Materials Literature
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Amorphous films of a photochromic spiropyran containing a mesogenic group melt, when exposed to heat together with irradiation, to yield a red fluid. This fluid contains aggregates of merocyanine molecules and exhibits marked contraction under light illumination. The mechanism of the photocontraction is dependent upon…
One of the contributions to the enthalpy of formation ΔH of substitutional metallic solid solutions is the elastic energy due to atomic size mismatch between solute and solvent. Starting with a formula due to Eshelby and valid in the dilute regime, a multi-step process is derived which permits to generalize Eshelby's…
We discuss properties of bound magnetic polarons in an antiferromagnetic semiconductor placed in an external magnetic field. When the strength of the exchange coupling between the electron spin and local moments is increased, there can be an abrupt transition between a large and a small bound magnetic polaron. Associa…
Starting with electron energies above a few keV, all materials show an increase in the number of secondary and backscattered primary electrons with decreasing primary energy. The number of secondary plus backscattered electrons becomes equal to the number of primaries at two energies called the first and second crosso…
Initial exposure of single-crystal graphite samples to lithium vapor from a molecular beam source results in no long-range order in the lithium overlayer as observed by low-energy electron diffraction over the temperature range 80-500 K and coverage range 0.01-5 monolayers. A hexagonal close-packed incommensurate stru…
Shifts in the optical-absorption edges induced by band-gap illumination and annealing under pressure have been studied for ${\mathrm{As}}_{2}$${\mathrm{S}}_{3}$ and Se. Both materials, if annealed at 1 atm beforehand, undergo a decrease in the band-gap energy with illumination under pressure. This decrease is accompan…
The fact that the optical characteristics of thin-film materials are generally different from those of the same materials in bulk form is well known. The differences depend very much on the conditions in which the deposition has been carried out. A good understanding of these differences, their causes, and the influen…
A new in situ combined electrochemistry and x-ray photoelectron spectroscopy (XPS) technique using solid polymer electrolytes has been used to characterize electrically conducting films of polypyrrole perchlorate. The technique allows in situ electrochemical oxidation and reduction (doping and undoping) in ultrahigh v…
The first physical-property measurements on laser-quenched amorphous Si are reported. The form of the vibrational spectrum and degree of structural order have been obtained by depolarized-Raman-scattering measurements. A thin layer prepared by 700-psec pulses of 3567-\AA{} radiation is found to have a bond-angle varia…
The effect of x-ray irradiation on the absorption and luminescence spectra of KDP, DKDP, and ADP has been investigated. σ-Polarized absorption bands at 390 and 550 nm are induced by low temperature irradiation in the three crystals. A π-polarized band has also been observed in KDP and DKDP peaked at 510 and 550 nm, re…
A theory describing the double-carrier injection and recombination in thin insulating crystals is developed and applied to the case of current flow in anthracene. The diffusion-free analysis indicates that the scaling J∝V2/d3 holds, even when recombination effects are present for any crystal thickness. The same scalin…
The optical constants of evaporated MgF2 films were determined over the 1050–1600-Å wavelength range from measured transmittance and near-normal incidence reflectance measurements. The complex refractive index was studied as a function of film deposition conditions and correlated with microstructural examinations by t…
A small-angle x-ray diffraction study using synchrotron radiation of paraffins ${\mathrm{C}}_{n}{\mathrm{H}}_{2n+2}$ with $19\ensuremath{\le}n\ensuremath{\le}27$ as a function of the temperature allowed us to characterize the molecular disorders of the rotator phases, associated with longitudinal molecular motions and…
This paper presents a general approach to the calculation of single-particle excitations in insulating crystals, with application to silicon and diamond. The method includes the energy dependence of the self-energy which is evaluated in the Green's-function---screened-Coulomb-interaction ("GW") approximation of Hedin…
In the shape-memory alloy, NiTi:Fe, the martensitic transformation is well separated from the premartensitic (PM) phase and the latter can be studied in detail. X-ray diffraction studies in the PM phase reveal satellites near ${\stackrel{\ensuremath{\rightarrow}}{q}}_{I}=\frac{1}{3}(0,\overline{1},1)$ and ${\stackrel{…
Na+, Li+, and K+ ions have been implanted in thermally grown oxides (Tox =1000 °C) of metal-oxide-silicon structures. The mobilities of the Na+ and Li+ ions have been determined by means of the isothermal transient ionic current method in the temperature range 100–300 °C. The K+ mobility has been obtained by means of…
A quantitative theory for the optical properties of crystalline electrochromic materials is introduced. It is based on the double injection model and includes ionized impurity scattering of free electrons. Solar and luminous properties are evaluated versus electron density for doped WO3 films. Our results point to the…
The heat of formation, $\ensuremath{\Delta}H$, of metal hydrides is empirically found to be linearly related to a characteristic energy $\ensuremath{\Delta}E$ of the electronic band structure of the host metal. Independently of the position of the host metal in the Periodic Table (simple metals, noble metals, transiti…
The bonding in hard, hydrogenated, amorphous carbon films ($a$-C:H) prepared by plasma decomposition of benzene was investigated by high-resolution electron-energy-loss spectroscopy. In all asgrown films we find that one-third of the carbon atoms are trigonally bonded and two-thirds of the carbon atoms are tetrahedral…
The electronic structure of the insulating antiferromagnetic transition-metal compounds MnO, FeO, CoO, and NiO, which have been regarded as the prototypes of the concept of a Mott insulator, is discussed with use of energy-band theory based on the local-spin-density treatment of exchange and correlation. It is shown t…