Structural, electronic, and optical properties of ZnOl_xSex alloys using first-principles calculations

The structural, electronic, and optical properties of binary ZnO, ZnSe compounds, and their ternary ZnOl_xSex alloys are computed using the accurate full potential linearized augmented plane wave plus local orbital （FP-LAPW ＋ lo） method in the rocksalt （B 1） and zincblende （B3） crystallographic phases. The electronic band structures, fundamental energy band gaps, and densities of states for ZnO1_xSex are evaluated in the range 0 〈 x 〈 1 using Wu-Cohen （WC） generalized gradient approximation （GGA） for the exchange-correlation potential. Our calculated results of lattice parameters and bulk modulus reveal a nonlinear variation for pseudo-binary and their ternary alloys in both phases and show a considerable deviation from Vegard＇s law. It is observed that the predicted lattice parameter and bulk modulus are in good agreement with the available experimental and theoretical data. We establish that the composition dependence of band gap is semi-metallic in B1 phase, while a direct band gap is observed in B3 phase. The calculated density of states is described by taking into account the contribution of Zn 3d, O 2p, and Se 4s, and the optical properties are studied in terms of dielectric functions, refractive index, reflectivity, and energy loss function for the B3 phase and are compared with the available experimental data.     

Mechanical behavior of Cu-Zr bulk metallic glasses （BMGs）： A molecular dynamics approach

In the present work, three-dimensional molecular dynamics simulation is carried out to elucidate the nanoindentation behaviors of CuZr Bulk metallic glasses (BMGs). The substrate indenter system is modeled using hybrid interatomic potentials including both many-body Finnis Sinclair (FS) and two-body Morse potentials. A spherical rigid indenter (diameter = 60(1 = 10-10 m)) is employed to simulate the indentation process. Three samples of BMGs including Cu25Zr75 , Cu50Zr50 , and Cu75Zr25 are designed and the metallic glasses are formed by rapid cooling from the melt state at about 2000 K. The radial distribution functions are analyzed to reveal the dynamical evolution of the structure of the atoms with different compositions and different cooling rates. The mechanical behavior can be well understood in terms of load-depth curves and Hardness-depth curves during the nanoindentation process. Our results indicate a positive linear relationship between the hardness and the Cu concentration of the BMG sample. To reveal the importance of cooling rate provided during the processing of BMGs, we investigate the indentation behaviors of Cu50Zr50 at three different quenching rates. Nanoindentation results and radial distribution function (RDF) curves at room temperature indicate that a sample can be made harder and more stable by slowing down the quenching rate.     

Flexible semi‐transparent silicon (100) fabric with high‐k/metal gate devices

Can we build a flexible and transparent truly high performance computer? High‐k/metal gate stack based metal–oxide–semiconductor capacitor devices are monolithically fabricated on industry's most widely used low‐cost bulk single‐crystalline silicon (100) wafers and then released as continuous, mechanically flexible, optically semi‐transparent and high thermal budget compatible silicon fabric with devices. This is the first ever demonstration with this set of materials which allows full degree of freedom to fabricate nanoelectronics devices using state‐of‐the‐art CMOS compatible processes and then to utilize them in an unprecedented way for wide deployment over nearly any kind of shape and architecture surfaces. Electrical characterization shows uncompromising performance of post release devices. Mechanical characterization shows extra‐ordinary flexibility (minimum bending radius of 1 cm) making this generic process attractive to extend the horizon of flexible electronics for truly high performance computers.

     

Thermal recrystallization of physical vapor deposition based germanium thin films on bulk silicon (100)

We demonstrate a simple, low‐cost, and scalable process for obtaining uniform, smooth surfaced, high quality mono‐crystalline germanium (100) thin films on silicon (100). The germanium thin films were deposited on a silicon substrate using plasma‐assisted sputtering based physical vapor deposition. They were crystallized by annealing at various temperatures ranging from 700 °C to 1100 °C. We report that the best quality germanium thin films are obtained above the melting point of germanium (937 °C), thus offering a method for in‐situ Czochralski process. We show well‐behaved high‐κ /metal gate metal–oxide–semiconductor capacitors (MOSCAPs) using this film. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Role of thermal and photobeta decays in processes of nucleosynthesis of problematic p nuclei of 113In, 115Sn, 92,94Mo, and 96,98Ru in massive stars

The temperature dependence of the rates of ¹¹³Cd →¹¹³In, ¹¹⁵In →¹¹⁵Sn, ⁹²Zr→⁹²Nb →⁹²Mo, ⁹⁴Zr→⁹⁴Nb →⁹⁴Mo, ⁹⁶Mo →⁹⁶Tc→⁹⁶Ru, and ⁹⁸Mo→⁹⁸Tc→⁹⁸Ru thermal beta transitions was studied at temperatures of massive-star matter in the range of 1 × 10⁸–6 × 10⁹ K. These decays are the possible channel of synthesis of the p nuclei of ¹¹³In, ¹¹⁵Sn, ⁹²,⁹⁴Mo, and ⁹⁶,⁹⁸Ru. The abundances of these nuclei present a challenge for models that study the explosivemechanism of synthesis. The contribution of photobeta decay to the synthesis of the aforementioned p nuclei was estimated. It was shown that the channel of thermal beta decay for ¹¹³In, ¹¹⁵Sn, ⁹⁴Mo, and ⁹⁸Ru p nuclei and the channel of photobeta decay for the ⁹⁶Mo p nucleus could be efficient at the high-temperature quasiequilibrium stage of massive-star evolution.     

Application of experimental design for optimization of erbium determination by high-resolution continuum source electrothermal atomic absorption spectrometry using lanthanum as a chemical modifier

ABSTRACT

In this paper, lanthanum was used as a chemical modifier for the direct determination of erbium by high-resolution continuum source electrothermal atomic absorption spectrometry. A two-step experimental design was used for optimization, first a full factorial design was conducted for identification of significant factors, and then a central composite design was carried out for final optimization of the significant factors. The optimum parameters were obtained as follows: atomization temperature of 2500°C, pyrolysis temperature of 1600°C, and pyrolysis time of 10?s in the presence of lanthanum as a chemical modifier. Under optimum conditions, the characteristic mass, limit of detection, and limit of quantification were 29?pg, 0.71, and 2.4?µg?L^?1, respectively. The precision of the method, estimated as the relative standard deviation for 10 replicate measurements of 50?µg?L^?1 of erbium, was 1.8%. The optimized method was applied to determine erbium content in sediments and rock samples. The determined values of erbium in sediment certified reference materials were in satisfactory agreement with the certified values according to the t-test for a 95% confidence level.     

Infrared Absorption Study of Some Cyclic Ureas,Cyclic Thioureas and Their N,N′-Dialkyl Derivatives

Abstract

In his communication on the detection limits for thermal emission spectroscopy of metallic species in flame media, Fassel (¹) attacks our previous statement that detection limits for Al, Be and Mo were available only for turbulent oxygen-supported hydrogen or acetylene flames. It should be borne in mind that he was referring to a preliminary communication (²) which naturally does not carry an extensive bibliography. It should also be noted that we were concerned, in context, with a comparison of the separated flame with conventional flames, not with highly unconventional flames such as those to which he refers. Whilst the point with which he takes issue was a very minor one, incorporated in our preliminary communication mainly as an “aside”, we firmly disagree with his observation. The flame he refers to (³) (⁴) is, in fact, a diluted oxy-acetylene flame which is supported by venting some air (and therefore nitrogen) to dilute the fuel-oxygen mixture. Fassel's communication (¹) erroneously refers to this as a 'premixed oxy-acetylene flame', whereas elsewhere (⁵) it is described more correctly as an oxygen-nitrogen-acetylene flame. The burner he long-pathlength carbonaceous flames (¹⁰). They also allow more sensitive molecular emission spectroscopy of sulphur in an air-hydrogen flame (¹¹), etc. We hope that this unfortunate correspondence will not distract attention from the main issue of our previous or previous preliminary communication on the separated nitrous oxide-acetylene flime.     

Common Fixed Point and Invariant Approximation Results for Gregus Type I-Contractions

A fixed point theorem of Ciric, Diviccaro et al., Fisher and Sessa, Gregus, Jungck, and Mukherjee and Verma is generalized to weakly compatible maps. As applications, common fixed point and approximation results for Gregus type I-contractions are obtained. Our results unify and generalize various known results to the more general classes of noncommuting mappings.     

Subweakly Biased Pairs and Jungck Contractions with Applications

The existence of common fixed point results for a weakly biased pair under Jungck contraction is established. We define a new class of subweakly biased pair which properly contains the classes of C _q -commuting, pointwise R-subweakly commuting and R-subweakly commuting maps and establish common fixed point results for this class of maps. As applications several invariant best approximation results are proved which unify, extend, and complement the well-known results.     

Langmuir probe and spectroscopic studies of RF generated helium-nitrogen mixture plasma

This paper reports the effect of helium percentage variation in a capacitive RF helium-nitrogen mixture plasma on various plasma parameters and concentration of nitrogen active species (N₂(C³Π _u) and N₂ ⁺(B²Σ _u ⁺)). Langmuir probe is used for determination of electron energy distribution functions, effective electron temperature, plasma potential and electron density. Optical emission spectroscopy is used for determination of electron temperature from Boltzmann's plot of He–I lines and the relative changes in the concentration of active species by measuring the emission intensities of nitrogen (0-0) bands of the second positive and the first negative systems. The results demonstrate that electron temperature, electron density and concentration of active species increase significantly with increase in helium percentage in the mixture and RF power.