Materials Literature
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We prepared magnetic cellulose porous microspheres (MCM) with mean diameter of ∼200 μm by employing the sol-gel transition (SGT) method from a mixture of magnemite ferrofluid and cellulose dissolved in 7 wt % NaOH/12% urea aqueous solvent precooled to -12 °C. Subsequently, the cellulose microspheres were activated wit…
Detection of specific DNA sequences is important to molecular biology research and clinical diagnostics. To improve the sensitivity of surface-enhanced Raman scattering spectroscopy (SERS), a variety of signal amplification methods has been developed, including Raman-active-dye, polymerase chain reaction (PCR) technol…
The authors have applied positron annihilation spectroscopy to study the effect of different growth conditions on vacancy formation in In- and N-polar InN grown by plasma-assisted molecular beam epitaxy. The results suggest that the structural quality of the material and limited diffusion of surface adatoms during gro…
Single phase Mn doped (2 at %) ZnO samples have been synthesized by solid-state reaction technique. Before the final sintering at 500 C, the mixed powders have been milled for different milling periods (6, 24, 48 and 96 hours). The grain sizes of the samples are very close to each other (~ 32 \pm 4 nm). However, the d…
The doping dependence of dry thermal oxidation rates in n-type 4H-SiC was investigated. The oxidation was performed in the temperature range 1000C to 1200C for samples with nitrogen doping in the range of 6.5e15/cm3 to 9.3e18/cm3, showing a clear doping dependence. Samples with higher doping concentrations displayed h…
We have performed density-functional calculations as well as employed a tight-binding theory, to study the effect of passivation of zigzag graphene nanoribbons (ZGNR) by hydrogen. We show that each edge C atom bonded with 2 H atoms open up a gap and destroys magnetism for small widths of the nanoribbon. However, a re-…
We report first principles investigations of the nonequilibrium transport properties of a Cu(111)|graphene interface. The Cu(111) electrode is found to induce a transmission minimum (TM) located -0.68eV below the Fermi level, a feature originating from the Cu-induced charge transfer resulting in n-type doped graphene…
Selected-area diffraction establishes that at least six different in-plane orientations of monolayer graphene on Pd(111) can form during graphene growth. From the intensities of low-energy electron microscopy images as a function of incident electron energy, we find that the work functions of the different rotational…
Measurements of the phonon density of states by inelastic neutron \emph{time-of-flight} scattering and specific heat measurements along with first principles calculations, provide compelling evidence for the existence of an Einstein oscillator ("\emph{rattler}") at $ω_{E1} \approx$ 5.0 meV in the filled skutterudite Y…
We have used neutron scattering and muon spin relaxation (muSR) to investigate the structural and magnetic properties of the beta-phase of elemental manganese doped with dilute amounts of indium. beta-Mn is an example of a topologically frustrated antiferromagnetically correlated metal - but which remains paramagnetic…
In this work, we investigate calcium titanate $[{\text{CaTiO}}_{3}(\text{CTO})]$ using x-ray diffraction and Raman spectroscopy up to 60 GPa and 55 GPa, respectively. Both experiments show that the orthorhombic $Pnma$ structure remains stable up to the highest pressures measured, in contradiction to ab initio predicti…
The structural properties of EuCo₂As₂ have been studied up to 35 GPa, through the use of x-ray diffraction in a diamond anvil cell at a synchrotron source. At ambient conditions, EuCo₂As₂ ) (I4/mmm) has a tetragonal lattice structure with a bulk modulus of 48 ± 4 GPa. With the application of pressure, the a axis exhib…
We study collective behavior of magnetic adatoms randomly distributed on the surface of a topological insulator. As a consequence of the spin-momentum locking on the surface, the RKKY-type interactions of two adatom spins depend on the direction of the vector connecting them, thus interactions of an ensemble of adatom…
We introduce an effective model for e(g) electrons to describe three-dimensional perovskite (La(1 - x)Sr(x)MnO(3) and La(1 - x)Ca(x)MnO(3)) manganites and study the magnetic and orbital order on a 4 × 4 × 4 cluster using correlated wavefunctions. The model includes the kinetic energy, and on-site Coulomb interactions…
We synthesize and study the structural and optical properties of nanocrystalline graphene monofluoride and graphite monofluoride, which are carbon-based wide band gap materials. Using laser excitations 2.41–5.08 eV, we identify six emission modes of graphite monofluoride, spanning the visible spectrum from red to viol…
A quantitative study was performed to investigate the impact of crystallographic dislocation defects, 21 including screw dislocation, basal plane dislocation, and threading edge dislocation, and their locations in 22 active and JTE region, on the reverse performance of 4H-SiC p-n diodes. It was found that higher leaka…
III-V nanowires are useful platforms for studying the electronic and mechanical properties of materials at the nanometer scale. However, the costs associated with commercial nanowire growth reactors are prohibitive for most research groups. We developed hot-wall and cold-wall metal organic vapor phase epitaxy (MOVPE)…
The electronic properties and nanostructure of InAs nanowires are correlated by creating multiple field effect transistors (FETs) on nanowires grown to have low and high defect density segments. 4.2 K carrier mobilities are ~4X larger in the nominally defect-free segments of the wire. We also find that dark field opti…
Transition-metal substitution in Fe pnictides leading to superconductivity is usually interpreted in terms of carrier doping to the system. We report on a density functional calculation of the local substitute electron density and demonstrate that substitutions like Co and Ni for Fe do not carrier dope but rather are…
Oxygen octahedral tilts underpin the functionality of a large number of perovskite-based materials and heterostructures with competing order parameters. We show how a precise analysis of atomic column shapes in Z-contrast scanning transmission electron microscopy images can reveal polarization and octahedral tilt beha…