Materials Literature
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Low-resistance ohmic contacts have been fabricated on a naturally occurring B-doped diamond crystal and on polycrystalline diamond films by B ion implantation and subsequent Ti/Au bilayer metallization. A high B concentration was obtained at the surface by ion implantation, a post-implant anneal, and a subsequent chem…
The pressure dependence of vibrational Raman scattering in polycrystalline ${\mathrm{Ge}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Si}}_{\mathit{x}}$ alloys is studied up to \ensuremath{\sim}100 kbar across the compositional range, and the mode Gr\"uneisen parameters \ensuremath{\gamma} for the Si-Si, Ge-Ge, and…
Electrical characteristics associated with radiation detection were measured on single-crystal natural type-IIa diamond using two techniques: charged particle-induced conductivity and time-resolved transient photoinduced conductivity. The two techniques complement each other: The charged particle-induced conductivity…
We present geometric and energetic properties of sodium clusters with 8, 14, 20, 30, and 40 atoms using an effective many-body interaction among sodium atoms in the framework of an improved isothermal molecular-dynamics approach. These clusters undergo two phase transitions and the two transition temperatures increase…
Angle-resolved ultraviolet photoelectron spectra using synchrotron radiation were measured for oriented thin films of bis(1,2,5-thiadiazolo)-p-quinobis(1,3-dithiole) on a cleaved highly oriented pyrolytic graphite (HOPG) surface. The observed takeoff angle dependence of the photoelectron intensity was analyzed by usin…
We investigate size-dependent nonlinear polarization due to Wannier excitons confined in CuCl quantum dots (QD's) with a radius R of 15--80 \AA{} embedded in glass. The third-order optical susceptibility ${\mathrm{\ensuremath{\chi}}}^{(3)}$ measured at 80 K increases as a function of radius and subsequently decreases…
The surface phonons and CH vibrational structure of diamond (100) and (111) surfaces have been examined using high-resolution electron-energy-loss spectroscopy. Experimental phonon features of (2\ifmmode\times\else\texttimes\fi{}1)-reconstructed diamond surfaces [H-free (100) and partially H-terminated (111)] agree we…
Abstract Polyimide fibers have been produced from both polyamic acid and polyimide resins, derived from 2, 2‐bis (3,4‐dicarboxyphenyl) hexafluoropropane dianhydride and 2, 2‐bis (4‐4‐aminophenoxy) phenyl) hexafluoropropane, by extrusion into various aqueous organic media. Polyimide fibers obtained from polyamic acid f…
We present a formalism to compute the optical-activity tensor in the long-wavelength limit neglecting local-field corrections with a nearly first-principles approach. The calculation of optical activity requires perturbation theory in the vector potential in order to describe the rotation of the plane of polarization…
Highly efficient infrared-to-visible upconversion has been observed in Er3+-doped BaCl2 phosphors. The composition optimized for maximum green emission was around 25ErCl3 (mol %), which contains 5–15 mol % more active Er3+ ions than those in the conventional Er3+-doped fluoride phosphors. Pumped by a 0.8 μm laser diod…
The electronic structure of \ensuremath{\beta}-phase NiTi has been calculated using a first-principles linear-combination-of-atomic-orbitals method. The resulting band structure was fitted with a nonorthogonal tight-binding Hamiltonian from which electron-phonon matrix elements were evaluated. The soft phonon near ${\…
The results of measurements of the optical band gap of ${\mathrm{Zn}}_{3}$${\mathrm{N}}_{2}$ films, which crystallize in cubic antibixbyite structure (space group: Ia3), are presented. The polycrystalline films are prepared by direct reaction between ${\mathrm{NH}}_{3}$ and zinc films on quartz substrates kept at 410…
A first-principles band calculation and theoretical simulation of scanning tunneling microscopy and spectroscopy (STM and STS) are performed on a stepped surface of graphite. The calculated band structure and the density of states are similar to those of fullerene tubules. Unlike in fullerene tubules, however, a local…
An elastic-plastic finite element method numerical model previously developed (see Part I of this article) for predicting thermal residual stresses at graded ceramic-metal interfaces has been applied to determine interface conditions favorable for achieving residual stress reductions. Using Al2O3-Ni as a model system,…
Magnetic properties of carbon nanotubes (CN's) are calculated in the effective-mass theory. The magnetic moment in a magnetic flux parallel to the tube axis oscillates as a function of the flux with period determined by the flux quantum and phase depending on whether CN is metallic or semiconducting. For a magnetic fi…
Electron and x-ray-diffraction studies of nanotubes have revealed that the distances between the graphitic sheets are larger by a few percent than those in bulk graphite. The mean value of the interlayer spacings is 0.344\ifmmode\pm\else\textpm\fi{}0.001 nm.
We have studied the microstructure and optical properties of free-standing porous Si thin films fabricated by electrochemical anodization. Raman-spectroscopy and transmission-electron-microscopy examinations show that Si crystallite spheres with diameters of several nanometers are dispersed in the amorphous phase. The…
We analytically study phonon transmission and localization in random superlattices by using a Green's-function approach. We derive expressions for the average transmission rate and localization length, or Lyapunov exponent, in terms of the superlattice-structure factor. This is done by considering the backscattering o…
The oxygen 1s x-ray-absorption spectra of ${\mathrm{SrTiO}}_{3}$ and ${\mathrm{TiO}}_{2}$, in both the rutile and anatase crystal structure, are analyzed using the oxygen p-projected density of states of ground-state band-structure calculations. Good agreement is found and it is concluded that multielectron effects, t…
An elastic-plastic finite element method numerical model has been formulated to study residual stresses developed at graded ceramic-metal interfaces during cooling. The results were compared with those obtained for sharp (nongraded) interfaces to assess the potential for achieving residual stress reductions. Analyses…