Materials Literature
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Temperature dependences of the dark conductivity and the photoconductivity for amorphous thin films of Ga 30 Se 70-x In x in the temperature range 298-328 K have been reported. The dark conductivity and the photoconductivity increase at all temperatures as the concentration of In (x=0, 5, 10, 15 and 20) increases. The…
Weak, low frequency disorder induced Raman scattering is observed in nanocrystalline, ‘‘glassy’’ carbon having an in-plane correlation length La≂30 Å. Similar, relatively more intense low frequency scattering is observed after the annealing of amorphous carbon films to 600 °C, suggesting the formation of quite small n…
Thin films of BaTiO3 were deposited on platinum coated silicon substrates by excimer laser (248 nm) ablation at 600 °C or ex situ crystallized at about the same annealing temperature. Films deposited at 600 °C showed good crystallinity and were characterized for ferroelectricity, dielectric constant, dielectric loss,…
Visible photoluminescence has been observed in crystallized a-Si:H/a-SiNx:H multiquantum-well structures at room temperature. The MQW heterostructures consisting of 72 layers were formed by computer controlled plasma-enhanced chemical-vapor deposition method and then crystallized by Ar+ laser annealing technique. The…
Siloxene (${\mathrm{Si}}_{6}$${\mathrm{O}}_{3}$${\mathrm{H}}_{6}$) and its derivatives show strong visible luminescence. By applying semiempirical quantum chemical calculations to the siloxene structure, we demonstrate that the presence of oxygen in a planar array of silicon atoms results in molecular orbitals confine…
We present carbon K emission spectra of diamond excited with high-resolution undulator radiation. The valence-band emission spectra are shown to be strongly dependent on the excitation energy, up to 20--30 eV above the C K edge. It is proposed that the dependence is indicative of the resonant inelastic scattering desc…
Abstract This paper presents a proprietary process developed to manufacture polyurethane (PU) pultruded composites. The blocked isocyanate (NCO)‐terminated PU prepolymer synthesized in this study was prepared from ε‐caprolactam blocked blends of toluene diisocyanate (TDI) and branched polyester. The processability and…
Abstract The photograftings of methacrylic acid (MAA), acrylic acid (AA), methacrylamide (MAAm), and acrylamide (AAm) as hydrophilic monomers onto polyethylene (PE) plates were carried out in the liquid phase. The contact‐angle measurement and the surface analysis by ESCA reveal that the grafted amount at which the PE…
The authors show that the phenomenological renormalization-group analysis based on the finite-size scaling hypothesis is very effective in analysing the critical properties of the localization-delocalization transition (LDT) of the wavefunctions in quasiperiodic systems. They have applied it successfully to the LDT of…
A neutron powder diffraction refinement of the structure parameters of five samples of magnesium cobalt oxide spinels Mg x Co 3-x O 4 (0<x<1) has been carried out. It was found that all spinels under study are inverse and there is a limit to the occupancy of the tetrahedral sites by Mg.
The photoluminescence of intentionally vanadium-doped ZnSe crystals displays at low temperatures (T approximately=4 K) the emission of the V 3+ (d 2 ), V 2+ (d 3 ) and V + (d 4 ) ions with different no-phonon structures at 5440, 4740 and 3640 cm -1 , respectively. The excitation spectra of the V 3+ and V 2+ luminescen…
It was demonstrated that the MgIn2O4 spinel is a very promising material as a transparent electronic conductor. By the measurements of diffuse reflectance spectra, the optical band gap of MgIn2O4 (∼3.4 eV) was found to be wider than that of ITO (indium tin oxide). Electrical conductivity of the sintered sample of MgIn…
We theoretically investigate excitonic effects on the optical properties of silicon quantum wires, based on ab initio electronic structure calculations. The Si wires have a direct, allowed band gap in the visible energy range and exhibit a strong optical anisotropy. Taking into account the electron-hole Coulomb intera…
We have performed photoluminescence studies on porous, p-type as well as n-type silicon wafers which have been prepared in air or in a dry nitrogen atmosphere, utilizing a spark-erosion technique. This sample preparation, which does not involve aqueous solutions or fluorine contaminants, yields similar photoluminescen…
We have calculated the electronic structure of spherical silicon crystallites containing up to 2058 Si atoms. We predict a variation of the optical band gap with respect to the size of the crystallites in very good agreement with available experimental results. We also calculate the electron-hole recombination time wh…
For the first time the emission properties of Tm3+ doped Y3Al5O12 are studied in the near UV and visible ranges at 4.2 and 295 K. The observed emission peaks are ascribed to the transitions between Tm3+ energy levels and an overall energy level scheme of the Tm3+ ion in Y3Al5O12 with radiative and nonradiative transit…
Vacancy behavior in Cu-26 Zn-4 Al and Cu-14 Al-4 Ni alloys during ageing is investigated and compared by means of positron annihilation (PA) and electrical resistivity measurements. For ageing in the martensitic state after direct quenching, the experimental results show that the S parameter of CuZnAl specimens, mea…
The EPR spectra of manganese in polycrystalline BaTiO3 and n-BaTiO3 (lanthanum-doped BaTiO3) are studied. The measurements are carried out in all four phases of BaTiO3 to follow the phase transformations of the ceramic material by means of the microscopic probe manganese. The valence state of manganese in BaTiO3 and n…
The optical transmission spectra of amorphous AsS films of composition As32S68 prepared by thermal evaporation are measured over the 0.3 to 2.0 μm spectral region. A simple straightforward procedure suggested by Swanepoel is applied for determining the index of refraction and layer thickness; the absorption coefficie…
Crystal structure of intermediate phase of PbZrO 3 was analyzed by neutron powder diffraction. Superlattice reflections of our sample appeared at M and R points. Intensities of fundamental reflections also changed in the phase. The structural modulations were associated with modes either Γ 15 + M 3 + R 25 or Γ 15 + M…