A5039331880- Advanced X-ray Imaging Techniques
- Semiconductor materials and devices
- X-ray Spectroscopy and Fluorescence Analysis
- Physics of Superconductivity and Magnetism
- Laser-Plasma Interactions and Diagnostics
- Multiferroics and related materials
- Ferroelectric and Piezoelectric Materials
- Electronic and Structural Properties of Oxides
- Advanced Electron Microscopy Techniques and Applications
- Astrophysical Phenomena and Observations
- Iron oxide chemistry and applications
- Nuclear Physics and Applications
- Surface and Thin Film Phenomena
- Magnetic and transport properties of perovskites and related materials
- Metal and Thin Film Mechanics
- Molecular Junctions and Nanostructures
- GaN-based semiconductor devices and materials
- Medical Imaging Techniques and Applications
- Superconductivity in MgB2 and Alloys
- Acoustic Wave Resonator Technologies
- Optical measurement and interference techniques
- Semiconductor materials and interfaces
- Particle accelerators and beam dynamics
- High-pressure geophysics and materials
- Electron and X-Ray Spectroscopy Techniques
Argonne National Laboratory
2013-2023
Oregon State University
2019
Washington State University
2018
Northwestern University
2009-2011
University of Tennessee at Knoxville
2009
University of Houston
2009
Pennsylvania State University
2009
University of California, Berkeley
2009
Rutgers, The State University of New Jersey
2009
Lawrence Berkeley National Laboratory
2009
Metal oxide semiconductor field-effect transistors, formed using silicon dioxide and silicon, have undergone four decades of staggering technological advancement. With fundamental limits to this technology close at hand, alternatives are being pursued enable new functionality device architectures. We achieved ferroelectric in intimate contact with by growing coherently strained strontium titanate (SrTiO3) films via molecular beam epitaxy direct no interfacial dioxide. observed...
Motivated by the advanced photon source upgrade, a new hard X-ray microscope called "Velociprobe" has been recently designed and built for fast ptychographic imaging with high spatial resolution. We are addressing challenges of high-resolution scanning novel hardware designs, motion controls, data acquisition strategies, including use high-bandwidth interferometric measurements. The granite, air-bearing-supported stages provides necessary long travel ranges coarse to accommodate real samples...
Abstract X-ray ptychographic tomography is a nondestructive method for three dimensional (3D) imaging with nanometer-sized resolvable features. The size of the volume that can be imaged almost arbitrary, limited only by penetration depth and available scanning time. Here we present rapidly accelerates operation over given through acquiring set data via large angular reduction compensating resulting ill-posedness deeply learned priors. proposed 3D reconstruction “RAPID” relies initially on...
The interplay between spin waves (magnons) and electronic structure in materials leads to the creation of additional bands associated with energy levels which are called magnon sidebands. large difference scales magnons (meV) (eV) makes this direct interaction weak hence sidebands difficult probe. Linear light absorption scattering techniques at low temperatures traditionally used probe these Here we show that optical second-harmonic generation, as lowest-order nonlinear process, can...
Systematic studies are presented on the effects of cantilever buckling in vector piezoresponse force microscopy (V-PFM) imaging polarization domains thin-film based (001)-oriented BiFeO3 nanostructures, as observed through coupling out-of-plane and in-plane PFM images. This effect is a strong function laser spot position cantilever, being strongest at free end, insignificant 60% length from pivot point. finding provides unique approach to V-PFM ferroelectric domains, yielding three...
Here we introduce angle-resolved piezoresponse force microscopy (AR-PFM), whereby the sample is rotated by 30° increments around surface normal vector and in-plane PFM phase signals are collected at each angle. We obtained AR-PFM images of BaTiO3 single crystal cube-on-cube epitaxial (001) BiFeO3 (BFO) thin film on SrRuO3/SrTiO3 substrate, confirmed that provides more unambiguous information polarization directions than conventional method. Moreover, found eight additional variants in BFO...
Control over the oxidation state and crystalline phase of thin-film iron oxides was achieved by low-temperature atomic layer deposition (ALD), utilizing a novel precursor, bis(2,4-methylpentadienyl)iron. This (T = 120 °C) route to conformal Fe3O4 or α-Fe2O3 thin films is determined choice oxygen source selected for second surface half-reaction. The approach employs ozone produce fully oxidized milder oxidant, H2O2, generate Fe(2+)/Fe(3+) spinel, Fe3O4. Both processes show self-limiting...
Spin-charge-lattice coupling mediated by multimagnon processes is demonstrated in multiferroic BiFeO3. Experimental evidence of two- and three-magnon excitations as well at electronic energy scales high temperatures are reported. Temperature dependent Raman experiments show up to five resonant enhancements the two-magnon excitation below Néel temperature. These shown be collective interactions between on-site Fe d-d resonance, phonons, multimagnons.
Niobium carbide thin films were synthesized by atomic layer deposition (ALD) using trimethylaluminum (TMA), NbF5, and NbCl5 precursors. In situ quartz crystal microbalance (QCM) measurements performed at 200 290 °C revealed controlled, linear with a high growth rate of 5.7 4.5 Å/cycle, respectively. The chemical composition, rate, structure, electronic properties the studied over temperature range 125–350 °C. Varying amounts impurities, including amorphous carbon (a-C), AlF3, NbFx, NbClx,...
Nanostructured hematite (α-Fe2O3) has been widely studied for use in a variety of thin film applications including solar energy conversion, water oxidation, catalysis, lithium-ion batteries, and gas sensing. Among established deposition methods, atomic layer (ALD) is leading technique controlled synthesis wide range nanostructured materials. In this work, ALD Fe2O3 demonstrated using FeCl3 H2O precursors at growth temperatures between 200 350 °C. Self-limiting with rate ∼0.6 Å per cycle....
Ptychography is a rapidly developing scanning microscopy which able to view the internal structures of samples at high resolution beyond illumination size. The achieved spatial theoretically dose-limited. A broadband source can provide much higher flux compared with monochromatic source; however, it conflicts necessary coherence requirements this coherent diffraction imaging technique. In paper, multi-wavelength reconstruction algorithm has been developed deal broad bandwidth in...
We report the dependence of ferroelectric domain configuration and switching behavior on shape (square versus round) epitaxial BiFeO3 (BFO) nanostructures. fabricated (001) oriented BFO(120 nm)/SrRuO3(SRO,125 nm) film layers SrTiO3 single crystals by rf magnetron sputter deposition, patterned them to square (500×500 nm2) round (502 nm in diameter) shaped nanostructures focused ion-beam lithography. The surface morphology crystalline structure were characterized scanning electron microscopy...
X-ray ptychography, a powerful scanning lensless imaging technique, has become attractive for nondestructively internal structures at nanoscale. Stage positioning overhead in conventional step-scan ptychography is one of the limiting factors on throughput. In this work, we demonstrate use advanced fly scan to achieve high-resolution ptychograms modern integrated circuits large field-of-view millimeter scale. By completely removing stage overheads between points, time millimeter-size sample...
We report investigations of molybdenum nitride (MoN) thin films with different thickness and disorder superconducting transition temperature 9.89 K $\ge{T_c}\ge$ 2.78 K. Using terahertz frequency-domain spectroscopy we explore the normal charge carrier dynamics for frequencies covering range from 3 to 38 cm$^{-1}$ (0.1 1.1 THz). The energy scales, i.e. critical $T_c$, pairing $\Delta$, superfluid stiffness $J$, density $n_s$ can be well described within Bardeen-Cooper-Schrieffer theory...
Synchrotron characterization techniques provide some of the most powerful tools for study film structure and chemistry. The brilliance tunability Advanced Photon Source allow access to scattering spectroscopic unavailable with in-house laboratory setups opportunity probe various atomic layer deposition (ALD) processes in situ starting at very first cycle. Here, we present design implementation a portable ALD instrument which possesses modular reactor scheme that enables simple experimental...
We report the use of atomic layer deposition (ALD) to synthesize thin superconducting films and multilayer superconductor-insulator (S-I) hetero-structures. ALD being applied opens way for a variety applications, including improving performance decreasing cost high energy particle accelerators, wires storage, bolometers radiation detection. Furthermore, atomic-scale thickness control afforded by enables study superconductivity associated phenomena in homogeneous layers ultra-thin film limit....
Atomic layer deposition was used to synthesize niobium silicide (NbSi) films with a 1:1 stoichiometry, using NbF5 and Si2H6 as precursors. The growth mechanism at 200 °C examined by in-situ quartz crystal microbalance (QCM) quadrupole mass spectrometer (QMS). This study revealed self-limiting reaction rate of 4.5 Å/cycle. NbSi found grow only on oxide-free prepared halogenated electronic properties, rate, chemical composition, structure the were studied over temperature range 150–400 °C. For...
Abstract X-ray ptychography is a rapidly developing coherent diffraction imaging technique that provides nanoscale resolution on extended field-of-view. However, the requirement of coherence and scanning mechanism limit throughput ptychographic imaging. In this paper, we propose using multiple illuminations instead single illumination in conventional ptychography. Multiple locations sample are simultaneously imaged by spatially separated beams, therefore, obtained field-of-view one scan can...
Noninvasive X-ray imaging of nanoscale three-dimensional objects, such as integrated circuits (ICs), generally requires two types scanning: ptychographic, which is translational and returns estimates the complex electromagnetic field through IC; combined with a tomographic scan, collects these projections from multiple angles. Here, we present Attentional Ptycho-Tomography (APT), an approach to drastically reduce amount angular scanning, thus total acquisition time. APT machine...
Heteroepitaxial growth of selected group IV-VI nitrides on various orientations sapphire (α-Al2O3) is demonstrated using atomic layer deposition. High quality, epitaxial films are produced at significantly lower temperatures than required by conventional deposition methods. Characterization electrical and superconducting properties reveals a reduced room temperature resistivity increased residual resistance ratio for deposited compared to polycrystalline samples concurrently fused quartz substrates.
A tunneling spectroscopy study is presented of superconducting MoN and Nb0.8Ti0.2N thin films grown by atomic layer deposition (ALD). The exhibited a gap 2 meV 2.4 meV, respectively, with corresponding critical temperature 11.5 K 13.4 K, among the highest reported Tc values achieved ALD technique. Tunnel junctions were obtained using mechanical contact method Au tip. While native oxides these provided poor tunnel barriers, high quality low zero bias conductance (below ∼10%) an artificial...
We report an elastic relaxation and increase in local strain variation correlated with ferroelectric domains within epitaxial BiFeO3 thin film nanostructures fabricated by combined electron-beam focused ion-beam nanolithography. Nano-focused x-ray diffraction microscopy provided new insights into the relationship between nanostructures, namely: (i) out-of-plane (C-axis) of as much −1.8% Δc/c a BFO film-based nanostructure relative to planar lattice constant; (ii) rotation trending from...
Three-dimensional inspection of nanostructures such as integrated circuits is important for security and reliability assurance. Two scanning operations are required: ptychographic to recover the complex transmissivity specimen, rotation specimen acquire multiple projections covering 3D spatial frequency domain. types rotational possible: tomographic laminographic. For flat, extended samples, which full 180° coverage not possible, latter preferable because it provides better domain compared...
In this communication, we report results of a high resolution sputter depth profiling analysis stack 16 alternating MgO and ZnO nanolayers grown by atomic layer deposition (ALD) with thickness ∼5.5 nm per layer.We used an improved dual beam approach featuring low energy normally incident direct current sputtering/milling ion (first beam).Intensities 24 Mg + 64 Zn secondary ions generated pulsed (second beam) were measured as function sample time-of-flight mass spectrometry (TOF...
As a coherent diffraction imaging technique, ptychography provides high-spatial resolution beyond Rayleigh's criterion of the focusing optics, but it is also sensitively affected by decoherence coming from spatial and temporal variations in experiment. Here we show that high-speed ptychographic data acquisition with short exposure can effectively reduce impact experimental variations. To reach cumulative dose required for given resolution, further demonstrate continuous multi-pass scan via...