimetals to host large spin-orbit torques, but many fundamental questions remain regarding the interfacial properties between Weyl semimetals and ferromagnetic metals. We are using epitaxial growth along with reflectivity-based scattering approaches to better understand the coupling between interfacial structure, magnetism, and charge-to-spin conversion. Our activities in this area are largely focused on transition metal germanides and stannides. These activities are in collaboration with Prof. Axel Hoffmann at UIUC.
MXenes are a large family of two-dimensional transition metal carbides described by the chemical formula Mn+1XnTx, where M is a transition metal, X is carbon or nitrogen, and Tx refers to surface groups such as O and F. Our group is working to better understand the intrinsic electronic properties of MXene and how to increase macroscopic conductivity by controlling the M-site composition and ordering. We are also researching the magnetic properties of MXenes with aims of realizing long-range magnetic order in this family of materials.