Materials Literature
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Conductivity and magnetoconductivity have been measured for various kinds of graphite crystals at low temperatures down to 0.03 K. Anomalous behaviours have been found in polycrystalline (but well oriented) specimens of graphite. At low temperatures below 0.1 K, the conductivity shows T 1/2 dependence in and without m…
Anharmonic decay of high-energy transverse acoustic (TA) phonons satisfying \ensuremath{\Elzxh}\ensuremath{\omega}\ensuremath{\gg}${k}_{B}$T is studied taking account of the elastic anisotropy of real crystalline solids. Dispersive effects are assumed to be small. We find that the decay rate is very anisotropic. The p…
Photoelectron spectroscopy, including emission from the Si 2p core level, was used to investigate the orientation dependence of the photoionization threshold \ensuremath{\xi}(\ensuremath{\alpha}) and the surface position of the valence-band edge below the Fermi level, ${E}_{\mathrm{VFS}}$(\ensuremath{\alpha}), on a cy…
The conduction of diamond implanted with carbon ions, at a target temperature of 250 \ifmmode^\circ\else\textdegree\fi{}C, was studied as a function of ion energy using the electrical sheet resistance of these implanted layers as a probe. It was found that ion doses at which the onset of hopping conduction occurs incr…
High-resolution angle-resolved photoemission has been used to study Al(111) and Al(001). Two new surface states at \ensuremath{\Gamma}\ifmmode\bar\else\textasciimacron\fi{} and K\ifmmode\bar\else\textasciimacron\fi{} of Al(111) were observed and characterized. Their energy positions are in good accord with recent self…
The superconducting transition temperature T c and the sizes of the resistive anomalies due to both the q 1 - and the q 2 -CDW formations are examined on single crystals of Ta-doped NbSe 3 . With addition of Ta, T c increases steeply from below 70 mK to 1.7 K but turns to decrease at 5 at%Ta. The sizes of the resistiv…
Ultraviolet-light excitation of thermochemically reduced ${\mathrm{MgAl}}_{2}$${\mathrm{O}}_{4}$ single crystals below room temperature produces a luminescence band with a peak at 2.69 eV. The excitation spectrum of the 2.69-eV band coincides with the broad F-center absorption band at 5.30 eV. The 2.69-eV band is also…
The band structures and density of states of all polycrystalline forms of ${\mathrm{SiO}}_{2}$ with known crystal structures are calculated using a first-principles orthogonalized linear combination of atomic orbitals method. These include 4:2-coordinated polymorphs of \ensuremath{\alpha}-quartz, \ensuremath{\beta}-qu…
The spontaneous decay rates of LA phonons are calculated in terms of the second- and third-order elastic constants in the isotropic model. It is shown that the dominant decay channel is LA\ensuremath{\rightarrow}TA+TA but not LA\ensuremath{\rightarrow}LA+TA and total decay rates at 1-THz frequency range from ${10}^{5}…
Thermal coupling and etch rate measurements are reported for polyethylene terephthalate and polyimide films irradiated at excimer laser wavelengths of 193, 248, and 308 nm. Thermal energy balance is observed up to a threshold fluence but above this the energy absorbed remains approximately constant, the excess energy…
Neutron and X-ray diffraction studies and magnetization measurements were carried out on single crystals of (Ba 1- x Sr x ) 2 Zn 2 Fe 12 O 22 . The substitution of Ba by Sr produces two effects on the crystal structure: a lattice deformation around the Sr ions and a redistribution of the Zn and Fe ions in the tetrahed…
Self-consistent, spin-polarized energy-band calculations have been performed for MnSb, for both ferromagnetic and antiferromagnetic spin alignments. For ferromagnetic MnSb we find a 3${d}^{5.5}$ configuration on the Mn atom, with a magnetic moment of 3.3${\ensuremath{\mu}}_{B}$ on the Mn sites, and -0.06${\ensuremath{…
The crystal structure of low cristobalite (SiO2) was refined at 10, 293, and 473 K from time-of-flight neutron powder diffraction data. One of the Si-O distances and one Si-O-Si angle change considerably: 10 K, 1.602(1) and 1.617(1) Å, 144.7(1)°; 473 K, 1.605(2) and 1.590(2) Å, 148.4(1)°. The angular distortion of the…
Luminescence yields and decay lifetimes were measured on some metalloporphyrins including the complexes of the IIIb metal group. The S2 emission was observed for AlClTPP (TPP: tetraphenylporphin), GaClTPP, and InClTPP as well as some other TPP metal complexes, ZnP (P:porphin) and H4P2+ (diacid), while it was not detec…
Ion-beam sputter deposition of tantalum oxide films was investigated for possible optical coating applications. Optical properties of such films were found to be a sensitive function of oxygen-to-argon ratio in the ion beam. Refractive index and absorption coefficient were determined in the 250–2000-nm wavelength rang…
Any arbitrary generalized gradient-index interference coating (including homogeneous and inhomogeneous layers) possesses a digital configuration (sequence of thin high- or low-index layers), which is spectrally equivalent at all wavelengths. Such digital configurations are found directly from arbitrary-index profiles…
The ${\mathrm{Ni}}_{80}$${\mathrm{P}}_{20}$ alloy system has been investigated in both liquid and amorphous solid forms using molecular-dynamics computer simulation. Atomic interactions were modeled by central pair potentials selected to represent roughly the atomic sizes and relative bond strengths. Self-diffusion co…
The feasibility of producing erbium-doped silicon light-emitting diodes by molecular beam epitaxy is demonstrated. The p-n junctions are formed by growing an erbium-doped p-type epitaxial silicon layer on an n-type silicon substrate. When the diodes are biased in the forward direction at 77 K they show an intense shar…
The depolarised Rayleigh scattering temperature dependence of the seventh, eighth, ninth and tenth homologues of 4,n-alkyloxybenzoic acid was investigated. A sharp increase of the scattered light intensity upon cooling was observed in the middle of the nematic phase. Polarised microscopic investigations confirmed the…
Single crystal E.P.R. spectra of Fe(III) doped in hexaimidazole zinc(II) dichloride tetrahydrate have been investigated. The spectra are characteristic of Fe(III) occupying a substitutional zinc site and where it is under the influence of a strong tetragonal crystal field from the six imidazole ring nitrogens: superpo…