Advances in Condensed Matter Physics The latest articles from Hindawi Publishing Corporation © 2015 , Hindawi Publishing Corporation . All rights reserved. Theoretical Approach to the Gauge Invariant Linear Response Theories for Ultracold Fermi Gases with Pseudogap Thu, 01 Oct 2015 13:36:24 +0000 Recent experimental progress allows for exploring some important physical quantities of ultracold Fermi gases, such as the compressibility, spin susceptibility, viscosity, optical conductivity, and spin diffusivity. Theoretically, these quantities can be evaluated from suitable linear response theories. For BCS superfluid, it has been found that the gauge invariant linear response theories can be fully consistent with some stringent consistency constraints. When the theory is generalized to stronger than BCS regime, one may meet serious difficulties to satisfy the gauge invariance conditions. In this paper, we try to construct density and spin linear response theories which are formally gauge invariant for a Fermi gas undergoing BCS-Bose-Einstein Condensation (BEC) crossover, especially below the superfluid transition temperature . We adapt a particular -matrix approach which is close to the formalism to incorporate noncondensed pairing in the normal state. We explicitly show that the fundamental constraints imposed by the Ward identities and -limit Ward identity are indeed satisfied. Hao Guo and Yan He Copyright © 2015 Hao Guo and Yan He. All rights reserved. The Correlation between the Energy Gap and the Pseudogap Temperature in Cuprates: The YCBCZO and LSHCO Case Thu, 01 Oct 2015 09:42:09 +0000 The paper analyzes the influence of the hole density, the out-of-plane or in-plane disorder, and the isotopic oxygen mass on the zero temperature energy gap (2Δ(0)) (YCBCZO) and (LSHCO) superconductors. It has been found that the energy gap is visibly correlated with the value of the pseudogap temperature (). On the other hand, no correlation between 2Δ(0) and the critical temperature () has been found. The above results mean that the value of the dimensionless ratio can vary very strongly together with the chemical composition, while the parameter does not change significantly. In the paper, the analytical formula which binds the zero temperature energy gap and the pseudogap temperature has been also presented. R. Szczȩśniak, M. W. Jarosik, and A. M. Duda Copyright © 2015 R. Szczȩśniak et al. All rights reserved. On New Families of Integrals in Analytical Studies of Superconductors within the Conformal Transformation Method Thu, 01 Oct 2015 09:39:20 +0000 We show that, by applying the conformal transformation method, strongly correlated superconducting systems can be discussed in terms of the Fermi liquid with a variable density of states function. Within this approach, it is possible to formulate and carry out purely analytical study based on a set of fundamental equations. After presenting the mathematical structure of the -wave superconducting gap and other quantitative characteristics of superconductors, we evaluate and discuss integrals inherent in fundamental equations describing superconducting systems. The results presented here extend the approach formulated by Abrikosov and Maki, which was restricted to the first-order expansion. A few infinite families of integrals are derived and allow us to express the fundamental equations by means of analytical formulas. They can be then exploited in order to find quantitative characteristics of superconducting systems by the method of successive approximations. We show that the results can be applied in studies of high- superconductors and other superconducting materials of the new generation. Ryszard Gonczarek, Mateusz Krzyzosiak, Adam Gonczarek, and Lucjan Jacak Copyright © 2015 Ryszard Gonczarek et al. All rights reserved. Momentum Distribution Functions in a One-Dimensional Extended Periodic Anderson Model Sun, 20 Sep 2015 11:10:49 +0000 We study the momentum distribution of the electrons in an extended periodic Anderson model, where the interaction, , between itinerant and localized electrons is taken into account. In the symmetric half-filled model, due to the increase of the interorbital interaction, the electrons become more and more delocalized, while the itinerancy of conduction electrons decreases. Above a certain value of the electrons become again localized together with the conduction electrons. In the less than half-filled case, we observe that causes strong correlations between the electrons in the mixed valence regime. I. Hagymási, J. Sólyom, and Ö. Legeza Copyright © 2015 I. Hagymási et al. All rights reserved. Progress in the Characterization of the Surface Species in Activated Carbons by means of INS Spectroscopy Coupled with Detailed DFT Calculations Thu, 17 Sep 2015 07:12:08 +0000 Activated carbons are materials with relevance in different industrial applications. Due to the inherent complexity and heterogeneity of their structures, an easy assignment of the species present on their surface has a challenging result. Only recently, with the possibility to collect well-resolved inelastic neutron spectra and to simulate by DFT methods more or less extended graphitic clusters, this task is starting to become feasible. Here we report our investigation on a steam activated carbon and we show that different vibrations in the region of out-of-plane C-H bending modes are specifically connected to hydrogen terminations belonging to extended and regular borders or to short and defective ones. Furthermore, simulations including heteroatoms such as oxygen allowed us to point out spectral regions with a contribution from carboxyl species. Andrea Piovano, Andrea Lazzarini, Riccardo Pellegrini, Giuseppe Leofanti, Giovanni Agostini, Svemir Rudić, Aram L. Bugaev, Carlo Lamberti, and Elena Groppo Copyright © 2015 Andrea Piovano et al. All rights reserved. Propagation Effects in the Spin-Wave Spectrum of the Ferromagnetic Thin Film Tue, 15 Sep 2015 09:54:12 +0000 Exchange spin waves propagating in magnetic thin films exhibit some dynamic effects, that is, the effects caused solely by the wave propagation. In this paper we put our attention in four phenomena of such kind: the surface (and subsurface) localization, the collapse of the bulk band into a single energy level, the reversal of the mode order in the spin-wave spectrum, and the dynamic separation of the thin film into two subsystems. We link these effects to properties of Hamiltonian matrix elements inherited from the spatial distribution of neighboring spins with respect to the film surface. We also provide necessary conditions for the occurrence of these effects. Sławomir Mamica Copyright © 2015 Sławomir Mamica. All rights reserved. Finite Conductivity Effects in Electrostatic Force Microscopy on Thin Dielectric Films: A Theoretical Model Sun, 13 Sep 2015 12:55:10 +0000 A study of the electrostatic force between an Electrostatic Force Microscope tip and a dielectric thin film with finite conductivity is presented. By using the Thomas-Fermi approximation and the method of image charges, we calculate the electrostatic potential and force as a function of the thin film screening length, which is a magnitude related to the amount of free charge in the thin film and is defined as the maximum length that the electric field is able to penetrate in the sample. We show the microscope’s signal on dielectric films can change significantly in the presence of a finite conductivity even in the limit of large screening lengths. This is particularly relevant in determining the effective dielectric constant of thin films from Electrostatic Force Microscopy measurements. According to our model, for example, a small conductivity can induce an error of more than two orders of magnitude in the determination of the dielectric constant of a material. Finally, we suggest a method to discriminate between permittivity and conductivity effects by analyzing the dependence of the signal with the tip-sample distance. E. Castellano-Hernández and G. M. Sacha Copyright © 2015 E. Castellano-Hernández and G. M. Sacha. All rights reserved. Formation, Energetics, and Electronic Properties of Graphene Monolayer and Bilayer Doped with Heteroatoms Thu, 10 Sep 2015 13:57:16 +0000 Doping with heteroatoms is one of the most effective methods to tailor the electronic properties of carbon nanomaterials such as graphene and carbon nanotubes, and such nanomaterials doped with heteroatom dopants might therefore provide not only new physical and chemical properties but also novel nanoelectronics/optoelectronics device applications. The boron and nitrogen are neighboring elements to carbon in the periodic table, and they are considered to be good dopants for carbon nanomaterials. We here review the recent work of boron and nitrogen doping effects into graphene monolayer as well as bilayer on the basis of the first-principles electronic structure calculations in the framework of the density-functional theory. We show the energetics and the electronic properties of boron and nitrogen defects in graphene monolayer and bilayer. As for the nitrogen doping, we further discuss the stabilities, the growth processes, and the electronic properties associated with the plausible nitrogen defect formation in graphene which is suggested by experimental observations. Yoshitaka Fujimoto Copyright © 2015 Yoshitaka Fujimoto. All rights reserved. Importance of Molecular Interactions in Colloidal Dispersions Wed, 09 Sep 2015 13:22:21 +0000 We review briefly the concept of colloidal dispersions, their general properties, and some of their most important applications, as well as the basic molecular interactions that give rise to their properties in equilibrium. Similarly, we revisit Brownian motion and hydrodynamic interactions associated with the concept of viscosity of colloidal dispersion. It is argued that the use of modern research tools, such as computer simulations, allows one to predict accurately some macroscopically measurable properties by solving relatively simple models of molecular interactions for a large number of particles. Lastly, as a case study, we report the prediction of rheological properties of polymer brushes using state-of-the-art, coarse-grained computer simulations, which are in excellent agreement with experiments. R. López-Esparza, M. A. Balderas Altamirano, E. Pérez, and A. Gama Goicochea Copyright © 2015 R. López-Esparza et al. All rights reserved. Electrochemical Characterization of Nanoporous Nickel Oxide Thin Films Spray-Deposited onto Indium-Doped Tin Oxide for Solar Conversion Scopes Sun, 06 Sep 2015 06:26:19 +0000 Nonstoichiometric nickel oxide () has been deposited as thin film utilizing indium-doped tin oxide as transparent and electrically conductive substrate. Spray deposition of a suspension of nanoparticles in alcoholic medium allowed the preparation of uniform coatings. Sintering of the coatings was conducted at temperatures below 500°C for few minutes. This scalable procedure allowed the attainment of films with mesoporous morphology and reticulated structure. The electrochemical characterization showed that electrodes possess large surface area (about 1000 times larger than their geometrical area). Due to the openness of the morphology, the underlying conductive substrate can be contacted by the electrolyte and undergo redox processes within the potential range in which is electroactive. This requires careful control of the conditions of polarization in order to prevent the simultaneous occurrence of reduction/oxidation processes in both components of the multilayered electrode. The combination of the open structure with optical transparency and elevated electroactivity in organic electrolytes motivated us to analyze the potential of the spray-deposited films as semiconducting cathodes of dye-sensitized solar cells of p-type when erythrosine B was the sensitizer. Muhammad Awais, Denis P. Dowling, Franco Decker, and Danilo Dini Copyright © 2015 Muhammad Awais et al. All rights reserved. Strain and Dimension Effects on the Threshold Voltage of Nanoscale Fully Depleted Strained-SOI TFETs Thu, 03 Sep 2015 13:07:00 +0000 A novel nanoscale fully depleted strained-SOI TFET (FD-SSOI TFET) is proposed and exhaustively simulated through Atlas Device Simulator. It is found that FD-SSOI TFET has the potential of improved on-current and steep subthreshold swing. Furthermore, the effect of strain and dimension on the threshold voltage of FD-SSOI TFET is thoroughly studied by developing a model based on its physical definition. The validity of the model is tested for FD-SSOI TFET by comparison to 2D device simulations. It is shown that the proposed model can predict the trends of threshold voltage very well. This proposed model provides valuable reference to the FD-SSOI TFETs design, simulation, and fabrication. Yu-Chen Li, He-Ming Zhang, Shu-lin Liu, and Hui-Yong Hu Copyright © 2015 Yu-Chen Li et al. All rights reserved. Rare Earth-Doped BiFeO3 Thin Films: Relationship between Structural and Magnetic Properties Mon, 31 Aug 2015 11:57:14 +0000 Rare Earth- (RE-) doped BiFeO3 (BFO) thin films were grown on LaAlO3 substrates by using pulsed laser deposition technique. All of BFO films doped with 10% of RE show a single phase of rhombohedral structure. The saturated magnetization in the Ho- and Sm-doped films is much larger than those reported in literature and was observed at a quite low field as of 0.2 T. As for Pr- and Nd-doped BFO films, Fe2+ amount is not dominant; thus, ferromagnetism is not favored. As the RE concentration goes up to 20%, all compounds have drastically gone through a structural transition. The RE-doped BFO films have changed from rhombohedral to either pure orthorhombic phase (for Ho, Sm), or a mixed phase of orthorhombic and tetragonal (for Pr, Nd), or pure tetragonal (for Eu). We observed magnetic properties of RE-doped BFO films have significantly changed. While 20% Ho/Sm-doped BFO films have ferromagnetism degraded in comparison with the 10% doping case, the 20% Pr/Nd-doped BFO thin films, whose structure is a mixed phase, have magnetic ordering improved due to the fact that the Fe2+ amount has become greater. It seems that one can control the magnetic properties of BFO films by using appropriate RE dopants and concentrations. Ngo Thu Huong, Seunghun Lee, Timur Sh. Atabaev, Makio Kurisu, and Nguyen Hoa Hong Copyright © 2015 Ngo Thu Huong et al. All rights reserved. An Infrared Spectroscopy Study of the Conformational Evolution of the Bis(trifluoromethanesulfonyl)imide Ion in the Liquid and in the Glass State Sun, 30 Aug 2015 12:20:27 +0000 We measure the far-infrared spectrum of N,N-Dimethyl-N-ethyl-N-benzylammonium (DEBA) bis(trifluoromethanesulfonyl)imide (TFSI) ionic liquid (IL) in the temperature range between 160 and 307 K. Differential scanning calorimetry measurements indicate that such IL undergoes a glass transition around 210 K. DFT calculations allow us to assign all the experimental absorptions to specific vibrations of the DEBA cation or of the two conformers of the TFSI anion. We find that the vibration frequencies calculated by means of the PBE0 functional are in better agreement with the experimental ones than those calculated at the B3LYP level, largely used for the attribution of vibration lines of ionic liquids. Experimentally we show that, in the liquid state, the relative concentrations of the two conformers of TFSI depend on temperature through the Boltzmann factor and the energy separation, H, is found to be 2 kJ/mol, in agreement with previous calculations and literature. However, in the glassy state, the concentrations of the cis-TFSI and trans-TFSI remain fixed, witnessing the frozen state of this phase. Oriele Palumbo, Francesco Trequattrini, Francesco Maria Vitucci, Maria Assunta Navarra, Stefania Panero, and Annalisa Paolone Copyright © 2015 Oriele Palumbo et al. All rights reserved. Photoproducts Formation from Salicylic Acid and Poly(allylamine hydrochloride) in Aqueous Solution Induced by UV-B Radiation Wed, 26 Aug 2015 14:21:12 +0000 We report on the investigation of the influence of UV-B radiation (306 nm) on the salicylic acid mixed with poly(allylamine hydrochloride), PAH, in aqueous solution. UV-Vis spectra versus irradiation time reveal kinetics of photoproducts formation. At pH 9 and 10 are found a growth regime and another of decay of photoproducts formation. In addition, the growth does not depend on temperature, whereas the decay showed a significant dependence on this parameter suggesting a thermally activated process. These processes were well fitted with first-order exponential functions. Romario J. da Silva, Nara C. de Souza, and Josmary R. Silva Copyright © 2015 Romario J. da Silva et al. All rights reserved. Self-Organization of Polymeric Fluids in Strong Stress Fields Wed, 26 Aug 2015 09:45:22 +0000 Analysis of literature data and our own experimental observations have led to the conclusion that, at high deformation rates, viscoelastic liquids come to behave as rubbery materials, with strong domination by elastic deformations over flow. This can be regarded as a deformation-induced fluid-to-rubbery transition. This transition is accompanied by elastic instability, which can lead to the formation of regular structures. So, a general explanation for these effects requires the treatment of viscoelastic liquids beyond critical deformation rates as rubbery media. Behaviouristic modeling of their behaviour is based on a new concept, which considers the medium as consisting of discrete elastic elements. Such a type of modeling introduces a set of discrete rotators settled on a lattice with two modes of elastic interaction. The first of these is their transformation from spherical to ellipsoidal shapes and orientation in an external field. The second is elastic collisions between rotators. Computer calculations have demonstrated that this discrete model correctly describes the observed structural effects, eventually resulting in a “chaos-to-order” transformation. These predictions correspond to real-world experimental data obtained under different modes of deformation. We presume that the developed concept can play a central role in understanding strong nonlinear effects in the rheology of viscoelastic liquids. A. V. Semakov, V. G. Kulichikhin, and A. Y. Malkin Copyright © 2015 A. V. Semakov et al. All rights reserved. Assessment of Functionals for First-Principle Studies of the Structural and Electronic Properties of -Bi2O3 Tue, 25 Aug 2015 12:43:32 +0000 Fully relativistic full-potential density functional calculations with an all-electron linearized augmented plane waves plus local orbitals method were carried out to perform a comparative study on the structural and electronic properties of the cubic oxide -Bi2O3 phase, which is considered as one of the most promising materials in a variety of applications including fuel cells, sensors, and catalysts. Three different density functionals were used in our calculations, LDA, the GGA scheme in the parametrization of Perdew, Burke, and Ernzerhof (PBE96), and the hybrid scheme of Perdew-Wang B3PW91. The examined properties include lattice parameter, band structure and density of states, and charge density profiles. For this modification the three functionals reveal the characteristics of a metal and the existence of minigaps at high symmetry points of the band structure when spin-orbit coupling is taken into account. Density of states exhibits hybridization of Bi 6s and O 2p orbitals and the calculated charge density profiles exhibit the ionic character in the chemical bonding of this compound. The B3PW91 hybrid functional provided a better agreement with the experimental result for the lattice parameter, revealing the importance of Hartree-Fock exchange in this compound. D. H. Galván, R. Núñez-González, R. Rangel, P. Alemany, and A. Posada-Amarillas Copyright © 2015 D. H. Galván et al. All rights reserved. Particle and Particle-Surfactant Mixtures at Fluid Interfaces: Assembly, Morphology, and Rheological Description Thu, 20 Aug 2015 12:44:13 +0000 We report here a review of particle-laden interfaces. We discuss the importance of the particle’s wettability, accounted for by the definition of a contact angle, on the attachment of particles to the fluid interface and how the contact angle is strongly affected by several physicochemical parameters. The different mechanisms of interfacial assembly are also addressed, being the adsorption and spreading the most widely used processes leading to the well-known adsorbed and spread layers, respectively. The different steps involved in the adsorption of the particles and the particle-surfactant mixtures from bulk to the interface are also discussed. We also include here the different equations of state provided so far to explain the interfacial behavior of the nanoparticles. Finally, we discuss the mechanical properties of the interfacial particle layers via dilatational and shear rheology. We emphasize along that section the importance of the shear rheology to know the intrinsic morphology of such particulate system and to understand how the flow-field-dependent evolution of the interfacial morphology might eventually affect some properties of materials such as foams and emulsions. We dedicated the last section to explaining the importance of the particulate interfacial systems in the stabilization of foams and emulsions. Armando Maestro, Eva Santini, Dominika Zabiegaj, Sara Llamas, Francesca Ravera, Libero Liggieri, Francisco Ortega, Ramón G. Rubio, and Eduardo Guzman Copyright © 2015 Armando Maestro et al. All rights reserved. New Topological Configurations in the Continuous Heisenberg Spin Chain: Lower Bound for the Energy Wed, 19 Aug 2015 11:30:33 +0000 In order to study the spin configurations of the classical one-dimensional Heisenberg model, we map the normalized unit vector, representing the spin, on a space curve. We show that the total chirality of the configuration is a conserved quantity. If, for example, one end of the space curve is rotated by an angle of 2π relative to the other, the Frenet frame traces out a noncontractible loop in and this defines a new class of topological spin configurations for the Heisenberg model. Rossen Dandoloff Copyright © 2015 Rossen Dandoloff. All rights reserved. Characterisation of PMMA/ATH Layers Realised by Means of Atmospheric Pressure Plasma Powder Deposition Mon, 17 Aug 2015 13:54:49 +0000 We report on the characteristics of aluminium trihydrate filled poly(methyl methacrylate) composite (PMMA/ATH) coatings realised by plasma deposition at atmospheric pressure. For this purpose, PMMA/ATH powder was fed to a plasma jet where the process and carrier gas was compressed air. The deposited coatings were investigated by X-ray photoelectron spectroscopy and water contact angle measurements. Further, the raw material was characterised before deposition. It was found that, with respect to the raw material, aluminium was uncovered in the course of the plasma deposition process which can be explained by plasma-induced etching of the PMMA matrix. As a result, the wettability of plasma-deposited PMMA/ATH was significantly increased. Even though a uniform coating film could not be realised as ascertained by confocal laser scanning microscopy, the deposited coatings feature notably enhanced characteristics which could be advantageous for further processing. Lena M. Wallenhorst, Sebastian Dahle, Matej Vovk, Lisa Wurlitzer, Leander Loewenthal, Nils Mainusch, Christoph Gerhard, and Wolfgang Viöl Copyright © 2015 Lena M. Wallenhorst et al. All rights reserved. Indentation Depth Dependent Mechanical Behavior in Polymers Mon, 17 Aug 2015 07:28:39 +0000 Various experimental studies have revealed size dependent deformation of materials at micro and submicron length scales. Among different experimental methods, nanoindentation testing is arguably the most commonly applied method of studying size effect in various materials where increases in the hardness with decreasing indentation depth are usually related to indentation size effects. Such indentation size effects have been observed in both metals and polymers. While the indentation size effects in metals are widely discussed in the literature and are commonly attributed to geometrically necessary dislocations, for polymer the experimental results are far sparser and there does not seem to be a common ground for their rationales. The indentation size effects of polymers are addressed in this paper, where their depth dependent deformation is reviewed along with the rationale provided in the literature. Farid Alisafaei and Chung-Souk Han Copyright © 2015 Farid Alisafaei and Chung-Souk Han. All rights reserved. Strain-Dependence of the Structure and Ferroic Properties of Epitaxial NiTiO3 Thin Films Grown on Different Substrates Thu, 13 Aug 2015 13:29:35 +0000 Polarization-induced weak ferromagnetism has been predicted a few years back in perovskite MTiO3 (M = Fe, Mn, and Ni). We set out to stabilize this metastable perovskite structure by growing NiTiO3 epitaxially on different substrates and to investigate the dependence of polar and magnetic properties on strain. Epitaxial NiTiO3 films were deposited on Al2O3, Fe2O3, and LiNbO3 substrates by pulsed laser deposition and characterized using several techniques. The effect of substrate choice on lattice strain, film structure, and physical properties was investigated. Our structural data from X-ray diffraction and electron microscopy shows that substrate-induced strain has a marked effect on the structure and crystalline quality of the films. Physical property measurements reveal a dependence of the weak ferromagnetism and lattice polarization on strain and highlight our ability to control the ferroic properties in NiTiO3 thin films by the choice of substrate. Our results are also consistent with the theoretical prediction that the ferromagnetism in acentric NiTiO3 is polarization induced. From the substrates studied here, the perovskite substrate LiNbO3 proved to be the most promising one for strong multiferroism. Tamas Varga, Timothy C. Droubay, Mark E. Bowden, Libor Kovarik, Dehong Hu, and Scott A. Chambers Copyright © 2015 Tamas Varga et al. All rights reserved. Computational Investigation of the Electronic and Optical Properties of Planar Ga-Doped Graphene Thu, 13 Aug 2015 12:15:14 +0000 We simulate the optical and electrical responses in gallium-doped graphene. Using density functional theory with a local density approximation, we simulate the electronic band structure and show the effects of impurity doping (0–3.91%) in graphene on the electron density, refractive index, optical conductivity, and extinction coefficient for each doping percentage. Here, gallium atoms are placed randomly (using a 5-point average) throughout a 128-atom sheet of graphene. These calculations demonstrate the effects of hole doping due to direct atomic substitution, where it is found that a disruption in the electronic structure and electron density for small doping levels is due to impurity scattering of the electrons. However, the system continues to produce metallic or semimetallic behavior with increasing doping levels. These calculations are compared to a purely theoretical 100% Ga sheet for comparison of conductivity. Furthermore, we examine the change in the electronic band structure, where the introduction of gallium electronic bands produces a shift in the electron bands and dissolves the characteristic Dirac cone within graphene, which leads to better electron mobility. Nicole Creange, Costel Constantin, Jian-Xin Zhu, Alexander V. Balatsky, and Jason T. Haraldsen Copyright © 2015 Nicole Creange et al. All rights reserved. High Performance Enhancement-Mode AlGaN/GaN MIS-HEMT with Selective Fluorine Treatment Mon, 10 Aug 2015 12:00:31 +0000 A novel enhancement-mode (E-mode) Metal-Insulator-Semiconductor- (MIS-) HEMT with selective fluorine ion (F−) treatment is proposed and its mechanism is investigated. The HEMT features the Selective F− treatment both in the AlGaN channel region and in the thick passivation layer between the gate and drain (SFCP-MIS-HEMT). First, the F− in the passivation layer not only extends the depletion region and thus enhances the average electric field (-field) between the gate and drain by the assisted depletion effect but also reduces the -field peak at the gate end, leading to a higher breakdown voltage (BV). Second, in the AlGaN channel region, the F− region realizes the E-mode and the region without F− maintains a high drain current (). Third, MIS structure suppresses the gate leakage current, increasing the gate swing voltage and the BV. Compared with a MIS-HEMT with F− treatment in whole channel (FC-MIS-HEMT), SFCP-MIS-HEMT increases the BV by 46% and the saturation drain current () by 28%. Chao Yang, Jiayun Xiong, Jie Wei, Junfeng Wu, Bo Zhang, and Xiaorong Luo Copyright © 2015 Chao Yang et al. All rights reserved. Chemical Functionalization Effects on Cubane-Based Chain Electronic Transport Sun, 09 Aug 2015 12:08:26 +0000 We report electronic structure calculations in chemically functionalized linear cubane-based chains. The effects of covalent chemical attachments on chain transport properties are examined with nonorthogonal tight-binding model (NTBM) considering Landauer-Büttiker formalism. The covalent bonding of even a single-type functional group is shown to considerably alter the conductance of the chain. For similar radical doping density, electronic characteristics are found to range from insulator to narrow-gap semiconductor depending on the nature of the covalent bonding. Therefore it has become possible to tune electronic properties of the cubane-based one-dimensional oligomers by the functionalization for nanoelectronic applications. Konstantin P. Katin and Mikhail M. Maslov Copyright © 2015 Konstantin P. Katin and Mikhail M. Maslov. All rights reserved. The Intramolecular Pressure and the Extension of the Critical Point’s Influence Zone on the Order Parameter Thu, 06 Aug 2015 12:28:11 +0000 The critical point affects the coexistence behavior of the vapor-liquid equilibrium densities. The length of the critical influence zone is under debate because for some properties, like shear viscosity, the extension is only a few degrees, while for others, such as the density order parameter, the critical influence zone covers up to hundreds of degrees below the critical temperature. Here we show that, for ethane, the experimental critical influence zone covers a wide zone of tens of degrees (below the critical temperature) down to a transition temperature, at which the apparent critical influence zone vanishes, and the transition temperature can be predicted through a pressure analysis of the coexisting bulk liquid phase, using a simple molecular potential. The liquid phases within the apparent critical influence zone show low densities, making them behave internally like their corresponding vapor phases. Therefore, Molecular Dynamics simulations reveal that the experimentally observed wide extension of the critical influence zone is the result of a vapor-like effect due to low bulk liquid phase densities. Jose Luis Rivera, Homero Nicanor-Guzman, and Roberto Guerra-Gonzalez Copyright © 2015 Jose Luis Rivera et al. All rights reserved. Microscale Fragmentation and Small-Angle Scattering from Mass Fractals Wed, 05 Aug 2015 17:15:43 +0000 Using the small-angle scattering method, we calculate here the mono- and polydisperse structure factor from an idealized fragmentation model based on the concept of renormalization. The system consists of a large number of fractal microobjects which are randomly oriented and whose positions are uncorrelated. It is shown that, in the fractal region, the monodisperse form factor is characterized by a generalized power-law decay (i.e., a succession of maxima and minima superimposed on a simple power-law decay) and whose scattering exponent coincides with the fractal dimension of the scatterer. The present analysis of the scattering structure factor allows us to obtain the number of fragments resulted at a given iteration. The results could be used to obtain additional structural information about systems obtained through microscale fragmentation processes. E. M. Anitas Copyright © 2015 E. M. Anitas. All rights reserved. Formation of Porous Apatite Layer during In Vitro Study of Hydroxyapatite-AW Based Glass Composites Thu, 30 Jul 2015 13:44:59 +0000 This research discussed the fabrication, characterization, and in vitro study of composites based on the mixture of hydroxyapatite powder and apatite-wollastonite (AW) based glass. AW based glass was prepared from the SiO2-CaO-MgO-P2O5-CaF2 glass system. This study focuses on the effect of composition and sintering temperature that influences the properties of these composites. Microstructural study revealed the formation of apatite layer on the composite surfaces when immersed in simulated body fluid (SBF) solution at 37°C. Composites containing ≥50 wt% AW based glass showed good bioactivity after 7 days of immersion in the SBF. A porous calcium phosphate (potentially hydroxycarbonate apatite, HCA) layer formed at the SBF-composite interface and the layer became denser at longer soaking period, for periods ranging from 7 to 28 days. Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) analysis showed that early stage of soaking occurred with the release of Ca and Si ions from the composites and the decrease of P ions with slow exchange rate. Pat Sooksaen, Natyada Pengsuwan, Sittipong Karawatthanaworrakul, and Surasak Pianpraditkul Copyright © 2015 Pat Sooksaen et al. All rights reserved. Analysis of Eu3+ Emission from Mg2TiO4 Nanoparticles by Judd-Ofelt Theory Mon, 27 Jul 2015 13:09:43 +0000 Eu3+ doped Mg2TiO4 (2 at% of Eu) nanoparticles which are 5 to 10 nm in diameter are prepared by Pechini-type polymerized complex route followed with the calcination in the temperature range from 400°C to 700°C. Emission spectra display characteristic (, 1, 2, 3, and 4) spin forbidden f-f electronic transitions of the Eu3+ ions with the most pronounced emission coming from transition and with the emission decays varying between 0.57 and 0.87 ms for samples prepared at different temperatures. Judd-Ofelt theoretical analysis of the emission spectra of Eu3+ ions was performed, which allowed calculating radiative and nonradiative emission probabilities, Judd-Ofelt intensity parameters, and the quantum efficiency of the Eu3+ emission in the Mg2TiO4 nanoparticles. The analyses showed the existence of high asymmetry around the metal ion sites. Also, the largest quantum efficiency of emission of 58.5% is found in nanoparticles prepared at 600°C. Katarina Vuković, Mina Medić, Milica Sekulić, and Miroslav D. Dramićanin Copyright © 2015 Katarina Vuković et al. All rights reserved. Experimental and Theoretical Studies on the Structure and Photoluminescent Properties of New Mononuclear and Homodinuclear Europium(III) β-Diketonate Complexes Mon, 27 Jul 2015 12:29:11 +0000 Two novel europium(III) complexes, a monomer and a homodimer, with 1-(4-chlorophenyl)-4,4,4-trifluoro-1,3-butanedione (Hcbtfa) and 5-chloro-1,10-phenanthroline (cphen) ligands, formulated as [Eu(cbtfa)3(cphen)] and [Eu2(cbtfa)4(cphen)2(CH3O)2], have been synthesized. Their structures have been elucidated by X-ray diffraction and their absorption and emission properties have been studied in the solid state. The experimental data has then been used to test the recently released LUMPAC software, a promising tool which can facilitate the design of more efficient lanthanide light-conversion molecular devices by combining ground state geometry, excited state energy, and luminescent properties calculations. João P. Martins, Pablo Martín-Ramos, Pedro Chamorro-Posada, Pedro S. Pereira Silva, Jesús Martín-Gil, Salvador Hernández-Navarro, and Manuela Ramos Silva Copyright © 2015 João P. Martins et al. All rights reserved. Exotic Superconductivity in Correlated Electron Systems Wed, 22 Jul 2015 12:44:23 +0000 Gang Mu, Viorel Sandu, Wei Li, and Bing Shen Copyright © 2015 Gang Mu et al. All rights reserved.