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Abstract: The model for amorphous semiconductor InSb (a-InSb) was constructed through the first principles calculations, based on the idea of “continuous random networks” (CRN). The results of structural parameters for a-InSb are in agreement with the available data both theoretically and experimentally. The structure of a-InSb is almost tetrahedrally bonded with a perfect average coordination number of four. Due to the influence of the disorders, the density of states for a-InSb has the smearing structure in contrast to crystalline InSb (c-InSb). As a consequence of the induction of disorders, modification phenomena occur at the band edge of a-InSb in contrast to that of c-InSb. [Copyright &y& Elsevier]

Abstract: First-principles calculations have been performed on the C-doped anatase TiO2. The doped TiO2 shows half-metallic properties and a 2.0 μB magnetic moment per cell. The magnetic coupling is closely related to the C–C distance. When the distance is shorter than a typical CC double bond (), the system is nonmagnetic and the dopants tend to form a cluster through a direct CC bonding interaction [Appl. Phys. Lett. 93 (2008) 132507]. When the distance is between 3.8 and , there exists strong ferromagnetic or antiferromagnetic coupling between two C atoms. The ferromagnetic coupling is induced by the bent C–Ti–C unit. When the distance is further increased, the system becomes paramagnetic. [Copyright &y& Elsevier]

Abstract: Ball mill grinding circuits are essentially multi-variable systems characterized with couplings, time-varying parameters and time delays. The control schemes in previous literatures, including detuned multi-loop PID control, model predictive control (MPC), robust control, adaptive control, and so on, demonstrate limited abilities in control ball mill grinding process in the presence of strong disturbances. The reason is that they do not handle the disturbances directly by controller design. To this end, a disturbance observer based multi-variable control (DOMC) scheme is developed to control a two-input-two-output ball mill grinding circuit. The systems considered here are with lumped disturbances which include external disturbances, such as the variations of ore hardness and feed particle size, and internal disturbances, such as model mismatches and coupling effects. The proposed control scheme consists of two compound controllers, one for the loop of product particle size and the other for the loop of circulating load. Each controller includes a PI feedback part and a feed-forward compensation part for the disturbances by using a disturbance observer (DOB). A rigorous analysis is also given to show the reason why the DOB can effectively suppress the disturbances. Performance of the proposed scheme is compared with those of the MPC and multi-loop PI schemes in the cases of model mismatches and strong external disturbances, respectively. The simulation results demonstrate that the proposed method has a better disturbance rejection property than those of the MPC and PI methods in controlling ball mill grinding circuits. [Copyright &y& Elsevier]

Abstract: The electronic structure in p-type δ-doping GaAs is calculated self-consistently by including the contribution of the photogenerated carrier. The theoretical results indicate that the band bending around the δ-doping region is induced by the injection of photogenerated holes into the potential well of the δ-doping GaAs. Moreover the band bending results in two photogenerated carrier-induced wells for electrons. The potential of the two wells is deepened with the increase of the photogenerated carrier density. The photoluminescence (PL) properties are explained in terms of the dependence of the confined electronic states and the Fermi level of the two-dimensional hole gas (2DHG) on the concentration of photogenerated carrier, which is in good agreement with experimental observation of the variation of peak position and intensity with the excitation light intensity. [Copyright &y& Elsevier]

Abstract: There is a significant diminution in the hydrostatic pressure coefficients (PCs) of the photoluminescence spectrum for InAs/GaAs quantum dots in comparison with that of bulk binary. We study this phenomenon with the nonlinear elasticity theory. The variation of the lattice and elastic constants plays an important role in the change of PCs, which causes the obvious decrease of the built-in strains of InAs/GaAs quantum dots under the hydrostatic pressure. The decrease will induce the novel change of the energy gap and the electronic confined energy. Finally, the change is shown in the measured small PCs of photoluminescence from quantum dots. Also the calculation reveals that the PCs are sensitive to the sizes of quantum dots because of the change of the electronic confined energy. The smaller the quantum dot is, the stronger the influence of this change on the PCs becomes. This effect gives rise to the increase of PCs when dot size is reduced. [Copyright &y& Elsevier]

Abstract: We have studied the electronic and magnetic properties of germanium doped with 3d-impurities (V–Ni) using first-principles band structure method. It is found that the ferromagnetic (FM) spin configuration is more energetically favorable than the antiferromagnetic (AFM) state for Mn-, Fe-, Co- and Ni-doped Ge, whereas the situation is reversed for V- and Cr-doped systems. The calculated electronic and magnetic structures of Mn-, Fe-, Co- and Ni-doped Ge show that half metallicity is obtained only for Mn-doped Ge that consistent with the integer value for the total magnetic moment, while Fe-, Co-, Ni-doped ones are metallic. Furthermore, the FM coupling between the Mn d states and the anion dangling-bond p states is believed to responsible for the stabilization of the FM order in Mn-doped Ge. [Copyright &y& Elsevier]

The effect of Nb doping of oxide perovskite SrTiO3 on the electronic properties is studied by semirelativistic linear muffin-tin orbital method with atomic sphere approximation (LMTO-ASA). The computational lattice constants are in good agreement with experimental data. The Fermi level of SrTi1−xNbxO3 with x⩾0.125 moves into the bottom of conduction band and the system shows metallic behavior. Due to the appearance of the charge impurity potential from Nb doping, there is a large distortion on the top of valence band for SrTi1−xNbxO3 with 0.125⩽x⩽0.25. The distortion becomes weak with x=0.5 because of the carriers screening effect. Our computational results also show that the Nb doping effect on the electronic structure of SrTi1−xNbxO3 cannot be described within a simple rigid-band model well. [Copyright &y& Elsevier]

The electronic and optical properties of Nb doped SrTiO3 are studied by ab initio linear muffin-tin orbital method in the atomic sphere approximation. The equilibrium lattice constants of SrTi1−xNbxO3 with x=0.0, 0.25 and 0.5 are found by minimization of the total energy curves. The computated lattice constants are in good agreement with experimental data. Our electronic band calculation shows that the Fermi level of SrTi1−xNbxO3 with x≥0.125 moves into the conduction bands and the system shows metallic behavior. The numerical results indicate that the Nb impurity atoms would lead to the distortion of the band edges. The complex dielectric function of SrTiO3 and Nb doped SrTiO3 are calculated using the random-phase approximation. The doping effect on the optical properties of SrTi1−xNbxO3 is discussed. [Copyright &y& Elsevier]

Background Surveys of the prevalence of atopic dermatitis (AD) have been carried out world-wide, but the results vary widely. The differences probably result from the use of different diagnostic criteria. Williams et al. proposed minimum, simplified, diagnostic criteria that require no invasive test and are easy to use. Pilot studies in European countries showed their suitability for implementation both in hospitals and in the community, and their high sensitivity and specificity. Objectives To evaluate the potential practical value of the criteria of Williams et al. in the Chinese population. Methods The criteria of Hanifin and Rajka (gold standard), Williams et al. and Kang and Tian were applied and compared in 111 patients with AD and 121 control subjects with other skin diseases in three out-patient centres in China. Results The criteria of Williams et al. showed a similar diagnostic efficiency to that of the gold standard, with the sensitivity, specificity and κ value reaching 95·50%, 97·52% and 0·93, respectively. No significant difference was found between the criteria of Williams et al. and those of Kang and Tian (χ2 = 0·69, P > 0·05). ‘Onset under the age of 2 years’, a criterion of Williams et al. could be used in subjects of any age. Conclusions The diagnostic efficiency of the criteria of Williams et al. was basically similar to those of Hanifin and Rajka and of Kang and Tian in our out-patient settings. However, those of Williams et al. were easier to apply and required no invasive tests. [ABSTRACT FROM AUTHOR]

Presents information on the technique, chemiluminescent analyzer, which is used in the measurement of nitric oxide (NO) emissions, which are in a diesel engine exhaust under transient engine operation. Cause for the formation of transient smoke; Details about the development of phenomenological models; Relation to the response of the chemiluminescent analyzer; Information on two phenomenological models; Indepth look at transient nitric oxide emission in diesel exhaust.

Highlights: [•] Al2O3/HfO2/Al2O3 gate stacks has been deposited on Si substrate by ALD. [•] Interface thermal stability related with annealing temperature has been studied. [•] Phase separation at 700°C and silicate formation at 900°C have been detected. [ABSTRACT FROM AUTHOR]

Abstract: Considering different universality classes of the QCD phase transitions, we perform the Monte Carlo simulations of the 3-dimensional models at vanishing and non-vanishing external field, respectively. Interesting high-order cumulants of the order parameter and energy from (Ising) spin model, and the cumulants of the energy from and spin models are presented. The generic features of the cumulants are discussed. They are instructive to the high-order cumulants of the net baryon number in the QCD phase transitions. [Copyright &y& Elsevier]

Abstract: Graphene is a basic building block for carbon materials of all dimensionalities and exhibits many unique electronic properties. But, for future applications of graphene, further tuning its electronic band structure is necessary. Recently, it has been demonstrated that graphene can react with atomic hydrogen, which transforms this zero-band-gap semimetal into an insulator [[17] Elias et al., Science 323 (2009) 610]. Here we investigate the electronic and vibrational properties of graphene sheets with H in various configurations by means of first-principles calculations based on density-function theory. It is found that the hydrogenation not only effectively modulates the band gap of graphene but also leads to the band gap transition from direct to indirect. Meanwhile, the emerging of the sp3 type bonds induced by the hydrogenation may introduce some new vibrational modes in graphene, which play a key role in determining the spectra signatures of the resulting graphene derivatives. Our results provide a satisfactory explanation for the experimentally observed changes of the Raman spectra in graphene during the hydrogenation. [Copyright &y& Elsevier]

Abstract: By use of first-principles calculations, we examine the effects of uniaxial strain on the electronic and magnetic properties of Co-doped ZnO nanowires. Our results show that the uniaxial strain can cause significant variation of magnetic interactions in different ways, which are strongly dependant on the configuration formed by Co atoms. For the configuration whose ground state is a ferromagnetic state, the uniaxial tensile strain leads to the enhancement of ferromagnetic interaction, which can be explained by the double-exchange model very well. It is also shown that the strength of the double-exchange interaction is dependent on the occupation of the Co-3 state. The present results indicate the strain can be used as an effective means in tuning the magnetic interactions in ZnO based one-dimensional diluted magnetic semiconductors. [Copyright &y& Elsevier]

Abstract: Using first-principles method we studied the compensation mechanism of As donor in Hg1− x Cd x Te based on the model Berding et al. (1998, 1999) of pair. We show that the binding of AsHg and results from donor-acceptor coupling, and the compensation of As donor can be clearly explained in terms of electronic deactivation by . The pairing physics derived from this study confirm the available theoretical and experimental results. [ABSTRACT FROM AUTHOR]

Abstract: We have investigated the electronic and magnetic properties of the room temperature ferromagnetic diluted magnetic semiconductor (DMS) (Zn,Cr)Te with density functional calculations. The electronic and magnetic properties of (Zn,Cr)Te are very similar with those of the typical DMS (Ga,Mn)As. The stronger ionicity of ZnTe plays a key role in the electronic and magnetic properties of (Zn,Cr)Te. [Copyright &y& Elsevier]

Based on first-principles calculations, we have systematically investigated the structural stability, electronic and magnetic properties of zigzag C 2 N nanoribbons (ZC 2 NNRs). Different from zigzag graphene nanoribbons (ZGNRs), the ground states of ZC 2 NNRs present ferromagnetic metal, antiferromagnetic semiconductor and spin semiconductor dependently on the edge configuration and width of nanoribbons. Our results suggest the ZC 2 NNRs have great potential applications in spintronic, thermoelectric and optoelectronic devices. [ABSTRACT FROM AUTHOR]

Using first-principles calculations, we investigate the atomic and electronic structure of La 3 GaGe 5 O 16 and its oxygen vacancies with an aim to evaluate the potential of La 3 GaGe 5 O 16 as a new persistent phosphor. We find that oxygen vacancies prefer the bridging sites within [Ge m O n ] groups over the bridging sites between groups. Oxygen vacancies are found to act as an electron trap center and their trap states are of conduction band character of the host. By comparison with other excellent persistent phosphors, we suggest that La 3 GaGe 5 O 16 cannot emerge as an efficient persistent phosphor, and the most likely cause is the formation of ring structure and rather localized conduction band of the host. The ring structure makes most of oxygen atoms structurally inactive and the localized conduction band results in low concentration of trapping electrons. Our results thus provide fundamental explanations for the inferior persistent performance of La 3 GaGe 5 O 16 phosphor. [ABSTRACT FROM AUTHOR]

In current work, effects of rapid thermal annealing on the interface chemical bonding states, band alignment, and electrical properties of atomic-layer-deposition-derived HfAlO/Al 2 O 3 gate stack on Si substrates have been studied by X-ray photoemission spectroscopy (XPS), UV–Vis transmission spectroscopy, and electrical measurements. XPS analyses have shown that HfAlO alloy and mixed silicate (Hf-Al-O-Si) increase after post-deposition annealing process. By means of UV–Vis transmission spectroscopy measurements, reduction in band gap for 400 o C-annealed sample has been observed. Accordingly, reduction in the valence band offset and increase in the conduction band offset have been detected for HfAlO/Al 2 O 3 /Si gate stack annealed at 400 °C. Various current conduction mechanisms, such as Poole-Frenkel emission, Fowler-Nordheim (FN) tunneling, and space-charge-limited (SCL) conduction, have been analyzed. Detailed electrical measurements reveal that current conduct mechanisms is SCL conduction at lower field region and FN tunneling and SCL conduction are dominant conduction mechanism at higher field region. [ABSTRACT FROM AUTHOR]

Using first-principles methods, we have investigated magnetic properties and thermospin effects of zigzag silicene nanoribbons (ZSiNRs) absorbed by a single Si atom. After a relaxation, a steady dumbbell-like structure is formed, which induces a weaker antiferromagnetic (AFM) coupling between two zigzag edges. Therefore, a band gap is opened, meanwhile the adsorbed ZSiNRs show a spin semiconducting property. A large spin thermopower and weak charge thermopower in adsorbed ZSiNR-based devices can be simultaneously achieved, which is attributed to a nearly perfect mirror symmetry of spin-up and spin-down transmission spectra relative to the Fermi level. [ABSTRACT FROM AUTHOR]

Deposition of HfTiO x gate dielectric films on n-type Si and quartz substrates by sol–gel technique has been performed and the optical, electrical characteristics of the as-deposited HfTiO x thin films as a function of baking temperature have been investigated. The components and optical properties of HfTiO x thin films related to baking temperature are investigated by energy dispersive spectrometer (EDS), ultraviolet–visible spectroscopy (UV–Vis), and spectroscopy ellipsometry (SE). By measurement of EDS, the Hf/Ti molar ratio of HfTiO x thin films is calculated to be about 1:1.20 at all baking temperature. The increase in band gap is observed with the increase of baking temperature. Additionally, the electrical properties based on Al/Si/HfTiO x /Al capacitor are analyzed by means of the high frequency capacitance-voltage ( C-V ) and the leakage current density-voltage ( J-V ) characteristics. Results have shown that 200 °C-baked sample demonstrates good electrical performance, including larger dielectric constant of 23.31 and lower leakage current density of 5.12 × 10 −5 A/cm 2 at the gate voltage of 1 V. Additionally, the leakage current conduction mechanisms as functions of baking temperatures are also discussed systematically. [ABSTRACT FROM AUTHOR]

The possibility to improve thermoelectric performance of carbon-based quantum devices is of fundamental and importance in the fields of energy conservation, environmental protection, and green energy. Here we propose an effective avenue to enhance the thermoelectric figure of merits (TE-FOMs) of an all-carbon quantum device with the help of first-principles methods, and the device is constructed by a zigzag-edged trigonal graphene (ZTG) connected with zigzag-edged graphene nanoribbons (ZGNR) electrodes through the carbon atomic chains (CACs). Using a gate field, the spin-up transmission peak can be tuned from the position below the Fermi level to that above the Fermi level. However, the position of the spin-down transmission peak above the Fermi level is insensitive to the gate field. Therefore, the device can be converted from the p type to n type for the spin-up component by a gate field, while for the spin-down component the device remains n type. Meanwhile, we also find that the charge (spin) TE-FOMs at the Fermi level can be increased to about eight (three) times as compared with the case in the absence of the gate field. These TE-FOMs can also be significantly improved by tuning the incident electron energy and temperature. [ABSTRACT FROM AUTHOR]

There have been some experimental suggestions about the correlation of the persistent luminescence (PL) mechanism of phosphors with host lattice defects. Oxygen vacancies have most often been invoked, but solid and direct evidence is scarce. We investigate the PL mechanism of Sr 2 MgSi 2 O 7 :Eu 2+ on the basis of first-principles calculations of oxygen vacancies. We find that oxygen vacancies occur in a high concentration and introduce a dispersive empty defect band, which is distributed over a wide energy range and located from shallow to deep depth, explaining well the persistent luminescence emission with an intense intensity and a long-lasting duration. Our basic understanding of the general trend of the trap depth and density of O1, O2, and O3 vacancies is applicable to the assignment of the defect structures observe in thermoluminescence spectra. We also propose a possible PL mechanism for Sr 2 MgSi 2 O 7 :Eu 2+ phosphor and provide some guides for the search and design of better PL materials. [ABSTRACT FROM AUTHOR]

The effect of nitrogen on the band offset of sputtering-derived InZnGaO 4 (IGZO)/Si heterostructures has been systematically investigated by x-ray photoelectron spectroscopy (XPS) measurements. Elemental analysis indicates that nitrogen has been successfully incorporated into the IGZO film. By using In 3d 5/2 , In 3d 3/2 and Ga 3d core level (CL) XPS spectra as references, values of valence band offsets (Δ E v ) of have been determined to be 2.56 ± 0.02 and 2.44 ± 0.02 eV for IGZO/Si and IGZO:N/Si heterojunctions, respectively. Using the experimental band gap of 3.59 and 3.50 eV of the IGZO/Si and IGZO:N/Si, the calculated values of conduction band offset (Δ E c ) is 0.09 ± 0.01 and 0.06 ± 0.01 eV, respectively. The results indicate that nitrogen incorporation leads to the reduction in band gap and Δ E v and the slight effect on the Δ E c has also been detected. [ABSTRACT FROM AUTHOR]

The optical properties, interface chemistry and band alignment of Hf 1− x Ti x O 2 ( x = 0.03, 0.08, 0.12 and 0.20) high- k gate dielectric thin films, deposited by RF sputtering on Si substrate, have been systematically investigated. The effect of TiO 2 incorporation on the interfacial chemical structure and energy-band discontinuities has been investigated by using X-ray photoelectron spectroscopy (XPS) and ultraviolet-visible spectroscopy (UV–vis). It has been found that the band gap and band offsets of the Hf 1− x Ti x O 2 thin film decrease with the increase of TiO 2 concentration. Meanwhile, the obtained band offsets are all over 1 eV. Thin film capacitors fabricated with the MOS configuration of Al/Hf 1− x Ti x O 2 /n-Si/Al exhibits excellent electrical properties with low interface state density, hysteresis voltage and low leakage current density. The suitable band gap, symmetrical band offsets relative to Si and prominent electrical properties render sputtering-derived Hf 1− x Ti x O 2 with 9% TiO 2 films as promising candidates for high- k gate dielectrics. [ABSTRACT FROM AUTHOR]

Mo-doped ZnO(MZO) films were deposited on Si (1 1 1) substrates by radio frequency sputtering at different substrate temperatures of 200, 300 and 400 °C. The effect of the substrate temperature on the structural and optical properties of the MZO films has been investigated. X-ray diffraction results reveal that all the films are polycrystalline with a hexagonal wurtzite structure with a preferential orientation according to the direction (0 0 2) plane. The crystallinity and surface morphologies of the films are strongly dependent on the growth temperature, which in turn exerts a great effect on microstructural and optical properties of the MZO films. The optical absorption measurements show high ultraviolet (UV) absorbance property of MZO with sharp and intense absorption band in this region and the optical band gap ( E g ) are 3.18, 3.22, 3.25 and 3.21 eV for the films deposited at room temperature, 200, 300 and 400 °C. The photoluminescence (PL) intensity of a strong broad violet–blue emission from MZO nanostructures with increasing deposited temperature was also observed. X-ray photoelectron spectroscopy (XPS) was employed to investigate the surface chemical composition of growth products. [ABSTRACT FROM AUTHOR]

Interfacial thermal stability and band alignment of ALD-derived Al 2 O 3 /HfO 2 /Al 2 O 3 /Ge gate stacks have been investigated by X-ray photoelectron spectroscopy (XPS) and spectroscopy ellipsometry (SE) as a function of annealing temperature. It has been found that reduction in interfacial GeO x component and formation of HfAlO alloy layer have been detected with increasing the annealing temperature from 500 to 700 °C. Combined with analysis from XPS and SE, the increase in conduction band offset and reductions in band gap and valence band offset have been observed. When annealing temperature reaches 700 °C, the valence band offset has been reduced to 0.88 eV, which is smaller than the minimal requirement of Δ E v values for high- k dielectrics and, thus, leads to unacceptably high leakage currents. Therefore, annealing temperature should be carefully controlled to guarantee excellent properties of Al 2 O 3 /HfO 2 /Al 2 O 3 /Ge gate stacks in future Ge-based MOS devices. [ABSTRACT FROM AUTHOR]

Highlights: [•] Sputtering-derived Hf1−xTi x O2 gate dielectrics have been deposited on Si substrates. [•] Increase in crystallization temperature and reduction in Eg have been observed. [•] Formation of silicate layer for 9% TiO2-doped HfO2/Si sample has been detected. [ABSTRACT FROM AUTHOR]

This study was conducted to investigate the effects of lycopene (LYC) on mitochondrial oxidative injury and dysfunction in the liver of aflatoxin B 1 (AFB 1)-exposed broilers. A total of 192 healthy 1-day-old male broilers were randomly divided into 3 groups with 8 replicates of 8 birds each. Birds in the 3 groups were fed basal diet (control), basal diet with 100 µg/kg AFB 1 , and basal diet with 100 µg/kg AFB 1 and 200 mg/kg LYC, respectively. The experiment lasted 42 d. The results showed that AFB 1 decreased average daily body weight gain (ADG), average daily feed intake, and gain to feed ratio (G :F) compared to the control group, the LYC supplementation increased ADG and G/F compared to AFB 1 group (P < 0.05). Broilers in the AFB 1 group had lower mitochondrial glutathione (mGSH) concentration and glutathione peroxidase (GSH-Px), manganese superoxide dismutase (MnSOD), and thioredoxin reductase activities, and higher hydrogen peroxide (H 2 O 2) and reactive oxygen species (ROS) concentrations than the control group (P < 0.05). The LYC increased mGSH concentration and GSH-Px and MnSOD activities, and decreased H 2 O 2 and ROS concentrations compared to AFB 1 group (P < 0.05). Broilers fed the AFB 1 diet showed increased mitochondrial swelling and decreased adenosine triphosphate concentration than the control group, and LYC had opposite effects (P < 0.05). The AFB 1 decreased the activities of mitochondrial electron transfer chain (ETC) complexes I, II, III, and V, downregulated the mRNA expression levels of hepatic MnSOD, thioredoxin 2, thioredoxin reductase, peroxiredoxin-3, peroxisome proliferator-activated receptor γ coactivator 1α, nuclear respiratory factor 1 , and mitochondrial transcription factor A compared with the control group (P < 0.05), and LYC increased activities of mitochondrial ETC complexes III and V, and upregulated mRNA expression levels of these genes in comparison to AFB 1 group (P < 0.05). In conclusion, the LYC protected broilers from AFB 1 -induced liver mitochondrial oxidative injury and dysfunction by stimulating mitochondrial antioxidant capacity and maintaining mitochondrial biogenesis. [ABSTRACT FROM AUTHOR]

Abstract: CoFe2O4/Co0.7Fe0.3 nanocomposite permanent magnets have been synthesized in one step by a hydrothermal method at reaction temperatures of 80, 120, 140, 160 and 180°C and characterized by XRD, SQUID, SEM, (HR)TEM, and SAED. All samples consisted of octahedral CoFe2O4 particles and spherical-like Co0.7Fe0.3 particles. The maximum magnetization and coercivity were 191emu/g and 1311Oe, respectively, values not previously observed for the CoFe2O4/Co0.7Fe0.3 system. This maximum magnetization was attributable to the larger mass ratio of Co0.7Fe0.3 to CoFe2O4, which were in intimate contact. Magnetic dipolar interaction plays a crucial role in magnetic properties and leads to the reduction of the magnetization and the Mr /Ms ratio. The coercivity of all samples exhibited complex variation with reaction temperature and its mechanism may deserve further investigation. [Copyright &y& Elsevier]

Abstract: Using first-principles methods, we have investigated structural and electronic properties of substitutional arsenic donor (AsHg), mercury vacancies (V Hg), and their complexes in arsenic doping of HgCdTe. The role of V Hg in arsenic activation has also been discussed. Counterintuitively, we find that AsHg and V Hg is a single donor and a single acceptor, respectively. The unpaired electron of AsHg makes it act as a nucleation center, driving arsenic interstitials into clusters, which is predicted as a potential candidate for arsenic deactivation. V Hg, exhibiting comparable formation energy with the AsHg donor as well as a shallow acceptor level, is a dominant compensating acceptor in as-grown materials. Coulomb interaction allows AsHg to bind at most one or two V Hg. The resulting complexes behave as compensating acceptors at low temperature. The model outlined for carrier compensation in arsenic-doped HgCdTe contacts well with experimental observations in arsenic activation. [Copyright &y& Elsevier]

Abstract: The as-grown arsenic-doped HgCdTe typically exhibits compensated n-type conductivity. Based on first-principles calculations, we identify Hg vacancies (V Hg) as a dominant defect species involved in the compensation. Arsenic donor (AsHg) and V Hg acceptor no doubt tend to combine into complex defects but little has been recognized about the features of the complex defects in precious studies. These features outlined in this work enable us to provide a consistent explanation for arsenic activation mechanism proposed by Zandian et al. [] and Berding et al. []. [Copyright &y& Elsevier]

Abstract: On the basis of a voltage compensation type active superconducting fault current limiter (SFCL) proposed in previous work, the effects of this type SFCL on distance relay protection are studied in this paper. Under the condition that the active SFCL is placed behind the relay element, its current-limiting impedance will be added into the measured impedance between the relay and the fault points. As a result, in order to prevent the refused operation of the relay, the measured impedance should be revised. According to the three different operation modes of the active SFCL, we present the corresponding three modified formulas. Furthermore, using MATLAB, the model of the dual-source power system with the active SFCL is built, and the impacts of the active SFCL on the distance relay protection are studied in detail under the different current-limiting modes and fault distances. The simulation results show that: without using the modified formulas, the introduction of the active SFCL will reduce the protection distance of the relay, and in the case that the modified formulas are adopted, the three modes of the active SFCL will not affect the measured impedance of the relay, and further the validities of the proposed modified formulas can be testified. [ABSTRACT FROM AUTHOR]

Abstract: We have proposed a voltage compensation type active superconducting fault current limiter (SFCL). In this paper, the influence of the SFCL on the transient stability of power system is investigated. For the typical one-machine infinite-bus system, the power-angle characteristics of generator with SFCL are studied in different working conditions, and the transient physical process is analyzed. Using MATLAB SIMULINK, the power-angle swing curves are simulated under different current-limiting modes, fault types and fault clearance times. The results show that the proposed SFCL can effectively reduce the transient swing amplitude of rotor and extend the critical clearance time under mode 1, compared with mode 2 and mode 3 having few effects on enhancing the transient stability. [Copyright &y& Elsevier]

Abstract: Shuttlelike yttrium hydroxide (Y(OH)3) microcrystals attached with microrods in the middle part were prepared for the first time via a facile solvothermal process in the absence of templates or surfactants. Yttrium oxide (Y2O3) with similar morphology was also prepared by calcining the as-prepared Y(OH)3 at 500°C for 4h. X-ray powder diffraction (XRD) results demonstrate that the as-prepared Y(OH)3 and Y2O3 are attributed to hexagonal phase and cubic phase, respectively. The length of the shuttles is about 15μm and the diameter is about 2μm. The attached rods have an average size of 3μm in length and 1μm in diameter. Furthermore, the surface of the rods and the shuttles is very smooth. The influences of solvent, concentrations of yttrium nitrate and sodium hydroxide on the morphologies of Y(OH)3 were investigated in detail. Y2O3:Eu3+ microstructures with similar morphology were also prepared and their photoluminescence (PL) properties were investigated. [Copyright &y& Elsevier]

Abstract: The bilayer InAs/In0.36Ga0.64As/GaAs(311B) quantum dots (QDs), including one InAs buried quantum dot (BQD) layer and the other InAs surface quantum dot (SQD) layer, have been grown by molecular beam epitaxy (MBE). The optical properties of these three samples have been studied by the piezoreflectance (PzR) spectroscopy. The PzR spectra do not exhibit only the optical transitions originated from the InAs BQDs, but the features originated from the InAs SQDs. After the InAs SQDs have been removed chemically, those optical transitions from InAs SQDs have been demonstrated clearly by investigating the PzR spectra of the residual InAs BQDs in these samples. The great redshift of these interband transitions of InAs SQDs has been well discussed. Due to the suitable InAs SQD sizes and the thickness of In0.36Ga0.64As layer, the interband transition of InAs SQDs has been shifted to ∼1.55μm at 77K. [Copyright &y& Elsevier]

Abstract: The 1D photonic crystals based on multilayer porous silicon are reported in this paper. The photonic structures are composed of alternating high and low dielectric function porous silicon layers by changing the porosity of porous silicon with a periodic electric pulse alternating between 10.0 and 70.0mA/cm2 during anodization on p+-type (100) silicon wafer with resistance range 0.01–0.02Ωcm. Omni-directional mirrors as well as narrow band filters working in the range around 1.55μm are designed and fabricated. Photonic crystal with such a structure exhibits high quality of filter behavior. [Copyright &y& Elsevier]

Abstract: Signatures associated with electronic states confined in two strained In x Ga1–x As/GaAs single quantum wells have been observed in its piezomodulated (PzR) and photomodulated (PR) reflectivity spectra. One comparison of the relative intensity between 11H and 11L signatures in PzR of GaAs/In0.14Ga0.86As SQW emphasizes the contribution of strain dependence of energies of the confined states; the other comparison of corresponding confined states between PzR and PR spectra in both samples has been introduced to interpret the discrepancy of the relative intensity in term of modulated strength, and the calculated ratio of energy shifts induced by strain to that of produced by surface electric field agree with the experimental observation. [Copyright &y& Elsevier]

Crystalline Si3N4/amorphous SiO2 nanocables have been synthesized from silicon substrates and N2 at 1250 °C without any catalyst. The morphology, composition profiles and photoluminescence of the nanocables have been studied. It has been demonstrated that an inner crystalline Si3N4 is formed whereas the outer SiO2 is amorphous. The nanocables are 90–110 nm in diameter and several micrometers in length, while the core-wires are 30–50 nm in diameter. Intense blue or near violet photoluminescence from these nanocables was observed. A tentative growth mechanism model for the crystalline Si3N4/amorphous SiO2 nanocables has been suggested and discussed. [Copyright &y& Elsevier]

The change of phonon energies of annealed InGaAs/GaAs quantum dots (QDs), was observed using selectively excited photoluminescence. X-ray diffraction and optical anisotropy analysis shows that the QDs’ structure mainly changes along the growth direction. [Copyright &y& Elsevier]

Abstract: Near-field effect has been recognized to play an important role in optical coupling of multiple quantum well infrared photodetectors (QWIP). Both the optical near-field effect and the plasmonic effect in the quantum well active region of QWIP device have been studied by the finite difference time-domain (FDTD) method at the optical frequency of 4.2THz. Our numerical results indicate that both the near-field effect and the plasmonic effect can induce an evanescent wave with the electrical component being parallel to the growth direction of quantum well. The induced electrical component in the QWIP growth direction is 2.5 times larger than that of the incident optical fields. The induced polarization can increase the optical coupling efficiency of QWIP and the detectivity of QWIP can be improved at 4.2THz. [Copyright &y& Elsevier]

Abstract: The optical properties of GaAsN films have been studied by photoluminescence (PL) and photo-modulation reflection (PR). The effects of postgrowth anneal on the band structure and optical efficiency have been shown basing on these measurements. Both the samples with close N content grown at different temperatures exhibit high crystalline quality according to the X-ray diffraction. The alloy films show remarkable stability against rapid thermal annealing (RTA) process. The blueshift of the PL peak energy is found to be 3.8meV when annealing up to 900°C, meanwhile the PL intensity increases significantly until RTA at 850°C. [Copyright &y& Elsevier]

• Charge transfer between adsorbed metals and BP builds an internal electric field. • Electronic structures of few-layer BP can be modulated by the Stark effect. • Phase transition of semiconductor-Dirac metal was found in few-layer BP. Few-layer black phosphorus (BP) is an important member in a family of two-dimensional materials because of its unique physical properties. But, for future applications, further tuning its electronic structure is necessary. Here we investigate, using ab initio density-function theory, the band structures of few-layer BP after the adsorption of the alkali metal atoms. It is shown that such adsorption can modify the band structures of few-layer BP in terms of the Stark effect. The charge transfer between the adsorbed atoms and few-layer BP is responsible for the internal electric field. Both the effects of the layer thickness and the concentration of adsorbed atoms on the band structures of few-layer BP are also quantitatively studied. The calculated results show that the band gap decreases with increasing the concentration of the adsorbed atoms. Further increasing the thickness of few-layer BP will close its band gap and induce the phase transition of semiconductor - Dirac metal. These findings imply that the electronic properties of few-layer BP can be modulated by adsorbing the alkali metal atoms. [ABSTRACT FROM AUTHOR]

Completely decomposed granite (CDG) soils in Shenzhen, China are usually subjected to loading-unloading due to the demolition/reconstruction of buildings and excavation/backfilling of foundation pits during the rapid development of the city. To investigate the mechanical behavior including the failure mode of the CDG soils under loading-unloading, consolidated drained triaxial tests along multi-stage loading-unloading paths were carried out in this study. Four types of loading sequences with one, two, three, and four loading-unloading cycles, respectively, were applied to investigate the mechanical properties of the CDG soil. Test results show that, as the number of the loading-unloading cycles increased from one to four, the effective cohesion (c') increased from 45.4 to 63.6 kPa; however, the effective friction angle (φ') first increased from 22.0° to 27.1° and then decreased to 19.0°. These results are mainly related to the strain-hardening property of the CDG soil after compressed by a relatively low deviator stress in the first two cycles and the structural damage of the specimens caused by a higher deviator stress in the last two cycles. In addition, the secant modulus also increased in the first two cycles, but decreased in the last two cycles due to the aggravation of soil structural damage. However, the unloading modulus (E ur) decreased all the way from 162.9 to 22.7 MPa is attributed to the number of loading-unloading cycles and the different confining stresses applied in the tests. The unloading modulus was not only affected by the confining pressure and, more importantly, also affected by the accumulated structural damage of soils. • Effects of cyclic loading-unloading path on mechanical behavior of the CDG are discussed. • Positive correlation between secant modulus and confining pressure was observed. • Positive correlation between unloading modulus and confining pressure was observed. • Shear failure of CDG with cyclic number, confining pressure was investigated. [ABSTRACT FROM AUTHOR]

Using a free-electron laser(FEL) source, we have studied the two-photon-absorption (TPA) effect in GaAs/AlGaAs quantum-well infrared photodetector (QWIP). The TPA-induced photoresponse in QWIPs has been measured under different FEL excitation power by the photoconductivity method. The effective-mass approximation theory is used for the QWIP structure to explain the photoresponse behavior. It is demonstrated that the TPA-induced photocarrier density is proportional to the square of the excitation power. Based on the experimental results, the TPA coefficients of QWIPs were obtained to be 0.0045, 0.0030, 0.0103, and 0.0061 cm/MW for the excitation lines of 10.6, 10.7, 11.9 and 13.2 μm, respectively. The dependence the TPA coefficients on the excitation wavelength is explained by our theoretical model. [ABSTRACT FROM AUTHOR]