Materials Literature
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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…
Thermal stresses in GaAs on sawtooth-patterned Si substrates are studied by elastic finite element analysis under the assumption of plane strain. A comprehensive description of the highly nonuniform stress distribution is given and the possibility of band gap engineering by adjusting the geometrical characteristics of…
Iron amalgams have been studied by Mossbauer spectroscopy and magnetization measurements between 7 and 425 K. The Mossbauer spectra at 12 K show that the iron is present in at least two different sites. After heat treatments the Mossbauer spectra change into the typical spectrum of alpha -Fe, and the magnetic moment p…
It is shown that in pulsed laser deposition, there exists an optimal target-substrate distance for each deposition O2 pressure necessary for the growth of high quality superconducting films. This result indicates that plasma dynamics plays an important role in forming the superconducting films. A scaling law of PD2=co…
By utilizing copper phthalocyanine (CuPc) and TiOx, we report the fabrication of organic–inorganic heteromultilayer structures as a new concept of optoelectronic material. These are based on an anticipated model where charge carrier photogeneration occurs in the CuPc layers, while the TiOx layers have the role of tran…
Inelastic neutron scattering experiments in K 2 SeO 4 , Cs 2 SeO 4 and K 2 CrO 4 are reported. The lowest Sigma 3 - Sigma 2 phonon branches along the alpha *-axis in their Pnam phase have been characterised for the three compounds. The results are compared with recent lattice dynamical simulations using rigid-ion mode…