Materials Literature
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We present a comprehensive study of epitaxially grown and As-coated GaAs(100) surfaces as a function of As desorption temperature and background pressure. We have used low-energy electron diffraction to determine surface reconstruction, and core-level and valence-band soft-x-ray photoemission spectroscopy to perform c…
Magnetization measurement and 55 Mn NMR study on a ferromagnet system La(Ni 2+ 1- x Mg x 2+ ) 0.5 Mn 0.5 4+ O 3 are made. The divalent and the tetravalent ions are found to be ordered to a considerable extent in the whole compositional range, and the ferromagnetic superexchange interactions between neighboring Mn 4+ a…
The electronic transport mechanism in polypyrrole is discussed in terms of Mott variable range hopping (VRH) in samples with a wide range of conductivities and which have been formed using different doping techniques. Samples were synthesized in both aqueous and organic media and samples were either doped during polym…
The microscopic mechanism of oxygen diffusion in yttria stabilized zirconia (YSZ) is investigated by means of a polyhedron analysis. It is shown that the probability of finding O ion in a tetrahedron increases as Y ions at the corners of the tetrahedron increase, and this tendency becomes marked with increasing dopant…
Thermally generated defects in ultrathin MgO films on Mo(100) have been investigated using high-resolution electron-energy-loss spectroscopy (HREELS) in the 0--9-eV spectral region. The results indicate that the MgO films are thermally stable and nearly free from defects up to a temperature of 1100 K, above which defe…
We have fabricated boron carbide thin films on Si(111) and other substrates by plasma-enhanced chemical-vapor deposition (PECVD). The PECVD of boron carbides from nido-cage boranes, specially nido-pentaborane(9) (B5H9), and methane (CH4) is demonstrated. The band gap is closely correlated with the boron to carbon rati…
We have recently demonstrated that the Meyer-Neldel (MN) rule (compensation law) may be understood as arising naturally when the activation energy for a process is significantly larger than both the typical excitations available and kT. This conclusion was supported by the results of two microscopic models, related to…
We demonstrate a cluster expansion technique that is capable of accurately predicting formation energies in binary substitutional systems---even for those with large atomic relaxations. Conventional cluster expansions converge rapidly only in the absence of atomic relaxations, and they fail for long-period lattice-mis…
We present an efficient scheme for including full-potential terms in the linear-muffin-tin-orbital method. It is based on direct evaluation of the integrals in the interstitial region by partitioning crystalline space into atomic-cell envelopes and using one-center spherical harmonics expansions. This leads to a fast…
It is established that vacancies in diamond migrate, during annealing, primarily in their neutral charge state, with an activation energy of 2.3\ifmmode\pm\else\textpm\fi{}0.3 eV. Negative vacancies are destroyed by first converting to neutral centers in a reversible charge transfer process. In relatively pure diamond…
Frequently it is useful to compare experimental values of the hyperpolarizabilities β and γ with calculated values. It is also often helpful to compare experimental values of β obtained from dc-electric field induced second harmonic generation (dc-SHG) experiments, e.g., with values obtained using the solvatochromism…
A new treatment of the phase behaviour of a colloid + nonadsorbing polymer mixture is described. The calculated phase diagrams show marked polymer partitioning between coexisting phases, an effect not considered in the usual effective-potential approaches to this problem. We also predict that under certain conditions…
A liquid-solution-phase technique for preparing submicrometer-sized silicon single crystals is presented. The synthesis is based on the reduction of SiCl(4) and RSiCl(3) (R = H, octyl) by sodium metal in a nonpolar organic solvent at high temperatures (385 degrees C) and high pressures (> 100 atmospheres). For R = H,…
An optically addressable spatial light modulator is developed that has a reversible storage capability and cascadability. It consists of a sandwich structure of a hydrogenated amorphous-silicon photoconductor, a dielectric mirror, and a surface-stabilized ferroelectric liquid crystal in a chiral smectic C phase. This…
Line (string) defects at which the molecular orientation changes by 0, \ensuremath{\pi}/2, or \ensuremath{\pi} rad are reported in few-layer-thick freely suspended tilted smectic liquid-crystal films. These defects are ubiquitous, appearing in chiral and nonchiral smectic-C, hexatic, and antiferroelectric phases, eith…
The authors present a theoretical and numerical study of certain properties of X-ray diffraction of finite-size Rudin-Shapiro and generalized Rudin-Shapiro multilayer heterostructures. They are compared with spectra obtained in similar conditions from other deterministically disordered multilayer systems, in particula…
Liposomes can be loaded with weak acids and bases, which exist in solutions in equilibrium with membrane permeable uncharged form, using various gradients across their membranes. Because in some cases the estimated drug concentration in the loaded liposomes exceeds their aqueous solubility we investigated the physical…
The scanning transmission x-ray microscope at the National Synchrotron Light Source has been used to record x-ray absorption near-edge structure (XANES) spectra from 0.01-square-micrometer regions of organic specimens. The spectral features observed reflect the molecular structure of the dominant absorbing atoms and p…
Abstract The correlation of 2D conjugation and the nonlinear properties of a series of polycyclic aromatic compounds were studied by performing semiempirical calculations using the MOPAC package. For linear polyacenes, both linear and nonlinear properties are found to be increased as the number of six‐membered rings i…
Piezoelectric materials lie at the heart of ultrasonic transducers. These materials convert electrical energy into mechanical form when generating an interrogating acoustic pulse and convert mechanical energy into an electric signal when detecting its echoes. This paper first surveys the piezoelectric materials in cur…