A5114376546- Semiconductor materials and devices
- Diamond and Carbon-based Materials Research
- Graphene research and applications
- Fullerene Chemistry and Applications
- Metal and Thin Film Mechanics
- Ion-surface interactions and analysis
- Electron and X-Ray Spectroscopy Techniques
- Surface and Thin Film Phenomena
- Advanced Materials Characterization Techniques
- ZnO doping and properties
- Magnetic properties of thin films
- Semiconductor Quantum Structures and Devices
- Catalytic Processes in Materials Science
- Semiconductor materials and interfaces
- 2D Materials and Applications
- High-Temperature Coating Behaviors
- Nanowire Synthesis and Applications
- Physics of Superconductivity and Magnetism
- X-ray Spectroscopy and Fluorescence Analysis
- High-pressure geophysics and materials
- Molecular Junctions and Nanostructures
- Plasma Diagnostics and Applications
- Silicon Nanostructures and Photoluminescence
- Intermetallics and Advanced Alloy Properties
- Quantum and electron transport phenomena
University of Virginia
2016-2025
Universität Hamburg
2023
Center for Free-Electron Laser Science
2023
Oak Ridge National Laboratory
2021
Auburn University
2021
Brookhaven National Laboratory
2021
McCormick (United States)
2010-2020
Charlottesville Medical Research
2016-2020
Charité - Universitätsmedizin Berlin
2019
Berlin-Brandenburger Centrum für Regenerative Therapien
2019
Ni-Cr based super-alloys have exceptional corrosion resistance, which is further improved with Mo alloying. The correlation between passive layer performance and composition was studied to gain a deeper mechanistic understanding of the role by comparing behavior Ni-22Cr Ni-22Cr-6Mo (wt%) alloys. layers were formed using galvanostatic holds create fast slow growth conditions high low current densities. A potentiostatic hold added initiate exposure aging. film characterized electrochemical...
Noncrystalline hydrocarbon films were deposited from methane plasmas in an electron-cyclotron-resonance plasma reactor. The characterized by infrared spectroscopy and high-energy ion-beam analysis. Film properties investigated as a function of the energy ions impinging on surface growing film. ion was varied applying dc bias to sample range 30 200 eV. measured with retarding field analyzer under identical experimental conditions. An abrupt change found sp3/sp2 ratio interval 80 120 Other...
The instantaneous kinetics of oxide formation and growth, in competition with passive film dissolution breakdown, were investigated for Ni-22 Cr Cr-6 Mo (wt%) during single step passivation at +0.2 VSCE. Experiments conducted selected acidic alkaline chloride-containing environments using simultaneous AC DC electrochemistry; including on-line Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). In parallel experiments, in-situ neutron reflectometry (NR) ex-situ X-ray photoelectron...
<title>Abstract</title> The oxidation of NiCrMo is studied in-operando with synchrotron-based X-ray photoelectron electron microscopy (XPEEM) and in-situ spectroscopy (XPS). XPEEM produces absorption spectroscopic (XAS) hyperspectral images time-resolved information about the oxide growth distribution. Oxide distribution in XAS quantified cosine similarity, time evolution roughness timeseries. Low energy diffraction (LEED) indicates that Cr<sub>2</sub>O<sub>3</sub> structure forms. In...
Combining spectroscopic methods probing both occupied as well unoccupied electronic states, the surface structure of ex situ prepared boron-nitride films is analyzed and compared to experimental theoretical bulk-electronic properties taken from literature. X-ray photoelectron spectroscopy applied probe core-level valence-band electron-energy-loss in reflection geometry investigate conduction band states excitations like plasmons core excitons. For with hexagonal structure, results...
The 2D nature of transition metal dichalcogenides (TMDs) makes their electronic and optical performance highly susceptible to the presence defects. At elevated temperatures, which can be reached during growth or in operation, additional defects introduced lead further material degradation. Therefore, by studying impact temperature on 2D-TMDs, formation respective degradation pathways established. geometric structure density thermally induced tungsten diselenide (WSe2) layers were examined...
The molecular-level processes responsible for fractal-dendritic growth of second-layer C60 islands on large and compact first-layer deposited graphite substrate are investigated by a combination scanning tunneling microscopy (STM) kinetic Monte Carlo (kMC) simulations. Molecular dynamics (MD) simulations performed to determine the activation barriers jump rates diffusion molecules layer. thermally activated processes, determined in MD simulations, used kMC explore connections between...
The effects of crystal orientation and prior etching on the polarization repassivation behavior Ni–Cr Ni–Cr–Mo alloys have been investigated in acidic chloride environment using dc potentiostatic ac single-frequency electrochemical impedance spectroscopy. Tests were conducted within passive region at potentials where local oxide breakdown was possible. Surface morphologies grains across a wide range orientations measured before after passivation atomic force microscopy. Oxide growth...
In the present work we describe an investigation of influence low-energy ion irradiation (1-keV ${\mathrm{Ar}}^{+}$) on surface structure polycrystalline diamond and amorphous carbon films with various degrees graphitization. Photoelectron spectroscopy (PES) excitation energies in ultraviolet x-ray regime is employed to monitor radiation-induced modification electronic which closely linked local bonding environment atoms. A comparison mean photoelectron escape depth thickness affected layer...
The initial growth stage of C60 thin film on graphite substrate has been investigated by scanning tunneling microscopy in ultrahigh vacuum at room temperature. layer grows a quasi-layer-by-layer mode and forms round, monolayer high islands the surface. are confined terraces surface mobility fullerenes across steps is low all layers. second subsequent layers adopt fractal-dendritic shape, which was confirmed calculating fractal dimension (D=1.74 prior to island coalescence) agreement with...
The interaction of oxygen with Ni-Cr(100) alloy surfaces is studied using scanning tunneling microscopy (STM) and spectroscopy (STS) to observe the initial steps oxidation formation alloy-oxide interface. progression was observed for Ni(100) thin films including Ni-8 wt % Cr(100) Ni-12 Cr(100), which were grown on MgO(100) in situ. These exposed between 1 150 L O2 at 500 °C, additional annealing performed 600 °C. Each step STM STS, differential conductance maps delivered spatially resolved...
The energy distributions of ions (IED) on the substrate in an electron cyclotron resonance discharge have been measured for methane at pressures 5.4 × 10−2 and 1.1 10−1 Pa, holders with diameters ranging from 2.2 to 9.5 cm dc-bias voltages between 0 −120 V. applied dc bias is fully converted into increase ion only smallest plate, has no effect largest diameter. For intermediate diameters, increases increasing pressure constant bias. This explained by a model taking account sheath anisotropic...
Intercalation of C60 molecules at the graphene-substrate interface by annealing leads to amorphous and crystalline structures. A comparison topography electronic structure with wrinkles moiré patterns confirms intercalation. The intercalated imprint a local strain/deformation on graphene layer whose magnitude is controlled intermolecular distance. exhibits superlattice peak in density states. This work provides control strain graphene.
While shell growth engineering to the atomic scale is important for tailoring semiconductor nanowires with superior properties, a precise knowledge of surface structure and morphology at different stages this type overgrowth has been lacking. We present systematic scanning tunneling microscopy (STM) study homoepitaxial twinned superlattices in zinc blende InAs that transforms {111}A/B-type facets nonpolar {110}-type. STM imaging along provides information on revealing distinct differences...
Growth of high quality two-dimensional transition metal dichalcogenide monolayers with the desired microstructure and morphology is critical for enabling key technological solutions. This a non-trivial problem because processing space vast lack priori guidelines impedes rapid progress. A machine learning approach discussed that leverages data present in published growth experiments to predict performance regions unexplored parameter space. Starting from literature on MoS2 thin films grown...
Polycrystalline diamond films were deposited in a MW-PECVD reactor employing bias-enhanced nucleation as pretreatment to promote the subsequent nucleation. The substrate temperature during was varied between 600° and 760 °C by external heating, while other deposition parameters namely microwave input power kept constant. Likewise, not changed growth period throughout experiment. formed analyzed electron energy loss spectroscopy (EELS) scanning microscopy (SEM). nuclei density (ND) obtained...
We used the characteristic changes in electronic structure of valence band amorphous carbon films upon formation graphitic clusters to monitor temperature induced graphitization a variety hydrogen-containing (a-C:H) as well hydrogen-free (a-C) films. The spectra films, which were prepared situ by ion-beam deposition and electron beam evaporation, determined using photoelectron spectroscopy with excitation energies ultraviolet regime (ultraviolet photoemission spectroscopy, HeI, hν=21.22 eV...
The metal-insulator transition (MIT) in vanadium dioxide the vicinity of room temperature makes it one most interesting materials for novel switching device applications. It is therefore essential to have a fundamental understanding VO2 surface when incorporated into multilayer structures or nanodevices. This study focuses on modification response thermal treatment during phase transition. Vacuum annealing at temperatures MIT triggers partial reduction surface, and thus initiates chemical...