A5029438901- Muon and positron interactions and applications
- Magnetic properties of thin films
- Graphene research and applications
- Atomic and Molecular Physics
- Magnetic Properties and Applications
- Ammonia Synthesis and Nitrogen Reduction
- Electron and X-Ray Spectroscopy Techniques
- Magnetic Properties of Alloys
- Advancements in Battery Materials
- Theoretical and Computational Physics
- Nuclear Physics and Applications
- Radiation Detection and Scintillator Technologies
- Magnetic and transport properties of perovskites and related materials
- Copper Interconnects and Reliability
- Advanced Chemical Physics Studies
- Particle accelerators and beam dynamics
- Catalytic Processes in Materials Science
- Carbon Nanotubes in Composites
- Plasma Diagnostics and Applications
- Physics of Superconductivity and Magnetism
- Particle Detector Development and Performance
- ZnO doping and properties
- Semiconductor materials and devices
- Electrohydrodynamics and Fluid Dynamics
- Laser-Ablation Synthesis of Nanoparticles
The University of Texas at Arlington
2014-2024
First Point Scientific
2020
Bhabha Atomic Research Centre
2020
Kazan Federal University
1998
Rice University
1987-1990
University of Michigan
1982-1988
A polarized beam of low-energy positrons has been used for the first time as a probe surface magnetism. The polarization, ${P}_{{e}^{\ensuremath{-}}}$, electrons captured at Ni(110) to form positronium is measured. temperature dependence fitted by power law, yields an exponent ${\ensuremath{\beta}}_{1}=0.7\ifmmode\pm\else\textpm\fi{}0.1$, in qualitative agreement with calculations critical surface-layer magnetization. Rapid quenching ferromagnetic order observed submonolayer coverages oxygen.
We have designed and fabricated TiN/SiO2/TiN–HfO2-based new metamaterial microstructures as an absorber of the visible wavelength, in range 400–700 nm, with exceptionally high absorption efficiency (>96%) for solar energy harvesting purposes generation heat upon electromagnetic energy. The finite element method-based COMSOL Multiphysics software simulations were used to optimize structural parameters visualize electric field power loss distribution structure. An optimized 2D unit cell...
We present the first study of positron-annihilation-induced Auger-electron emission from a well defined overlayer-metal system. A 0.5 monolayer S on Cu(110) produced fourfold reduction in positron induced Cu ${M}_{2}$,3VV Auger peak. The attenuation is accounted for by theoretical calculations indicating that surface state displaced away overlayer, decreasing annihilation rate positrons with core electrons.
We report the first direct observation of electron emission into vacuum as a result VVV Auger transition resulting from relaxation deep hole in valence band. A beam low energy (<1.25eV) positrons was used to deposit onto surface samples consisting single layer graphene, multi-layer graphene and graphite. The distribution electrons emitted annihilation positron showed peak extending up ~12 eV with maximum at ~4eV. observed ~17 times larger than previously induced C KVV peak. An analysis based...
Positron-annihilation-induced Auger electron spectroscopy (PAES), electron-induced spectroscopy, and low-energy diffraction have been used to study the composition structure of vapor-deposited Pd films on Cu(100). Our results show that PAES intensity from saturates while Cu attenuates near zero by one monolayer deposition at 173 K. This is confirmation top-layer selectivity in metal-on-metal systems. Changes intensities provide a direct indication intermixing topmost layer as film deposited...
The apparatus used in the first direct measurement of energy spectra positron annihilation-induced Auger electrons is described. consists a magnetically guided low-energy beam, UHV surface preparation and characterization chamber, an spectrometer. spectrometer includes trochoidal monochromator microchannel plate detector. A permanent magnet mounted behind sample to produce field gradient which redirects outgoing along axis. combination permits total kinetic with effective angular acceptance...
Efficient and targeted delivery of impermeable exogenous material such as small molecules, proteins plasmids into cells in culture well vivo is great importance for drug, vaccine gene different therapeutic strategies. Though advent optoporation by ultrafast laser microbeam has allowed spatial targeting cells, the requirement high peak power to create holes on cell membrane not practical also challenging vivo. Here, we report development use uniquely non-reactive crystalline magnetic carbon...
We report measurements of the positron work functions ${\mathrm{\ensuremath{\varphi}}}^{+}$ polycrystalline samples Fe, Mo, Ni, Pt, Ti, and V. The were obtained by measuring energy spectrum slow positrons reemitted metal surfaces when bombarded with keV-energy positrons. Two methods used to extract functions. first method provides an absolute measurement. second infers function from \ensuremath{\Sigma}=${\mathrm{\ensuremath{\mu}}}^{+}$+${\mathrm{\ensuremath{\mu}}}^{\mathrm{\ensuremath{-}}}$...
Magnetic thermal hysteresis in $\mathrm{Co}∕\mathrm{Gd}$, $\mathrm{Co}\mathrm{Ni}∕\mathrm{Gd}$, and $\mathrm{Fe}∕\mathrm{Gd}$ multilayers is investigated by measurements of the total magnetic moment. A measurement magnetization as a function temperature for antiferromagnetically coupled displays characteristic bow-tie shape indicating superheating supercooling. The width can be tuned an external field, with values $150\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ at fields near...
Both positrons and electrons can be bound to metal surfaces by image-correlation interactions. For electrons, the image potential dominates, preventing electron from escaping into vacuum. positrons, a consistent picture of trapping process has not been developed. We investigate effect alkali-metal-atom adsorption on binding Ni surfaces. Thermal desorption positronium is observed for temperatures down 325 K cryogenic predicted. The slow variation activation energy with coverage indicates that...
Spin-polarized Auger electron spectroscopy is found to have applications for monitoring element-specific magnetization in composite systems. Here, we report on an application of such a study performed Gd-Co system. Special emphasis given $4d$-core-hole-initiated decays Gd interacting with Co subnetwork within the energy region 30--150 eV. Prominent resonant $(4\stackrel{\ensuremath{\rightarrow}}{d}4f)$ and nonresonant lines involving $4d({\mathrm{N}}_{45}),$ $5s({\mathrm{O}}_{1}),$...
We show that tunable magnetic thermal hysteresis can be realized for a simple ferrimagnetic CoGd alloy. The magnetization of Co0.8Gd0.2 alloy shows bow-tie curve as function temperature, which indicates supercooled and superheated phase transitions. width the tuned by an external field, with values 190 K at fields near 100 Oe 20 400 Oe. Experimental results are in reasonable agreement theoretical calculations.
We investigate the coercivity and exchange bias effect in Fe/Gd multilayers. Antiferromagnetically coupled (Fe 4 nm/Gd nm)4 multilayer has a compensation temperature (Tcomp) of approximately 90 K. observe that inhomogeneous ferrimagnet makes local minimum near Tcomp. When 16-nm-thick Gd layer is deposited over multilayer, emerges due to interfacial interaction thick overlayer Fe surface multilayer. Negative positive were observed below above Tcomp, respectively. In addition, there continuous...
We present a spectroscopic method which utilizes virtual photons to selectively measure the electronic structure of topmost atomic layer. These are created when incident positrons transition from vacuum states bound surface on sample and can transfer sufficient energy excite electrons into vacuum. The short interaction range restricts penetration depth approximately Thomas-Fermi screening length. Measurements analysis kinetic energies emitted made single layer graphene deposited Cu clean...
The attenuation of the Cu ${\mathit{M}}_{2,3}$VV Auger peak with Cs coverage on Cu(100) was measured using positron-annihilation-induced electron spectroscopy (PAES) and conventional (electron-induced) spectroscopy. data (obtained at both 303 163 K) indicate that below a critical (\ensuremath{\sim}0.7 monolayer) positrons are trapped Cu/Cs interface in agreement theoretical calculations. We observe sharp (less than 0.02 monolayer wide) drop normalized PAES intensity indicating transition to...
Temperature dependent static magnetic properties of $\mathrm{Co}∕\mathrm{Gd}$ multilayers, grown on SmCo, are experimentally investigated by means SQUID magnetometry. The $\mathrm{Sm}\mathrm{Co}∕(\mathrm{Co}∕\mathrm{Gd})$ system shows an exchange spring behavior above the compensation temperature $({T}_{\mathrm{comp}})$ at which magnetization antiferromagnetically coupled multilayer is zero. Below ${T}_{\mathrm{comp}}$, a tunable negative coercivity state (inverse hysteresis) appears, due to...
The trapping of positrons at surface defects that develop during the epitaxial growth a Ni film on Ni(110) substrate is established. Trapping detected by resultant decrease in positronium formed electron capture after incident 900-eV thermalize target. Ion-bombardment-induced are also investigated. It found ledges dominant site both surfaces. average ledge spacing ion-bombarded surface, annealing specified temperature, determined analyzing broadening low-energy diffraction (LEED) spot...
Data is presented which demonstrate that positron annihilation‐induced auger electron spectroscopy (PAES) can be used to eliminate secondary electrons in the energy range of Auger electrons. In PAES core–hole excitations necessary for (AES) are created by annihilation core using low (<25 eV) positrons. Secondary cannot through collisional processes with energies excess an Ek≊Ep (the primary beam energy). Spectra obtained a Cu (110) surface signals peak‐to‐background ratios 50:1 (more than...