Materials Literature
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The pressure, temperature, and frequency dependence of the dielectric properties of a single crystal of Sr0.6Ba0.4Nb2O6 are measured across its c-axis. A linear relationship of the Curie temperature (Tc) with pressure (p) is observed with dTcdp = −6.8 K/kbar. The transition is interpreted in terms of the displacement…
Deposition and study of calcium films were achieved under ultrahigh vacuum. The latter was obtained with the use of an ion pump and a helium cryopump. The temperature of the substrate ranged between 90 and 400 K. The electrical resistance was measured with the use of a four-probe method with a constant current. Film t…
Four different open chain forms of methanol dimer have been identified in nitrogen matrices through temperature and IR irradiation effects. Each form is characterized by two OH stretching vibration frequencies, one (D1) close to the monomer frequency (3664 cm−1) and corresponding to the oxygen perturbed (electron dono…
We assess the importance of the impurity states of a doped trans-polyacetylene chain. The impurity potential is modeled by a point charge that is located off the chain and is screened phenomenologically. The common assumption that the dopant levels of a dimerized chain closely approximate the hydrogenic levels of a po…
The real and imaginary parts of the complex dielectric permittivity of the supercooled smectic G phase of N-(4′-n-pentyloxybenzylidene)-4-n-butylaniline have been measured from 50 Hz to 200 kHz and 77 to 260 K. The glass transition temperature of the smectic phase is 181 K. Two relaxation regions were observed; one ab…
Ab initio self-consistent-field---linear combination of atomic orbitals---molecular-orbitals calculations on undoped and lithium-doped $p$-quaterphenyl, a model chain for poly-($p$-phenylene), demonstrate dramatic changes in geometrical and electronic structures upon doping. For a charge transfer of less than $0.1e$ p…
The elastic reflectance spectra for low-energy electrons (0-30 eV) of fcc metals show characteristic structure related to critical points in the energy bands. The (111) surfaces of Au, Ag, Pd, Cu, Ni, and Al have been investigated and all have spectra consisting of a sharp reflectance peak followed by a broad, more in…
The refractive index of a layer is a sensitive function of the preparation conditions. Normal incidence measurement of the optical properties can reveal possible inhomogeneity of index. We propose a method of automatic determination of the complex refractive index and thickness of a layer which includes systematic mea…
X-ray-photoemission spectra of monoclinic, trigonal, and amorphous selenium have been first measured with the same photoelectron spectrometer in order to directly compare the valence electronic states of the three allotropes of selenium. It has been found that the $4p$ lone pair and the $4s$ band of monoclinic seleniu…
We present a new study of the surface-plasmon contribution to surface-enhanced Raman scattering from molecules adsorbed onto metallic gratings. To this end, we use a rigorous electromagnetic theory of diffraction, i.e., a theory in which the groove depth is not considered as a perturbative parameter. The rigorous feat…
Using a natural type IIb diamond, which is p-type semiconducting, as a substrate material, and implanting this diamond with carbon ions to induce n-type regions, diode and bipolar transistor action could be obtained. Owing to the geometrical positions of the collector, base, and emitter, which in this case were latera…
Optical bistable operation in the transmission characteristics of a nematic liquid crystal film is observed. The mechanism for the bistability is the self-focusing of light via optically induced molecular reorientations. The process occurs at very modest cw input laser power on the order of 0.3 W (intensity of ∼500 W/…
The periodic lattice distortion associated with a charge-density wave in $1T$-V${\mathrm{Se}}_{2}$ was investigated by x-ray diffraction. The charge-density-wave transition was observed at 110 K. From the observation of the satellite reflections the wave vector of the periodic lattice distortion was determined to be $…
Highly conductive films of zinc oxide have been prepared by rf magnetron sputtering deposition on a substrate suspended perpendicular to the target under an applied external magnetic field in pure argon gas. It is shown that a film with low resistivity (5×10−4 Ω cm) and high optical transmission (>85% between 4…
The bonding and spectroscopic properties of graphite are investigated by carrying out first-principles, self-consistent electronic structure calculations, and by comparing the results with high-resolution data from recent x-ray diffraction and angle-resolved photoemission measurements. The theoretical valence-charge d…
The ultraviolet photoemission and optical absorption spectra of pyrrole and polypyrrole are analyzed using the spectroscopically parametrized CNDO/S3 model. Calculated charge densities, bond orders, and orbital eigenvalues for pyrrole are compared with the extensive literature on this molecule. The densities of valenc…
Carbon fibers prepared from thermal decomposition of benzene at \ensuremath{\sim} 1100\ifmmode^\circ\else\textdegree\fi{}C are studied by Raman spectroscopy as a function of heat-treatment temperature. The structural ordering at each heat-treatment temperature is monitored by observation of both the Raman-allowed ${E}…
The crystallization of a Lennard-Jones liquid has been studied with molecular-dynamics techniques. In particular, the motion of the fcc (100) interface has been measured for a range of temperatures below the melting point. The crystallization rates are not limited by the mobility of atoms in the bulk liquid; measurabl…
Defect-state calculations on all-trans polyacetylene and polyparaphenylene have been performed in the framework of the adiabatic H\"uckel Hamiltonian with $\ensuremath{\sigma}$-bond compressibility. In polyacetylene, the study of the energetics of the separation of the radical (neutral defect) -ion (charged defect) pa…
The lattice parameters of the compound cadmium stanni-diphosphide (CdSnP 2 ) have been determined at different temperatures in the range 28 to 536 degrees C. From these data, the thermal expansion and the tetragonal distortion have been evaluated at various temperatures. The linear thermal expansion coefficients along…