A5012250744- Electronic and Structural Properties of Oxides
- Magnetic and transport properties of perovskites and related materials
- Semiconductor materials and devices
- Advanced Condensed Matter Physics
- Ferroelectric and Piezoelectric Materials
- Multiferroics and related materials
- Magnetic properties of thin films
- Semiconductor Quantum Structures and Devices
- Surface and Thin Film Phenomena
- Magnetic Properties and Synthesis of Ferrites
- ZnO doping and properties
- Acoustic Wave Resonator Technologies
- Iron-based superconductors research
- Semiconductor materials and interfaces
- Advanced Materials Characterization Techniques
- Quantum Dots Synthesis And Properties
- Advancements in Semiconductor Devices and Circuit Design
- Electron and X-Ray Spectroscopy Techniques
- Ferroelectric and Negative Capacitance Devices
- High Temperature Alloys and Creep
- Photonic and Optical Devices
- Physics of Superconductivity and Magnetism
- Thermal properties of materials
- Advanced Thermoelectric Materials and Devices
- Advanced ceramic materials synthesis
Duke University
2023-2025
North Carolina State University
2017-2024
North Central State College
2023
Massachusetts Institute of Technology
2019
The University of Texas at Arlington
2019
Yale University
2010-2017
Interface (United States)
2010-2017
University of Michigan
2006-2013
Paul Scherrer Institute
2009-2012
Brookhaven National Laboratory
2012
The complete atomic structure of a five-monolayer film LaAlO3 on SrTiO3 has been determined for the first time by surface x-ray diffraction in conjunction with coherent Bragg rod analysis phase-retrieval method and further structural refinement. Cationic mixing at interface results dilatory distortions formation metallic La(1-x)SrxTiO3. By invoking electrostatic potential minimization, ratio Ti{4+}/Ti{3+} across was determined, from which lattice dilation could be quantitatively explained...
The integration of complex oxides on silicon presents opportunities to extend and enhance technology with novel electronic, magnetic, photonic properties. Among these materials, barium titanate (BaTiO3) is a particularly strong ferroelectric perovskite oxide attractive dielectric electro-optic Here we demonstrate nanophotonic circuits incorporating BaTiO3 thin films the ubiquitous silicon-on-insulator (SOI) platform. We grow epitaxial, single-crystalline directly SOI engineer integrated...
We demonstrate magnetic field control of surface plasmon excitations in noble-metal/ferromagnetic/noble metal trilayers, analogous to the effects previously observed semiconductor structures. show that coupling an external plasmon-polariton wave vector is greatly enhanced metallic structure due ferromagnetic nature one its constituents. The could be used modulate response ultrasensitive spectroscopic applications.
We experimentally demonstrate a novel approach to substantially modify orbital occupations and symmetries in electronically correlated oxides. In contrast methods using strain or confinement, this tuning is achieved by exploiting charge transfer inversion symmetry breaking atomically layered heterostructures. illustrate the technique LaTiO3−LaNiO3−LaAlO3 system; combination of x-ray absorption spectroscopy ab initio theory reveals electron concomitant polar fields, resulting ∼50% change...
Metallic electronic transport in nickelate heterostructures can be induced and confined to two dimensions (2D) by controlling the structural parameters of nickel–oxygen planes.
Abstract Functional oxides are an untapped resource for futuristic devices and functionalities. These functionalities can range from high temperature superconductivity to multiferroicity novel catalytic schemes. The most prominent route transforming these ideas a single device in the lab practical technologies is by integration with semiconductors. Moreover, coupling semiconductors herald new unexpected that exist neither of individual materials. Therefore, oxide epitaxy on provides...
A two-dimensional, anisotropic superconductivity was recently found at the KTaO
Rashba spin–orbit coupling locks the spin with momentum of charge carriers at broken inversion interfaces, which could generate a large galvanic response. Here, we demonstrate spin-to-charge conversion (inverse Rashba–Edelstein effect) in KTaO3(111) two-dimensional electron systems. We explain results context electronic structure, orbital character, and texture interfaces. also show that angle dependence on in-plane magnetic field exhibits nontrivial behavior, matches symmetry Fermi states....
The magnetic properties of iron-doped cobalt ferrite (Co${}_{1\ensuremath{-}x}$Fe${}_{2+x}$O${}_{4}$) (001) thin films grown epitaxially on MgO substrates are investigated by superconducting quantum interference device magnetometry and soft x-ray linear circular dichroisms. All Co${}_{1\ensuremath{-}x}$Fe${}_{2+x}$O${}_{4}$ (0.01 \ensuremath{\leqslant} $x$ 0.63) samples have out-of-plane easy axes large coercive fields, unlike Fe${}_{3}$O${}_{4}$, due to a Co${}^{2+}$ orbital moment. moments...
We describe a general materials design approach that produces large orbital energy splittings (orbital polarization) in nickelate heterostructures, creating two-dimensional single-band electronic surface at the Fermi energy. The resulting structure mimics of high temperature cuprate superconductors. two key ingredients are: (i) construction atomic-scale distortions about Ni site via charge transfer and internal electric fields, (ii) use three component (tri-component) superlattices to break...
Acting like thermal resistances, ferroelectric domain walls can be manipulated to realize dynamic modulation of conductivity (k), which is essential for developing novel phononic circuits. Despite the interest, little attention has been paid achieving room-temperature in bulk materials due challenges obtaining a high switching ratio (khigh /klow ), particularly commercially viable materials. Here, 2.5 mm-thick Pb(Mg1/3 Nb2/3 )O3 -xPbTiO3 (PMN-xPT) single crystals demonstrated. With use...
Surface x-ray diffraction was used to determine the atomic structures of ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{MnO}}_{3}$ thin films, grown monolayer by on ${\mathrm{SrTiO}}_{3}$ pulsed laser deposition. Structures for one-, two-, three-, four-, six-, and nine-monolayer-thick films were solved using Coherent Bragg rod analysis phase-retrieval method subsequent structural refinement. Four important results found. First, out-of-plane lattice constant is elongated across...
The strong interfacial coupling at the 3d-5d transition metal-oxide interfaces has generated excitement due to possibility of engineering a wide range quantum phenomena and functionalities. Here, we investigate electronic structural properties LaCrO3/KTaO3 heterostructures. High-quality LaCrO3 films were grown on KTaO3 substrates using molecular beam epitaxy. These heterostructures show robust two-dimensional electron gas metallic behavior down liquid helium temperature. Using...
Nanosized perovskite ferroelectrics are widely employed in several electromechanical, photonics, and thermoelectric applications. Scaling of ferroelectric materials entails a severe reduction the lattice (phonon) thermal conductivity, particularly at sub-100 nm length scales. Such conductivity can be accurately predicted using information phonon mean free path (MFP) distribution. The current understanding MFP distribution is still inconclusive despite critical management implications. Here,...
The nature of superconductivity and its interplay with strong spin-orbit coupling at the KTaO3(111) interfaces remain a subject debate. To address this problem, we grew epitaxial LaMnO3/KTaO3(111) heterostructures. We show that is robust against in-plane magnetic field, critical field reaching ∼25 T in optimally doped superconducting order parameter highly sensitive to carrier density. argue drives formation anomalous quasiparticles vanishing moment, providing significant condensate immunity...
Tailoring the microscopic structures of oxide interfaces and surfaces to realize desired electronic properties is intense interest. The authors modulate conductivity LaNiO${}_{3}$ films as thin three unit cells by precisely controlling composition topmost atomic layer. Three-dimensional x-ray imaging combined with first-principles theory exposes correlation between surface termination electrical conductivity, which could be widely exploited in logic, memory, or sensor applications.
The complex phase diagrams of strongly correlated oxides arise from the coupling between physical and electronic structure. This can lead to a renormalization boundaries when considering thin films rather than bulk crystals due reduced dimensionality epitaxial strain. well-established RNiO3 diagram shows systematic dependence metal-insulator transition perovskite A-site rare-earth ion, R. Here, we explore equivalent for nickelate under compressive We determine solid solution Nd1-yLayNiO3...
We determine the surface reconstruction of SrTiO3 used to achieve superconducting FeSe films in experiments, which is different from 1x1 TiO2 terminated assumed by most previous theoretical studies. In particular, we identify existence a double layer at SrTiO3-FeSe interface that plays two important roles. First, it facilitates epitaxial growth FeSe. Second, ab initio calculations reveal strong tendency for electrons transfer an oxygen deficient when present. As better electron donor than...
The superconducting order parameter at the KTaO3 interfaces and its dependence on interface orientation remains a subject of debate. superconductivity these exhibits strong resilience against in-plane magnetic field violates Pauli limit. critical violation limit, however, have not been investigated. To address this problem, we grew epitaxial LaMnO3/KTaO3 heterostructures using molecular beam epitaxy. We show that is extremely robust field. Our results indicate orientation, despite impacting...
We present the growth and characterization of layered heterostructures comprised LaTiO3 SrTiO3 epitaxially grown on Si (001). Magnetotransport measurements show that sheet carrier densities scale with number LaTiO3/SrTiO3 interfaces, consistent presence an interfacial 2-dimensional electron gas (2DEG) at each interface. Sheet 8.9 × 1014 cm−2 per interface are observed. Integration such high density oxide 2DEGs silicon provides a bridge between exceptional properties functionalities...
The effect of film thickness on the magnetic properties ultrathin Fe-doped cobalt ferrite (Co${}_{1\ensuremath{-}x}$Fe${}_{2+x}$O${}_{4}$) grown MgO (001) substrates is investigated by superconducting quantum interference device magnetometry and x-ray linear dichroism, while distribution Co${}^{2+}$ cations between octahedral tetrahedral lattice sites studied with absorption spectroscopy. For films thinner than 10 nm, there a large enhancement moment; conversely, remanent magnetization...
A single atomic layer of ZrO2 exhibits ferroelectric switching behavior when grown with an atomically abrupt interface on silicon. Hysteresis in capacitance-voltage measurements a gate stack demonstrate that reversible polarization the structure couples to carriers First-principles computations confirm existence multiple stable states and energy shift semiconductor electron result from between these states. This monolayer represents new class materials for achieving devices transcend...