Transistors made in laser recrystallized polysilicon on insulator films

lpcvd polycrystalline silicon films were deposited on thermally oxidized silicon as well as onlpcvd silicon nitride deposited on silicon. Acw argon ion laser was used to recrystallize the polysilicon film into large grains (grain size from 5μm to 40μm). Boron was then implanted and standard N-channel silicon gate process and N-channel metal gate process were carried out to realisemosfets on this material. Channel mobilities upto 450 cm²/V-sec for electrons have been measured. This thin filmmosfet has a four-terminal structure with a top and a bottom gate and the influence of one gate on the drain current due to the other gate has been investigated. Comparison of theI _D v-V _D curves of the devices with physical models was found in good agreement.     

Optical properties of bismuth granules in a glass matrix

Optical absorption characteristics for ultra-fine bismuth particles having dimensions around 10 nm and dispersed in both silicate and vanadium phosphate glass matrices have been investigated in the wavelength range 300 to 700 nm. Bismuth particles in vanadium phosphate matrix show an absorption peak around 440 nm whereas in silicate glass matrix they give two peaks in the ranges 500 to 530 nm and 420 to 430 nm respectively. The peak positions in all the glass-bismuth metal systems are predicted in fair agreement with experiment by Maxwell-Garnett (mg), as extended by Polder and van Santen (mg-pvs) and Bruggeman (br) effective medium theories. It is observed, however, thatmg-pvs andbr models give the best fit to experimental data over the entire wavelength range studied.     

Controllable synthesis of TiO2 nanomaterials by assisting with l-cysteine and ethylenediamine

This paper reports a facile l-cysteine-assisted solvothermal synthesis of TiO₂ nanomaterials using ethylenediamine (En) and distilled water as solvent. The influence of reaction time, temperature, l-cysteine and solvent was initially investigated. Results demonstrated the reaction temperature, l-cysteine and En significantly imposed impact on the phase and morphology of the particles. Amorphous nanosheets, mixed-crystal nanorods and pure anatase nanoparticles were controllably synthesized by varying reaction temperature. The formation of the amorphous nanosheets and mixed-crystal nanorods were directly affected by the presence of l-cysteine and En. And the presence of En distinctly affected the crystal phase of the products, which was rarely mentioned in other studies. Moreover, the photocatalytic activities of three typical samples were excellent. The possible formation mechanism of the sample was also discussed.     

Assessment of research fields in Scopus and Web of Science in the view of national research evaluation in Slovenia

Web of Science (wos) and scopus have often been compared with regard to user interface, countries, institutions, author sets, etc., but rarely employing a more systematic assessment of major research fields and national production. The aim of this study was to appraise the differences among major research fields in scopus and wos based on a standardized classification of fields and assessed for the case of an entire country (Slovenia). We analyzed all documents and citations received by authors who were actively engaged in research in Slovenia between 1996 and 2011 (50,000 unique documents by 10,000 researchers). Documents were tracked and linked to scopus and wos using complex algorithms in the Slovenian cobiss bibliographic system and sicris research system where the subject areas or research fields of all documents are harmonized by the Frascati/oecd classification, thus offsetting some major differences between wos and scopus in database-specific subject schemes as well as limitations of deriving data directly from databases. scopus leads over wos in indexed documents as well as citations in all research fields. This is especially evident in social sciences, humanities, and engineering & technology. The least citations per document were received in humanities and most citations in medical and natural sciences, which exhibit similar counts. Engineering & technology reveals only half the citations per document compared to the previous two fields. Agriculture is found in the middle. The established differences between databases and research fields provide the Slovenian research funding agency with additional criteria for a more balanced evaluation of research.     

Photoluminescence,thermally stimulated luminescence and electron paramagnetic resonance studies of U6+ doped BaSO4

U⁶⁺ doped BaSO₄ samples were synthesized by precipitation route. PL, TL and EPR investigations of γ and self α irradiated samples were carried out. PL spectra of these samples give structured broad band peaking around 518 nm with five vibronic bands centred around 498·4, 516·0, 533·7, 554·0 and 575·1 nm, respectively and the average frequency of symmetric stretching of O=U=O in the ground electronic state was found to be 674 cm^?1. Trap level spectroscopic studies of U doped BaSO₄ give glow peaks at 411, 488 and 512 K, respectively and their spectral characteristics are typical of UO \(_{2}^{2+}\) emission. EPR studies of γ-irradiated U⁶⁺:BaSO₄ sample have shown the presence of sulphoxy centred radicals like SO \(_{4}^{-}\) and SO \(_{3}^{-}\) in addition to OH^?, O \(_{3}^{-}\) and SH^2?. TSL peaks at 411 and 488 K were correlated with thermal destruction of SO \(_{4}^{-}\) and SO \(_{3}^{-}\) radicals.     

Yield criteria of hexagonal symmetry in the π-plane

The theory of plasticity operates with different yield criteria of incompressible behavior for isotropic materials. Mostly known are the criteria of Tresca, Schmidt-Ishlinsky and von Mises. The first two criteria have a hexagonal symmetry, and the criterion of von Mises has a rotational symmetry in the π-plane. All these criteria do not distinguish between tension and compression (no strength differential effect), but numerous problems are treated in the engineering practice using these criteria. Within this paper, the yield criteria with hexagonal symmetry for isotropic incompressible materials are compared. For this purpose, their geometries in the π-plane will be presented in polar coordinates. The radii at the angles of 15^? and 30^? will be related to the radius at 0^?. Based on these two relations, well-known criteria will be shown in one diagram. The extreme shapes of the yield surfaces are restricted by two criteria: the unified yield criterion (UYC) and the multiplicative ansatz criterion (MAC). The examinations of the UYC and MAC depict a linear combination of these extreme yield surfaces. The resulting criterion with two parameters describes all possible convex forms of hexagonal symmetry. On the other hand, this criterion has one disadvantage: It is not possible to solve explicitly the equation for the equivalent stress. Other known criteria (Sokolovsky, Ishlinsky-Ivlev, Dodd-Naruse, Drucker) are depicted in the proposed diagram and compared with the above mentioned criteria. Further criteria are derived from the consideration of solids with orthogonal symmetry planes in the shear stress space. New criteria are introduced for practical applications. The constraints of convexity are established for them. The proposed consideration of the yield criteria simplifies the selection of a proper criterion. The extreme solutions for the analysis of construction parts can be found using these criteria.     

A structure-preserving energy function for stability analysis of AC/DC systems

Direct stability analysis ofAC/DC power systems using a structure-preserving energy function (SPEF) is proposed in this paper. The system model considered retains the load buses thereby enabling the representation of nonlinear voltage dependent loads. TheHVDC system is represented with the same degree of detail as is normally done in transient stability simulation. The converter controllers can be represented by simplified or detailed models. Two or multi-terminalDC systems can be considered. The stability analysis is illustrated with a 3-machine system example and encouraging results have been obtained.     

Electrical behaviour of doped-yttria stabilized zirconia ceramic materials

Single-phase sintered ceramic materials (ZrO₂)_1?x {(Y₂O₃) _y (RE₂O₃)_{1-y x} }_x (RE=Nd, Ce, Dy, Er), were synthesized and electrical conductivity and transport number measurements were made as a function of temperature between 500 and 1200° C. The activation energies of conduction were determined, and it was found that the charge carriers in these solid solutions are oxygen ions. The fabricated electrolyte discs were used in cells of the type \(P_{O_2 }\) , Pt/zirconia solid solution/ \(P_{\mathop O\limits^{'} _2 }\) , platinum where \(P_{O_2 }\) =air (0.21 atm) and \(P_{\mathop O\limits^{'} _2 }\) =1 atm or argon-O₂ mixtures. Below 700° C, the e.m.f. deviated from the theoretical values for completely ionic conduction; good agreement was observed above this temperature.     

Internal oxidation of Fe-Si alloys in γ-phase region

Internal oxidation measurements of Fe-0.070, 0.219, 0.483, and 0.920 wt % Si alloys were made in the γ-phase region in order to discuss kinetics of internal oxidation, to evaluate the diffusion coefficient of oxygen in the internal oxidation layer, and to determine the diffusion coefficient of oxygen in γ-iron. Internal oxidation of these alloys was conducted at temperatures between 1223 and 1323 K using a powder mixture of iron and Fe₂O₃. The internal oxidation front in Fe-Si alloys with between 0.070 and 0.483 wt % Si advances in parallel to the specimen surface. The internal oxidation in these alloys obeys a parabolic rate law, which indicates that the internal oxidation is controlled by an oxygen diffusion process in the alloy. The diffusion coefficient of oxygen, D _O ^IO , in the internal oxidation layer where SiO₂ particles disperse was determined by using the thermodynamic data for the solution of oxygen in γ-iron. D _O ^IO increases with the increase of the volume fraction of the oxide, f ^IO, in the oxidation layer at a given temperature. The diffusion coefficient of oxygen, D _O, in γ-iron was evaluated by extrapolating D _O ^IO to f ^IO=0. D _O may be given by the following equation: $$D_O = \left( {6.42\begin{array}{*{20}c} { + 4.37} \\ { - 2.60} \\ \end{array} } \right) \times 10^{ - 5} exp \left[ { - \frac{{159 \pm 5(kj mol^{ - 1} )}}{{RT}}} \right]m^2 \sec ^{ - 1} $$ .     

Phase relations in M 2 I O-P2O5-Fe2O3-CaO(CaF2) (MI = Na, K) high-temperature solutions and the structure of Na2.5CaFe1.5(PO4)3

Phase relations in high-temperature solutions of the M ₂ ^I O-P₂O₅-Fe₂O₃-CaO(CaF₂) (M^I = Na, K) systems (M ₂ ^I O/P₂O₅ = 0.7, 1.0, 1.3; Ca/P = 0.3; Ca/Fe = 1.0; Δt = 1000–680°C) have been studied. The nature of the calcium precursor has been shown to influence the phase relations in the multicomponent alkali metal phosphate high-temperature solutions. The synthesized compounds have been characterized by X-ray powder diffraction and IR spectroscopy, and the crystal structure of the new phosphate Na_2.5CaFe_1.5(PO₄)₃ has been determined by single-crystal X-ray structure analysis.     

Insights into the structural,electronic, and magnetic properties of Fe2−x Ti x O3/Fe2O3 thin films with x = 0.44 grown on Al2O3 (0001)

The interface between hematite (α-Fe ₂ ^III O₃) and ilmenite (Fe^IITiO₃), a weak ferrimagnet and an antiferromagnet, respectively, has been suggested to be strongly ferrimagnetic due to the formation of a mixed valence layer of Fe²⁺/Fe³⁺ (1:1 ratio) caused by compensation of charge mismatch at the chemically abrupt boundary. Here, we report for the first time direct experimental evidence for a chemically distinct layer emerging at heterointerfaces in the hematite—Ti-doped-hematite system. Using molecular beam epitaxy, we have grown thin films (~25 nm thickness) of α-Fe₂O₃ on α-Al₂O₃ (0001) substrates, which were capped with a ~25 nm thick Fe_2?x Ti _x O₃ layer (x = 0.44). An additional 3 nm cap of α-Fe₂O₃ was deposited on top. The films were structurally characterized in situ with surface X-ray diffraction, which showed a partial low index orientation relationship between film and substrate in terms of the [0001] axis and revealed two predominant domains with \( (0001) _{{{\text{Fe}}_{2} {\text{O}}_{3} }} \;||\;(0001) _{{{\text{Al}}_{2} {\text{O}}_{3} }}, \) one with \( [10\bar{1}0]_{{{\text{Fe}}_{2} {\text{O}}_{3} }} \;||\;[10\bar{1}0]_{{{\text{Al}}_{2} {\text{O}}_{3} }}, \) and a twin domain with \( [01\bar{1}0]_{{{\text{Fe}}_{2} {\text{O}}_{3} }} \;||\;\;[10\bar{1}0]_{{{\text{Al}}_{2} {\text{O}}_{3} }}. \) Electron energy loss spectroscopy profiles across the Fe_2?x Ti _x O₃/Fe₂O₃ interface show that Fe²⁺/Fe³⁺ ratios peak right at the interface. This strongly suggests the formation of a chemically distinct interface layer, which might also be magnetically distinct as indicated by the observed magnetic enhancement in the Fe_2?x Ti _x O₃/α-Fe₂O₃/Al₂O₃ system compared to the pure α-Fe₂O₃/Al₂O₃ system.     

Improved microwave dielectric properties of La(Mg0.5Sn0.5)O3 ceramic with Ba2+ substitution

The microwave dielectric properties of La(Mg_0.5?xBa_xSn_0.5)O₃ ceramics were examined with a view to their exploitation for wireless communications. The La(Mg_0.5?xBa_xSn_0.5)O₃ ceramics were prepared by the conventional solid-state method with various sintering temperatures. The La(Mg_0.5?xBa_xSn_0.5)O₃ ceramics contained La₂Sn₂O₇. An apparent density of 6.54 g/cm³, a dielectric constant ( $ \varepsilon_{r} $ ε r ) of 20.1, a quality factor (Q  $ \times $ ×  f) of 51,600 GHz, and a temperature coefficient of resonant frequency ( $ \tau_{f} $ τ f ) of ?82 ppm/°C were obtained for La(Mg_0.43Ba_0.07Sn_0.5)O₃ ceramics that were sintered at 1,550 °C for 4 h.     

Thermodynamic Functions of Fermi Gas with Quadruple BCS-Type Binding Potential with d_{x^2 - y^2 } -Wave-Pairing Symmetry

A gas of spin 1/2 fermions with an interaction V+W = -|Λ|^-1 ∑_k,k′ g _k,k′χ(k)χ(k′) $b_{\text{k}}^{\text{*}} b_{ - {\text{k}}}^{\text{*}}$ b _k′ b _-k′ - 2γ ∑_kχ(k)n _k+ n _k-, where n _k± = $a_{{\text{k}} \pm }^{\text{*}}$ a _k±, b _k = a _k+ a _k- and a _kσ, $a_{{\text{k'}}\sigma '}^{\text{*}}$ satisfy Fermi anticommutation relations, is investigated in the $d_{x^2 - y^2}$ -pairing case. W+V₄ is nonzero only within a thin layer of one-fermion energies around the chemical potential μ, and χ(k) denotes the characteristic function of the corresponding range of momenta. Two cases are studied: 1⁰ γ = 0, 2⁰ γ = 0.10025 eV. In the first case the system exhibits a first order transition, in the second, the transition is second order. Temperature dependence of the system's thermodynamic functions is examined and compared with that of the s-pairing case.     

Surface and grain-boundary energies in yttria-stabilized zirconia (YSZ-8 mol%)

The multiphase equilibration technique has been used to measure the equilibrium angles that develop at the interphase boundaries of a solid-liquid-vapour system after annealing and also the surface (γ_sv)and the grain-boundary, (γ_ss) energies of polycrystalline yttria-stabilized zirconia (8 mol% Y₂O₃). The data was recorded in the temperature range 1573–1873 K. Linear temperature functions were obtained for the surface energy $$\gamma _{SV} (Jm^{ - 2} ) = 1.927 - 0.428x10^{ - 3} T$$ and for the grain-boundary energy $$\gamma _{SS} (Jm^{ - 2} ) = 1.215 - 0.358x10^{ - 3} T$$      

Analogies between Kirchhoff plates and Saint-Venant beams under flexure

New exact solutions for isotropic Kirchhoff plates, with no kinematic boundary constraints, are inferred by an analogy with the cross-section warping of orthotropic, homogeneous Saint-Venant beams bent and twisted by a shear force. The procedure is based on a formal equivalence between the elastic equilibrium conditions, respectively, for the tangential stresses in terms of a warping function in a Saint-Venant beam and for the bending–twisting moment in a Kirchhoff plate. The analysis refers to simply or multiply connected plates with an isotropic elastic stiffness proportional to the beams warping function. The result extends the one provided by the author for the special case of simple torsion (Barretta, Acta Mech 224(12):2955–2964, 2013). An example for a circular plate is developed, thus providing a new benchmark for computational mechanics.     

Functionalization and characterization of ZnS quantum dots using biocompatible l-cysteine

In this work, the functionalization of ZnS quantum dots using the thiol group of l-cysteine for different concentrations has been reported. Chemical precipitation method was used for the synthesis of nascent as well as l-cysteine functionalized ZnS quantum dots for optimized values of pH and molar concentrations of the precursors. Morphological studies were done by X-ray diffraction (XRD) and TEM. Optical measurements were done by UV–visible, Fourier transform infrared (FTIR) and energy resolved photoluminescence studies. Particle size was calculated by using Brus equation. Appreciable changes in morphological and optical properties of ZnS quantum dots were observed in few cases. XRD results shows that, the primary crystallite size decreases with increasing the capping concentration, however, the crystal structure remain same for all the used concentrations of l-cysteine. UV–visible analysis shows that band gap and particle size is also tunable with l-cysteine capping. FTIR studies confirmed l-cysteine capping on the surface of quantum dots. As l-cysteine is non toxic and stable compound, the surface modification of ZnS quantum dots with l-cysteine not only prevents the aggregation of quantum dots but also make them available for the interaction with the target materials and make them suitable for specific biomedical applications.     

Novel antibacterial electrospun mats based on poly(d,l-lactide) nanofibers and zinc oxide nanoparticles

This investigation addresses the morphological, mechanical, and antibacterial evaluation of nanocomposite mats based on poly(d,l-lactide) nanofibers with different zinc oxide nanoparticles (nano-ZnO) concentration, that were elaborated by two techniques, i.e., electrospinning of polymer/ZnO solutions and the combination of electrospinning of polymer solutions with electrospraying of nano-ZnO dispersions. The analysis of the precursory solutions was carried out in order to understand the achieved morphology of nanofibers. The obtained poly(d,l-lactide)/ZnO fibrous mats showed a uniform morphology with an average porosity ca. 55 % and average pore size around 45 μm. The presence of ZnO nanoparticles increased the toughness of the mats, and an optimal nano-ZnO concentration (i.e., 3 wt%) was observed at which the tensile strength and Young’s modulus could be improved. Concerning to the antibacterial properties, a relatively low concentration of nanoparticles provoked a growth inhibition of the Gram-negative Escherichia coli and the Gram-positive Staphylococcus aureus bacteria. The mats have potential features for use as antimicrobial wound dressings.     

Scanning transmission electron microscopy and microdiffraction techniques

At the moment scanning transmission electron microscopy (stem) instruments are not competetive with conventionaltem instruments for high resolution bright field imaging. For studies of the structure and defects of crystalline materials, their special virtues lie in the application of dark field imaging modes combined with observations of microdiffraction patterns from regions of diameter comparable with the microscope resolution limit (currently about 5 Å). They also offer capabilities for microanalysis by use of energy dispersive x-ray spectroscopy (eds) or electron energy loss spectroscopy (els). In principle the spatial resolution of these microanalysis methods is comparable to that of the imaging modes but in practice it is limited by poor signal-to-noise ratios or by the nonlocalized nature of the inelastic scattering process. The capabilities for microdiffraction are illustrated by sequences of diffraction patterns obtained as the incident beam is moved within the unit cell of a crystal of large (20 Å) periodicity. Applications of more immediate practical significance include diffraction studies of small crystallites of gold 20 to 50 Å in diameter and of the near-amorphous, thin oxide layers formed on chromium and iron films at room temperature. Microdiffraction, combined with reflection electron microscopy andels analysis, provides a powerful new approach to the study of the surface structure of crystals, including bulk samples, and the investigation of surface reactions. In particular, if a beam of small diameter (10–20 Å) is made to run along the face of a small crystal, the diffraction pattern andels curves are very sensitive to the form of the potential distribution at the surface and the excitations of the surface states of the crystal.     

Is There a Unified Description of Conductivity of Layered Cuprates ?

We present a novel approach to the analysis of the normal state in-plane $\sigma _{ab} $ and out-of-plane σ_c conductivities of anisotropic layered crystals such as oxygen deficient YBa ₂ Cu ₃ O _x . It can be shown that the resistive anisotropy is determined by the ratio of the phase coherence lengths in the respective directions; i.e., $\sigma _{ab} /\sigma _c = \ell _{ab}^2 /\ell _c^2 $ . From the idea that at all doping levels and temperatures T the out-of-plane transport in these crystals is incoherent, follows that $\ell _c $ is T-independent, equal to the spacing $\ell _0 $ between the neighboring bilayers. Thus, the T-dependence of $\ell _{ab} $ is given by the measured anisotropy, and $\sigma _{ab} (\ell _{ab} )$ dependence is obtained by plotting $\sigma _{ab} {\text{ }}vs{\text{ }}\ell = {\text{ (}}\sigma _{ab} /\sigma _c )^{1/2} \ell _0 $ .The analysis of several single crystals of YBa ₂ Cu ₃ O _x (6.35 < x < 6.93) shows that for all of them $\sigma _{ab} (\ell ) $ is described by a universal dependence $\sigma _{ab} /\overline \sigma = f(\ell /\overline \ell ) $ with doping dependent parameters $\overline \sigma {\text{ }}and{\text{ }}\overline \ell $ .