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Abstract: In this study, the periodic viaduct is used as an example to introduce a new type of phononic crystal structure: the “open”-type phononic crystal structure. A numerical model for analysis of the energy band of a periodic viaduct undergoing out-of-plane vibration is developed in this study. The most remarkable characteristic of the proposed model for the energy band of the periodic viaduct is that it can take into account the coupling between the periodic viaduct and the half-space soil. The viaduct considered in this study is assumed to be a regularly periodic arrangement of unit cells along its longitudinal direction. For simplicity, each unit cell is assumed to be consisted of a pile foundation, a pier and a horizontal beam. To obtain the compliances for the pile foundations, the pile-soil interaction problem is solved by the fictitious pile method first. Using the transfer matrix method and the obtained compliances for the pile foundations, the impedances for the piers are obtained. Based on the Bloch theorem and the transfer matrix method, the nonlinear polynomial eigenvalue equation for the periodic viaduct is derived using the impedance of the piers. Utilizing the obtained nonlinear eigenvalue equation, the approximate linear eigenvalue equation for the periodic viaduct is obtained and numerical results for the energy bands of the periodic viaduct are presented. Numerical results of this paper show that for the out-of-plane vibration of the periodic viaduct, there are three kinds of lattice waves propagating in the periodic viaduct. Moreover, in a low frequency range, all three lattice waves are evanescent, which will lead to the localization of lattice waves in the periodic viaduct. [Copyright &y& Elsevier]

Abstract: Energy bands formed by rotation–vibrational states of molecules in the presence of symmetry and their qualitative modifications under variation of some control parameters are studied within the semi-quantum model. Rotational variables are treated as classical whereas a finite set of vibrational states is considered as quantum. In the two-state approximation the system is described in terms of a fiber bundle with the base space being a two-dimensional sphere, the classical phase space for rotational variables. Generically this rank 2 complex vector bundle can be decomposed into two complex line bundles characterized by a topological invariant, the first Chern class. A general method of explicit calculation of Chern classes and of their possible modifications under variation of control parameters in the presence of symmetry is suggested. The construction of iso-Chern diagrams which split the space of control parameters into connected domains with fixed Chern numbers is suggested. A detailed analysis of the rovibrational model Hamiltonian for a invariant molecule possessing two vibrational states transforming according to the two-dimensional irreducible representation is done to illustrate non-trivial restrictions imposed by symmetry on possible values of Chern classes. [Copyright &y& Elsevier]

Novel devices incorporating multiple layers of new materials increase the complexity of device structures, particularly in field-effect transistors, capacitors, and nonvolatile memory (NVM). The mounting complexity of these devices increases the difficulty of generating energy band diagrams and performing device parameter calculations whether these calculations are done by hand, using spreadsheets, or via mathematical programs. Although finite-element Poisson–Schrodinger equation solvers are available to perform the calculations, the cost and time spent learning them can be a hindrance. A straightforward GUI interactive simulation tool is presented that quickly calculates and displays energy bands, electric fields, potentials, and charge distributions for 1-D metal–multilayered-dielectrics–semiconductor stacks. Fixed charge can be inserted into dielectric layers. The freeware program calculates device parameters, (e.g., effective oxide thickness, flat-band voltage (VFB), threshold voltage (Vt), stack capacitance) and layer parameters (e.g., capacitance, potential, electric field, tunneling distance). Calculated data can be exported. Using the simulation tool, trap-based flash NVM is examined. Device performance characteristics such as the Vt and VFB shifts of three different stacks are examined. Comparisons between the program and a finite-element Poisson–Schrodinger equation solver are performed to validate the program's accuracy. [ABSTRACT FROM PUBLISHER]

The fantastic physical properties of single-walled silicon nanotubes (SWSiNTs) under mechanical strain make them promising materials for fabricating nanoscale electronic devices or transducers. Here we investigate the energy band and band-gap properties of the SWSiNTs calculated from the tight-binding model approximation. The results show that the band-gap properties are very sensitive to the deformation degree and the helicity of the SWSiNTs. The results can be employed to guide the design of nanoelectronic devices based on silicon nanotubes. [ABSTRACT FROM AUTHOR]

Abstract: Complex superlattice, i.e. with a period consisting of more than two different layers has generated intense interest since the discovery of the superlattice. But since there are too many configurations to pick out the needed one, and for the limit of crystal growth technique, they were not well studied. In this paper, based on an empirical tight-binding model, electronic and optical properties of complex superlattices are calculated. Useful empirical parameters corresponding to the congregation of one kind of cations are defined. The energy bands, especially the lowest conduction band and the top of the valence band, have a simple trend with the change of the empirical parameter. Type-I to type-II transition problems are also discussed in this paper. [Copyright &y& Elsevier]

The electronic density of states (DOS) and energy bands of doped anatase TiO2 are studied by the full potential linearized augmented plane wave (FPLAPW) method based on the density functional theory. After doping with transition metal atoms, the band gap of TiO2 is narrowed, doping with transition metal cation makes both valence bands and conduction bands move towards lower position. [ABSTRACT FROM AUTHOR]

Abstract: The structural, optical, and electronic properties of PrPO4 have been investigated by means of single-crystal X-ray diffraction. Atomic arrangement of PrPO4 structure is based on corner and edge sharing PrO9 polyhedra and PO4 tetrahedra. The energy band structure, density of states, dielectric constant, refractive index and the chemical bonds have been investigated by density functional methods (DFT). The calculated total and partial densities of states indicate that the top of valence bands is mainly built upon O-2p states which interact with P-3p states via σ(P–O) interactions, and the low conduction bands mostly originates from Pr-4f states. The P–O bond is mostly covalent in character and the interactions between Pr and O atoms are ionic. [Copyright &y& Elsevier]

Using the homovalent cation substitution strategy, a new sulfate, Cs2Ca3(SO4)4, was successfully prepared using the spontaneous crystallization technique. A single-crystal structure measurement suggested that it crystallizes in space group P21/c, with lattice parameters and molecules per unit cell of a = 9.9153(8), b = 9.3760(6), c = 9.8044(9), β = 118.365(3)°, V = 802.04(11), and Z = 2. In the structure of Cs2Ca3(SO4)4, CaO6 octahedra and SO4 tetrahedra are interconnected via a corner-sharing mode to form a three-dimensional framework comprising large cavities filled with Cs+ cations. First-principles calculations and diffuse reflectance spectra indicated that Cs2Ca3(SO4)4 has a large energy band gap. Moreover, structural comparisons with similar compounds were conducted to explain the role of cations in tuning structural symmetry and birefringence. This paper helps to explain the size effect of cations on structural evolution. [ABSTRACT FROM AUTHOR]

Abstract: Trimetallic unsupported NiMoW sulfide catalysts were prepared of by decomposition-sulfidation of bimetallic Mo-W thiosalts precursors impregnated with Ni. The catalytic activity of the catalysts was determined, both in situ and ex situ, in the dibenzothiophene (DBT) hydrodesulfuration (HDS) reaction. The sample with a relative composition R1=Mo/[Mo−W]=0.85 and R2=Ni/[Mo+W]=0.5 presented a substantial increment (k =23×10−7 mol/sg) with selectivity to hydrogenation by a factor of 1.24 over hydrodesulfuration. Scanning electron microscopy (SEM) micrographs showed changes in morphology as a function of R1 suggesting that distinct crystalline phases were formed. Also, X-ray diffraction (XRD) measurements of precursors and catalysts revealed that the bimetallic thiosalt structure presents the same planes of the rhombohedral structure as ammonium thiomolybdate (ATM) or ammonium thiotungstate (ATT) indicating that redistribution of Mo and W occurred preferably in specific orientations as the (002), (020) and (310). The ammonium thiomolybdate-thiotungstate (ATMW) bimetallic thiosalt with R1=0.85 showed very different structure from the original Mo or W single precursors, among all the samples. Extended Hückel calculations revealed that promotion of (Mo-W)S2 precursors with Ni forming trimetallic NiMoWS catalysts after sulfidation, increases the availability of electrons over the Fermi level increasing the metallic character of the catalysts. [Copyright &y& Elsevier]

Local density functional is investigated using the full-potential linearized augmented plane wave (FP-LAPW) method for YN in the hexagonal structure and the rocksalt structure and for hexagonal structures linking a layered hexagonal phase with wurtzite structure along a homogeneous strain transition path. It is found that the wurtzite ScN is unstable and the layered hexagonal phase, labeled as h0, in which atoms are approximately fivefold coordinated, is metastable, and the rocksalt ScN is stable. The electronic structure, the physical properties of the intermediate structures and the energy band structure along the transition are presented. It is noticeable that the study of ScN provides an opportunity to apply this kind of material (in wurtzite[h]-derived phase). [ABSTRACT FROM AUTHOR]

Abstract: A sodium gadolinium phosphate crystal, Na3GdP2O8, has been synthesized by a high-temperature solution reaction, and it exhibits a new structural family of the alkali-metal-rare-earth phosphate system. Although many compounds with formula M3LnP2O8 have been reported, but they were shown to be orthorhombic [R. Salmon, C. Parent, M. Vlasse, G. LeFlem, Mater. Res. Bull. 13 (1978) 439] rather than monoclinic as shown in this paper. Single-crystal X-ray diffraction analysis shows the structure to be monoclinic with space group C2/c and the cell parameters: a=27.55 (25), b=5.312 (4), c=13.935(11)Å, β=91.30(1)°, and V=2038.80Å3, Z=4. Its structure features a three-dimensional GdP2O8 3− anionic framework with two different types of interesting tunnels at where Na atoms are located by different manners. The framework is constructed by Gd polyhedra and isolated PO4 tetrahedra. It is different from the structure of K3NdP2O8 [R. Salmon, C. Parent, M. Vlasse, G. LeFlem, Mater. Res. Bull. 13 (1978) 439] with space group P21/m that shows only one type of tunnel. The emission spectrum and the absorption spectrum of the compound have been investigated. Additionally, the calculations of band structure, density of states, dielectric constants, and refractive indexes have been also performed with the density functional theory method. The obtained results tend to support the experimental data. [Copyright &y& Elsevier]

Abstract: We discuss the energy band structure near the valence band maximum based on photoemission yield spectroscopy experiments using a hydrogen-terminated heavily boron-doped homoepitaxial diamond film with concentration of 3×1020 cm−3. The experimental results showed a metallic photoemission behavior with a negative electron affinity surface. Based on the fitting as metallic photoemission behavior with a Fowler plot, the Fermi level should be at 5.35 eV below the conduction band minimum, which means that the Fermi level lies at 0.12 eV (5.47–5.35 eV) above the valence band maximum. Thus the film shows metallic conduction by the Mott transition, but not as degenerate semiconductor. [Copyright &y& Elsevier]

Abstract: In CuGaS2 crystals absorption and luminescence spectra at the temperature 9K at excitation by different wavelengths of Ar laser are investigated. A series of lines available in luminescence and absorption spectra is found. Another series of lines is found only in absorption spectra. The found series of lines of absorption and luminescence are determined by excitons bound on neutral acceptor. A model of electron transitions between the energy levels of the exciton bound on neutral acceptor is proposed. [Copyright &y& Elsevier]

The superfine structure of Bose-Einstein condensate of alkali atoms due to the spin coupling have been investigated in the mean field approximation. In the limit of large number of atoms, we obtained the analytical solution for the fully condensed states and the states with one-atom excited. It was found that the energy of the one-atom excited state could be smaller than the energy of the fully condensed state, even two states have similar total spin. [ABSTRACT FROM AUTHOR]

Abstract: In this study, ternary and binary europium complexes of o-phthalic acid are synthesized. Their compositions are characterized by element analysis and IR spectra and ascertained to be Eu2(o-phthalic)34(H2O) and Eu2(o-phthalic)3(phen)22(H2O), respectively. The UV–Vis spectrum and photoluminescence spectra are also analyzed. Meanwhile, the energy transfer models have been set up and structure of energy band and optical gap of the ternary complex powder were obtained by the UV–Vis spectrum. [Copyright &y& Elsevier]

Energy band diagrams for MOS devices are essential for understanding device performance and reliability. Introduction of high-k gate stacks with a silicon dioxide (SiO2) interfacial layer requires an even greater understanding of the energy band behavior. A program that quickly determines the band diagrams based on a simple analytical model was created. It is used to explore the behavior of various oxide stacks with the ability to easily vary important parameters like oxide material, electron affinity, bandgap, dielectric constant, and thickness. The usefulness of this program to predict potential reliability issues is also demonstrated [ABSTRACT FROM PUBLISHER]

Abstract: A new noncentrosymmetric three-dimensional tellurite with second-order nonlinear optical property, BaMo2Te2O11(H2O), was synthesized by the hydrothermal reaction of Ba(OH)2, TeO2 and MoO3. It is characterized by single-crystal X-ray diffraction and spectral properties. The compound contains {Mo(1)Mo(2)O10} n infinite spiral chains, which are linked into infinite anionic layers along ab plane by Te(1)O5 and Te(2)O4 polyhedra. Ba2+ cations are intercalated between the layers. Energy band of the compound is calculated and analyzed, the band gap is 3.23eV, it indicates the solid-state compound of BaMo2Te2O11(H2O) is an insulator and the value is consistent well with the experimental value of 3.18eV. [Copyright &y& Elsevier]

Abstract: An alkali metal-rare earth phosphate crystal of NaLa(PO3)4 has been synthesized by high temperature solid-state reactions and structurally characterized by single crystal X-ray diffraction analysis, for the first time. It crystallizes in the monoclinic P21/n space group with lattice parameters: , , , , , . It is composed of LaO8 polyhedra and [(PO3)4]4− chains sharing oxygen atoms to form a three-dimensional framework, delimiting intersecting tunnels in which the sodium ions are located. The IR spectrum, absorption spectrum, and emission spectrum of the compound have been investigated. The absorption edge is located at 340nm (3.60eV). The calculated total and partial densities of states indicate that the top of valence bands is mainly built upon O-2p states which interact with P-3p states via σ (P–O) interactions, and the low conduction bands mostly originates from unoccupied La-5d states. The P–O bond is mostly covalent in character, and the ionic character of the Na–O bond is larger than that in the La–O bond. [Copyright &y& Elsevier]

Electronic structures of several zigzag- and armchair-carbon-doped boron nitride nanotubes (BNNTs) were calculated by ROB3LYP method of density functional theory (DFT). The electro-conductivities of these nanotubes were discussed by means of obtained Fermi energies, energy bands and density of states (DOS), and were compared with those of pure BNNT. The influence of different C-doping (C substituting B or N) on the conductivity was also discussed. [Copyright &y& Elsevier]

Abstract: A novel compound Ba2ZnV2O8 has been synthesized in high temperature solution reaction and its crystal structure has been characterized by means of single crystal X-ray diffraction analysis. It crystallizes in monoclinic system and belongs to space group P21/c with , , , . It builds up from 1-D branchy chains of [ZnV2O84-]∞, and the Ba2+ cations are located in the space among these chains. The IR spectrum, ultraviolet-visible diffuse reflection integral spectrum and fluorescent spectra of this compound have been investigated. The calculated results of energy band structure by the density functional theory method show that the solid-state compound of Ba2ZnV2O8 is an insulator with direct band gap of 3.48eV. The calculated total and partial density of states indicate that the top valence bands are contributions from the mixings of O-2p, V-3d, and Zn-3d states and low conduction bands mostly originate from unoccupied antibonding states between the V-3d and O-2p states. The V–O bonds are mostly covalence characters and Zn–O bonds are mostly ionic interactions, and the ionic interaction strength is stronger between the Ba–O than between the Zn–O. The refractive index of nx, ny, and nz is estimated to be 1.7453, 1.7469, and 1.7126, respectively, at wavelength of 1060nm for Ba2ZnV2O8 crystal. [Copyright &y& Elsevier]

A single crystal of the compound Sr3P4O13 has been found and the crystal structure has been characterized by means of single crystal X-ray diffraction analysis. The compound crystallizes in triclinic system and belongs to space group P&1macr;. It builds up from SrO7 polyhedra and P4O13-6 anions and has a layered structure, and the Sr atoms are located in the interlayer space. The absorption and luminescence spectrum of Sr3P4O13 microcrystals have been measured. The calculated results of crystal energy band structure by the DFT show that the solid state of Sr3P4O13 is an isolator with direct band gap. The calculated total and partial density of states indicate that the top valence bands are contributions from P 3p and O 2p states and low conduction bands mostly originate from Sr atomic states. The calculated optical response functions expect that the Sr3P4O13 is a low refractive index, and it is possible that the Sr3P4O13 is used to make transparent material between the UV and FR light zone. [Copyright &y& Elsevier]

We propose co-doping systems in emission layers of red and green organic light-emitting diodes (OLEDs). The luminance-voltage, luminous and power efficiency-voltage characteristics, operational stability, and the energy bands of materials were measured. In red OLED devices, we propose an emitting assist (EA) dopant for better luminance efficiency and power efficiency with pure red emission and improved operational stability. The EA dopant (rubrene) did not emit itself but assisted the energy transfer from a host (Alq) to an emitting dopant (DCJTB). By doping rubrene, the luminance efficiency increased from 1.7 to 4.3 cd/A (from 0.6 to 1.9 lm/W) with chromaticity of (x=0.64, y=0.36) unchanged. An improved lifetime was also observed. In green OLED devices, we introduced hole transporting material (NPB) into an emission layer for better charge injection balance. The green devices with the emitting dopant (C545T) achieved the luminance efficiency of 8.5 cd/A compared with 6.9 cd/A without NPB. We studied the co-doping methods and use of this approach for active-matrix full color display. The power consumption of white emission at 100 cd/m2 was reduced by 32%. The effectiveness of these co-doping methods was demonstrated for practical applications. [ABSTRACT FROM PUBLISHER]

A new electrical conductive crystal PyEt[Ni(dmit)2]2 (dmit = 4,5-dimercapto-1,3-dithiole-2-thione) has been synthesized and its X-ray structure has been determined to be in monoclinic system, C2/c space group. In PyEt[Ni(dmit)2]2 crystal, the conducting component [Ni(dmit)2]0.5- is face-to-face packed forming molecular column along the c-direction, and these molecular columns are then side-by-side extended along the a-direction forming a kind of two-dimensional conducting sheet on (010). The measured conductivity at room temperature along a certain direction on (010) plane is 10 S · cm-1. From 282 to 269 K, the crystal shows metallic behavior but changes to semiconductor below 269 K. Based on the measured crystal structure and calculated band structure, this conductor-semiconductor phase transformation can be primarily interpreted: The metallic conductivity is corresponding to the uniform molecular column and the atomic-lattice-chain structure of Ni chain, while the semi-conductive behavior to staggered molecular column and the atomic-zigzag-chain structure of Ni chain. [ABSTRACT FROM AUTHOR]

The bands, densities of states, and spectrum of the permittivity ℇ2 of a CdO crystal have been calculated by the FP–LMTO method. The ℇ2, ℇ1, -Im ℇ-1, and Re ℇ-1 spectra for the CdO crystal in the range 1–30 eV have been obtained on the basis of the experimental spectrum of reflection. The spectra were decomposed into elementary components and their main parameters were calculated. The obtained spectrum of the transverse components was compared with the theoretical spectrum of ℇ2. [ABSTRACT FROM AUTHOR]

We have performed the low-frequency Raman measurement of MBE grown Ge/Si superlattice. Raman spectra were excited by He–Ne laser, and diode-pump YAG 532 nm laser, as well as several lines from Ar[sup +] laser. Folded acoustic phonons of the Ge/Si superlattice were clearly found. The resonant effects were observed for the Ge/Si superlattices while the Raman spectra excited by the laser lines around 500 nm. A clearly resonance enhanced phonon signals are found for the spectrum excited by 532 nm laser line, and continuous emission can be clearly seen. By the continuous emission theory, we carried out a resonance band at 2.32 eV, which is closed to the E[sub 1] band of Germanium. Few weak resonant bands were also found near 2.32 eV, which may be related to confined band or the resonance band of interface layer between Si and Ge. [ABSTRACT FROM AUTHOR]

The electrical conductive molecular crystals (Me3NEt)[Pd(dmit) 2]2 and (NEt4)[Pd (dmit) 2]2 (dmit = 4,5-dimercapto-1,3-dithiole-2-thione) have been prepared, and their crystal structures and conductivity-temperature curves have been determined. The fact that the conductivity at room temperature of (Me3NEt)[Pd(dmit) 2]2 (σ = 58 Ω-1 cm-1) is much higher than that of (Net4)-[Pd(dmit)2]2 (σ = 2.2 Ω-1.cm-1) has been rationally explained by the results of energy band calculations. (MeNEt3)[Pd(dmit)2]2 belongs to monoclinic system, P21/m space group and (Net4)[Pd (dmit)2]2 belongs to triclinic system, $$P\bar 1$$ space group. The structural conducting component of the crystals is the planar coordinative anion [Pd(dmit)2]0.5- which forms the face-to-face dimmer. [Pd(dmit)2]- 2These dimers have been further constructed to be a kind of two-dimensional (2-D) conductive molecular sheet by means of S_S intermolecular interactions. The tiny difference of the above 2-D molecular sheets of the two title crystals has resulted in one order of magnitude difference of conductivities. [ABSTRACT FROM AUTHOR]

Porous silicon has been studied with photoluminescence, photoluminescence excitation, and photoacoustic spectroscopy. From the luminescence data, an energy-level diagram related to the luminescence is constructed. The diagram is confirmed in detail by the photoacoustic spectra. The results are discussed with the conclusion that they are in good agreement with the surface-band oxyhydride-like emitter, which recently has been established as the source for the photoluminescence from porous silicon. [ABSTRACT FROM AUTHOR]

• Bi 3−x Y x O 4 Cl solid solution were successfully synthesized by solid-phase method. • The absorption edge of Bi 3−x Y x O 4 Cl could be adjusted from about 500–740 nm. • The conduction band minimum energy satisfied the redox potential for both H+/H 2. • Bi 3−x Y x O 4 Cl solid solution showed the visible light photocatalytic H 2 evolution activity. [Display omitted] The solid solution constructed by two or more semiconductors with different bandgaps can effectively modulate the energy band, satisfying the redox potential for both H+/H 2 and O 2 /H 2 O. In this paper, Sillen-Aurivillius compounds with layered structure Bi 3 O 4 Cl and Y 3 O 4 Cl solid solution (Bi 3−x Y x O 4 Cl) were successfully synthesized by the solid-phase method. The absorption edge of Bi 3−x Y x O 4 Cl could be dramatically changed from about 500–740 nm with the increase of Bi elements, which accounted for the entire UV-Vis region of the solar spectrum. Furthermore, the bandgaps for Bi 3−x Y x O 4 Cl could be adjusted from about 2.6–2.0 eV with the decreased Y/Bi ratio from 2 to 0.2. Significantly, the conduction band minimum energy (CBM) of Bi 3−x Y x O 4 Cl all satisfied the redox potential for H+/H 2 , which showed excellent visible-light photocatalytic water splitting. [ABSTRACT FROM AUTHOR]

By adopting the first-principles plane wave pseudopotential method based on density functional theory, the electronic structure properties of single-layer MoS2 (molybdenum disulfide) crystals under biaxial strain are studied. The calculation results in this paper show that when a small strain is applied to a single-layer MoS2, its band structure changes from a direct band gap to an indirect band gap. As the strain increases, the energy band still maintains the characteristics of the indirect band gap, and the band gap shows a linear downward trend. Through further analysis of the density of states, sub-orbital density of states, thermodynamic parameters and Raman spectroscopy, it revealed the variation of single-layer MoS2 with strain. This provides a theoretical basis for realizing the strain regulation of MoS2. [ABSTRACT FROM AUTHOR]

The gap modulation by effectively external control is an intriguing feature of the black phosphorene which may enable a flexible design and optimization of electronics. In this paper, combined electric field and external strain effects are systematically investigated to tailor the electrical properties of bilayer black phosphorene (BP) in four stacking order by using density functional theory (DFT). The electronic structures and density of states of bilayer black phosphorene can be modulated by the two external controls, the direct semiconductor-indirect semiconductor-metal transitions emerge under uniaxial in-plain strains and vertical electric field. The band gap is more likely to be modulated by the electric field under compressive strain along armchair direction for the AB stacking structures. The greater the compressive strain, the gap closed at a lower electric field. The partial density of states (PDOS) shows the energy band was mainly contributed by p orbital, and the partial charge density of the VBM and CBM further indicates the shifting trend of electrons and holes between the double layers. Our results provide potential reference information for nano-electronic and optoelectronic applications. • We consider the combination effect of in-plain external force and vertical electric field in bilayer phosphorene. We adopt PBE-TS-DFTD method for structure optimization. • Four stacking orders are considered comprehensively, both the armchair and zigzag direction of the applied in-plain strain are considered. • We report a different modulation effects between compressive force and tensile force under electric field. The direct semiconductors to indirect semiconductors turning points are discussed. • Detailed partial charge density of the VBM and CBM explains the mechanism. [ABSTRACT FROM AUTHOR]

We report optical absorption and emission features of Eu doped Y 2 O 3 nanoparticles synthesised by a gradually-heated solution combustion method. An X-ray diffraction analysis reveals that the samples exhibit body centred cubic structure. The crystallite size of an undoped Y 2 O 3 sample was estimated to be ~19.87 nm but it is found to increase up to 46.38 nm in a sample doped with 4% Eu. The samples have spherical structure of diameter ~23–57 nm. Analysis of optical absorption spectra indicates an apparent increase of optical band gap from 5.00 eV to 5.24 eV after the doping. This apparent widening of band gap is explained with reference to the Burstein-Moss effect. The Eu doped samples produce a primary emission band at 447 ± 1 nm and a secondary band between 480 and 630 nm. Analysis reveals that the primary band is composed of two overlapping components with peak maxima at 446 ± 1 nm and 455 ± 3 nm. These emission bands are attributed to the transition from degenerate 5d → 4f level of Eu2+ ion. The absorption and emission features have been discussed with reference to an energy band model. • Y 2 O 3 :Eu nanoparticle is synthesised by gradually-heated solution combustion method. • Samples have spherical structure of diameter ~23–57 nm. • There is an apparent increase of band gap from 5.00 to 5.24 eV after doping of Eu. • There is a primary PL emission band at 447 ± 1 nm and a secondary one at ~480–630 nm. • The Burstein-Moss effect and PL emission bands are explained by energy band models. [ABSTRACT FROM AUTHOR]

The article surveys the main unsolved problems of the electronic structure of nonmetals in a wide energy region of fundamental absorption. [ABSTRACT FROM AUTHOR]

An environment-friendly inverted indium phosphide red quantum dot light-emitting diode (InP QLED) was fabricated using Mg-doped zinc oxide (ZnMgO) as the electron transport layer (ETL). The effects of ZnMgO ETL on the performance of InP QLED were investigated. X-ray diffraction (XRD) analysis indicated that ZnMgO film has an amorphous structure, which is similar to zinc oxide (ZnO) film. Comparison of morphology between ZnO film and ZnMgO film demonstrated that Mg-doped ZnO film remains a high-quality surface (root mean square roughness: 0.86 nm) as smooth as ZnO film. The optical band gap and ultraviolet photoelectron spectroscopy (UPS) analysis revealed that the conduction band of ZnO shifts to a more matched position with InP quantum dot after Mg-doping, resulting in the decrease in turn-on voltage from 2.51 to 2.32 V. In addition, the ratio of irradiation recombination of QLED increases from 7% to 25% using ZnMgO ETL, which can be attributed to reduction in trap state by introducing Mg ions into ZnO lattices. As a result, ZnMgO is a promising material to enhance the performance of inverted InP QLED. This work suggests that ZnMgO has the potential to improve the performance of QLED, which consists of the ITO/ETL/InP QDs/TCTA/MoO3/Al, and Mg-doping strategy is an efficient route to directionally regulate ZnO conduction bands. [ABSTRACT FROM AUTHOR]

The energy band structure of mechanically free and compressed RbKSO4 single crystals is investigated. It is established that the top of the valence band is located at the D point of the Brillouin zone [k = (0.5, 0.5, 0)], the bottom of the conduction band lies at the Γ point, and the minimum direct band gap Eg is equal to 5.80 eV. The bottom of the conduction band is predominantly formed by the K s, Li p, Rb s, and Rb p states hybridized with the S p and O p antibonding states. The pressure coefficients of the energy position of the valence and conduction band states and the band gap Eg are determined.

The dependencies of the birefringence Δni of K2SO4 crystals in wide spectral (250-800 nm) ranges, as well as the effect of uniaxial mechanical stresses on them have been studied. The values of ni for K2SO4 are found to be rather sensitive to the uniaxial stress. The spectral characteristics of the refractive indices ni of free and mechanically clamped K2SO4 crystals have been studied. The refractive indices turned out to decrease under the effect of uniaxial stress. The variations in the refraction, electron polarizability and the position of the center of the effective ultraviolet absorption band have been calculated. It is shown that the positions of the isotropic points in these crystals can be controlled by thermal and spectral methods.

Currently, two-dimensional (2D) layered organic–inorganic hybrid perovskites with good stability against moisture have attracted great interest, which are potential substitute for three-dimensional (3D) lead halide CH 3 NH 3 PbX 3 (MAPbX 3) (X = I, Br, Cl) perovskites. Herein, we reported a one-pot solvothermal approach for the preparation of 2D hybrid perovskite (HO(CH 2) 2 NH 3) 2 PbBr 4 (EA 2 PbBr 4) with ethanolamine organic layer. Electrochemical measurements including current-voltage measurements, impedance spectroscopy and Mott-Schottky were investigated to derive detailed electronic and band energetic structures. Moreover, through the accelerated moisture-tolerance and photocatalytic degradation test, the novel 2D product exhibited greatly enhanced stability compared to 3D MAPbBr 3 perovskites and the lower efficiency due to the insulating properties of the organic cations in 2D (HO(CH 2) 2 NH 3) 2 PbBr 4. 2D hybrid perovskite (HO(CH 2) 2 NH 3) 2 PbBr 4 (EA 2 PbBr 4) with ethanolamine organic layer was prepared and exhibited the improved moisture stability (∼1 min) compared to CH 3 NH 3 PbBr 3 (<2 s) in an accelerated moisture-tolerance test by time-resolved electrochemical analysis. Image 1 • 2D hybrid perovskite (HO(CH 2) 2 NH 3) 2 PbBr 4 (EA 2 PbBr 4) with ethanolamine organic layer was prepared by solvothermal route. • Electrochemical measurements were investigated to derive its detailed electronic and band energetic structures. • EA 2 PbBr 4 exhibited improved stability (∼1 min) compared to CH 3 NH 3 PbBr 3 (< 2 s) in an accelerated moisture-tolerance test. • CH 3 NH 3 PbBr 3 displayed higher photocatalytic degradation of MG dyes compared to EA 2 PbBr 4. • Improved performances originated from the special surface chemical state and crystal structure. [ABSTRACT FROM AUTHOR]

Abstract: This report analyzes the imaging errors in what are called “artifacts” by a CdTe detector with the energy differentiation ability using the photon counting mode. The selection of specific energy level in each metal sample allows nominating the images with less artifact. In addition, inspection of μx is the supportive method to judge the energy level. Photon counting CdTe detector with the energy differentiation ability is a system that can provide the information of projection data at different energy bands to establish the accuracy image of any materials. [ABSTRACT FROM AUTHOR]

Abstract: The magnetocrystalline anisotropy energy (MAE) of Fe16N2 with a body-centered tetragonal (BCT) structure is calculated using its approximate energy bands, inclusive of the spin–orbit interaction and exchange splitting (E x) based on the tight-binding approximation (TBA). Taking E x=0.1093Ry, the calculated anisotropy constants of Fe16N2 are in agreement with the measured constants, K 1, K 2 and K 3, and the average magnetic moment is evaluated to be about 2.3 μ B/Fe atom, which is close to that obtained from the first-principles calculation by Sakuma. In contrast, the estimated unidirectional anisotropy constant K u (=K 1+K 2) for Fe16C2 becomes negative for the same E x as for Fe16N2. Taking E x=0.1110Ry, the calculated magenetic moment for Fe16C2 qualitatively agrees with the experimental result for the disordered-state α′-Fe–C. [Copyright &y& Elsevier]