Materials Literature
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The formation of a novel surface reconstruction upon Co deposition on freshly cleaved Ge(111)2x1 surfaces is studied by means of scanning tunneling microscopy (STM) at low temperature. The deposited Co atoms are immobile at substrate temperatures of 4.5K, while they can diffuse along the upper pi-bonded chains at a te…
To study temperature dependent elastic constants, a new computational method is proposed by combining continuum elasticity theory and first principles calculations. A Gibbs free energy function with one variable with respect to strain at given temperature and pressure was derived, hence the full minimization of the Gi…
By using the most sensitive two-point correlation functions introduced to date, we reconstruct the microstructures of two-phase random media with heretofore unattained accuracy. Such media arise in a host of contexts, including porous and composite media, ecological structures, biological media, and astrophysical stru…
The local structure of superconducting single crystals of K${}_{0.8}$Fe${}_{1.6+x}$Se${}_{2}$ with $Tc$ $=$ 32.6 K was studied by x-ray absorption spectroscopy. Near-edge spectra reveal that the average valence of Fe is 2+. The room temperature structure about the Fe, K, and Se sites was examined by iron, selenium, an…
The structural, elastic, electronic and optical (x = 0) properties of doped Sn1-xBixO2 and Sn1-xTaxO2 (0 \leq x \leq 0.75) are studied by using the first-principles pseudopotential plane-wave method within the local density approximation. The independent elastic constants Cij and other elastic parameters of these comp…
Unsupported catalyst for green chemistry: The aerobic oxidation and coupling of primary alcohols (methanol, ethanol, n-butanol) to give the corresponding aldehydes and esters at temperatures below 100 °C is facilitated by unsupported nanoporous gold catalysts. The experimental conditions employed allow a close compari…
We use in situ scanning tunneling microscopy (STM) to investigate intercalation of the ferromagnetic 3d metals Ni and Fe underneath a graphene monolayer on Rh(111). Upon thermal annealing of graphene/Rh(111) with the deposited metal on top, we observe the formation of epitaxial monatomic nanoislands grown pseudomorphi…
We report shear modulus (G) and internal friction (Q(-1)) measurements of large-area monolayer graphene films grown by chemical vapor deposition on copper foil and transferred onto high-Q silicon mechanical oscillators. The shear modulus, extracted from a resonance frequency shift at 0.4 K where the apparatus is most…
Graphene nanoribbon folds with single and double closed edges are studied using density functional theory methods. The van der Waals dispersive interactions are included via semiempirical pairwise optimized potential. The geometrical phases of the single and double folded ribbons are obtained. The electronic structure…
Unusually large thermopower modulation is demonstrated using a field effect transistor structure on a thermoelectric material. An electric field application provides an extremely thin (∼2 nm) two-dimensional electron gas (2DEG), which exhibits unusually large thermopower, approximately five times larger than that of t…
The electronic structure of CoO is studied by resonant inelastic soft X-ray scattering spectroscopy using photon energies across the Co 2p absorption edges. The different spectral contributions from the energy-loss structures are identified as Raman scattering due to d-d and charge-transfer excitations. For excitation…
X-ray scattering spectra of Cu and Ni metals have been measured using monochromatic synchrotron radiation tuned from far above to more than 10 eV below threshold. Energy conservation in the scattering process is found to be sufficient to explain the modulation of the spectral shape, neglecting momentum conservation an…
Using scanning tunneling microscopy and spectroscopy, we have studied the local density of states (LDOS) of graphene over step edges in boron nitride. Long-wavelength oscillations in the LDOS are observed with maxima parallel to the step edge. Their wavelength and amplitude are controlled by the energy of the quasipar…
Two-phase random textures abound in a host of contexts, porous and composite media, ecological structures, biological media and astrophysical structures. Questions surrounding the spatial structure of such textures continue to pose many theoretical challenges. For example, can two-point correlation functions be identi…
Recent simulations have studied the formation of patterns in a binary mixture of immiscible surfactants absorbed onto the surface of a spherical nanoparticle. The resulting patterns (Janus, spots and stripes) were in good agreement with experimental results. We perform dissipative particle dynamics (DPD) simulations t…
The electronic structure of the heavy fermion compound CeB6 is probed by resonant inelastic soft X-ray scattering using photon energies across the Ce 3d and 4d absorption edges. The hybridization between the localized 4f orbitals and the delocalized valence-band states is studied by identifying the different spectral…
Resonant soft X-ray Raman scattering measurements on NiO have been made at photon energies across the Ni 2p absorption edges. The details of the spectral features are identified as Raman scattering due to d-d and charge-transfer excitations. The spectra are interpreted within the single impurity Anderson model, includ…
Exchange bias training effect in ferromagnetic/antiferromagnetic bilayers is investigated. In some systems the evolution of the exchange bias field $H_E$ with the number of cycle $n$ cannot be fitted by the empirical $1/\sqrt{n}$ function. A unified expression is derived from a discretized Landau-Khalatnikov equation…
The studies of spin phenomena in semiconductor low dimensional systems have grown into the rapidly developing area of the condensed matter physics: spintronics. The most urgent problems in this area, both fundamental and applied, are the creation of charge carrier spin polarization and its detection as well as electro…
Electrical charging of metal surfaces due to photoelectric generation of carriers is of concern in trapped ion quantum computation systems, due to the high sensitivity of the ions' motional quantum states to deformation of the trapping potential. The charging induced by typical laser frequencies involved in doppler co…