Materials Literature
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The crystal structure of potassium tungsten tetraselenide is based on isolated, slightly distorted WSe4 tetrahedra joined via K+ ions. The compound is isotypic with the previously reported Rb and Cs analogues and crystallizes in the β-K2SO4 structure type.
The atomic structure and tunneling spectra of a cleaved surface of a 2H-NbSe 2 single crystal were studied by scanning tunneling microscopy at 4.2 K. Small domains with \(\sqrt{13} \times \sqrt{13}\) modulation were found adjacent to the flat surface with a 3 ×3 intrinsic charge density wave (CDW). The surface atom ar…
The optical and magnetic properties of the spin-Peierls system, segregated-stack charge-transfer complexes, 1,6-pyrenediamine (DAP)-tetracyanoquinodimethane (TCNQ) and DAP-2,5-dimethyl-TCNQ (DMTCNQ), are investigated to gain insight into the nonlinear excitations in the spin-Peierls system. The band filling of the sys…
The specific heat C of Si:(P,B) with carrier concentration N between 0.8 and 17.8\ifmmode\times\else\texttimes\fi{}${10}^{18}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}$ and compensation ratio varying from 0.25 to 1 was measured in the temperature range between 0.06 and 3 K and in magnetic fields up to 6 T. Above the…
Equations of motion which describe the nonlinear optical response of conjugated polyenes using a collective electronic-oscillator representation are derived. Specific signatures of electronic correlations which enter as anharmonicities and scattering between oscillators are predicted in ultrafast resonant four-wave mi…
The effective dielectric function, effective absorption coefficient and effective refractive index for a model of porous silicon (PS) are calculated using the volume and surface averaging method. The model consists of periodic Si wires with different surface coverages. This approach allows to obtain analytical results…
Wurtzite-type semiconductors such as GaN and ZnO exhibit intrinsic electric-field gradients at the nuclear sites due to the hexagonal lattice symmetry. We have determined these field gradients ${\mathrm{V}}_{\mathrm{ZZ}}$ for all the nuclear sites by a magnetic double-resonance scheme. Shallow donors, which are presen…
We propose and experimentally demonstrate the use of metal-covered lamellar relief gratings as a polarizing beam splitter operating at a single wavelength near Littrow incidence. We report the characteristics of a grating produced by holography and reactive ion etching that was calculated for operation as beam splitte…
We present low-energy electron-diffraction (LEED) and photoemission measurements of single-crystal surfaces of ${\mathrm{VO}}_{2}$ , made possible using samples oriented and characterized in situ. LEED shows that the (100) surface has a (1\ifmmode\times\else\texttimes\fi{}2) reconstruction, but the (110) and (101) sur…
Nanometer-scale crystal silicon films surrounded by ${\mathrm{SiO}}_{2}$ were prepared by oxidizing silicon-on-insulator substrates prepared from SIMOX (separation by implantation of oxygen) and crystallized hydrogenated amorphous silicon films. Average silicon layer thickness was determined from reflection spectra. W…
The Auger-emission process from solids can be very complex, with a variety of processes producing intensity in the final spectra. The ${\mathrm{L}}_{2,3}$-${\mathrm{M}}_{4,5}$${\mathrm{M}}_{4,5}$ (${\mathrm{L}}_{2,3}$-MM) Auger spectra of the 3d transition metals, in particular, show many complicating effects. Auger p…
The origin of magnetic coupling in ${\mathrm{KNiF}}_{3}$ and ${\mathrm{K}}_{2}$ ${\mathrm{NiF}}_{4}$ is studied by means of an ab initio cluster model approach. By a detailed study of the mapping between eigenstates of the exact nonrelativistic and spin model Hamiltonians it is possible to obtain the magnetic coupling…
An expression of refractive indices for AlGaAs is presented which agrees reasonably with the experimental results by H. C. Casey Jr., D. D. Shell, and M. B. Panish [Appl. Phys. Lett. 24, 63 (1974)]. This expression is approximately derived by using the method of least squares and is applicable to a determination of th…
The purpose of the present paper is to report the crystal structure of a new phase of tetralithium diphosphate identified by single-crystal X-ray diffraction. The structure consists of layers built from Li—O tetrahedra and pyrophosphate groups connected to each other through edges and vertices.
We present an extension of the configurational bias Monte Carlo method for the efficient simulation of off–lattice polymer systems. Elementary moves consist in regrowing internal segments of a polymer chain. We show that the method satisfies the detailed balance condition. We apply it to three well known simple models…
The exciton and two-exciton states in semiconductor quantum dots much larger in size than the exciton Bohr radius are investigated, and the energies and oscillator strengths of several exciton and biexciton states are calculated. The presence of weakly correlated exciton-pair states are identified and these have a lar…
Although the AlxGa1−xAs alloy system has been extensively investigated, there are still considerable uncertainties in measuring the value of x. Here a new AlxGa1−xAs calibration structure, grown by molecular beam epitaxy, has been used to establish unambiguous alloy compositions. Such “standard’’ AlxGa1−xAs layers wer…
We present theoretical results for the frequency-dependent dielectric response, both for the electric field parallel and perpendicular to the c axis of graphite. The calculations are performed using a full-potential linear muffin-tin orbital method. Our calculations show fair agreement with experimental data and the d…
Silica glasses were repeatedly densified by multiple shock reverberations in stainless-steel capsules. The limit of increase in density was about 2.47 Mg/m3 after the first shock loading. Further increase in density was observed after duplicate shock loading, but limited at about 2.55 Mg/m3. Triplicate shock loading w…
We used x-ray photoelectron spectroscopy to investigate the chemistry of O impurity atoms in CdS thin films grown for photovoltaic purposes by chemical-bath deposition (CBD). We compared the Cd 3d photoline, O 1s photoline, Cd MNN Auger line, and O KLL Auger line taken from a CBD CdS thin film, CdS single-crystal refe…