Materials Literature
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Electronic transport properties of the stable binary Cd5.7Yb quasicrystal and a quasicrystal in the Y–Mg–Zn family is presented. Electrical conductivity in these systems is an order of magnitude higher than other quasicrystals, resulting in larger thermal conductivity values due to enhanced electronic contributions (λ…
Structural and transport properties of individual micron-sized graphitic disks with less than one hundred graphene layers are measured. Mesoscopic devices of any arbitrary geometry can be fabricated at the center of such disks by focussed ion beam lithography, with the rest of the disk serving as low-resistance contac…
Closed end (10, 10) single walled carbon nanotubes (SWNTs) have been opened by oxidation at their ends and at wall defect sites, using ozone. Oxidation with ozone, followed by heating to 973 K to liberate CO and CO2, causes etching of the nanotube surface at carbon atom vacancy defect sites. The rate of adsorption of…
We present studies of the ultrafast dynamics of photoexcited carriers in thin-film nanocrystalline silicon materials in which the degree of crystallinity has been systematically varied by controlling the deposition conditions. Femtosecond pump-probe measurements reveal a multicomponent response that can be understood…
The theoretical approach is developed to describe the dynamics of inhomogeneous cross-linked polymers consisting of cross-link agglomerations. An inhomogeneous polymer is treated as an ensemble of noninteracting cross-linked regions (domains) of different sizes. We model an internal architecture of the domains in a ra…
Ostwald ripening occurs near equilibrium conditions when larger clusters grow at the expense of dissolving smaller clusters. We propose that ripening kinetics for growth and dissolution can be represented by a general population balance equation (PBE) for the cluster size distribution (CSD). This PBE can also describe…
As a model for composite materials of piezoelectric ceramic and metal, lead zirconate titanate (PZT) and platinum (Pt) particulate composites were fabricated by power processing. The electrical and mechanical properties of the PZT–Pt composites were measured as a function of the Pt volume fraction. The relative dielec…
Cubic (3C) SiC layers with initial biaxial stress value of about 0.4 GPa are observed by micro-Raman scattering measurements to be completely relaxed after formation of a porous network in the 3C-SiC/Si heterostructure. The porous heterostructure is obtained by an anodization procedure in HF acid solutions usually use…
We employ molecular dynamics (MD) simulations to study the structure of vitreous boron oxide. Although six-membered boroxol rings have been observed at fractions over 60% by various experimental techniques, simulation methods have not produced similar results. We adapt the polarization model, which includes many body…
In this study, α-Fe/Nd2Fe14B nanocomposite magnets with strong crystallographic texture were prepared by controlled melt spinning. For a relatively low wheel speed of 10 m/s, the c-axis texture of the Nd2Fe14B crystals is predominantly perpendicular to the plane of the ribbon, but it switches to parallel to the ribbon…
Switching behavior of 90° domains in epitaxial Pb(Zr0.32Ti0.68)O3 thin films under applied bias voltage was investigated in situ using synchrotron x-ray diffraction, and contribution of the switching to ferroelectric P–E hysteresis curve could be estimated. The electric field in the region illuminated by x ray was mad…
A method is reported for controlling the diameter of single-walled carbon nanotubes (SWCNTs) during the electric-arc-discharge process. Using argon as inert atmosphere provides smaller diameters as compared with those when pure helium is used. Varying the gas mixture from argon to helium changes the diameter distribut…
In an effort to understand the anomalous behavior of the viscosity of liquid beryllium fluoride relative to other liquids in the strong/fragile classification we have carried out ion dynamics computer simulations of BeF2 over a temperature range which overlaps with the experimental viscosity data. Using the simple rig…
We studied the morphological evolution during spinodal phase separation and subsequent coarsening in systems with a strong dependence of elastic constants on the composition. An efficient numerical method is developed for solving the two-dimensional inhomogeneous elastic equilibrium equations by using the conjugate gr…
The magnetization of Ga1−xMnxN (x<0.1) crystals was measured as a function of the magnetic field and temperature. Paramagnetic behavior typical of spin S=5/2 expected for Mn2+ (d5) magnetic centers was observed in the temperature range of 2 K<T<300 K. On the other hand, antiferromagnetic coupling…
The dynamics of oligomer desorption from surfaces have been studied by measuring the desorption kinetics of a set of n-alkanes from the surface of single crystalline graphite. Desorption rates were measured using a set of 21 monodispersed n-alkanes (CNH2N+2,5⩽N⩽60) each adsorbed at coverages in the range <0.1 t…
Multilayer "ferromagnet-layered antiferromagnet" (Fe/Cr) structures frustrated due to the roughness of layer interfaces are studied by numerical modeling methods. The "thickness-roughness" phase diagrams for the case of thin ferromagnetic film on the surface of bulk antiferromagnet and for two ferromagnetic layers sep…
Strategies and concepts for the design of THz emitters based on the quantum cascade scheme are analyzed and modeled in terms of a fully three-dimensional Monte Carlo approach; this allows for a proper inclusion of both carrier-carrier and carrier-phonon scattering mechanisms. Starting from the simulation of previously…
We present an atomistic theory of electronic transport through single organic molecules that reproduces the important features of the current-voltage characteristics observed in recent experiments. We trace these features to their origin in the electronic structure of the molecules and their local atomic environment.…
We present trends in the multilayer relaxations of several vicinals of Cu(100) and Cu(111) of varying terrace widths and geometry. The electronic structure calculations are based on density functional theory in the local density approximation with norm-conserving, non-local pseudopotentials in the mixed basis represen…