First principles calculation of the opto-electronic properties of (110) growth axis SiGe superlattices

Using two versions of the first principles full potential linear muffin-tin orbitals method (FPLMTO) which enable an accurate treatment of the interstitial regions, the electronic and optical properties of (110) growth axis Si/SiGe superlattices are investigated. A comparative study with (001) growth axis superlattices is made. In particular, it is found that the bottom of the conduction band (CB) is closer to Γ$\Gamma$ in the (110) system but the optical activity is not enhanced. Furthermore, the absorption spectra of the superlattices are calculated and are found to be quite different from those of bulk Si and Ge but fairly close to their average.     

Alloy formation at the Ni–Al interface for nickel films deposited on Al(110) surfaces

Alloy formation at the Ni–Al interface for thin nickel films deposited on Al(110) surfaces has been studied using high-energy ion scattering/channeling (HEIS) and X-ray photoelectron spectroscopy (XPS). For nickel atoms deposited at room temperature on Al(110), a large amount of nickel–aluminum intermixing occurs at the interface. For the first two monolayers (ML) of deposited nickel, an NiAl-like compound is formed. The intermixing continues with a different rate, forming an Ni₃Al-like compound for nickel coverages from 2 to 8 ML, at which point a nickel metal film begins to grow on the surface. Nickel atoms deposited at 250°C on the Al(110) surface exhibit no surface compound formation, but diffuse up to 400 Å into the aluminum substrate. Interatomic potentials based on the embedded-atom method (EAM) are used in a Monte Carlo approach to simulate the evolution of the Ni–Al(110) interface as a function of the nickel coverage. The calculated ion-scattering yields and X-ray photoelectron intensities from nickel and aluminum atoms in these simulated interfaces are in good quantitative agreement with the experimental results. The simulations show a high-density Ni–Al alloy forming at the Al(110) surface which apparently inhibits outward diffusion of aluminum, leading to the more nickel-rich alloy and finally nickel film growth. The ion-scattering simulations show an unusually large amount of backscattering occurring below the Ni–Al(110) interface, apparently associated with defocusing of the incident ion beam.     

Effect of sintering temperature and soaking time on the magnetic properties and transmission behavior of nano crystalline Mg0.8Mn0.2Al0.1Fe1.9O4

Journal of Sol-Gel Science and Technology - In this study, Mg–Mn–Al ferrite with a chemical composition of Mg0.8Mn0.2Al0.1Fe1.9O4 was synthesized via the sol–gel auto-combustion...     

The effects of surface treated carbon fibers and CaCO<Subscript>3</Subscript> nanoparticles inclusions on the mechanical performances of PA6/ABS-based composites

The mechanical and morphological characteristics of PA6/ABS (60/40)-based hybrid composite containing HNO₃-treated short carbon fibers (HSCF) and CaCO₃ nanoparticles have been experimentally studied. A counter-rotating twin-screw extruder and an injection molding machine were employed to produce different samples containing 10 wt % of HSCF and 0, 2, 5 and 8 wt % of CaCO₃ nanoparticles. The SEM observations indicated high-quality adhesion between HNO₃-surface treated carbon fibers and PA6/ABS polymer matrix. In addition, the morphological studies showed that the inclusion of CaCO₃ nanoparticles caused a significant effect on the ABS particle dispersion in PA6/ABS matrix. The mechanical properties assessments revealed that the incorporation of 10 wt % HSCF into the PA6/ABS can significantly improve tensile strength (82%), tensile modulus (107%), flexural strength (98%), flexural modulus (104%) and impact resistance (24%). The inclusion of CaCO₃ nanoparticles, in the presence of 10 wt % HSCF, led to the noticeable improvements of tensile strength (128% for 2 wt % CaCO₃), tensile modulus (199% for 5 wt % CaCO₃), flexural strength (146% for 5 wt % CaCO₃), flexural modulus (204% for 5 wt % CaCO₃) and impact resistance (46% for 2 wt % CaCO₃). The surface treatment of carbon fibers, dispersion conditions of nanoparticles and ABS phase in polymeric matrix were found to be the major important factors affecting the mechanical properties.     

Electronic properties of cubic ScGaAs and ScGaN ternaries and superlattices

The electronic properties of both Sc_xGa_1−xAs and Sc_xGa_1−xN ternary alloy and superlattice systems are investigated within the first-principles full-potential linear muffin-tin orbitals method (FPLMTO) in its atomic sphere approximation (ASA) using the technique of empty spheres, which allows an accurate treatment of the interstitial regions. The phase transition from the rocksalt (B1) to the zinc blende (B3) structure is investigated and the possibility of zinc blende/zinc blende GaN/Sc_xGa_1−xN and GaAs/Sc_xGa_1−xAs superlattices is expected. Wide and direct gaps are found to be possible in these systems, predicting them as good candidates for optoelectronic applications.     

Cross-ranking of Decision Making Units in Data Envelopment Analysis

Data Envelopment Analysis (DEA) is a mathematical model that evaluates the relative efficiency of Decision Making Units (DMUs) with multiple input and output. In some applications of DEA, ranking of the DMUs are important. For this purpose, a number of approaches have been introduced. Among them is the cross-efficiency method. The method utilizes the result of the cross-efficiency matrix and averages the cross-efficiency scores of each DMU. Ranking is then performed based on the average efficiency scores. In this paper, we proposed a new way of handling the information from the cross-efficiency matrix. Based on the notion that the ranking order is more important than individual efficiency score, the cross-efficiency matrix is converted to a cross-ranking matrix. A cross-ranking matrix is basically a cross-efficiency matrix with the efficiency score of each element being replaced with the ranking order of that efficiency score with respect to the other efficiency scores in a column. By so doing, each DMU assume the role of a decision maker and how they voted or ranked the other DMUs are reflected in their respective column of the cross-ranking matrix. These votes are then aggregated using a preference aggregation method to determine the overall ranking of the DMUs. Comparison with an existing cross-efficiency method indicates a relatively better result through usage of the proposed method.     

Growth of ultrathin Pd films on Al(001) surfaces

High-energy ion backscattering spectroscopy (HEIS) and X-ray photoelectron spectroscopy (XPS) were used to determine the growth mode and the interface structure of ultrathin Pd films deposited on Al(001) surfaces at room temperature. Measured Al and Pd surface peak areas for MeV He⁺ ions incident normal to the surface show that Pd atoms intermix with and displace Al substrate atoms. The mixing continues for Pd coverages from 0–5 monolayers, at which point a Pd metal film begins to grow on the alloy surface. XPS measurements of the Pd 3d photopeaks show a chemical shift that is consistent with the formation of an AlPd-like compound during the mixing phase, and Pd metal thereafter. HEIS results further reveal that the alloyed overlayer as well as the Pd metal film have some degree of axial alignment with respect to the Al substrate. The XPS intensity measurements are consistent with this two-stage growth model.     

Synthesis and Characterization of Nitrobenzoylthiourea Derivatives as Potential Conductive Biodegradable Thin Films

Abstract

The application of thiourea derivatives as conjugated molecular wire candidates in the field of material sciences has attracted great attention recently. To date, conjugated thiourea systems as molecular wires are surprisingly unexplored although the well-known rigid π-systems promise a wide range of electronic properties. Due to this matter, five novel thiourea derivatives A-ArC(O)NHC(S)NHAr-D with polar head and tail groups, namely NO₂ (acceptor A) and alkoxy with varying chain lengths (donor D = OC_nH_2n+1, n = 6, 7, 8, 9, 10), were successfully synthesized and characterized. All compounds were characterized by IR, UV-vis, ¹H and ¹³C NMR spectroscopy, and CHNS elemental microanalysis. The investigation of their potential as dopant systems in polymer conducting films has been accomplished by incorporating of chitosan via the solution casting technique. The conductivity values were obtained using impedance spectroscopy. They show that the ionic conductivities of the N-(4-alkoxyphenyl)-N’-(4-nitrobenzoyl)thioureas increase with increasing chain length of the alkoxy chain. The compounds exhibit great potential for the exploration of future applications as doping systems in conductive materials.     

Synthesis,radiolabeling and biological distribution of a new dioxime derivative as a potential tumor imaging agent

A novel dioxime derivative (2E,2′E,3E,3′E)-3,3′-(pyrimidine-4,5-diylbis(azanylylidene))bis(butan-2-one)dioxime was synthesized with a yield of 65%. IR, elemental analysis, mass spectroscopy and ¹H-NMR were used to characterize the structure of the synthesized compound. ^99mTc-dioxime was radio-synthesized with a high radiochemical yield of 97.8 ± 0.5% and in vitro stability of 6 h under the optimum conditions. The preclinical evaluation of ^99mTc-dioxime in solid tumor-bearing mice showed high accumulation in solid tumor cells with a high Target/Non-Target ratio of 5.14 at 30 min post-injection. This study suggests that ^99mTc-dioxime derivative is a promising candidate as a new ^99mTc-based tumor-imaging agent after further preclinical studies.