Pair interactions of heavy vortices in quantum fluids

Science.gov (United States)

Pshenichnyuk, Ivan A.

2018-02-01

The dynamics of quantum vortex pairs carrying heavy doping matter trapped inside their cores is studied. The nonlinear classical matter field formalism is used to build a universal mathematical model of a heavy vortex applicable to different types of quantum mixtures. It is shown how the usual vortex dynamics typical for undoped pairs qualitatively changes when heavy dopants are used: heavy vortices with opposite topological charges (chiralities) attract each other, while vortices with the same charge are repelled. The force responsible for such behavior appears as a result of superposition of vortices velocity fields in the presence of doping substance and can be considered as a special realization of the Magnus effect. The force is evaluated quantitatively and its inverse proportionality to the distance is demonstrated. The mechanism described in this paper gives an example of how a light nonlinear classical field may realize repulsive and attractive interactions between embedded heavy impurities.

Heavy quark effective theory and heavy baryon transitions

International Nuclear Information System (INIS)

Hussain, F.

1992-01-01

The heavy quark effective theory (HQET) is applied to study the weak decay of heavy mesons and heavy baryons and to predict the form factors for heavy to heavy and heavy to light transitions. 28 refs, 10 figs, 2 tabs

Sequestration of radionuclides and heavy metals by hydroxyapatite doped with Fe, Cu and Sn

International Nuclear Information System (INIS)

Neidel, Linnah L.; Moore, Robert Charles; Salas, Fred; Grouios, Fotini; Holt, Kathleen Caroline; Helean, Katheryn B.

2005-01-01

Apatite, Ca 5 (PO 4 ) 3 (F,OH,Cl)(P6 3 /m, Z=2), is the most abundant phosphate mineral on Earth. The end-member hydroxyapatite, Ca 5 (PO 4 ) 3 OH(P2 1 /b), is the primary mineral component in bones and teeth and tends to scavenge and sequester heavy metals in the human body. Hydroxyapatite has also been shown to be effective at sequestering radionuclides and heavy metals in certain natural systems (Dybowska et al., 2004). Hydroxyapatite has been the focus of many laboratory studies and is utilized for environmental remediation of contaminated sites (Moore et al., 2002). The crystal structure of apatite tolerates a great deal of distortion caused by extensive chemical substitutions. Metal cations (e.g. REE, actinides, K, Na, Mn, Ni, Cu, Co, Zn, Sr, Ba, Pb, Cd, Fe) substitute for Ca, and oxyanions (e.g. AsO 4 3- , SO 4 2- , CO 3 2- , SiO 4 4- , CrO 4 2- ) replace PO 4 3- through a series of coupled substitutions that preserve electroneutrality. Owing to the ability of apatite to incorporate 'impurities'(including actinides) gives rise to its proposed use as a waste form for radionuclides. Recent work at Sandia National Laboratory demonstrated that hydroxyapatite has a strong affinity for U, Pu, Np, Sr and Tc reduced from pertechnetate (TcO 4 - ) by SnCl 2 (Moore et al., 2002). Based on these earlier promising results, an investigation was initiated into the use of apatite-type materials doped with aliovalent cations including Fe, Cu and Sn as Tc-scavengers. Synthetic Fe and Cu-doped hydroxyapatite samples were prepared by precipitation of Ca, from Ca-acetate, and P, from ammonium phosphate. The Fe and Cu were introduced as chlorides into the Ca-acetate solution. Stannous chloride was used as a reducing agent and was apparently incorporated into the crystal structures of the hydroxyapatite samples in small, as yet undetermined quantities.

Sequestration of Radionuclides and Heavy Metals by Hydroxyapatite Doped with Fe, Cu and Sn

International Nuclear Information System (INIS)

K.B. Helean; R.C. Moore

2005-01-01

Apatite, Ca 5 (PO 4 ) 3 (F,OH,Cl) (P6 3 /m, Z=2), is the most abundant phosphate mineral on Earth. The end-member hydroxyapatite, Ca 5 (PO 4 ) 3 OH (P2 1 /b), is the primary mineral component in bones and teeth and tends to scavenge and sequester heavy metals in the human body. Hydroxyapatite has also been shown to be effective at sequestering radionuclides and heavy metals in certain natural systems (Dybowska et al., 2004). Hydroxyapatite has been the focus of many laboratory studies and is utilized for environmental remediation of contaminated sites (Moore et al., 2002). The crystal structure of apatite tolerates a great deal of distortion caused by extensive chemical substitutions. Metal cations (e.g. REE, actinides, K, Na, Mn, Ni, Cu, Co, Zn, Sr, Ba, Pb, Cd, Fe) substitute for Ca, and oxyanions (e.g. AsO 4 3- , SO 4 2- , CO 3 2- , SiO 4 4- , CrO 4 2- ) replace PO 4 3- through a series of coupled substitutions that preserve electroneutrality. Owing to the ability of apatite to incorporate ''impurities'' (including actinides) gives rise to its proposed use as a waste form for radionuclides. Recent work at Sandia National Laboratory demonstrated that hydroxyapatite has a strong affinity for U, Pu, Np, Sr and Tc reduced from pertechnetate (TcO 4 - ) by SnCl 2 (Moore et al., 2002). Based on these earlier promising results, an investigation was initiated into the use of apatite-type materials doped with aliovalent cations including Fe, Cu and Sn as Tc-scavengers. Synthetic Fe and Cu-doped hydroxyapatite samples were prepared by precipitation of Ca, from Ca-acetate, and P, from ammonium phosphate. The Fe and Cu were introduced as chlorides into the Ca-acetate solution. Stannous chloride was used as a reducing agent and was apparently incorporated into the crystal structures of the hydroxyapatite samples in small, as yet undetermined quantities

Doping effect in Si nanocrystals

Science.gov (United States)

Li, Dongke; Xu, Jun; Zhang, Pei; Jiang, Yicheng; Chen, Kunji

2018-06-01

Intentional doping in semiconductors is a fundamental issue since it can control the conduction type and ability as well as modify the optical and electronic properties. To realize effective doping is the basis for developing semiconductor devices. However, by reducing the size of a semiconductor, like Si, to the nanometer scale, the doping effects become complicated due to the coupling between the quantum confinement effect and the surfaces and/or interfaces effect. In particular, by introducing phosphorus or boron impurities as dopants into material containing Si nanocrystals with a dot size of less than 10 nm, it exhibits different behaviors and influences on the physical properties from its bulk counterpart. Understanding the doping effects in Si nanocrystals is currently a challenge in order to further improve the performance of the next generation of nano-electronic and photonic devices. In this review, we present an overview of the latest theoretical studies and experimental results on dopant distributions and their effects on the electronic and optical properties of Si nanocrystals. In particular, the advanced characterization techniques on dopant distribution, the carrier transport process as well as the linear and nonlinear optical properties of doped Si nanocrystals, are systematically summarized.

Muon studies of heavy fermions

International Nuclear Information System (INIS)

Heffner, R.H.

1991-01-01

Recent muon spin relaxation (μSR) studies have been particularly effective in revealing important properties of the unusual magnetism and superconductivity found in heavy fermion (HF) systems. In this paper μSR experiments elucidating the symmetry of superconducting order parameter in UPt 3 and UBe 13 doped with thorium and reviewed. Also discussed is the correlation between the enhanced superconducting specific heat jump and the reduced Kondo temperature in B-doped UBe 13 , indicating possible direct experimental evidence for a magnetic pairing mechanism in HF superconductors. 23 refs., 3 figs

Heavy baryon transitions and the heavy quark effective theory

International Nuclear Information System (INIS)

Hussain, F.

1992-01-01

Heavy baryon decays are studied in the context of the Bethe-Salpeter approach to the heavy quark effective theory. A drastic reduction, in the number of independent form factors, is found. Results are presented both for heavy to heavy and heavy to light baryon decays. (orig.)

Thermopower studies of doped CeAl sub 2 and UAl sub 2

CERN Document Server

Park, J G

1997-01-01

We have studied the thermopower of U doped CeAl sub 2 and Ce and La doped UAl sub 2. Despite different ground state properties of CeAl sub 2 and UAl sub 2 , the former being an antiferromagnetic heavy-fermion compound and the latter non-magnetic, we have found that not only thermopower data for pure CeAl sub 2 and UAl sub 2 are similar but also the thermopower results of doped samples behave similarly. Although the similarity seen in pure systems is yet to be understood, we interpret the doping effects as the results of changes in energy dependent relaxation time with doping. (author)

Heavy rain effects

Science.gov (United States)

Dunham, R. Earl, Jr.

1994-01-01

This paper summarizes the current state of knowledge of the effect of heavy rain on airplane performance. Although the effects of heavy rain on airplane systems and engines are generally known, only recently has the potential aerodynamic effect of heavy rain been recognized. In 1977 the United States Federal Aviation Administration (FAA) conducted a study of 25 aircraft accidents and incidents which occurred between 1964 and 1976 in which low-altitude wind shear could have been a contributing factor. Of the 25 cases (23 approach or landing and 2 take-off) in the study, ten cases had occurred in a rain environment, and in five cases these were classified as intense or heavy rain encounters. These results led to the reconsideration of high-intensity, short-duration rainfall as a potential weather-related aircraft safety hazard, particularly in the take-off and/or approach phases of flight.

First-principles study of the effects of Silicon doping on the Schottky barrier of TiSi2/Si interfaces

Science.gov (United States)

Wang, Han; Silva, Eduardo; West, Damien; Sun, Yiyang; Restrepo, Oscar; Zhang, Shengbai; Kota, Murali

As scaling of semiconductor devices is pursued in order to improve power efficiency, quantum effects due to the reduced dimensions on devices have become dominant factors in power, performance, and area scaling. In particular, source/drain contact resistance has become a limiting factor in the overall device power efficiency and performance. As a consequence, techniques such as heavy doping of source and drain have been explored to reduce the contact resistance, thereby shrinking the width of depletion region and lowering the Schottky barrier height. In this work, we study the relation between doping in Silicon and the Schottky barrier of a TiSi2/Si interface with first-principles calculation. Virtual Crystal Approximation (VCA) is used to calculate the average potential of the interface with varying doping concentration, while the I-V curve for the corresponding interface is calculated with a generalized one-dimensional transfer matrix method. The relation between substitutional and interstitial Boron and Phosphorus dopant near the interface, and their effect on tuning the Schottky barrier is studied. These studies provide insight to the type of doping and the effect of dopant segregation to optimize metal-semiconductor interface resistance.

Doping in sport: effects, harm and misconceptions.

Science.gov (United States)

Birzniece, V

2015-03-01

Doping in sport is a widespread problem not just among elite athletes, but even more so in recreational sports. In scientific literature, major emphasis is placed on doping detection, whereas detrimental effects of doping agents on athletes' health are seldom discussed. Androgenic anabolic steroids are well known for their positive effects on muscle mass and strength. Human growth hormone also increases muscle mass, although the majority of that is an increase in extracellular fluid and not the functional muscle mass. In recreational athletes, growth hormone does not have major effect on muscle strength, power or aerobic capacity, but stimulates anaerobic exercise capacity. Erythropoietin administration increases oxygen-carrying capacity of blood improving endurance measures, whereas systemic administration of beta-adrenergic agonists may have positive effect on sprint capacity, and beta-adrenergic antagonists reduce muscle tremor. Thus, there are certain drugs that can improve selective aspects of physical performance. However, most of the doping agents exert serious side-effects, especially when used in combination, at high doses and for a long duration. The extent of long-term health consequences is difficult to predict, but likely to be substantial, especially when gene doping is considered. This review summarises the main groups of doping agents used by athletes, with the main focus on their effects on athletic performance and adverse effects. © 2014 Royal Australasian College of Physicians.

Heavy baryons in the heavy quark effective theory

International Nuclear Information System (INIS)

Koerner, J.G.; Thompson, G.

1991-10-01

We give a mini-review of recent results on current-induced transitions between heavy baryons (and between heavy and light baryons) in the light of the new spin and flavour symmetries of the Heavy Quark Effective Theory (HQET). We discuss the structure of the 1/m corrections to the heavy mass limit and outline a diagrammatic proof that there are no 0(1/m) correction to the Voloshin-Shifman normalization condition at zero recoil. (orig.)

Heavy quark effective theory and study of heavy hadron spectra

International Nuclear Information System (INIS)

Dong Yubing

1995-01-01

By employing the heavy quark effective theory, the spectra of heavy hadrons, such as heavy mesons (Q-barq), heavy baryons (QQq and Qqq) and heavy multiquark systems (Q-barQ-barqq) are studied systemically. The results are compared with the predictions for Q-barQ-barqq in potential model

Heavy fermion and actinide materials

International Nuclear Information System (INIS)

1993-01-01

During this period, 1/N expansions have been systematically applied to the calculation of the properties of highly correlated electron systems. These studies include examinations of (a) the class of materials known as heavy fermion semi-conductors, (b) the high energy spectra of heavy fermion systems, and (c) the doped oxide superconductors

Striking the Right Balance : Effectiveness of Anti-Doping Policies

NARCIS (Netherlands)

de Hon, O.M.

2016-01-01

Doping, and anti-doping, is in the news on a continuous basis. At the core of these stories and discussions is the question how effective anti-doping policies are to curb the use of doping in sports. Anti-doping policies are based on ethical values, a juridical framework, laboratory analyses,

Doping dependence of Meissner effect in cuprate superconductors

International Nuclear Information System (INIS)

Feng Shiping; Huang Zheyu; Zhao Huaisong

2010-01-01

Within the t-t'-J model, the doping dependence of the Meissner effect in cuprate superconductors is studied based on the kinetic energy driven superconducting mechanism. Following the linear response theory, it is shown that the electromagnetic response consists of two parts, the diamagnetic current and the paramagnetic current, which exactly cancels the diamagnetic term in the normal state, and then the Meissner effect is obtained for all the temperature T ≤ T c throughout the superconducting dome. By considering the two-dimensional geometry of cuprate superconductors within the specular reflection model, the main features of the doping and temperature dependence of the local magnetic field profile, the magnetic field penetration depth, and the superfluid density observed on cuprate superconductors are well reproduced. In particular, it is shown that in analogy to the domelike shape of the doping dependent superconducting transition temperature, the maximal superfluid density occurs around the critical doping δ ∼ 0.195, and then decreases in both lower doped and higher doped regimes.

Relativistic heavy-atom effects on heavy-atom nuclear shieldings

Science.gov (United States)

Lantto, Perttu; Romero, Rodolfo H.; Gómez, Sergio S.; Aucar, Gustavo A.; Vaara, Juha

2006-11-01

The principal relativistic heavy-atom effects on the nuclear magnetic resonance (NMR) shielding tensor of the heavy atom itself (HAHA effects) are calculated using ab initio methods at the level of the Breit-Pauli Hamiltonian. This is the first systematic study of the main HAHA effects on nuclear shielding and chemical shift by perturbational relativistic approach. The dependence of the HAHA effects on the chemical environment of the heavy atom is investigated for the closed-shell X2+, X4+, XH2, and XH3- (X =Si-Pb) as well as X3+, XH3, and XF3 (X =P-Bi) systems. Fully relativistic Dirac-Hartree-Fock calculations are carried out for comparison. It is necessary in the Breit-Pauli approach to include the second-order magnetic-field-dependent spin-orbit (SO) shielding contribution as it is the larger SO term in XH3-, XH3, and XF3, and is equally large in XH2 as the conventional, third-order field-independent spin-orbit contribution. Considering the chemical shift, the third-order SO mechanism contributes two-thirds of the difference of ˜1500ppm between BiH3 and BiF3. The second-order SO mechanism and the numerically largest relativistic effect, which arises from the cross-term contribution of the Fermi contact hyperfine interaction and the relativistically modified spin-Zeeman interaction (FC/SZ-KE), are isotropic and practically independent of electron correlation effects as well as the chemical environment of the heavy atom. The third-order SO terms depend on these factors and contribute both to heavy-atom shielding anisotropy and NMR chemical shifts. While a qualitative picture of heavy-atom chemical shifts is already obtained at the nonrelativistic level of theory, reliable shifts may be expected after including the third-order SO contributions only, especially when calculations are carried out at correlated level. The FC/SZ-KE contribution to shielding is almost completely produced in the s orbitals of the heavy atom, with values diminishing with the principal

Composition effects on optical properties of Tb.sup.3+./sup.-doped heavy germanate glasses

Czech Academy of Sciences Publication Activity Database

Chen, G.; Yang, Y.; Zhao, D.; Xia, F.; Baccaro, S.; Cecilia, A.; Nikl, Martin

2005-01-01

Roč. 88, č. 2 (2005), s. 293-296 ISSN 0002-7820 Institutional research plan: CEZ:AV0Z10100521 Keywords : luminescence * transmission * germanate glass es * Tb-doped Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.586, year: 2005

Electrical and optical properties of Si-doped Ga2O3

Science.gov (United States)

Li, Yin; Yang, Chuanghua; Wu, Liyuan; Zhang, Ru

2017-05-01

The charge densities, band structure, density of states, dielectric functions of Si-doped β-Ga2O3 have been investigated based on the density functional theory (DFT) within the hybrid functional HSE06. The heavy doping makes conduction band split out more bands and further influences the band structure. It decreases the band gap and changes from a direct gap to an indirect gap. After doping, the top of the valence bands is mainly composed by the O-2p states, Si-3p states and Ga-4p states and the bottom of the conduction bands is almost formed by the Si-3s, Si-3p and Ga-4s orbits. The anisotropic optical properties have been investigated by means of the complex dielectric function. After the heavy Si doping, the position of absorption band edges did not change much. The slope of the absorption curve descends and indicates that the absorption became more slow for Si-doped β-Ga2O3 than undoped one due to the indirect gap of Si-doped β-Ga2O3.

Doping and musculoskeletal system: short-term and long-lasting effects of doping agents.

Science.gov (United States)

Nikolopoulos, Dimitrios D; Spiliopoulou, Chara; Theocharis, Stamatios E

2011-10-01

Doping is a problem that has plagued the world of competition and sports for ages. Even before the dawn of Olympic history in ancient Greece, competitors have looked for artificial means to improve athletic performance. Since ancient times, athletes have attempted to gain an unfair competitive advantage through the use of doping substances. A Prohibited List of doping substances and methods banned in sports is published yearly by the World Anti-Doping Agency. Among the substances included are steroidal and peptide hormones and their modulators, stimulants, glucocorticosteroids, β₂-agonists, diuretics and masking agents, narcotics, and cannabinoids. Blood doping, tampering, infusions, and gene doping are examples of prohibited methods indicated on the List. Apart from the unethical aspect of doping, as it abrogates fair-play's principle, it is extremely important to consider the hazards it presents to the health and well-being of athletes. The referred negative effects for the athlete's health have to do, on the one hand, by the high doses of the performance-enhancing agents and on the other hand, by the relentless, superhuman strict training that the elite or amateur athletes put their muscles, bones, and joints. The purpose of this article is to highlight the early and the long-lasting consequences of the doping abuse on bone and muscle metabolism. © 2010 The Authors Fundamental and Clinical Pharmacology © 2010 Société Française de Pharmacologie et de Thérapeutique.

Effects of pressure on doped Kondo insulators

International Nuclear Information System (INIS)

Lee, Chengchung; Xu, Wang

1999-08-01

The effects of pressure on the doped Kondo insulators (KI) are studied in the framework of the slave-boson mean-field theory under the coherent potential approximation (CPA). A unified picture for both electron-type KI and hole-type KI is presented. The density of states of the f-electrons under the applied pressures and its variation with the concentration of the Kondo holes are calculated self-consistently. The specific heat coefficient, the zero-temperature magnetic susceptibility as well as the low temperature electric resistivity of the doped KI under various pressures are obtained. The two contrasting pressure-dependent effects observed in the doped KI systems can be naturally explained within a microscopic model. (author)

Simulation study on single event burnout in linear doping buffer layer engineered power VDMOSFET

International Nuclear Information System (INIS)

Jia Yunpeng; Su Hongyuan; Hu Dongqing; Wu Yu; Jin Rui

2016-01-01

The addition of a buffer layer can improve the device's secondary breakdown voltage, thus, improving the single event burnout (SEB) threshold voltage. In this paper, an N type linear doping buffer layer is proposed. According to quasi-stationary avalanche simulation and heavy ion beam simulation, the results show that an optimized linear doping buffer layer is critical. As SEB is induced by heavy ions impacting, the electric field of an optimized linear doping buffer device is much lower than that with an optimized constant doping buffer layer at a given buffer layer thickness and the same biasing voltages. Secondary breakdown voltage and the parasitic bipolar turn-on current are much higher than those with the optimized constant doping buffer layer. So the linear buffer layer is more advantageous to improving the device's SEB performance. (paper)

Morphology evolution of hydrothermally grown ZnO nanostructures on gallium doping and their defect structures

Energy Technology Data Exchange (ETDEWEB)

Pineda-Hernandez, G. [Facultad de Ingenieria Quimica, Benemerita Universidad Autonoma de Puebla, C.P. 72570 Puebla, Pue. (Mexico); Escobedo-Morales, A., E-mail: alejandroescobedo@hotmail.com [Facultad de Ingenieria Quimica, Benemerita Universidad Autonoma de Puebla, C.P. 72570 Puebla, Pue. (Mexico); Pal, U. [Instituto de Fisica, Benemerita Universidad Autonoma de Puebla, Apdo. Postal J-48, C.P. 72570 Puebla, Pue. (Mexico); Chigo-Anota, E. [Facultad de Ingenieria Quimica, Benemerita Universidad Autonoma de Puebla, C.P. 72570 Puebla, Pue. (Mexico)

2012-08-15

In the present article, the effect of gallium doping on the morphology, structural, and vibrational properties of hydrothermally grown ZnO nanostructures has been studied. It has been observed that incorporated gallium plays an important role on the growth kinetics and hence on the morphology evolution of the ZnO crystals. Ga doping in high concentration results in the contraction of ZnO unit cell, mainly along c-axis. Although Ga has high solubility in ZnO, heavy doping promotes the segregation of Ga atoms as a secondary phase. Incorporated Ga atoms strongly affect the vibrational characteristics of ZnO lattice and induce anomalous Raman modes. Possible mechanisms of morphology evolution and origin of anomalous Raman modes in Ga doped ZnO nanostructures are discussed. -- Highlights: Black-Right-Pointing-Pointer Ga doped ZnO nanostructures were successfully grown by hydrothermal chemical route. Black-Right-Pointing-Pointer Ga doping has strong effect on the resulting morphology of ZnO nanostructures. Black-Right-Pointing-Pointer Anomalous vibrational modes in wurtzite ZnO lattice are induced by Ga doping. Black-Right-Pointing-Pointer Incorporated Ga atoms accommodate at preferential lattice sites.

First-principles study of doping effect on the phase transition of zinc oxide with transition metal doped

International Nuclear Information System (INIS)

Wu, Liang; Hou, Tingjun; Wang, Yi; Zhao, Yanfei; Guo, Zhenyu; Li, Youyong; Lee, Shuit-Tong

2012-01-01

Highlights: ► We study the doping effect on B4, B1 structures and phase transition of ZnO. ► We calculate the phase transition barrier and phase transition path of doped ZnO. ► The transition metal doping decreases the bulk modulus and phase transition pressure. ► The magnetic properties are influenced by the phase transition process. - Abstract: Zinc oxide (ZnO) is a promising material for its wide application in solid-state devices. With the pressure raised from an ambient condition, ZnO transforms from fourfold wurtzite (B4) to sixfold coordinated rocksalt (B1) structure. Doping is an efficient approach to improve the structures and properties of materials. Here we use density-functional theory (DFT) to study doped ZnO and find that the transition pressure from B4 phase to B1 phase of ZnO always decreases with different types of transition metal (V, Cr, Mn, Fe, Co, or Ni) doped, but the phase transition path is not affected by doping. This is consistent with the available experimental results for Mn-doped ZnO and Co-doped ZnO. Doping in ZnO causes the lattice distortion, which leads to the decrease of the bulk modulus and accelerates the phase transition. Mn-doped ZnO shows the strongest magnetic moment due to its half filled d orbital. For V-doped ZnO and Cr-doped ZnO, the magnetism is enhanced by phase transition from B4 to B1. But for Mn-doped ZnO, Fe-doped ZnO, Co-doped ZnO, and Ni-doped ZnO, B1 phase shows weaker magnetic moment than B4 phase. These results can be explained by the amount of charge transferred from the doped atom to O atom. Our results provide a theoretical basis for the doping approach to change the structures and properties of ZnO.

Spin Hall Effect in Doped Semiconductor Structures

Science.gov (United States)

Tse, Wang-Kong; Das Sarma, Sankar

2006-03-01

We present a microscopic theory of the extrinsic spin Hall effect based on the diagrammatic perturbation theory. Side-jump (SJ) and skew-scattering (SS) contributions are explicitly taken into account to calculate the spin Hall conductivity, and we show their effects scale as σxy^SJ/σxy^SS ˜(/τ)/ɛF, where τ being the transport relaxation time. Motivated by recent experimental work we apply our theory to n-doped and p-doped 3D and 2D GaAs structures, obtaining analytical formulas for the SJ and SS contributions. Moreover, the ratio of the spin Hall conductivity to longitudinal conductivity is found as σs/σc˜10-3-10-4, in reasonable agreement with the recent experimental results of Kato et al. [Science 306, 1910 (2004)] in n-doped 3D GaAs system.

VOx effectively doping CVD-graphene for transparent conductive films

Science.gov (United States)

Ji, Qinghua; Shi, Liangjing; Zhang, Qinghong; Wang, Weiqi; Zheng, Huifeng; Zhang, Yuzhi; Liu, Yangqiao; Sun, Jing

2016-11-01

Chemical vapor deposition(CVD)-synthesized graphene is potentially an alternative for tin-doped indium oxide (ITO) transparent conductive films (TCFs), however its sheet resistance is still too high to meet many demands. Vanadium oxide has been widely applied as smart window materials, however, no study has been reported to use it as dopant to improve the conductivity of graphene TCFs. In this study, we firstly reported that VOx doping can effectively lower the sheet resistance of CVD-graphene films while keeping its good optical properties, whose transmittance is as high as 86-90%. The optimized VOx-doped graphene exhibits a sheet resistance as low as 176 Ω/□, which decreases by 56% compared to the undoped graphene films. The doping process is convenient, stable, economical and easy to operate. What is more, VOx can effectively increase the work function(WF) of the film, making it more appropriate for use in solar cells. The evolution of the VOx species annealed at different temperatures below 400 °C has been detailed studied for the first time, based on which the doping mechanism is proposed. The prepared VOx doped graphene is expected to be a promising candidate for transparent conductive film purposes.

Effect of iron doping on Y-Ba-Cu-O

International Nuclear Information System (INIS)

Abd Halim Shaari; Mansor Hashim; Sidek Hj Abd Aziz; Laily Rafiah Abdullah

1991-01-01

Study on the effect of iron doping at different values of doping percentage (0.00< x<0.06) and hence the influence of magnetic iron on Y-Ba-Cu-O superconductor has been carried out. The conventional technique of sintering is used in preparing the ceramic materials. The crystal structure and their lattice parameters are determined from X-ray diffraction measurements. Observation on the dependence of resistance on temperature is made between room temperature to the boiling point of liquid nitrogen, using four-probe techniques. Magnetisation properties namely the Meissner Effect is also observed by levitating a small piece of permanent magnet on the cooled sample. The X-ray diffraction data show that the phase transitions have been observed; from orthorhombic to tetragonal when the iron doping exceeded ∼0.02. Transition temperature, Tc decrease from ∼87.7K to ∼83K. Meissner Effect is observed for sample doped up to 2% only

Co-doping effects on luminescence and scintillation properties of Ce doped Lu3Al5O12 scintillator

International Nuclear Information System (INIS)

Kamada, Kei; Nikl, Martin; Kurosawa, Shunsuke; Beitlerova, Alena; Nagura, Aya; Shoji, Yasuhiro; Pejchal, Jan; Ohashi, Yuji; Yokota, Yuui; Yoshikawa, Akira

2015-01-01

The Mg, Ca, Sr and Ba 200 ppm co-doped Ce:Lu 3 Al 5 O 12 single crystals were prepared by micro pulling down method. Absorption and luminescence spectra were measured together with several other scintillation characteristics, namely the scintillation decay and light yield to reveal the effect of the co-doping. The scintillation decays were accelerated by both Mg and Ca co-dopants. The Mg co-doped samples showed the fastest decay and the highest light yield among the co-doped samples

Effect of doping on the electron transport in polyfluorene

Energy Technology Data Exchange (ETDEWEB)

Bajpai, Manisha, E-mail: mansa83@gmail.com [Soft Materials Research Laboratory, Centre of Material Sciences, Institute of Interdisciplinary Studies, University of Allahabad, Allahabad, 211002 (India); Department of Physics, Banaras Hindu University, Varanasi-221005 (India); Srivastava, Ritu [Physics for Energy Harvesting Division, National Physical Laboratory (Council of Scientific and Industrial Research), Dr K. S. Krishnan Road, New Delhi 110012 (India); Dhar, Ravindra [Soft Materials Research Laboratory, Centre of Material Sciences, Institute of Interdisciplinary Studies, University of Allahabad, Allahabad, 211002 (India); Tiwari, R. S. [Department of Physics, Banaras Hindu University, Varanasi-221005 (India)

2016-05-06

In this paper, electron transport of pure and DMC doped polyfluorne (PF) films have been studied at various doping concentrations. Pure films show space charge limited conduction with field and temperature dependent mobility. The J–V characteristics of doped PF were ohmic at low voltages due to thermally released carriers from dopant states. At higher voltages the current density increases nonlinearly due to field dependent mobility and carrier concentration thereby filling of tail states of HOMO of the host. The conductivity of doped films were analyzed using the Unified Gaussian Disorder Model (UGDM). The carrier concentration obtained from the fitting show a non-linear dependence on doping concentration which may be due to a combined effect of thermally activated carrier generation and increased carrier mobility.

Baryons in the heavy quark effective theory

International Nuclear Information System (INIS)

Mannel, T.; Roberts, W.; Ryzak, Z.

1990-08-01

We show how to incorporate baryons in the heavy quark effective theory. A convenient formalism is exhibited and applied to semileptonic weak decays of heavy baryons and to exclusive production of heavy baryons in e + e - annihilation. (orig.)

The effects of carbon nano filaments (CNT and CNF) doping on high temperature superconductors Y-123

International Nuclear Information System (INIS)

Dadras, S.; Daadmehr, V.

2007-01-01

Full text: This paper is based on the effects of carbon nano filaments (carbon nano tubes and carbon nano fibers) doping on Y-123 studies. We synthesized Y-123 with different contents of CNT and CNF doping. The samples were prepared from powders of Y 2 O 3 , BaCO 3 and Cu O by the solid state reaction. After calcination in air, we mixed Y-123 powder with different percentage of carbon nano filaments weight, produced by the CVD method. For obtaining more homogenous mixing, we have suspended it in an organic solvent with an ultrasonic mixer to prevent agglomeration of CNT. The CNT-Y-123 powder was dried afterwards, and pressed as pellet samples, in about 1mm thick, 10mm diameter, and 1gr weight, and sintered in oxygen atmosphere. We tried to find the transport effects on CNT and CNF doping in 123 systems. The strong coupling between grains in CNT doped samples caused the flow of inter-granular currents. Therefore the presence of CNT in high temperature superconductor samples increases the critical current density. Among various carbon precursors, carbon nano tubes (CNT) are very interesting because of their nano meter diameter which may make them as effective pinning centers, compared to the ordinary carbon. The carbon nano tubes are functioning like columnar defects produced by heavy-ion irradiation. Nano phase particles or aggregates embodied in the superconductor matrix can pin the flux lines effectively and enhance the intra-grain transport critical current density in high applied magnetic fields. Nano phase size particles in the size range of about 5-10 nm can be used as flux pinning centers for low field applications. The effects of carbon and carbon dioxide in Y-123 were studied by several groups, but none of them argued the effects of carbon nano tubes doping on Y-123. Uno et al. found that Jc was related to the carbon concentration, but they showed that Tc value and other physical properties did not change. In carbon doped Y-123 samples, Tc decreases with

Doping effects in InN/GaN short-period quantum well structures-Theoretical studies based on density functional methods

Science.gov (United States)

Strak, Pawel; Kempisty, Pawel; Sakowski, Konrad; Krukowski, Stanislaw

2014-09-01

Density functional theory studies were conducted to determine an influence of the carrier concentration on the optical and electronic properties of InN/GaN superlattice system. The oscillator strength values, energy gaps and the band profiles were obtained. The band profiles were found to be strongly affected for technically possible heavy n-type doping while for p-type doping the carrier influence, both screening and band shift, is negligible. Blue shift of the transition energy between conduction band minima and valence band maxima was observed for high concentrations of both type carriers.

The Electric and Optical Properties of Doped Small Molecular Organic Light-Emitting Devices

International Nuclear Information System (INIS)

Kwang-Ohk Cheon

2003-01-01

Organic light-emitting devices (OLEDs) constitute a new and exciting emissive display technology. In general, the basic OLED structure consists of a stack of fluorescent organic layers sandwiched between a transparent conducting-anode and metallic cathode. When an appropriate bias is applied to the device, holes are injected from the anode and electrons from the cathode; some of the recombination events between the holes and electrons result in electroluminescence (EL). Until now, most of the efforts in developing OLEDs have focused on display applications, hence on devices within the visible range. However some organic devices have been developed for ultraviolet or infrared emission. Various aspects of the device physics of doped small molecular OLEDs were described and discussed. The doping layer thickness and concentration were varied systematically to study their effects on device performances, energy transfer, and turn-off dynamics. Low-energy-gap DCM2 guest molecules, in either α-NPD or DPVBi host layers, are optically efficient fluorophores but also generate deep carrier trap-sites. Since their traps reduce the carrier mobility, the current density decreases with increased doping concentration. At the same time, due to efficient energy transfer, the quantum efficiency of the devices is improved by light doping or thin doping thickness, in comparison with the undoped neat devices. However, heavy doping induces concentration quenching effects. Thus, the doping concentration and doping thickness may be optimized for best performance

The Electric and Optical Properties of Doped Small Molecular Organic Light-Emitting Devices

Energy Technology Data Exchange (ETDEWEB)

Cheon, Kwang-Ohk [Iowa State Univ., Ames, IA (United States)

2003-01-01

Organic light-emitting devices (OLEDs) constitute a new and exciting emissive display technology. In general, the basic OLED structure consists of a stack of fluorescent organic layers sandwiched between a transparent conducting-anode and metallic cathode. When an appropriate bias is applied to the device, holes are injected from the anode and electrons from the cathode; some of the recombination events between the holes and electrons result in electroluminescence (EL). Until now, most of the efforts in developing OLEDs have focused on display applications, hence on devices within the visible range. However some organic devices have been developed for ultraviolet or infrared emission. Various aspects of the device physics of doped small molecular OLEDs were described and discussed. The doping layer thickness and concentration were varied systematically to study their effects on device performances, energy transfer, and turn-off dynamics. Low-energy-gap DCM2 guest molecules, in either α-NPD or DPVBi host layers, are optically efficient fluorophores but also generate deep carrier trap-sites. Since their traps reduce the carrier mobility, the current density decreases with increased doping concentration. At the same time, due to efficient energy transfer, the quantum efficiency of the devices is improved by light doping or thin doping thickness, in comparison with the undoped neat devices. However, heavy doping induces concentration quenching effects. Thus, the doping concentration and doping thickness may be optimized for best performance.

Potential thermoelectric performance of hole-doped Cu2O

International Nuclear Information System (INIS)

Chen, Xin; Parker, David; Du, Mao-Hua; Singh, David J

2013-01-01

High thermoelectric performance in oxides requires stable conductive materials that have suitable band structures. Here we show, based on an analysis of the thermopower and related properties using first-principles calculations and Boltzmann transport theory in the relaxation time approximation, that hole-doped Cu 2 O may be such a material. We find that hole-doped Cu 2 O has a high thermopower of above 200 μV K −1 even with doping levels as high as 5.2 × 10 20 cm −3 at 500 K, mainly attributed to the heavy valence bands of Cu 2 O. This is reminiscent of the cobaltate family of high-performance oxide thermoelectrics and implies that hole-doped Cu 2 O could be an excellent thermoelectric material if suitably doped. (paper)

Decoupling the Lattice Distortion and Charge Doping Effects on the Phase Transition Behavior of VO2 by Titanium (Ti4+) Doping

Science.gov (United States)

Wu, Yanfei; Fan, Lele; Liu, Qinghua; Chen, Shi; Huang, Weifeng; Chen, Feihu; Liao, Guangming; Zou, Chongwen; Wu, Ziyu

2015-01-01

The mechanism for regulating the critical temperature (TC) of metal-insulator transition (MIT) in ions-doped VO2 systems is still a matter of debate, in particular, the unclear roles of lattice distortion and charge doping effects. To rule out the charge doping effect on the regulation of TC, we investigated Ti4+-doped VO2 (TixV1-xO2) system. It was observed that the TC of TixV1-xO2 samples first slightly decreased and then increased with increasing Ti concentration. X-ray absorption fine structure (XAFS) spectroscopy was used to explore the electronic states and local lattice structures around both Ti and V atoms in TixV1-xO2 samples. Our results revealed the local structure evolution from the initial anatase to the rutile-like structure around the Ti dopants. Furthermore, the host monoclinic VO2 lattice, specifically, the VO6 octahedra would be subtly distorted by Ti doping. The distortion of VO6 octahedra and the variation of TC showed almost the similar trend, confirming the direct effect of local structural perturbations on the phase transition behavior. By comparing other ion-doping systems, we point out that the charge doping is more effective than the lattice distortion in modulating the MIT behavior of VO2 materials. PMID:25950809

Perturbative effect of heavy particles in an effective-Lagrangian approach

International Nuclear Information System (INIS)

Hagiwara, T.; Nakazawa, N.

1981-01-01

An effective-Lagrangian approach is summarized to estimate the perturbative effect of heavy-mass particles in the leading-logarithmic approximation: the logarithmic corrections to mass-suppressed amplitudes are given in a concise form. We apply the formalism to a simplified model with two scalar fields where one is heavy and the other is light. We derive an effective Lagrangian by calculating heavy-particle one-loop diagrams. Solving renormalization-group equations derived from the effective Lagrangian by light-particle one-loop corrections, we obtain logarithmic corrections to the mass-suppressed amplitudes. The results are confirmed by explicit two-loop calculation in the full theory, up to order O((1/M 2 )1nM 2 ), where M is a heavy scalar mass. It is found that the boundary condition for solving the renormalization-group equations must be specified by the renormalization at the heavy-particle mass. It must also be emphasized that in an effective-Lagrangian approach minimal subtraction is not a proper method of renormalization. The necessity to adopt the conventional momentum-shell subtraction is stressed. Several applications of this formalism are also mentioned

VO{sub x} effectively doping CVD-graphene for transparent conductive films

Energy Technology Data Exchange (ETDEWEB)

Ji, Qinghua; Shi, Liangjing [State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Dingxi Road, Shanghai 200050 (China); Zhang, Qinghong [State Key Laboratory of Modification of Chemical Fibers and Polymer Materials, College of Material Science and Engineering, Donghua University, 2999 North Renmin Road, Shanghai 201620 (China); Wang, Weiqi; Zheng, Huifeng [State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Dingxi Road, Shanghai 200050 (China); Zhang, Yuzhi [The Key Laboratory of Inorganic Coating Materials, Shanghai Institute of Ceramics, Chinese Academy of Sciences,1295 Dingxi Road, Shanghai 200050 (China); Liu, Yangqiao, E-mail: yqliu@mail.sic.ac.cn [State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Dingxi Road, Shanghai 200050 (China); Sun, Jing, E-mail: jingsun@mail.sic.ac.cn [State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Dingxi Road, Shanghai 200050 (China)

2016-11-30

Highlights: • Doping process operated easily. • Sheet resistance decreased efficiently after doping. • Sheet resistance of doped graphene is stable after exposed in the air. • Mechanism of doping process is studied. - Abstract: Chemical vapor deposition(CVD)-synthesized graphene is potentially an alternative for tin-doped indium oxide (ITO) transparent conductive films (TCFs), however its sheet resistance is still too high to meet many demands. Vanadium oxide has been widely applied as smart window materials, however, no study has been reported to use it as dopant to improve the conductivity of graphene TCFs. In this study, we firstly reported that VO{sub x} doping can effectively lower the sheet resistance of CVD-graphene films while keeping its good optical properties, whose transmittance is as high as 86–90%. The optimized VO{sub x}-doped graphene exhibits a sheet resistance as low as 176 Ω/□, which decreases by 56% compared to the undoped graphene films. The doping process is convenient, stable, economical and easy to operate. What is more, VO{sub x} can effectively increase the work function(WF) of the film, making it more appropriate for use in solar cells. The evolution of the VO{sub x} species annealed at different temperatures below 400 °C has been detailed studied for the first time, based on which the doping mechanism is proposed. The prepared VO{sub x} doped graphene is expected to be a promising candidate for transparent conductive film purposes.

Heavy quark fragmentation functions in the heavy quark effective theory

International Nuclear Information System (INIS)

Martynenko, A.P.; Saleev, V.A.

1996-01-01

The fragmentation of b-bar-antiquark into polarized B c * -mesons and b-quark into P-wave (c-bar b) states in the Heavy Quark Effective Theory. The heavy quark fragmentation functions in longitudinally and transversely polarized S-wave b-bar c-states and P-wave mesons containing b-, c-quarks also, with the exact account of corrections of first order in 1/m b . 20 refs., 2 figs

Radiation effect of doping and bias conditions on NPN bipolar junction transistors

International Nuclear Information System (INIS)

Xi Shanbin; Wang Yiyuan; Xu Fayue; Zhou Dong; Li Ming; Wang Fei; Wang Zhikuan; Yang Yonghui; Lu Wu

2011-01-01

In this paper,we investigate 60 Co γ-ray irradiation effects and annealing behaviors of NPN bipolar junction transistors of the same manufacturing technology but different doping concentrations. The transistors of different doping concentrations differ in responses of the radiation effect. More degradation was observed with the transistors of low concentration-doped NPN transistors than the high concentration-doped NPN transistors. The results also demonstrate that reverse-biased transistors are more sensitive to radiation than the forward-biased ones. Mechanisms of the radiation responses are analyzed. (authors)

Nitrogen-doped graphene films from simple photochemical doping for n-type field-effect transistors

Energy Technology Data Exchange (ETDEWEB)

Li, Xinyu [College of Science, Guilin University of Technology, Guilin 541004 (China); Department of Physics and Nanjing National Laboratory of Microstructures, Nanjing University, Nanjing 210093 (China); Tang, Tao; Li, Ming, E-mail: liming928@163.com, E-mail: lixinyu5260@163.com [College of Science, Guilin University of Technology, Guilin 541004 (China); He, Xiancong, E-mail: liming928@163.com, E-mail: lixinyu5260@163.com [School of Materials Science and Engineering, Nanjing Institute of Technology, Nanjing 211167 (China)

2015-01-05

Highly nitrogen-doped GO (NGO) and n-type graphene field effect transistor (FET) have been achieved by simple irradiation of graphene oxide (GO) thin films in NH{sub 3} atmosphere. The electrical properties of the NGO film were performed on electric field effect measurements, and it displays an n-type FET behavior with a charge neutral point (Dirac point) located at around −8 V. It is suggested that the amino-like nitrogen (N-A) mainly contributes to the n-type behavior. Furthermore, compared to the GO film irradiated in Ar atmosphere, the NGO film is much more capable to improve the electrical conductivity. It may attribute to nitrogen doping and oxygen reduction, both of which can effectively enhance the electrical conductivity.

Simulation study on single event burnout in linear doping buffer layer engineered power VDMOSFET

Science.gov (United States)

Yunpeng, Jia; Hongyuan, Su; Rui, Jin; Dongqing, Hu; Yu, Wu

2016-02-01

The addition of a buffer layer can improve the device's secondary breakdown voltage, thus, improving the single event burnout (SEB) threshold voltage. In this paper, an N type linear doping buffer layer is proposed. According to quasi-stationary avalanche simulation and heavy ion beam simulation, the results show that an optimized linear doping buffer layer is critical. As SEB is induced by heavy ions impacting, the electric field of an optimized linear doping buffer device is much lower than that with an optimized constant doping buffer layer at a given buffer layer thickness and the same biasing voltages. Secondary breakdown voltage and the parasitic bipolar turn-on current are much higher than those with the optimized constant doping buffer layer. So the linear buffer layer is more advantageous to improving the device's SEB performance. Project supported by the National Natural Science Foundation of China (No. 61176071), the Doctoral Fund of Ministry of Education of China (No. 20111103120016), and the Science and Technology Program of State Grid Corporation of China (No. SGRI-WD-71-13-006).

Effects of heavy metals on soil microbial community

Science.gov (United States)

Chu, Dian

2018-02-01

Soil is one of the most important environmental natural resources for human beings living, which is of great significance to the quality of ecological environment and human health. The study of the function of arable soil microbes exposed to heavy metal pollution for a long time has a very important significance for the usage of farmland soil. In this paper, the effects of heavy metals on soil microbial community were reviewed. The main contents were as follows: the effects of soil microbes on soil ecosystems; the effects of heavy metals on soil microbial activity, soil enzyme activities and the composition of soil microbial community. In addition, a brief description of main methods of heavy metal detection for soil pollution is given, and the means of researching soil microbial community composition are introduced as well. Finally, it is concluded that the study of soil microbial community can well reflect the degree of soil heavy metal pollution and the impact of heavy metal pollution on soil ecology.

Effects of CuO co-doping on γ-ray irradiation resistance of active ions doped phosphate glasses

Energy Technology Data Exchange (ETDEWEB)

Zhang, Zhihuan [Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 (China); ENEA-UTTMAT, Via Anguillarese 301, 00123 Rome (Italy); Baccaro, Stefania; Cemmi, Alessia [ENEA-UTTMAT, Via Anguillarese 301, 00123 Rome (Italy); Shen, Wei [Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 (China); Chen, Guorong, E-mail: grchen@ecust.edu.cn [Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 (China)

2013-09-15

The effect of copper ion doping on the γ-ray irradiation resistance of Mn{sup 2+} and Pr{sup 3+} doped phosphate glasses has been studied. UV–visible transmission spectra and photoluminescence spectra have been measured before and after γ-irradiation to characterize the radiation-induced defects. The electron paramagnetic resonance spectra of the irradiated samples with, and without Cu ions have been compared to show the ability of Cu ions to suppress the generation of radiation-induced color centers. The differential transmission spectra and the radiation-induced absorption coefficients have also been calculated for discussion of the observed phenomena. The much improved γ-irradiation resistance of Mn{sup 2+} and Pr{sup 3+} doped phosphate glasses has been demonstrated through CuO co-doping.

Electrochemical doping of mesoporous silicon with Er: the effect of the current intensity

Energy Technology Data Exchange (ETDEWEB)

Mula, Guido, E-mail: guido.mula@unica.it [Dipartimento di Fisica, Università degli Studi di Cagliari, Cittadella Universitaria di Monserrato, S.P. 8 km 0.700, 09042 Cagliari (Italy); Pinna, Elisa [Dipartimento di Fisica, Università degli Studi di Cagliari, Cittadella Universitaria di Monserrato, S.P. 8 km 0.700, 09042 Cagliari (Italy); Falqui, Andrea [Nanochemistry, Istituto Italiano di Tecnologia, Via Morego 30, 16163 Genova (Italy); Dipartimento di Scienze Chimiche e Geologiche, Università degli Studi di Cagliari, Cittadella Universitaria di Monserrato, S.P. 8 km 0.700, 09042 Cagliari (Italy); Ruffilli, Roberta [Dipartimento di Scienze Chimiche e Geologiche, Università degli Studi di Cagliari, Cittadella Universitaria di Monserrato, S.P. 8 km 0.700, 09042 Cagliari (Italy); Palmas, Simonetta; Mascia, Michele [Dipartimento di Ingegneria Meccanica Chimica e dei Materiali, Università degli Studi di Cagliari, Piazza d’Armi, 09126 Cagliari (Italy)

2014-08-30

Graphical abstract: - Highlights: • A multidisciplinary approach on porous Si electrochemical Er doping is proposed. • The phenomena taking place at the large developed surface of porous silicon are studied. • Electrochemical, optical and structural characterizations are used. • The early stages of doping are studied by electrochemical impedance spectroscopy. • The dependence of the final amount of Er deposited on the current intensity and not only on the transferred charge is shown. - Abstract: There is an ongoing intense research for cost-effective Er-doped Si-based light-emitting devices at the 1.5 μm wavelength. The efficient electrochemical Er-doping of porous silicon for this purpose requires a good understanding of the phenomena involved, since those taking place at the pores inner surface control the doping process. However, almost no attention has been given, to date, to the relevant effects of the current intensity onto the doping results. In this work, the effect of the current intensity on the doping process is explored by means of electrochemical impedance spectroscopy, optical reflectivity and energy dispersive spectrometry via scanning electron microscopy. The combined analysis of all results strongly suggests that the formation of a gel-like Er ethanolate, unaffected by changes in the sample thickness, occurs from the very first stages of the doping process. Moreover, while for constant current doping processes we show that, under any given doping condition, the doping level is proportional to the transferred charge, we demonstrate that performing the doping process using different current intensities may lead to dramatically different results.

To dope or not to dope

DEFF Research Database (Denmark)

Overbye, Marie Birch; Knudsen, Mette Lykke; Pfister, Gertrud Ursula

2013-01-01

tAim: This study aims to examine the circumstances which athletes say affect their (hypothetical) consid-erations of whether to dope or not and explore the differences between athletes of different gender, ageand sport type.Methods: 645 elite athletes (mean age: 22.12; response rate: 43%) represe......tAim: This study aims to examine the circumstances which athletes say affect their (hypothetical) consid-erations of whether to dope or not and explore the differences between athletes of different gender, ageand sport type.Methods: 645 elite athletes (mean age: 22.12; response rate: 43......%) representing 40 sports completed aweb-based questionnaire. Participants were asked to imagine themselves in a situation in which theyhad to decide whether to dope or not to dope and then evaluate how different circumstances would affecttheir decisions.Results: Multiple circumstances had an effect on athletes......’ hypothetical decisions. The most effective deter-rents were related to legal and social sanctions, side-effects and moral considerations. Female athletesand younger athletes evaluated more reasons as deterrents than older, male athletes. When confrontedwith incentives to dope, the type of sport was often...

Facile hydrothermal preparation of recyclable S-doped graphene sponge for Cu2+ adsorption

International Nuclear Information System (INIS)

Zhao, Lianqin; Yu, Baowei; Xue, Fumin; Xie, Jingru; Zhang, Xiaoliang; Wu, Ruihan; Wang, Ruijue; Hu, Zhiyan; Yang, Sheng-Tao; Luo, Jianbin

2015-01-01

Graphical abstract: S-doped graphene sponge was prepared via hydrothermal treatment, where S-doped graphene sponge had an adsorption capacity of 228 mg/g for Cu 2+ . - Highlights: • S-doped graphene sponge was prepared by hydrothermal treatment for heavy metal adsorption. • S-doped graphene sponge had a huge adsorption capacity for Cu 2+ , which was 40 times higher than that of active carbon. • S-doped graphene sponge could be easily regenerated by washing with acidic thiourea. - Abstract: Graphene sponge (GS) has been widely employed for water purification, but adsorption capacity loss frequently occurs during the formation of spongy structure. In this study, we reported the hydrothermal preparation of S-doped GS for the removal of Cu 2+ with a huge adsorption capacity of 228 mg/g, 40 times higher than that of active carbon. The adsorption isotherm could be well fitted into the Freundlich model with a K F value of 36.309 (L/mg) 1/n . The equilibrium adsorption could be fully achieved in the first 5 min. In the thermodynamics study, the negative ΔG indicated that the adsorption was spontaneous and physisorption in nature. The positive ΔH implied that the adsorption was endothermic. The changes of both pH and ionic strength had no apparent influence on the adsorption. S-doped GS could be easily regenerated by washing with acidic thiourea. Moreover, S-doped GS could be used for the adsorption of other heavy metal ions, too. The implication to the applications of S-doped GS in water treatment is discussed

Effect of vanadium and yttrium doping on BSCCO superconductors

International Nuclear Information System (INIS)

Mohamed, S.B.; Halim, S.A.; Azhan, H.; Sidek, H.A.A; Tee, T.W.; Hassan, Z.A.

1999-01-01

The effect of vanadium and yttrium doping on the superconductivity is investigated. The doping was done on the calcium site ranging from x=0.00-0.10. The temperature dependence of electrical resistance and AC susceptibility measurements were made on these samples. The zero resistance for vanadium doped samples varied from 107 K (x = 0.00) to 68.5K (x = 0.10), whereas for yttrium doped samples it varied from 107 K (x = 0.00) to 54K (x 0.10). The volume fraction of the 2223 phase for both dopalit decreases witli increasing doping concentration. The nature of the temperature derivative of the resistance curves indicates the presence of a superconducting transition between grains coupled by weak links. The AC susceptibility data show enrichment of the volume fraction of the low Tc phase at higher compositions. The presence of low Tc phase (∼70 K) is visible in the susceptibility data. X-ray diffraction confirms the presence of mixed phases in the samples. (author)

Thermoluminescence of gamma rays irradiated LiF nanocubes doped with different elements

Energy Technology Data Exchange (ETDEWEB)

Salah, Numan, E-mail: nsalah@kau.edu.sa [Center of Nanotechnology, King Abdulaziz University, Jeddah 21589 (Saudi Arabia); Alharbi, Najlaa D. [Center of Nanotechnology, King Abdulaziz University, Jeddah 21589 (Saudi Arabia); Sciences Faculty for Girls, King Abdulaziz University, Jeddah 21589 (Saudi Arabia); Habib, Sami S. [Department of Aeronautical Engineering, King Abdulaziz University, Jeddah 21589 (Saudi Arabia)

2015-05-15

Lithium fluoride (LiF) doped with proper activator is a highly sensitive phosphor, widely used as a dosimeter for ionizing radiations. This work reports on the thermoluminesence (TL) response of LiF nanocubes doped with different impurities. These nanocubes were synthesized by the co-precipitation method and characterized by different techniques. The dopants used in this study are Eu, Tb, Dy, Cu and Ag. The gamma radiation induced TL glow peaks are located in the temperature range 120–125 °C. These samples have different TL sensitivities, where Eu doped one is found to be the most TL sensitive. Further irradiations in the dose range from 10 Gy to 30 kGy were performed to LiF:Eu and the obtained result is explained using a proposed multilevel TL model. According to this model, Eu dopant (in Eu{sup 3+} ionic form) could induce shallow and deep electron traps in the host of LiF nanocubes. These traps differ in their response according to the doses. The optimum concentration of Eu ions in LiF host is found to be 0.2 mol%. It is also found that LiF nanocubes are thermally stable in the range of 30–400 °C with a single phase. This property along with the good sensitivity of Eu doped one makes this tissue equivalent nanomaterial a proper candidate for heavy dose measurement like swift heavy ions used in radiotherapy. - Highlights: • Nanocubes of pure and doped LiF were produced by the co-precipitation method. • They were doped with Eu, Tb, Dy, Cu and Ag and studied for their TL response. • The gamma radiation induced TL glow peaks are located in the range 120–125 °C. • The Eu doped one is found to be the most TL sensitive, followed by Tb. • The tissue equivalent LiF:Eu nanocubes might be useful for heavy dose measurement.

Thermoluminescence of gamma rays irradiated LiF nanocubes doped with different elements

International Nuclear Information System (INIS)

Salah, Numan; Alharbi, Najlaa D.; Habib, Sami S.

2015-01-01

Lithium fluoride (LiF) doped with proper activator is a highly sensitive phosphor, widely used as a dosimeter for ionizing radiations. This work reports on the thermoluminesence (TL) response of LiF nanocubes doped with different impurities. These nanocubes were synthesized by the co-precipitation method and characterized by different techniques. The dopants used in this study are Eu, Tb, Dy, Cu and Ag. The gamma radiation induced TL glow peaks are located in the temperature range 120–125 °C. These samples have different TL sensitivities, where Eu doped one is found to be the most TL sensitive. Further irradiations in the dose range from 10 Gy to 30 kGy were performed to LiF:Eu and the obtained result is explained using a proposed multilevel TL model. According to this model, Eu dopant (in Eu 3+ ionic form) could induce shallow and deep electron traps in the host of LiF nanocubes. These traps differ in their response according to the doses. The optimum concentration of Eu ions in LiF host is found to be 0.2 mol%. It is also found that LiF nanocubes are thermally stable in the range of 30–400 °C with a single phase. This property along with the good sensitivity of Eu doped one makes this tissue equivalent nanomaterial a proper candidate for heavy dose measurement like swift heavy ions used in radiotherapy. - Highlights: • Nanocubes of pure and doped LiF were produced by the co-precipitation method. • They were doped with Eu, Tb, Dy, Cu and Ag and studied for their TL response. • The gamma radiation induced TL glow peaks are located in the range 120–125 °C. • The Eu doped one is found to be the most TL sensitive, followed by Tb. • The tissue equivalent LiF:Eu nanocubes might be useful for heavy dose measurement

La doping effect on TZM alloy oxidation behavior

International Nuclear Information System (INIS)

Yang, Fan; Wang, Kuai-She; Hu, Ping; He, Huan-Cheng; Kang, Xuan-Qi; Wang, Hua; Liu, Ren-Zhi; Volinsky, Alex A.

2014-01-01

Highlights: • The oxidation can be resisted by doping La into TZM alloy. • La doped TZM alloy has more compact organization. • It can rise the starting temperature of severe oxidation reaction by more than 50 °C. • Effectively slow down the oxidation rate. • Provide guidance for experiments of improving high-temperature oxidation resistance. - Abstract: Powder metallurgy methods were utilized to prepare lanthanum-doped (La-TZM) and traditional TZM alloy plates. High temperature oxidation experiments along with the differential thermal analysis were employed to study the oxidation behavior of the two kinds of TZM alloys. An extremely volatile oxide layer was generated on the surface of traditional TZM alloy plates when the oxidation started. Molybdenum oxide volatilization exposed the alloy matrix, which was gradually corroded by oxygen, losing its quality with serious surface degradation. The La-TZM alloy has a more compact structure due to the lanthanum doping. The minute lanthanum oxide particles are pinned at the grain boundaries and refine the grains. Oxide layer generated on the matrix surface can form a compact coating, which effectively blocks the surface from being corroded by oxidation. The oxidation resistance of La-TZM alloys has been enhanced, expanding its application range

Photorefractive effect at 775 nm in doped lithium niobate crystals

Energy Technology Data Exchange (ETDEWEB)

Nava, G.; Minzioni, P.; Cristiani, I.; Degiorgio, V. [Department of Electrical, Computer, and Biomedical Engineering, and CNISM, University of Pavia, 27100 Pavia (Italy); Argiolas, N.; Bazzan, M.; Ciampolillo, M. V.; Pozza, G.; Sada, C. [Physics and Astronomy Departement, University of Padova, 35131 Padova (Italy)

2013-07-15

The photorefractive effect induced by 775-nm laser light on doped lithium niobate crystals is investigated by the direct observation in the far field of the transmitted-beam distortion as a function of time. Measurements performed at various Zr-doping concentrations and different light intensities show that the 775-nm light beam induces a steady-state photorefractive effect comparable to that of 532-nm light, but the observed build-up time of the photovoltaic field is longer by three-orders of magnitude. The 775-nm photorefractivity of lithium niobate crystals doped with 3 mol. % ZrO{sub 2} or with 5.5 mol. % MgO is found to be negligible.

Perilous Effects of Heavy Metals Contamination on Human Health

Directory of Open Access Journals (Sweden)

Naseem Zahra

2017-06-01

Full Text Available Heavy metals form a versatile group of high density elements that vary considerably in their biological roles and chemical properties. Although many heavy metals are essential trace elements yet they have long been recognized as environmental pollutants due their toxic effects. Increased industrialization, urbanization anthropogenic activities like mining, smelting and other agricultural activities have resulted in accumulation of heavy metals in the environment. Heavy metals such as nickel, cadmium, zinc, copper, mercury, arsenic and chromium are not easily degradable and tend to build up in soil. These heavy metals through various routes such as fish and plants make their way into the human body and are known to have serious detrimental effects on human health at elevated levels. The harmful effects of some important heavy metals on human health have been discussed.

Suppression of irradiation effects in gold-doped silicon detectors

International Nuclear Information System (INIS)

McPherson, M.; Sloan, T.; Jones, B.K.

1997-01-01

Two sets of silicon detectors were irradiated with 1 MeV neutrons to different fluences and then characterized. The first batch were ordinary p-i-n photodiodes fabricated from high-resistivity (400 Ω cm) silicon, while the second batch were gold-doped powder diodes fabricated from silicon material initially of low resistivity (20 Ω cm). The increase in reverse leakage current after irradiation was found to be more in the former case than in the latter. The fluence dependence of the capacitance was much more pronounced in the p-i-n diodes than in the gold-doped diodes. Furthermore, photo current generation by optical means was less in the gold doped devices. All these results suggest that gold doping in silicon somewhat suppresses the effects of neutron irradiation. (author)

Observation of point defects in impurity-doped zinc selenide films using a monoenergetic positron beam

International Nuclear Information System (INIS)

Miyajima, T.; Okuyama, H.; Akimoto, K.; Mori, Y.; Wei, L.; Tanigawa, S.

1992-01-01

We studied point defects in ZnSe films grown by molecular beam epitaxy using the positron annihilation method. We found that doping with Ga atoms induces vacancy-type defects such as Zn vacancies, and that heavy doping with oxygen atoms induces interstitial type defects. We think that these defects are one of the causes of active carrier saturation in doped ZnSe films. (author)

Photon structure functions with heavy particle mass effects

Energy Technology Data Exchange (ETDEWEB)

Uematsu, Tsuneo, E-mail: uematsu@scphys.kyoto-u.jp [Graduate School of Science, Kyoto University, Kitashirakawa, Sakyo-ku, Kyoto, 606-8502 (Japan); Maskawa Institute for Science and Culture, Kyoto Sangyo University, Kamigamo, Kita-ku, Kyoto 603-8555 (Japan)

2013-01-15

In the framework of the perturbative QCD we investigate heavy particle mass effects on the unpolarized and polarized photon structure functions, F{sub 2}{sup γ} and g{sub 1}{sup γ}, respectively. We present our basic formalism to treat heavy particle mass effects to NLO in perturbative QCD. We also study heavy quark effects on the QCD sum rule for the first moment of g{sub 1}{sup γ}, which is related to axial anomaly. The photon structure function in supersymmetric QCD is also briefly discussed.

Formation of Infrared Femtosecond Laser Induced Colour Centres in Tb3+-Doped and Tb3+/Ce3+-Codoped Heavy Germanate Glasses

Institute of Scientific and Technical Information of China (English)

CHEN Guo-Rong(陈国荣); YANG Yun-Xia(杨云霞); QIU Jian-Rong(邱建荣); JIANG Xiong-Wei(姜雄伟); K.Hirao

2003-01-01

The formation of infrared femtosecond laser induced colour centres was observed in Tb3+-doped and Tb3+ /Ce3+-codoped heavy germanate glasses.A rectangular scan was made by focusing the laser beam inside the glass samples.A three-dimensional yellowish block was created from the path and it corresponded to the appearance of broad absorption bands in the absorption spectra.The irradiation induced absorption coefficient μ(λ)was used to characterize the distribution of radiation induced colour centres in the samples,whose peak was located at 380nm and extended to the longer wavelength.Ce3+ ions were found not only to inhibit the formation of colour centres,but also to enhance the recovery.

Effect of indium and antimony doping in SnS single crystals

Energy Technology Data Exchange (ETDEWEB)

Chaki, Sunil H., E-mail: sunilchaki@yahoo.co.in; Chaudhary, Mahesh D.; Deshpande, M.P.

2015-03-15

Highlights: • Single crystals growth of pure SnS, indium doped SnS and antimony doped SnS by direct vapour transport (DVT) technique. • Doping of In and Sb occurred in SnS single crystals by cation replacement. • The replacement mechanism ascertained by EDAX, XRD and substantiated by Raman spectra analysis. • Dopants concentration affects the optical energy bandgap. • Doping influences electrical transport properties. - Abstract: Single crystals of pure SnS, indium (In) doped SnS and antimony (Sb) doped SnS were grown by direct vapour transport (DVT) technique. Two doping concentrations of 5% and 15% each were employed for both In and Sb dopants. Thus in total five samples were studied viz., pure SnS (S1), 5% In doped SnS (S2), 15% In doped SnS (S3), 5% Sb doped SnS (S4) and 15% Sb doped SnS (S5). The grown single crystal samples were characterized by evaluating their surface microstructure, stoichiometric composition, crystal structure, Raman spectroscopy, optical and electrical transport properties using appropriate techniques. The d.c. electrical resistivity and thermoelectric power variations with temperature showed semiconducting and p-type nature of the as-grown single crystal samples. The room temperature Hall Effect measurements further substantiated the semiconducting and p-type nature of the as-grown single crystal samples. The obtained results are deliberated in detail.

Characteristic analysis on the physical properties of nanostructured Mg-doped CdO thin films—Doping concentration effect

Directory of Open Access Journals (Sweden)

K. Usharani

2015-06-01

Full Text Available Highly conductive and transparent magnesium-doped cadmium oxide (CdO:Mg thin films have been deposited on suitably cleaned glass substrates maintained at 375 °C by spray pyrolysis technique using perfume atomizer. The magnesium content in the films is varied from 0 to 8 at% in steps of 2 at%. The effect of Mg doping on the structural, morphological, optical and electrical properties of the CdO thin films has been studied. All the films exhibited cubic structure with a preferential orientation along the (1 1 1 plane irrespective of the Mg doping level. SEM analysis showed that the film morphology modifies from spherical shaped grains to closely packed cauliflower shaped nanostructures with Mg doping. Except for the film coated with 2 at% Mg dopant, all the other doped films exhibited a blue shift in the optical band gap. Electrical studies revealed that the CdO:Mg film coated with 8 at% Mg dopant had a minimum resistivity of 0.0853×101 Ω-cm.

Hole states in diamond p-delta-doped field effect transistors

International Nuclear Information System (INIS)

Martinez-Orozco, J C; Rodriguez-Vargas, I; Mora-Ramos, M E

2009-01-01

The p-delta-doping in diamond allows to create high density two-dimensional hole gases. This technique has already been applied in the design and fabrication of diamond-based field effect transistors. Consequently, the knowledge of the electronic structure is of significant importance to understand the transport properties of diamond p-delta-doped systems. In this work the hole subbands of diamond p-type delta-doped quantum wells are studied within the framework of a local-density Thomas-Fermi-based approach for the band bending profile. The calculation incorporates an independent three-hole-band scheme and considers the effects of the contact potential, the delta-channel to contact distance, and the ionized impurity density.

Hole states in diamond p-delta-doped field effect transistors

Energy Technology Data Exchange (ETDEWEB)

Martinez-Orozco, J C; Rodriguez-Vargas, I [Unidad Academica de Fisica, Universidad Autonoma de Zacatecas, Calzada Solidaridad Esquina con Paseo la Bufa S/N, CP 98060 Zacatecas, ZAC. (Mexico); Mora-Ramos, M E, E-mail: jcmover@correo.unam.m [Facultad de Ciencias, Universidad Autonoma del Estado de Morelos, Av. Universidad 1001, Col. Chamilpa, CP 62209 Cuernavaca, MOR. (Mexico)

2009-05-01

The p-delta-doping in diamond allows to create high density two-dimensional hole gases. This technique has already been applied in the design and fabrication of diamond-based field effect transistors. Consequently, the knowledge of the electronic structure is of significant importance to understand the transport properties of diamond p-delta-doped systems. In this work the hole subbands of diamond p-type delta-doped quantum wells are studied within the framework of a local-density Thomas-Fermi-based approach for the band bending profile. The calculation incorporates an independent three-hole-band scheme and considers the effects of the contact potential, the delta-channel to contact distance, and the ionized impurity density.

The effect of Au and Ni doping on the heavy fermion state of the Kondo lattice antiferromagnet CePtZn

Energy Technology Data Exchange (ETDEWEB)

Dhar, S. K., E-mail: sudesh@tifr.res.in [DCMPMS, T.I.F.R., Homi Bhabha Road, Colaba, Mumbai 400005 (India); Aoki, Y.; Suemitsu, B.; Miyazaki, R. [Department of Physics, Tokyo Metropolitan University, Minami-Ohsawa 1-1, Hachioji-Shi, Tokyo (Japan); Provino, A.; Manfrinetti, P. [Departimento Physica Chemicale, Universita di Genova, Via Dodecaneso, 16146 Genova (Italy)

2014-05-07

We have probed the effect of doping CePtZn with Au and Ni and also investigated in detail the magnetic behavior of the iso-structural CeAuZn. A magnetic ground state is observed in both CePt{sub 0.9}Au{sub 0.1}Zn and CePt{sub 0.9}Ni{sub 0.1}Zn with T{sub N} = 2.1 and 1.1 K and the coefficient of the linear term of electronic heat capacity γ = 0.34 and 0.9 J/mol K{sup 2}, respectively. The corresponding values for CePtZn are 1.7 K and 0.6 J/mol K{sup 2}. The altered values of T{sub N} and γ show that the electronic correlations in CePtZn are affected by doping with Au and Ni. CeAuZn orders magnetically near 1.7 K and its electrical resistivity shows a normal metallic behavior. Together with a γ of 0.022 J/mol K{sup 2} the data indicate a weak 4f-conduction electron hybridization in CeAuZn characteristic of normal trivalent cerium based systems.

Hydrogen storage in pure and Li-doped carbon nanopores: combined effects of concavity and doping.

Science.gov (United States)

Cabria, I; López, M J; Alonso, J A

2008-04-14

Density functional calculations are reported for the adsorption of molecular hydrogen on carbon nanopores. Two models for the pores have been considered: (i) The inner walls of (7,7) carbon nanotubes and (ii) the highly curved inner surface of nanotubes capped on one end. The effect of Li doping is investigated in all cases. The hydrogen physisorption energies increase due to the concavity effect inside the clean nanotubes and on the bottom of the capped nanotubes. Li doping also enhances the physisorption energies. The sum of those two effects leads to an increase by a factor of almost 3 with respect to the physisorption in the outer wall of undoped nanotubes and in flat graphene. Application of a quantum-thermodynamical model to clean cylindrical pores of diameter 9.5 A, the diameter of the (7,7) tube, indicates that cylindrical pores of this size can store enough hydrogen to reach the volumetric and gravimetric goals of the Department of Energy at 77 K and low pressures, although not at 300 K. The results are useful to explain the experiments on porous carbons. Optimizations of the pore size, concavity, and doping appear as promising alternatives for achieving the goals at room temperature.

Effect of silicon, tantalum, and tungsten doping and polarization on bioactivity of hydroxyapatite

Science.gov (United States)

Dhal, Jharana

Hydroxyapatite (HAp) ceramics has important applications as bone graft because of the structural and compositional similarities with bone tissue. However, inferior osteogenic capacity to bone and poor mechanical properties have been identified to be major disadvantages of synthetic HAp compared to the living bone tissue. The objective of the current study is to evaluate the effect of doping with higher valent cations (Tungsten, tantalum, and silicon) and polarization or combination of both on change in property of doped HAp and subsequent impact its bioactivity. In vitro study with human osteoblast cells was used to investigate the influences of doping and polarization on bone cell-materials interactions. The bioactivity of doped HAp was compared with pure HAp. Effect of doping and polarization on the change in HAp was investigated by monitoring change in mineral phases, stored charge, and activation energy of HAp. Activation energy of depolarization was used to explain the possible mechanism of polarization in doped samples. Bioactivity of HAp increased when doped with tantalum and tungsten. Polarization further increased the bioactivity of tungsten- and tantalum-doped samples. Increase in bioactivity on polarized and doped samples was attributed to increase in surface energy and increase in surface wettability. Whereas, an increase in bioactivity on doped unpolarized surface was attributed to change in microstructure. Polarized charge calculated from TSDC indicates that polarized charge decreases on tantalum- and tungsten-doped HAp. The decrease in polarized charge was attributed to the presence of significant amount of different phases that may hinder the ionic motion in doped samples. However, for silicon-doped HAp, TSDC study showed no difference in the mechanism of polarization between doped and undoped samples. Increase in silicon doping decreased the grain size though mechanism is not affected by grain size. Total stored charge decreased with increase in

Doped Organic Transistors.

Science.gov (United States)

Lüssem, Björn; Keum, Chang-Min; Kasemann, Daniel; Naab, Ben; Bao, Zhenan; Leo, Karl

2016-11-23

Organic field-effect transistors hold the promise of enabling low-cost and flexible electronics. Following its success in organic optoelectronics, the organic doping technology is also used increasingly in organic field-effect transistors. Doping not only increases device performance, but it also provides a way to fine-control the transistor behavior, to develop new transistor concepts, and even improve the stability of organic transistors. This Review summarizes the latest progress made in the understanding of the doping technology and its application to organic transistors. It presents the most successful doping models and an overview of the wide variety of materials used as dopants. Further, the influence of doping on charge transport in the most relevant polycrystalline organic semiconductors is reviewed, and a concise overview on the influence of doping on transistor behavior and performance is given. In particular, recent progress in the understanding of contact doping and channel doping is summarized.

Effect of nitrogen doping on titanium carbonitride-derived adsorbents used for arsenic removal

Energy Technology Data Exchange (ETDEWEB)

Han, Jisun [Department of Materials Science and Engineering, Seoul National University, Seoul 151-742 (Korea, Republic of); Lee, Soonjae [Center for Water Resource Cycle Research, Korea Institute of Science and Technology, Hwarang-ro 14-gil 5, Seongbuk-gu, Seoul 136-791 (Korea, Republic of); Choi, Keunsu [Computational Science Research Center, Korea Institute of Science and Technology, Hwarang-ro 14-gil 5, Seongbuk-gu, Seoul 136-791 (Korea, Republic of); Kim, Jinhong [Samsung Electronics Co.Ltd.,(Maetan dong) 129, Samsung-ro Yeongtong-gu, Suwonsi, Gyeonggi-do 443-742, Repubilc of Korea (Korea, Republic of); Ha, Daegwon [Department of Materials Science and Engineering, Seoul National University, Seoul 151-742 (Korea, Republic of); Lee, Chang-Gu [Center for Water Resource Cycle Research, Korea Institute of Science and Technology, Hwarang-ro 14-gil 5, Seongbuk-gu, Seoul 136-791 (Korea, Republic of); An, Byungryul [Department of Civil Engineering, Sangmyung University, Cheonan, Chungnam 31066 (Korea, Republic of); Lee, Sang-Hyup [Center for Water Resource Cycle Research, Korea Institute of Science and Technology, Hwarang-ro 14-gil 5, Seongbuk-gu, Seoul 136-791 (Korea, Republic of); Mizuseki, Hiroshi, E-mail: mizuseki@kist.re.kr [Computational Science Research Center, Korea Institute of Science and Technology, Hwarang-ro 14-gil 5, Seongbuk-gu, Seoul 136-791 (Korea, Republic of); Choi, Jae-Woo, E-mail: plead36@kist.re.kr [Center for Water Resource Cycle Research, Korea Institute of Science and Technology, Hwarang-ro 14-gil 5, Seongbuk-gu, Seoul 136-791 (Korea, Republic of); Department of Energy and Environmental Engineering, University of Science and Technology (UST), Daejeon 305-350 (Korea, Republic of); Kang, Shinhoo, E-mail: shinkang@snu.ac.kr [Department of Materials Science and Engineering, Seoul National University, Seoul 151-742 (Korea, Republic of)

2016-01-25

Highlights: • The N-doping can improve the As adsorption performance of carbon-based materials. • The material features high micro- and small meso-pores with exceptional surface area. • Pyrrolic N atoms distributed uniformly on the micropores act as adsorption sites. • The synthesis temperature affected pore properties and surface functional groups. - Abstract: Arsenic in water and wastewater is considered to be a critical contaminant as it poses harmful health risks. In this regard, to meet the stringent regulation of arsenic in aqueous solutions, nitrogen doped carbon-based materials (CN) were prepared as adsorbents and tested for the removal of arsenic ion from aqueous solutions. Nitrogen-doped carbon (CNs) synthesized by chlorination exhibited well-developed micro- and small meso-pores with uniform pore structures. The structure and characteristics of the adsorbents thus developed were confirmed by field-emission scanning electron microscopy, transmission electron microscopy, Brunauer–Emmett–Teller analysis, X-ray diffraction, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy. Among the CNs developed, CN700 exhibited high adsorption capacity for arsenic (31.08 mg/g). The adsorption efficiency for arsenic ion was confirmed to be affected by pyrrolic nitrogen and micro-pores. These results suggest that CNs are useful adsorbents for the treatment of arsenic, and in particular, CN700 demonstrates potential for application as an adsorbent for the removal of anionic heavy metals from wastewater and sewage.

Effect of Boron Doping on High-Resolution X-Ray Diffraction Metrology

Science.gov (United States)

Faheem, M.; Zhang, Y.; Dai, X.

2018-03-01

The effect of boron (B) doping on high-resolution X-ray diffraction (HXRD) metrology has been investigated. Twelve samples of Si1-xGex films were epitaxially grown on Si (100) substrates with different thicknesses, germanium (Ge) concentrations and with/without B dopants. Secondary ion mass spectroscopy (SIMS) and HXRD were employed for measurements of B doping, Ge concentration, strain, and thickness of the layers. The SIMS results show the absence of B in two samples while the rest of the samples have B doping in the range of 8.40 × 1018-8.7 × 1020 atoms/cm3 with Ge concentration of 13.3-55.2 at.%. The HXRD measurements indicate the layers thickness of 7.07-108.13 nm along with Ge concentration of 12.82-49.09 at.%. The difference in the Ge concentration measured by SIMS and HXRD was found to deend on B doping. For the undoped samples, the difference is 0.5 at.% and increases with B doping but with no linear proportionality. The difference in the Ge concentration was 7.11 at.% for the highly B-doped (8.7 × 1020 atoms/cm3) sample. The B doping influences the Si1-xGex structure, causing a change in the lattice parameter and producing tensile strains shifting Si1-xGex peaks towards Si (100) substrate peaks in the HXRD diffraction patterns. As a result, Vegard's law is no longer effective and makes a high impact on the HXRD measurement. The comparison between symmetric (004) and asymmetric (+113, +224) reciprocal space mappings (RSM) showed a slight difference in Ge concentration between the undoped and lower B-doped samples. However, there is a change of 0.21 at.% observed for the highly doped Si1-xGex samples. RSM's (+113) demonstrate the small SiGe peak broadening as B doping increases, which indicates a minor crystal distortion.

Heavy-quark fragmentation functions in the effective theory of heavy quarks

International Nuclear Information System (INIS)

Martynenko, A.P.; Saleev, V.A.

1996-01-01

The effective theory of heavy quarks is used to study b-bar-antiquark fragmentation in polarized Bc* mesons and b-quark fragmentation into P-wave (c-barb) states. The functions of heavy-quark fragmentation into longitudinally and transversely polarized S-wave (b-barc) states and into P-wave mesons containing b and c quarks are calculated. First-order corrections in 1/mb are taken into account exactly in these calculations. The results are shown to be consistent with the corresponding QCD calculations

Cancellation of renormalon ambiguities in the heavy quark effective theory

International Nuclear Information System (INIS)

Neubert, M.; Sachrajda, C.T.

1995-01-01

Recently, it has been shown that the concept of the pole mass of a heavy quark becomes ambiguous beyond perturbation theory, because of the presence of infrared renormalons. We argue that the predictions of the heavy quark effective theory, whose construction is based on the pole mass, are free of such ambiguities. In the 1/m Q expansion of physical quantities, infrared and ultraviolet renormalons compensate each other between coefficient functions and matrix elements. We trace the appearance of these compensations for current-induced exclusive heavy-to-heavy and heavy-to-light transitions, and for inclusive decays of heavy hadrons. In particular, we show that the structure of the heavy quark expansion is not obscured by renormalons, and none of the predictions of the heavy quark effective theory are invalidated. ((orig.))

Synthesis and Fluorescence Property of Mn-Doped ZnSe Nanowires

Directory of Open Access Journals (Sweden)

Dongmei Han

2010-01-01

Full Text Available Water-soluble Mn-doped ZnSe luminescent nanowires were successfully prepared by hydrothermal method without any heavy metal ions and toxic reagents. The morphology, composition, and property of the products were investigated. The experimental results showed that the Mn-doped ZnSe nanowires were single well crystallized and had a zinc blende structure. The average length of the nanowires was about 2-3 μm, and the diameter was 80 nm. With the increase of Mn2+-doped concentration, the absorbance peak showed large difference. The UV-vis absorbance spectrum showed that the Mn-doped ZnSe nanowires had a sharp absorption band appearing at 360 nm. The PL spectrum revealed that the nanowires had two distinct emission bands centered at 432 and 580 nm.

Synthesis of silver doped hydroxyapatite nanospheres using Ouzo effect

Directory of Open Access Journals (Sweden)

Marija Prekajski

2016-09-01

Full Text Available Nanoemulsion technique, based on Ouzo effect, was applied for synthesis of the pure and silver doped (2.5 and 5 mol% calcium hydroxyapatite (HAp. After calcination at 500 °C fully crystallized powders were obtained. X-ray powder diffraction analysis accompanied with Rietveld refinement revealed that the synthesized powders were single-phase hydroxyapatite. Raman spectroscopy also confirmed that the synthesized powders were single-phase. The obtained HAp particles were spherical in shape and their sizes were in the nanometer range which was revealed by field emission scanning electron microscopy analysis (FESEM. The successful synthesis of the single-phase Ag doped HAp showed that nanoemulsion method is a simple technique for obtaining pure and doped hydroxyapatite nanospheres.

Effects of Different Doping Ratio of Cu Doped CdS on QDSCs Performance

Directory of Open Access Journals (Sweden)

Xiaojun Zhu

2015-01-01

Full Text Available We use the successive ionic layer adsorption and reaction (SILAR method for the preparation of quantum dot sensitized solar cells, to improve the performance of solar cells by doping quantum dots. We tested the UV-Vis absorption spectrum of undoped CdS QDSCs and Cu doped CdS QDSCs with different doping ratios. The doping ratios of copper were 1 : 100, 1 : 500, and 1 : 1000, respectively. The experimental results show that, under the same SILAR cycle number, Cu doped CdS quantum dot sensitized solar cells have higher open circuit voltage, short circuit current density photoelectric conversion efficiency than undoped CdS quantum dots sensitized solar cells. Refinement of Cu doping ratio are 1 : 10, 1 : 100, 1 : 200, 1 : 500, and 1 : 1000. When the proportion of Cu and CdS is 1 : 10, all the parameters of the QDSCs reach the minimum value, and, with the decrease of the proportion, the short circuit current density, open circuit voltage, and the photoelectric conversion efficiency are all increased. When proportion is 1 : 500, all parameters reach the maximum values. While with further reduction of the doping ratio of Cu, the parameters of QDSCs have a decline tendency. The results showed that, in a certain range, the lower the doping ratio of Cu, the better the performance of quantum dot sensitized solar cell.

Heavy Ion Current Transients in SiGe HBTs

Science.gov (United States)

Pellish, Jonathan A.; Reed, Robert A.; Vizkelethy, Gyorgy; McMorrow, Dale; Ferlet-Cavrois, Veronique; Baggio, Jacques; Paillet, Philipe; Duhanel, Olivier; Phillips, Stanley D.; Sutton, Akil K.;

Development of a pepper-pot emittance meter for diagnostics of low-energy multiply charged heavy ion beams extracted from an ECR ion source

Energy Technology Data Exchange (ETDEWEB)

Nagatomo, T., E-mail: nagatomo@riken.jp; Kase, M.; Kamigaito, O.; Nakagawa, T. [Nishina Center for Accelerator Based Science, RIKEN, Wako, Saitama 351-0198 (Japan); Tzoganis, V. [Nishina Center for Accelerator Based Science, RIKEN, Wako, Saitama 351-0198 (Japan); Cockcroft Institute, Daresbury, Warrington WA4 4AD (United Kingdom); Department of Physics, University of Liverpool, Liverpool, Merseyside L69 3BX (United Kingdom)

2016-02-15

Several fluorescent materials were tested for use in the imaging screen of a pepper-pot emittance meter that is suitable for investigating the beam dynamics of multiply charged heavy ions extracted from an ECR ion source. SiO{sub 2} (quartz), KBr, Eu-doped CaF{sub 2}, and Tl-doped CsI crystals were first irradiated with 6.52-keV protons to determine the effects of radiation damage on their fluorescence emission properties. For such a low-energy proton beam, only the quartz was found to be a suitable fluorescent material, since the other materials suffered a decay in fluorescence intensity with irradiation time. Subsequently, quartz was irradiated with heavy {sup 12}C{sup 4+}, {sup 16}O{sup 4+}, and {sup 40}Ar{sup 11+} ions, but it was found that the fluorescence intensity decreased too rapidly to measure the emittance of these heavy-ion beams. These results suggest that a different energy loss mechanism occurs for heavier ions and for protons.

Heavy metals effect in Drosophila melanogaster germinal cells

International Nuclear Information System (INIS)

Rosa Duque de la, M.E.

1984-01-01

Heavy metals occur naturally and some of them are very important in cellular metabolism. Industrial development has increased metal concentration in the environment and in the living organisms tissues. This increase promotes the human risk to suffer teratogenesis, carcinogenesis and mutagenesis. Different biological systems have been used to proof the genetic effect of heavy metals including Drosophila. In the present work chromium, cadmium, lead, zinc and arsenic salts were administered to Drosophila females and males adults in order to determine the genetic effect produced by these compounds, in both femenine and masculine germinal cells. The mating system used (''Oster males'' and y 2 wsup(a)/y 2 wsup(a); e/e females) permited to determine among two succesive generations, the mutagenic effects produced by heavy metals in Drosophila. The salts administration to adult flies was made by injection. Non-disjunction, X-chromosome loss, and sex linked recessive lethals frequency was increased by heavy metals. It was observed a fertility disminution between F 1 descendants from individuals treated with the metalic salts. It was demonstrated that heavy metals can interact with genetic material at different levels in the two types of gametic cells to produce genetic damage. (author)

Isoelectronic Ln doping in p-GaN and its effects on InGaN light-emitting diodes

International Nuclear Information System (INIS)

Kim, C. S.; Cheong, H. S.; Kang, D. S.; Kim, J. Y.; Hong, C. H.; Suh, E. K.; Lee, H. J.; Cho, H. K.; Adesida, I.

2004-01-01

The effects of isoelectronic In doping in a Mg-doped p-GaN layer on device performance of InGaN light-emitting diodes (LED) were investigated. It was found that there was a decrease of Hall resistivity and contact resistivity in p-GaN with In doping, compared to typical Mg-doped p-GaN. Isoelectronic In doping in p-GaN seems to cause a kind of surfactant effect and/or purification effect similar to the In-doped GaN case, which exhibits a decrease of non-radiative recombination centers and an enhancement of carrier concentration. Light output power and operating voltage were improved by applying an In-doped p-GaN contact layer to the LED.

Spectroscopic studies of the physical origin of environmental aging effects on doped graphene

International Nuclear Information System (INIS)

Chang, J.-K.; Hsu, C.-C.; Liu, S.-Y.; Wu, C.-I.; Gharib, M.; Yeh, N.-C.

2016-01-01

The environmental aging effect of doped graphene is investigated as a function of the organic doping species, humidity, and the number of graphene layers adjacent to the dopant by studies of the Raman spectroscopy, x-ray and ultraviolet photoelectron spectroscopy, scanning electron microscopy, infrared spectroscopy, and electrical transport measurements. It is found that higher humidity and structural defects induce faster degradation in doped graphene. Detailed analysis of the spectroscopic data suggest that the physical origin of the aging effect is associated with the continuing reaction of H_2O molecules with the hygroscopic organic dopants, which leads to formation of excess chemical bonds, reduction in the doped graphene carrier density, and proliferation of damages from the graphene grain boundaries. These environmental aging effects are further shown to be significantly mitigated by added graphene layers.

Effective-field theories for heavy quarkonium

International Nuclear Information System (INIS)

Brambilla, Nora; Pineda, Antonio; Soto, Joan; Vairo, Antonio

2005-01-01

This article reviews recent theoretical developments in heavy-quarkonium physics from the point of view of effective-field theories of QCD. We discuss nonrelativistic QCD and concentrate on potential nonrelativistic QCD. The main goal will be to derive Schroedinger equations based on QCD that govern heavy-quarkonium physics in the weak- and strong-coupling regimes. Finally, the review discusses a selected set of applications, which include spectroscopy, inclusive decays, and electromagnetic threshold production

Atomic-scale effects of chromium-doping on defect behaviour in uranium dioxide fuel

Energy Technology Data Exchange (ETDEWEB)

Guo, Zhexi; Ngayam-Happy, Raoul, E-mail: raoul.ngayam-happy@psi.ch; Krack, Matthias; Pautz, Andreas

2017-05-15

The effects of doping conventional UO{sub 2} fuel with chromium are studied through atomistic simulations using empirical force field methods. We first analyse the stable structures of unirradiated doped fuel by determining the preferred lattice configuration of chromium ions and oxygen vacancies within the matrix. In order to understand the physical effects of the dopants, we investigate the energy change upon inserting isolated defects and Frenkel pairs in the vicinity of chromium. The behaviour of point defects is then studied with collision cascade simulations and relaxation of doped simulation cells containing Frenkel pairs. The defective structures are analysed using an in-house tool named ASTRAM. Results indicate definite effects of chromium-doping on the ease with which defects are formed. Moreover, the extent of Cr effects on the residual damage following a displacement cascade is dependent on the dopant distribution and concentration in the fuel matrix.

Atomic-scale effects of chromium-doping on defect behaviour in uranium dioxide fuel

International Nuclear Information System (INIS)

Guo, Zhexi; Ngayam-Happy, Raoul; Krack, Matthias; Pautz, Andreas

2017-01-01

The effects of doping conventional UO 2 fuel with chromium are studied through atomistic simulations using empirical force field methods. We first analyse the stable structures of unirradiated doped fuel by determining the preferred lattice configuration of chromium ions and oxygen vacancies within the matrix. In order to understand the physical effects of the dopants, we investigate the energy change upon inserting isolated defects and Frenkel pairs in the vicinity of chromium. The behaviour of point defects is then studied with collision cascade simulations and relaxation of doped simulation cells containing Frenkel pairs. The defective structures are analysed using an in-house tool named ASTRAM. Results indicate definite effects of chromium-doping on the ease with which defects are formed. Moreover, the extent of Cr effects on the residual damage following a displacement cascade is dependent on the dopant distribution and concentration in the fuel matrix.

Bioaccumulation and toxic effects of some heavy metals in ...

African Journals Online (AJOL)

The contamination of the aquatic systems with heavy metals from natural anthropogenic sources has become a global problem which poses threats to ecosystems and natural communities. Hence this study reviews the effects of heavy metals in freshwater fishes. Fishes bioaccumulate heavy metals (including cadmium, zinc ...

Coupled channels effects in heavy ion elastic scattering

International Nuclear Information System (INIS)

Bond, P.D.

1977-01-01

The effects of inelastic excitation on the elastic scattering of heavy ions are considered within a coupled channels framework. Both Coulomb and nuclear excitation results are applied to 18 O + 184 W and other heavy ion reactions

Effects of Photonic Crystals on the Light Output of Heavy Inorganic Scintillators

CERN Document Server

Knapitsch, Arno; Fabjan, Christian W; Leclercq, Jean-Louis; Letartre, Xavier; Mazurczyk, Radoslaw; Lecoq, Paul

2013-01-01

Photonic crystals (PhCs) are optical materials which can affect the propagation of light in multiple ways. In recent years PhCs contributed to major technological developments in the field of semiconductor lasers, light emitting diodes and photovoltaic applications. In our case we are investigating the capabilities of photonic crystal slabs with the aim to improve the performance of heavy inorganic scintillators. To study the combination of scintillators and PhCs we use a Monte-Carlo program to simulate the light propagation inside a scintillator and a rigorous coupled wave analysis (RCWA) framework to analyse the optical PhC properties. The simulations show light output improvements of a wide range of scintillating materials due to light scattering effects of the PhC slabs. First samples have been produced on top of 1.2 × 2.6 × 5 mm LSO (cerium-doped Lutetium Oxyorthosilicate, Lu_2SiO_5:Ce^3+) scintillators using electron beam lithography and reactive ion etching (RIE). Our samples show a 30-60% light outp...

Highly concentrated, stable nitrogen-doped graphene for supercapacitors: Simultaneous doping and reduction

Energy Technology Data Exchange (ETDEWEB)

Jiang Baojiang [College of Materials Science and Chemical Engineering, Harbin Engineering University, Harbin (China); Key Laboratory of Functional Inorganic Material Chemistry, Ministry of Education of the People' s Republic of China, Heilongjiang University, Harbin (China); Tian Chungui; Wang Lei; Sun Li; Chen Chen; Nong Xiaozhen [Key Laboratory of Functional Inorganic Material Chemistry, Ministry of Education of the People' s Republic of China, Heilongjiang University, Harbin (China); Qiao Yingjie, E-mail: qiaoyingjie@hrbeu.edu.cn [College of Materials Science and Chemical Engineering, Harbin Engineering University, Harbin (China); Fu Honggang, E-mail: fuhg@vip.sina.com [Key Laboratory of Functional Inorganic Material Chemistry, Ministry of Education of the People' s Republic of China, Heilongjiang University, Harbin (China)

2012-02-01

In this work, we developed a concentrated ammonia-assisted hydrothermal method to obtain N-doped graphene sheets by simultaneous N-doping and reduction of graphene oxide (GO) sheets. The effects of hydrothermal temperature on the surface chemistry and the structure of N-doped graphene sheets were also investigated. X-ray photoelectron spectroscopy (XPS) study of N-doped graphene reveals that the highest doping level of 7.2% N is achieved at 180 Degree-Sign C for 12 h. N binding configurations of sample consist of pyridine N, quaternary N, and pyridine-N oxides. N doping is accompanied by the reduction of GO with decreases in oxygen levels from 34.8% in GO down to 8.5% in that of N-doped graphene. Meanwhile, the sample exhibits excellent N-doped thermal stability. Electrical measurements demonstrate that products have higher capacitive performance than that of pure graphene, the maximum specific capacitance of 144.6 F/g can be obtained which ascribe the pseudocapacitive effect from the N-doping. The samples also show excellent long-term cycle stability of capacitive performance.

Highly concentrated, stable nitrogen-doped graphene for supercapacitors: Simultaneous doping and reduction

Science.gov (United States)

Jiang, Baojiang; Tian, Chungui; Wang, Lei; Sun, Li; Chen, Chen; Nong, Xiaozhen; Qiao, Yingjie; Fu, Honggang

2012-02-01

In this work, we developed a concentrated ammonia-assisted hydrothermal method to obtain N-doped graphene sheets by simultaneous N-doping and reduction of graphene oxide (GO) sheets. The effects of hydrothermal temperature on the surface chemistry and the structure of N-doped graphene sheets were also investigated. X-ray photoelectron spectroscopy (XPS) study of N-doped graphene reveals that the highest doping level of 7.2% N is achieved at 180 °C for 12 h. N binding configurations of sample consist of pyridine N, quaternary N, and pyridine-N oxides. N doping is accompanied by the reduction of GO with decreases in oxygen levels from 34.8% in GO down to 8.5% in that of N-doped graphene. Meanwhile, the sample exhibits excellent N-doped thermal stability. Electrical measurements demonstrate that products have higher capacitive performance than that of pure graphene, the maximum specific capacitance of 144.6 F/g can be obtained which ascribe the pseudocapacitive effect from the N-doping. The samples also show excellent long-term cycle stability of capacitive performance.

Enhanced blue responses in nanostructured Si solar cells by shallow doping

Science.gov (United States)

Cheon, Sieun; Jeong, Doo Seok; Park, Jong-Keuk; Kim, Won Mok; Lee, Taek Sung; Lee, Heon; Kim, Inho

2018-03-01

Optimally designed Si nanostructures are very effective for light trapping in crystalline silicon (c-Si) solar cells. However, when the lateral feature size of Si nanostructures is comparable to the junction depth of the emitter, dopant diffusion in the lateral direction leads to excessive doping in the nanostructured emitter whereby poor blue responses arise in the external quantum efficiency (EQE). The primary goal of this study is to find the correlation of emitter junction depth and carrier collection efficiency in nanostructured c-Si solar cells in order to enhance the blue responses. We prepared Si nanostructures of nanocone shape by colloidal lithography, with silica beads of 520 nm in diameter, followed by a reactive ion etching process. c-Si solar cells with a standard cell architecture of an Al back surface field were fabricated varying the emitter junction depth. We varied the emitter junction depth by adjusting the doping level from heavy doping to moderate doping to light doping and achieved greatly enhanced blue responses in EQE from 47%-92% at a wavelength of 400 nm. The junction depth analysis by secondary ion mass-spectroscopy profiling and the scanning electron microscopy measurements provided us with the design guide of the doping level depending on the nanostructure feature size for high efficiency nanostructured c-Si solar cells. Optical simulations showed us that Si nanostructures can serve as an optical resonator to amplify the incident light field, which needs to be considered in the design of nanostructured c-Si solar cells.

Room temperature transparent conducting magnetic oxide (TCMO properties in heavy ion doped oxide semiconductor

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Juwon Lee

2017-08-01

Full Text Available Bismuth doped ZnO (ZnBi0.03O0.97 thin films are grown using pulsed laser deposition. The existence of positively charged Bi, absence of metallic zinc and the Zn-O bond formation in Bi doped ZnO are confirmed using X-ray Photoelectron Spectroscopy (XPS. Temperature dependent resistivity and UV-visible absorption spectra show lowest resistivity with 8.44 × 10-4 Ω cm at 300 K and average transmittance of 93 % in the visible region respectively. The robust ferromagnetic signature is observed at 350 K (7.156 × 10-4 emu/g. This study suggests that Bi doped ZnO films should be a potential candidate for spin based optoelectronic applications.

Localization effects in heavy ion collisions

International Nuclear Information System (INIS)

Donangelo, R.J.

1984-01-01

Radial and angular localization in heavy ion reactions on deformed nuclei is discussed. A theoretical method appropriate to study these localization effects is briefly described and then applied to the determination of deformed heavy ion potentials from inclastic scattering data. It is argued that one-and two-nucleon transfer reactions on deformed nuclei can provide a probe of nuclear structure in high angular momentum states and be at least qualitatively analyzed in the light of these localization concepts. (Author) [pt

Effect of silver nanoparticles on the dielectric properties of holmium doped silica glass

International Nuclear Information System (INIS)

Rejikumar, P.R.; Jyothy, P.V.; Mathew, Siby; Thomas, Vinoy; Unnikrishnan, N.V.

2010-01-01

The effect of silver nanoparticle co-doping on the dielectric properties of holmium doped silica glasses was studied. Silver nanoparticles of size between 20 and 22 nm were produced by the sol-gel technique. One of the samples showed an icosahedral morphology of the nanocrystal formed, along with spherical morphology. It was found that the tuning of the dielectric constant values could be accomplished by co-doping. The sample, with 1 wt% of Ho, had low dielectric constant values within the range 100 Hz-3 MHz due to the formation of quasi-molecular structures of holmium. This effect was evaded to some extent with silver co-doping as a result of the interdispersion of holmium complexes. Also it was found that the co-doping produced a higher dielectric loss which was calculated from the tan δ-log f graph. The Cole-Cole parameters and the Jonscher power law parameters were also calculated and are presented.

Effect of doping on the Raman lineshape and intensity of graphene

Science.gov (United States)

Casiraghi, Cinzia; Basko, Denis M.; Ferrari, Andrea C.

2010-03-01

Graphene can be doped by applying a gate voltage [1-2]. Doping strongly affects the G and 2D Raman peaks: i) the G peak upshifts for increasing doping, while its width decreases [1]; ii) the 2D upshifts for p-doping, while it downshifts for n-doping [2]. iii) the ratio between the 2D and G peaks intensity decreases for increasing doping [2]. The 2D intensity is strongly affected by the electron-electron scattering rate, which increases with doping [3]. Similar Raman peaks variations were observed for non-gated samples, as an effect of charged impurities [4]. Here we use the 2D peak intensity variation with doping to extract the electron-phonon scattering rate [3,5]. We note that in non-gated samples, where the Fermi level shift is induced by charged impurities, we can probe the 2D peak dependence much closer to the Dirac point than in gated ones [5]. We find an electron-phonon coupling scattering rate of 60 ps-1 at 2.41 eV excitation energy [3,5]. [4pt] [1] S. Pisana et al, Nature Mat. 6, 198 (2007)[0pt] [2] A. Das et al., Nature Nanotech. 3, 210 (2008)[0pt] [3] D. M. Basko et al. PRB 80, 165413 (2009)[0pt] [4] C. Casiraghi et al., APL 91, 233108 (2007)[0pt] [5] C. Casiraghi, arXiv:0908.4480

XPS studies of nitrogen doping niobium used for accelerator applications

Science.gov (United States)

Yang, Ziqin; Lu, Xiangyang; Tan, Weiwei; Zhao, Jifei; Yang, Deyu; Yang, Yujia; He, Yuan; Zhou, Kui

2018-05-01

Nitrogen doping study on niobium (Nb) samples used for the fabrication of superconducting radio frequency (SRF) cavities was carried out. The samples' surface treatment was attempted to replicate that of the Nb SRF cavities, which includes heavy electropolishing (EP), nitrogen doping and the subsequent EP with different amounts of material removal. The surface chemical composition of Nb samples with different post treatments has been studied by XPS. The chemical composition of Nb, O, C and N was presented before and after Gas Cluster Ion Beam (GCIB) etching. No signals of poorly superconducting nitrides NbNx was found on the surface of any doped Nb sample with the 2/6 recipe before GCIB etching. However, in the depth range greater than 30 nm, the content of N element is below the XPS detection precision scope even for the Nb sample directly after nitrogen doping treatment with the 2/6 recipe.

Ba-DOPED ZnO MATERIALS: A DFT SIMULATION TO INVESTIGATE THE DOPING EFFECT ON FERROELECTRICITY

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Luis H. da S. Lacerda

2016-04-01

Full Text Available ZnO is a semiconductor material largely employed in the development of several electronic and optical devices due to its unique electronic, optical, piezo-, ferroelectric and structural properties. This study evaluates the properties of Ba-doped wurtzite-ZnO using quantum mechanical simulations based on the Density Functional Theory (DFT allied to hybrid functional B3LYP. The Ba-doping caused increase in lattice parameters and slight distortions at the unit cell angle in a wurtzite structure. In addition, the doping process presented decrease in the band-gap (Eg at low percentages suggesting band-gap engineering. For low doping amounts, the wavelength characteristic was observed in the visible range; whereas, for middle and high doping amounts, the wavelength belongs to the Ultraviolet range. The Ba atoms also influence the ferroelectric property, which is improved linearly with the doping amount, except for doping at 100% or wurtzite-BaO. The ferroelectric results indicate the ZnO:Ba is an strong option to replace perovskite materials in ferroelectric and flash-type memory devices.

The rebound effect for heavy industry: Empirical evidence from China

International Nuclear Information System (INIS)

Lin, Boqiang; Li, Jianglong

2014-01-01

Energy efficiency improvement will reduce the effective price of energy services, and hence at least partially mitigate original expected energy conservation. Therefore, the magnitude of rebound effect is important for the design and timing of an effective energy conservation policy. Under the framework of translog cost share equations, we estimates the direct rebound effect for heavy industry in China for the first time by conducting an empirical research on the relationship between the direct rebound effect and the ease with which energy services can substitute for other inputs. Additionally, asymmetric price responses are specified in the model for the rebound effect estimation. Empirical results in our paper indicate that the rebound effect for heavy industry in China is about 74.3%. This reveals that energy efficiency improvement can save energy to a certain degree since the rebound effect is less than 100% (“back-fire”), but most of the expected reduction in heavy industry energy consumption is mitigated. These findings prove that energy pricing reforms and energy taxes should be further implemented to achieve effective energy conservation in China’s 12th Five Years Plan. - Highlights: • Heavy industry is energy intensive and accounts for over 60% of China’s energy consumption. • Direct rebound effect for heavy industry in China is estimated for the first time. • Asymmetric price responses are specified in the model for the direct rebound effect estimation. • Finding the existence of direct rebound effect in China’s heavy industry with a magnitude of 74.3%. • Proving that energy pricing reforms and energy taxes should be further implemented

Heavy-heavy and heavy-light quarks interactions generated by QCD vacuum

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Musakhanov Mirzayusuf

2017-01-01

Full Text Available The QCD vacuum is populated by instantons that correspond to the tunneling processes in the vacuum. This mechanism creates the strong vacuum gluon fields. As result, the QCD vacuum instantons induce very strong interactions between light quarks, initially almost massless. Such a strong interactions bring a large dynamical mass M of the light quarks and bound them to produce almost massless pions in accordance with the spontaneous breaking of the chiral symmetry (SBCS. On the other hand, the QCD vacuum instantons also interact with heavy quarks and responsible for the generation of the heavy-heavy and heavy-light quarks interactions, with a traces of the SBCS. If we take the average instanton size ρ¯=0.33$\\bar \\rho = 0.33$ fm, and the average inter-instanton distance R¯=1$\\bar R = 1$ fm we obtain the dynamical light quark mass to be M = 365 MeV and the instanton media contribution to the heavy quark mass ΔM=70 MeV. These factors define the coupling between heavy-light and heavy-heavy quarks induced by the QCD vacuum instantons. We consider first the instanton effects on the heavy-heavy quarks potential, including its spin-dependent part. We also discuss those effects on the masses of the charmonia and their hyperfine mass splittings. At the second part we discuss the interaction between a heavy and light quarks generated by instantons and it’s effects.

Effect of Al doping on phase formation and thermal stability of iron nitride thin films

Energy Technology Data Exchange (ETDEWEB)

Tayal, Akhil [Amity Center for Spintronic Materials, Amity University, Sector 125, Noida 201 303 (India); Gupta, Mukul, E-mail: mgupta@csr.res.in [Amity Center for Spintronic Materials, Amity University, Sector 125, Noida 201 303 (India); Pandey, Nidhi [Amity Center for Spintronic Materials, Amity University, Sector 125, Noida 201 303 (India); Gupta, Ajay [UGC-DAE Consortium for Scientific Research, University Campus, Khandwa Road, Indore 452 001 (India); Horisberger, Michael [Laboratory for Developments and Methods, Paul Scherrer Institut, CH-5232 Villigen PSI (Switzerland); Stahn, Jochen [Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut, CH-5232 Villigen PSI (Switzerland)

2015-11-25

In the present work, we systematically studied the effect of Al doping on the phase formation of iron nitride (Fe–N) thin films. Fe–N thin films with different concentration of Al (Al = 0, 2, 3, 6, and 12 at.%) were deposited using dc magnetron sputtering by varying the nitrogen partial pressure between 0 and 100%. The structural and magnetic properties of the films were studied using x-ray diffraction and polarized neutron reflectivity. It was observed that at the lowest doping level (2 at.% of Al), nitrogen rich non-magnetic Fe–N phase gets formed at a lower nitrogen partial pressure as compared to the un-doped sample. Interestingly, we observed that as Al doping is increased beyond 3 at.%, nitrogen rich non-magnetic Fe–N phase appears at higher nitrogen partial pressure as compared to un-doped sample. The thermal stability of films were also investigated. Un-doped Fe–N films deposited at 10% nitrogen partial pressure possess poor thermal stability. Doping of Al at 2 at.% improves it marginally, whereas, for 3, 6 and 12 at.% Al doping, it shows significant improvement. The obtained results have been explained in terms of thermodynamics of Fe–N and Al–N. - Highlights: • Doping effects of Al on Fe–N phase formation is studied. • Phase formation shows a non-monotonic behavior with Al doping. • Low doping levels of Al enhance and high levels retard the nitridation process. • Al doping beyond 3 at.% improve thermal stability of Fe–N films.

Raman scattering of monolayer graphene: the temperature and oxygen doping effects

International Nuclear Information System (INIS)

Zhou Haiqing; Qiu Caiyu; Yu Fang; Yang Huaichao; Chen Minjiang; Hu Lijun; Guo Yanjun; Sun Lianfeng

2011-01-01

Raman spectra of monolayer graphene at various temperatures (303-473 K) are measured. In Raman scattering with wave numbers ranging from 1200 to 3400 cm -1 , the four main Raman peaks (G, 2D, T + D and 2D') show temperature-dependent behaviour, but have different frequency shifts with increase in temperature. We propose that the peak frequency shift is related mainly to the elongation of C-C bond due to thermal expansion or anharmonic coupling of phonon modes, and oxygen-induced strong hole doping on the graphene surface. The doping effect can be confirmed from the frequency shifts, full-width at half-maximum as well as the area and intensity ratios of G and 2D peaks in temperature-dependent Raman scattering of graphene, room-temperature Raman spectra of pristine graphene and graphene cooled down after Raman measurement at 473 K in air. Therefore, the oxygen doping effect and temperature effect coexist in temperature-dependent Raman scattering of monolayer graphene.

Effect of nitrogen doping of graphene oxide on hydrogen and hydroxyl adsorption

Energy Technology Data Exchange (ETDEWEB)

Min, Byeong June; Jeong, Hae Kyung [Daegu University, Kyungsan (Korea, Republic of)

2014-05-15

We investigate how nitrogen-doping affects the hydrogen (H) and the hydroxyl (OH) adsorption on graphene oxide (GO) and on nitrogen-doped GO (NGO) via pseudopotential plane wave density functional calculations within the local spin density approximation. We find that the nitrogen doping brings about drastic changes in the hydrogen and the hydroxyl adsorption energetics, but its effects depend sensitively on the nitrogen configuration in NGO. The H and the OH adsorption energies are comparable only for pyrrolic NGO. In GO and quarternary NGO, the H adsorption energy is greater than the OH adsorption energy while the trend is reversed in pyridinic NGO. Also, the OH adsorption process is less affected by nitrogen-doping than the H adsorption is.

Two different formulations of the heavy quark effective theory

International Nuclear Information System (INIS)

Balk, S.; Ilakovac, A.; Koerner, J.G.; Pirjol, D.

1994-01-01

We point out that there exist two different formulations of the Heavy Quark Effective Theory (HQET). The one formulation of HQET was mostly developed at Harvard and involves the use of the equation of motion to eliminate the small components of the heavy quark field. The second formulation, developed in Mainz, involves a series of Foldy-Wouthuysen-type field transformations which diagonalizes the heavy quark Lagrangian in terms of an effective quark and antiquark sector. Starting at O(1/m Q 2 ) the two formulations are different in that their effective Lagrangians, their effective currents, and their effective wave functions differ. However, when these three differences are properly taken into account, the two alternative formulations lead to identical transition or S-matrix elements. This is demonstrated in an explicit example at O(1/m Q 2 ). We point to an essential difficulty of the Harvard HQET in that the Harvard effective fields are not properly normalized starting at order O(1/m Q 2 ). We provide explicit higher order expressions for the effective fields and the Lagrangian in the Mainz approach, and write down an O(1/m Q 2 ) nonabelian version of the Pauli equation for the heavy quark effective field. (orig.)

Measuring of nonlinearity of dye doped liquid crystals using of self phase modulation effect

International Nuclear Information System (INIS)

Abedi, M.; Jafari, A.; Tajalli, H.

2007-01-01

Self phase modulation in dye doped liquid crystals has investigated and the nonlinearity of dye doped liquid crystals is measured by this effect. The Self phase modulation effect can be used for producing optical micro rings that have many applications in photonics and laser industries.

The effect of Ni and Fe doping on Hall anomaly in vortex state of doped YBCO samples

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M Nazarzadeh

2010-09-01

Full Text Available We have investigated hall effect on YBa2Cu3-xMxO7-δ (M=Ni, Fe bulk samples, with dopant amount 0 ≤ x ≤ 0.045 for Ni and 0 ≤ x ≤ 0.03 for Fe, with magnetic field (H=2.52, 4.61, 6.27 kOe perpendicular to sample’s surface with constant current 100 mA. Our study shows that as both dopants increases, TC decreases and it decreases faster by Ni . In these ranges of dopant and magnetic field the Hall sign reversal has been observed in all samples once and also ∆max has occurred in lower temperatures, its magnitude increases by Ni, and in Fe doped samples except in sample with dopant amount x=0.03, which almost decreases, that it can show effect of magnetic doping on hall effect.

Integrability in heavy quark effective theory

Science.gov (United States)

Braun, Vladimir M.; Ji, Yao; Manashov, Alexander N.

2018-06-01

It was found that renormalization group equations in the heavy-quark effective theory (HQET) for the operators involving one effective heavy quark and light degrees of freedom are completely integrable in some cases and are related to spin chain models with the Hamiltonian commuting with the nondiagonal entry C( u) of the monodromy matrix. In this work we provide a more complete mathematical treatment of such spin chains in the QISM framework. We also discuss the relation of integrable models that appear in the HQET context with the large-spin limit of integrable models in QCD with light quarks. We find that the conserved charges and the "ground state" wave functions in HQET models can be obtained from the light-quark counterparts in a certain scaling limit.

Effects of Co{sup 2+} doping on physicochemical behaviors of hierarchical NiO nanostructure

Energy Technology Data Exchange (ETDEWEB)

Ding, Caihua [Beijing Key Laboratory of Construction Tailorable Advanced Functional Materials and Green Applications, School of Materials Science & Engineering, Beijing Institute of Technology, Beijing, 100081 (China); Gao, WenChao [College of Engineering, Peking University, Beijing, 100871 (China); Zhao, Yongjie, E-mail: zhaoyjpeace@gmail.com [Beijing Key Laboratory of Construction Tailorable Advanced Functional Materials and Green Applications, School of Materials Science & Engineering, Beijing Institute of Technology, Beijing, 100081 (China); Zhao, Yuzhen; Zhou, Heping [State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing, 100084 (China); Li, Jingbo; Jin, Haibo [Beijing Key Laboratory of Construction Tailorable Advanced Functional Materials and Green Applications, School of Materials Science & Engineering, Beijing Institute of Technology, Beijing, 100081 (China)

2016-12-30

Highlights: • A series of Co{sup 2+} doped NiO materials were synthesized by a facile hydrothermal method. • Co{sup 2+} doping would bring about a series influence to the as-obtained NiO products. • Hierarchical NiO nanostructure transformed from nanosheets to nanoneedles with Co{sup 2+} doping. • The catalytic properties of NiO were significantly improved via the introduction of Co{sup 2+}. • Excellent catalytic activity was ascribed to the synergistic effect between Co{sup 2+} and NiO. - Abstract: A series of Co{sup 2+} doped NiO materials (Ni{sub 1−x}Co{sub x}O with x = 0, 0.125, 0.25 and 0.5) were synthesized using a facile hydrothermal method followed by a calcination process. The effects of Co{sup 2+} doping on the structural, morphological, magnetic and catalytic properties of NiO were systematically investigated. The results indicated that Co{sup 2+} doping would bring about a series influence to the as-obtained NiO product. The XRD results indicated that within the region of 0 ≤ x ≤ 0.25 the doped products revealed a pure NiO phase. The elementary unit for the hierarchy NiO gradually transformed from nanosheets to nanoneedles with the increase of Co{sup 2+} doping content. As-obtained Co{sup 2+} doped NiO products showed ferromagnetism at room temperature and the magnetization value was increased with the increase of Co{sup 2+} doping content. The catalytic properties of NiO concerning the thermal decomposition of ammonium perchlorate (AP) were significantly improved via the introduction of Co{sup 2+}. The Ni{sub 1−x}Co{sub x}O products with x = 0.25 showed the best catalytic performance to AP, which could decrease the beginning and ending decomposition temperature of AP by 44 and 108 °C. The change of morphology, enhancement of electrical conductivity and the synergistic effect between Co{sup 2+} and NiO were the main factors responsible for the improvement of physicochemical behaviors.

The UKB prescription and the heavy atom effects on the nuclear magnetic shielding of vicinal heavy atoms.

Science.gov (United States)

Maldonado, Alejandro F; Aucar, Gustavo A

2009-07-21

Fully relativistic calculations of NMR magnetic shielding on XYH3 (X = C, Si, Ge and Sn; Y = Br, I), XHn (n = 1-4) molecular systems and noble gases performed with a fully relativistic polarization propagator formalism at the RPA level of approach are presented. The rate of convergence (size of basis set and time involved) for calculations with both kinetic balance prescriptions, RKB and UKB, were investigated. Calculations with UKB makes it feasible to obtain reliable results for two or more heavy-atom-containing molecules. For such XYH3 systems, the influence of heavy vicinal halogen atoms on sigma(X) is such that heavy atom effects on heavy atoms (vicinal plus their own effects or HAVHA + HAHA effects) amount to 30.50% for X = Sn and Y = I; being the HAHA effect of the order of 25%. So the vicinal effect alone is of the order of 5.5%. The vicinal heavy atom effect on light atoms (HALA effect) is of the order of 28% for X = C and Y = I. A similar behaviour, but of opposite sign, is observed for sigma(Y) for which sigmaR-NR (I; X = C) (HAHA effect) is around 27% and sigmaR-NR(I; X = Sn) (HAVHA + HAHA effects) is close to 21%. Its electronic origin is paramagnetic for halogen atoms but both dia- and paramagnetic for central atoms. The effect on two bond distant hydrogen atoms is such that the largest variation of sigma(H) within the same family of XYH3 molecules appears for X = Si and Y = I: around 20%. In this case sigma(H; X = Sn, Y = I) = 33.45 ppm and sigma(H; X = Sn, Y = H) = 27.82 ppm.

Heavy-ion radiation induced bystander effect in mice

Science.gov (United States)

Liang, Shujian; Sun, Yeqing; Zhang, Meng; Wang, Wei; Cui, Changna

2012-07-01

Radiation-induced bystander effect is defined as the induction of damage in neighboring non-hit cells by signals released from directly-irradiated cells. Recently, Low dose of high LET radiation induced bystander effects in vivo have been reported more and more. It has been indicated that radiation induced bystander effect was localized not only in bystander tissues but also in distant organs. Genomic, epigenetic, metabolomics and proteomics play significant roles in regulating heavy-ion radiation stress responses in mice. To identify the molecular mechanism that underlies bystander effects of heavy-ion radiation, the male mice head were exposed to 2000mGy dose of 12C heavy-ion radiation and the distant organ liver was detected on 1h, 6h, 12h and 24h after radiation, respectively. MSAP was used to monitor the level of polymorphic DNA methylation changes. The results show that heavy-ion irradiate mouse head can induce liver DNA methylation changes significantly. The percent of DNA methylation changes are time-dependent and highest at 6h after radiation. We also prove that the hypo-methylation changes on 1h and 6h after irradiation. But the expression level of DNA methyltransferase DNMT3a is not changed. UPLC/Synapt HDMS G2 was employed to detect the proteomics of bystander liver 1h after irradiation. 64 proteins are found significantly different between treatment and control group. GO process show that six of 64 which were unique in irradiation group are associated with apoptosis and DNA damage response. The results suggest that mice head exposed to heavy-ion radiation can induce damage and methylation pattern changed in distant organ liver. Moreover, our findings are important to understand the molecular mechanism of radiation induced bystander effects in vivo.

Effects of hydrogen on Mn-doped GaN: A first principles calculation

International Nuclear Information System (INIS)

Wu, M.S.; Xu, B.; Liu, G.; Lei, X.L.; Ouyang, C.Y.

2013-01-01

First-principles calculations based on spin density functional theory are performed to study the effects of H on the structural, electronic and magnetic properties of the Mn-doped GaN dilute magnetic semiconductors. Our results show that the interstitial H atom prefers to bond with N atom rather than Mn atom, which means that H favors to form the N–H complex rather than Mn–H complex in the Mn-doped GaN. After introducing one H atom in the system, the total magnetic moment of the Mn-doped GaN increases by 25%, from 4.0μ B to 5.0μ B . The physics mechanism of the increase of magnetic moment after hydrogenation in Mn-doped GaN is discussed

Heavy metal removal from aqueous solutions using engineered magnetic biochars derived from waste marine macro-algal biomass.

Science.gov (United States)

Son, Eun-Bi; Poo, Kyung-Min; Chang, Jae-Soo; Chae, Kyu-Jung

2018-02-15

Despite the excellent sorption ability of biochar for heavy metals, it is difficult to separate and reuse after adsorption when applied to wastewater treatment process. To overcome these drawbacks, we developed an engineered magnetic biochar by pyrolyzing waste marine macro-algae as a feedstock, and we doped iron oxide particles (e.g., magnetite, maghemite) to impart magnetism. The physicochemical characteristics and adsorption properties of the biochar were evaluated. When compared to conventional pinewood sawdust biochar, the waste marine algae-based magnetic biochar exhibited a greater potential to remove heavy metals despite having a lower surface area (0.97m 2 /g for kelp magnetic biochar and 63.33m 2 /g for hijikia magnetic biochar). Although magnetic biochar could be effectively separated from the solution, however, the magnetization of the biochar partially reduced its heavy metal adsorption efficiency due to the biochar's surface pores becoming plugged with iron oxide particles. Therefore, it is vital to determine the optimum amount of iron doping that maximizes the biochar's separation without sacrificing its heavy metal adsorption efficiency. The optimum concentration of the iron loading solution for the magnetic biochar was determined to be 0.025-0.05mol/L. The magnetic biochar's heavy metal adsorption capability is considerably higher than that of other types of biochar reported previously. Further, it demonstrated a high selectivity for copper, showing two-fold greater removal (69.37mg/g for kelp magnetic biochar and 63.52mg/g for hijikia magnetic biochar) than zinc and cadmium. This high heavy metal removal performance can likely be attributed to the abundant presence of various oxygen-containing functional groups (COOH and OH) on the magnetic biochar, which serve as potential adsorption sites for heavy metals. The unique features of its high heavy metal removal performance and easy separation suggest that the magnetic algae biochar can potentially

Effect of tellurium doping on the structural, optical, and electrical properties of CdO

Energy Technology Data Exchange (ETDEWEB)

Dakhel, A.A. [Department of Physics, College of Science, University of Bahrain, P.O. Box 32038 (Bahrain)

2010-08-15

Te-doped CdO thin-films (1%, 3%, and 5%) have been prepared by a vacuum evaporation method on glass and silicon-wafer substrates. The prepared films were characterised by X-ray fluorescence, X-ray diffraction, UV-VIS-NIR absorption spectroscopy, and dc-electrical measurements. Experimental data indicate that Te ions doping slightly stresses the host CdO crystalline structure and changes the optical and electrical properties. The bandgap of the host CdO was suddenly narrowed by about 23% due to a little (1%) doping with Te ions. This bandgap shrinkage was explained by effects of trap levels overlapping with conduction band. The electrical behaviours of the Te-doped CdO films show that they are degenerate semiconductors with a bandgap of 1.7-2.2 eV. The 1% Te-doped CdO film shows increase its mobility by about 5 times, conductivity by {proportional_to}140 times, and carrier concentration by {proportional_to}27 times, relative to undoped CdO film. From transparent-conducting-oxide point of view, Te is sufficiently effective for CdO doping. Finally, the absorption in the NIR spectral region was studied in the framework of the classical Drude theory. (author)

Superconducting Gap Symmetry of LaFeP(O,F Observed by Impurity Doping Effect

Directory of Open Access Journals (Sweden)

Shigeki Miyasaka

2016-08-01

Full Text Available We have investigated Mn, Co and Ni substitution effects on polycrystalline samples of LaFePO0.95F0.05 by resistivity and magnetoresistance measurements. In LaFe1-xMxPO0.95F0.05 (M = Mn, Co and Ni, the superconducting transition temperature (Tc monotonously decreases with increasing the impurity doping level of x. There is a clear difference of Tc suppression rates among Mn, Co and Ni doping cases, and the decreasing rate of Tc by Mn doping as a magnetic impurity is larger than those by the nonmagnetic doping impurities (Co/Ni. This result indicates that in LaFePO0.95F0.05, Tc is rapidly suppressed by the pair-breaking effect of magnetic impurities, and the pairing symmetry is a full-gapped s-wave. In the nonmagnetic impurity-doped systems, the residual resistivity in the normal state has nearly the same value when Tc becomes zero. The residual resistivity value is almost consistent with the universal value of sheet resistance for two-dimensional superconductors, suggesting that Tc is suppressed by electron localization in Co/Ni-doped LaFePO0.95F0.05.

UV-visible, infrared and Raman spectroscopic and thermal studies of tungsten doped lead borate glasses and the effect of ionizing gamma irradiation

International Nuclear Information System (INIS)

El-Kheshen, Amany A.; El-Batal, Fatma H.; Marzouk, Samir Y.

2008-01-01

Ultraviolet-visible, infrared and Raman spectroscopy together with thermal properties were measured for undoped and WO 3 - doped (up to 10%) lead borate glasses. Also, the effect of gamma irradiation was followed by UV-visible measurements. The UV visible spectrum of the undoped glass reveals before irradiation intense ultraviolet bands due to the combined effects of trace iron impurities (Fe 3+ ) and Pb 2+ ions which remain unchanged with the addition of WO 3 . Infrared and Raman measurements show characteristic bands due to borate group and the possible sharing of lead-oxygen and tungsten-oxygen groups. The studied glasses show obvious resistance to gamma irradiation. The thermal and density data are correlated with the introduction of highly polarizable and heavy (W 6+ ) ions and to the change in structural arrangement with varying glass composition. (author)

Deformation effects in the heavy ion quarter-point angle

International Nuclear Information System (INIS)

Almeida, F.I.A. de; Hussein, M.S.

1984-01-01

The effects of static and dynamic deformation on the heavy-ion elastic scattering quarter-point angle are discussed and analyzed in the sudden approximation. Simple expressions are derived within the Fresnel model and applications to several heavy-ion systems are presented. (Author) [pt

Effect of Fe and C doping on the thermal release of helium from aluminum

International Nuclear Information System (INIS)

Xiang, X.; Chen, C.A.; Liu, K.Z.; Peng, L.X.; Rao, Y.C.

2010-01-01

The effect of Fe and C doping on the thermal release of helium from Al implanted with 10 keV, 4.0 x 10 21 ion/m 2 He at room temperature (RT) has been investigated by thermal helium desorption spectrometry (THDS) and transmission electron microscope (TEM). The results show that Fe and C doping have significant impact on the release of helium from Al and the extent depends on the doping fluence. Proper fluence of Fe and C doping would lead to the retardation of the release of helium from Al, while excessive fluence of Fe and C doping would result in more desorption peaks and the release of helium in lower temperature ranges. Fe and C doping have different influence on the release of helium from Al, and the difference is related with the secondary phases forming in the samples.

Effect of heavy particles in low-energy light-particle processes

International Nuclear Information System (INIS)

Chan, L.H.; Hagiwara, T.; Ovrut, B.

1979-01-01

The ''decoupling theorem'' of Appelquist and Carazzone is found not always to be applicable to light-scalar-particle processes in spontaneously broken theories. If the Higgs scalar is considered to be light, then Higgs-scalar processes see the effect of heavy fermions and heavy vector gauge bosons at the one-loop level. If there is more than one scalar multiplet in a spontaneously broken gauge theory, the effect of a heavy Higgs particle in light-scalar-particle processes is significant at the tree level. In the latter case, such an effect can be absorbed completely into an effective phi 4 coupling constant, lambda/sub eff/, of the light particle provided that lambda/sub eff/ is positive definite

Effects of doping on spin correlations in the periodic Anderson model

International Nuclear Information System (INIS)

Bonca, J.; Gubernatis, J.E.

1998-01-01

We studied the effects of hole doping on spin correlations in the two-dimensional periodic Anderson model, mainly at the full and three-quarters-full lower bands cases. In the full lower band case, strong antiferromagnetic correlations develop when the on-site repulsive interaction strength U becomes comparable to the quasiparticle bandwidth. In the three-quarters full case, a kind of spin correlation develops that is consistent with the resonance between a (π,0) and a (0,π) spin-density wave. In this state the spins on different sublattices appear uncorrelated. Hole doping away from the completely full case rapidly destroys the long-range antiferromagnetic correlations, in a manner reminiscent of the destruction of antiferromagnetism in the Hubbard model. In contrast to the Hubbard model, the doping does not shift the peak in the magnetic structure factor from the (π,π) position. At dopings intermediate to the full and three-quarters full cases, only weak spin correlations exist. copyright 1998 The American Physical Society

Magnetic Doping and Kondo Effect in Bi 2 Se 3 Nanoribbons

KAUST Repository

Cha, Judy J.; Williams, James R.; Kong, Desheng; Meister, Stefan; Peng, Hailin; Bestwick, Andrew J.; Gallagher, Patrick; Goldhaber-Gordon, David; Cui, Yi

2010-01-01

A simple surface band structure and a large bulk band gap have allowed Bi2Se3 to become a reference material for the newly discovered three-dimensional topological insulators, which exhibit topologically protected conducting surface states that reside inside the bulk band gap. Studying topological insulators such as Bi2Se3 in nanostructures is advantageous because of the high surfaceto-volume ratio, which enhances effects from the surface states; recently reported Aharonov-Bohm oscillation in topological insulator nanoribbons by some of us is a good example. Theoretically, introducing magnetic impurities in topological insulators is predicted to open a small gap in the surface states by breaking time-reversal symmetry. Here, we present synthesis of magnetically doped Bi 2Se3 nanoribbons by vapor-liquid-solid growth using magnetic metal thin films as catalysts. Although the doping concentration is less than ∼2 %. low-temperature transport measurements of the Fe-doped Bi2Se3 nanoribbon devices show a clear Kondo effect at temperatures below 30 K, confirming the presence of magnetic impurities in the Bi2Se3 nanoribbons. The capability to dope topological insulator nanostructures magnetically opens up exciting opportunities for spintronics. © 2010 American Chemical Society.

Magnetic Doping and Kondo Effect in Bi 2 Se 3 Nanoribbons

KAUST Repository

Cha, Judy J.

2010-03-10

A simple surface band structure and a large bulk band gap have allowed Bi2Se3 to become a reference material for the newly discovered three-dimensional topological insulators, which exhibit topologically protected conducting surface states that reside inside the bulk band gap. Studying topological insulators such as Bi2Se3 in nanostructures is advantageous because of the high surfaceto-volume ratio, which enhances effects from the surface states; recently reported Aharonov-Bohm oscillation in topological insulator nanoribbons by some of us is a good example. Theoretically, introducing magnetic impurities in topological insulators is predicted to open a small gap in the surface states by breaking time-reversal symmetry. Here, we present synthesis of magnetically doped Bi 2Se3 nanoribbons by vapor-liquid-solid growth using magnetic metal thin films as catalysts. Although the doping concentration is less than ∼2 %. low-temperature transport measurements of the Fe-doped Bi2Se3 nanoribbon devices show a clear Kondo effect at temperatures below 30 K, confirming the presence of magnetic impurities in the Bi2Se3 nanoribbons. The capability to dope topological insulator nanostructures magnetically opens up exciting opportunities for spintronics. © 2010 American Chemical Society.

Mesoscopic quantum effects in a bad metal, hydrogen-doped vanadium dioxide

Science.gov (United States)

Hardy, Will J.; Ji, Heng; Paik, Hanjong; Schlom, Darrell G.; Natelson, Douglas

2017-05-01

The standard treatment of quantum corrections to semiclassical electronic conduction assumes that charge carriers propagate many wavelengths between scattering events, and succeeds in explaining multiple phenomena (weak localization magnetoresistance (WLMR), universal conductance fluctuations, Aharonov-Bohm oscillations) observed in polycrystalline metals and doped semiconductors in various dimensionalities. We report apparent WLMR and conductance fluctuations in H x VO2, a poor metal (in violation of the Mott-Ioffe-Regel limit) stabilized by the suppression of the VO2 metal-insulator transition through atomic hydrogen doping. Epitaxial thin films, single-crystal nanobeams, and nanosheets show similar phenomenology, though the details of the apparent WLMR seem to depend on the combined effects of the strain environment and presumed doping level. Self-consistent quantitative analysis of the WLMR is challenging given this and the high resistivity of the material, since the quantitative expressions for WLMR are derived assuming good metallicity. These observations raise the issue of how to assess and analyze mesoscopic quantum effects in poor metals.

Anomalous magneto-elastic and charge doping effects in thallium-doped BaFe2As2

Science.gov (United States)

Sefat, Athena S.; Li, Li; Cao, Huibo B.; McGuire, Michael A.; Sales, Brian; Custelcean, Radu; Parker, David S.

2016-01-01

Within the BaFe2As2 crystal lattice, we partially substitute thallium for barium and report the effects of interlayer coupling in Ba1-xTlxFe2As2 crystals. We demonstrate the unusual effects of magneto-elastic coupling and charge doping in this iron-arsenide material, whereby Néel temperature rises with small x, and then falls with additional x. Specifically, we find that Néel and structural transitions in BaFe2As2 (TN = Ts = 133 K) increase for x = 0.05 (TN = 138 K, Ts = 140 K) from magnetization, heat capacity, resistivity, and neutron diffraction measurements. Evidence from single crystal X-ray diffraction and first principles calculations attributes the stronger magnetism in x = 0.05 to magneto-elastic coupling related to the shorter intraplanar Fe-Fe bond distance. With further thallium substitution, the transition temperatures decrease for x = 0.09 (TN = Ts = 131 K), and this is due to charge doping. We illustrate that small changes related to 3d transition-metal state can have profound effects on magnetism. PMID:26867821

Nonthermal Photocoercivity Effect in Low-Doped (Ga,Mn)As Ferromagnetic Semiconductor

Science.gov (United States)

Kiessling, T.; Astakhov, G. V.; Hoffmann, H.; Korenev, V. L.; Schwittek, J.; Schott, G. M.; Gould, C.; Ossau, W.; Brunner, K.; Molenkamp, L. W.

2011-12-01

We report a photoinduced change of the coercive field of a low doped Ga1-xMnxAs ferromagnetic semiconductor under very low intensity illumination. This photocoercivity effect (PCE) is local and reversible, which enables the controlled formation of localized magnetization domains. The PCE arises from a light induced lowering of the domain wall pinning energy as confirmed by test experiments on high doped, fully metallic ferromagnetic Ga1-xMnxAs.

Effect of Si/Fe ratio on the boron and phosphorus doping efficiency of β-FeSi2 by magnetron sputtering

International Nuclear Information System (INIS)

Xu Jiaxiong; Yao Ruohe

2011-01-01

Boron-doped or phosphorus-doped β-FeSi 2 thin films have been prepared on silicon substrate by magnetron sputtering. Effects of Si/Fe ratio on the boron and phosphorus doping efficiencies have been studied from the resistivities of doped β-FeSi 2 thin films and current-voltage characteristics of doped β-FeSi 2 /Si heterojunctions. The experimental results reveal that the carrier concentration and doping efficiency of boron or phosphorus dopants at the Fe-rich side are higher than that at the Si-rich side. The effect of Si/Fe ratio can be deduced from the comparison of the formation energies under two extreme conditions. At the Fe-rich limit condition, the formation energy of boron or phosphorous doping is lower than that at the Si-rich condition. Therefore, the activation of impurities is more effective at the Fe-rich side. These results demonstrate that the boron-doped and phosphorous-doped β-FeSi 2 thin films should be kept at the Fe-rich side to avoid the unexpected doping sites and low doping efficiency.

Passivation effects in B doped self-assembled Si nanocrystals

International Nuclear Information System (INIS)

Puthen Veettil, B.; Wu, Lingfeng; Jia, Xuguang; Lin, Ziyun; Zhang, Tian; Yang, Terry; Johnson, Craig; Conibeer, Gavin; Perez-Würfl, Ivan; McCamey, Dane

2014-01-01

Doping of semiconductor nanocrystals has enabled their widespread technological application in optoelectronics and micro/nano-electronics. In this work, boron-doped self-assembled silicon nanocrystal samples have been grown and characterised using Electron Spin Resonance and photoluminescence spectroscopy. The passivation effects of boron on the interface dangling bonds have been investigated. Addition of boron dopants is found to compensate the active dangling bonds at the interface, and this is confirmed by an increase in photoluminescence intensity. Further addition of dopants is found to reduce the photoluminescence intensity by decreasing the minority carrier lifetime as a result of the increased number of non-radiative processes

Mn doping effect on structure and magnetism of epitaxial (FePt)1-xMnx films

International Nuclear Information System (INIS)

Huang, J.C.A.; Chang, Y.C.; Yu, C.C.; Yao, Y.D.; Hu, Y.M.; Fu, C.M.

2003-01-01

We study the structure and perpendicular magnetism of molecular beam epitaxy grown (FePt) 1-x Mn x films with doping concentration x=0, 1%, 2%, 3%, 4%, and 5%. The (FePt) 1-x Mn x films were made by multilayers growth of [Fe/Pt/Mn]xN at 100 deg. C and annealed at 600 deg. C. X-ray diffraction scans indicate that relatively better L1 0 ordered structure for low Mn doping (x 3%. The perpendicular magnetic anisotropy effect of the (FePt) 1-x Mn x films tends to decrease with the increase of Mn doping for x>1%. However, the x=1% doped films possess slightly better perpendicular magnetic anisotropy effect than the zero doped film. The perpendicular magnetic anisotropy constant are of about 1.3x10 7 and 1.6x10 7 erg/cm 3 for x=0% and x=1%, respectively

Doping Polymer Semiconductors by Organic Salts: Toward High-Performance Solution-Processed Organic Field-Effect Transistors.

Science.gov (United States)

Hu, Yuanyuan; Rengert, Zachary D; McDowell, Caitlin; Ford, Michael J; Wang, Ming; Karki, Akchheta; Lill, Alexander T; Bazan, Guillermo C; Nguyen, Thuc-Quyen

2018-04-24

Solution-processed organic field-effect transistors (OFETs) were fabricated with the addition of an organic salt, trityl tetrakis(pentafluorophenyl)borate (TrTPFB), into thin films of donor-acceptor copolymer semiconductors. The performance of OFETs is significantly enhanced after the organic salt is incorporated. TrTPFB is confirmed to p-dope the organic semiconductors used in this study, and the doping efficiency as well as doping physics was investigated. In addition, systematic electrical and structural characterizations reveal how the doping enhances the performance of OFETs. Furthermore, it is shown that this organic salt doping method is feasible for both p- and n-doping by using different organic salts and, thus, can be utilized to achieve high-performance OFETs and organic complementary circuits.

The effect of DCJTB doping concentration in PVK on the chromatic coordinate of electroluminescence

Energy Technology Data Exchange (ETDEWEB)

Zhang, F J; Xu, Z; Zhao, S L; Wang, L W; Yuan, G C [Key Laboratory of Luminescence and Optical Information (Beijing Jiaotong University), Ministry of Education (China); Zhao, D W [School of Electrical and Electronic Engineering, Nanyang Technological University, Nanyang Avenue, Singapore 639798 (Singapore)], E-mail: fjzhang@bjtu.edu.cn

2008-05-15

The dominant mechanism of electroluminescence (EL) from 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl) -4H-pyran (DCJTB) doped in poly-(N-vinyl-carbazole) (PVK) system was demonstrated to be a charge carrier trapped by DCJTB molecular rather than Foerster energy transfer from PVK to DCJTB. The chromatically coordinate EL emission of PVK:DCJTB changes from (0.41, 0.31) to (0.67, 0.31) with an increase in DCJTB doping concentration. The emission peak in DCJTB shows red-shift and the shoulder emission peak at 656 nm becomes stronger as the doping concentration increases. The effect of DCJTB doping concentration on EL spectra is attributed to strong dipole-dipole interaction between the DCJTB molecule with an increase in doping concentration.

Heavy components coupling effect on building response spectra generation

International Nuclear Information System (INIS)

Liu, T.H.; Johnson, E.R.

1985-01-01

This study investigates the dynamic coupling effect on the floor response spectra between the heavy components and the Reactor Interior (R/I) building in a PWR. The following cases were studied: (I) simplified models of one and two lump mass models representing building and heavy components, and (II) actual plant building and heavy component models. Response spectra are developed at building nodes for all models, using time-history analysis methods. Comparisons of response spectra from various models are made to observe the coupling effects. In some cases, this study found that the coupling would reduce the response spectra values in certain frequency regions even if the coupling is not required according to the above criteria. (orig./HP)

Doping effect on the optical properties of ZnO nanostructures

Energy Technology Data Exchange (ETDEWEB)

Stoehr, M. [Frederick Seitz Materials Research Laboratory, University of Illinois,104 South Goodwin Avenue, Urbana, IL 61801 (United States); Institut Universitaire de Technologie, Universite de Haute Alsace, 61 rue Albert Camus, 68093 Mulhouse Cedex (France); Juillaguet, S. [Groupe d' Etude des Semi-conducteurs, Universite Montpellier II, Place Eugene Bataillon, 34095 Montpellier Cedex 5 (France); Kyaw, T.M.; Wen, J.G. [Institut Universitaire de Technologie, Universite de Haute Alsace, 61 rue Albert Camus, 68093 Mulhouse Cedex (France)

2007-04-15

High quality undoped and Ga{sub 2}O{sub 3} or In{sub 2}O{sub 3} doped ZnO nanostructures are grown by chemical vapor transport and condensation. The doping effect on the optical properties is investigated by photoluminescence. At room temperature, photoluminescence on Ga{sub 2}O{sub 3} doped ZnO nanostructures reveals an enhancement of the ultraviolet near band edge emission at 390 nm, while the intensity of the deep level emission at 530 nm weakens. At 5 K, an intense neutral-donor-bound exciton (D{sup 0}X) line dominates the undoped and doped ZnO photoluminescence spectra. The presence of well resolved two-electron satellite lines allow to determine the type of donors. At 5 K, the results indicate that ZnO nanostructures grown with 10% of Ga{sub 2}O{sub 3} display an excellent optical quality, proved by an intense D{sup 0}X line, a high intensity ratio between the D{sup 0}X line and the deep level emission as well as the presence of numerous phonon replicas of the main lines. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Thermo-optical effects in high-power Ytterbium-doped fiber amplifiers

DEFF Research Database (Denmark)

Hansen, Kristian Rymann; Alkeskjold, Thomas Tanggaard; Broeng, Jes

2011-01-01

We investigate the effect of temperature gradients in high-power Yb-doped fiber amplifiers by a numerical beam propagation model, which takes thermal effects into account in a self-consistent way. The thermally induced change in the refractive index of the fiber leads to a thermal lensing effect...

Effect of B doping on optical, electrical properties and defects of ZnO films

Energy Technology Data Exchange (ETDEWEB)

Mao, Caiying [State Key Laboratory of Mechanical Transmission, College of Physics, Chongqing University, Chongqing, 400044 (China); Fang, Liang, E-mail: lfang@cqu.edu.cn [State Key Laboratory of Mechanical Transmission, College of Physics, Chongqing University, Chongqing, 400044 (China); Zhang, Hong; Li, Wanjun [Key Laboratory of Optoelectronic Functional Materials of Chongqing, College of Physics and Electronic Engineering, Chongqing Normal University, Chongqing 401331 (China); Wu, Fang, E-mail: fang01234@163.com [State Key Laboratory of Mechanical Transmission, College of Physics, Chongqing University, Chongqing, 400044 (China); Qin, Guoping [Key Laboratory of Optoelectronic Functional Materials of Chongqing, College of Physics and Electronic Engineering, Chongqing Normal University, Chongqing 401331 (China); Ruan, Haibo, E-mail: rhbcqu@aliyun.com [Chongqing Key Laboratory of Micro/Nano Materials Engineering and Technology, Research Center for Materials Interdisciplinary Sciences, Chongqing University of Arts and Sciences, Chongqing, 402160 (China); Kong, Chunyang, E-mail: kchy@163.com [Key Laboratory of Optoelectronic Functional Materials of Chongqing, College of Physics and Electronic Engineering, Chongqing Normal University, Chongqing 401331 (China)

2016-08-15

Boron doped ZnO (BZO) films with B content in the range of 0–6 at.% were deposited on quartz glass substrates by RF magnetron sputtering technique. The effects of B doping content on microstructure, optical and electrical properties of BZO films were systematically investigated by XRD, SEM, AFM, XPS, PL, UV–vis–near infrared spectrophotometer and Hall-effect measurement, respectively. It is found that the crystal quality of ZnO films can be improved as B doping content increases to no larger than 4 at.% and will be deteriorated at higher B doping content. The grain size and surface roughness of the films reduce with the increase of B doping content. The BZO films exhibit tensile stress and the stress increases with B content. The transmittance of the BZO films is revealed to be 90% in the visible region. As the B doping content increases from 0 to 6 at.%, the optical band gap of BZO films enhances from 3.28 to 3.57 eV, which is found to increase linearly with the tensile stress in the films. The lowest resistivity of 1.58 × 10{sup −3} (Ω cm) is obtained at 2 at.% B doping content. XPS and PL analyses demonstrated that B doping can promote the formation of defects of zinc interstitials (Zn{sub i}) and oxygen vacancies (V{sub O}). - Highlights: • The relationship of band gap (E{sub g}) and stress (σ) in BZO is deduced. • XPS and PL illustrate B doping can promote the formation of Zn{sub i} and V{sub O} in BZO. • The lowest resistivity (1.58 × 10{sup −3} Ω cm) is obtained at 2 at.% B content.

Heavy quark effective theory, interpolating fields and Bethe-Salpeter amplitudes

International Nuclear Information System (INIS)

Hussain, F.; Thomspon, G.

1994-07-01

We use the LSZ reduction theorem and interpolating fields, along with the heavy quark effective theory, to investigate the structure of the Bethe-Salpeter amplitude for heavy hadrons. We show how a simple form of this amplitude, used extensively in heavy hadron decay calculations, follows naturally up to O(1/M) from these field theoretic considerations. (author). 13 refs, 1 tab

Investigation of doping and particle size effect on structural, magnetic and magnetoresistance properties of manganites

Directory of Open Access Journals (Sweden)

M. Hakimi

2008-06-01

Full Text Available  In this paper after introduction of manganites, we have studied the effect of particle size and doping on structural, magnetic and magnetoresistance of LSMO manganite samples. The magnetoresistance measurements show that, by decreasing the particle size LFMR increases. Also the results show that the LFMR increases at low doping levels and decreases at high doping levels. The spin dependent tunneling and scattering at the grain boundaries is the origin of increasing the LFMR at low doping levels. Also the substitution of impurity ions at Mn sites and subsequently weaking of double exchange is responsible for decreasing of LFMR at high doping level.

Continuous growth of low-temperature Si epitaxial layer with heavy phosphorous and boron doping using photoepitaxy

International Nuclear Information System (INIS)

Yamazaki, T.; Minakata, H.; Ito, T.

1990-01-01

The authors grew p + -n + silicon epitaxial layers, heavily doped with phosphorus and boron, continuously at 650 degrees C using low-temperature photoepitaxy. Then N + photoepitaxial layer with a phosphorus concentration above 10 17 cm -3 grown on p - substrate shows high-density surface pits, and as a result, poor crystal quality. However, when this n + photoepitaxial layer is grown continuously on a heavily boron-doped p + photoepitaxial layer, these surface pits are drastically decreased, disappearing completely above a hole concentration of 10 19 cm -3 in the p + photoepitaxial layer. The phosphorus activation ratio and electron Hall mobility in the heavily phosphorus-doped n + photoexpitaxial layer were also greatly improved. The authors investigated the cause of the surface pitting using a scanning transmission electron microscope, secondary ion mass spectroscopy, and energy-dispersive x-ray spectroscopy. They characterized the precipitation of phosphorus atoms on the crystal surface at the initial stage of the heavily phosphorus-doped n + photoexpitaxial layer growth

Spin-dependent relativistic effect on heavy quarkonium properties in medium

International Nuclear Information System (INIS)

Dong Yubing

1997-01-01

Spin-dependent relativistic effect on the binding and dissociation of the heavy quarkonium in a thermal environment is investigated. The result shows that the interactions could influence the heavy quarkonium properties in medium

Effect of reaction temperature on structure and fluorescence properties of nitrogen-doped carbon dots

Energy Technology Data Exchange (ETDEWEB)

Zhang, Yi [Key Laboratory of Interface Science and Engineering in Advanced Materials (Taiyuan University of Technology), Ministry of Education, Taiyuan 030024 (China); College of Chemistry and Chemical Engineering, Taiyuan University of Technology, Taiyuan 030024 (China); Department of Chemistry and Chemical Engineering, Lyuliang University, Lyuliang 033001 (China); Research Center on Advanced Materials Science and Technology, Taiyuan University of Technology, Taiyuan 030024 (China); Wang, Yaling [Key Laboratory of Interface Science and Engineering in Advanced Materials (Taiyuan University of Technology), Ministry of Education, Taiyuan 030024 (China); Research Center on Advanced Materials Science and Technology, Taiyuan University of Technology, Taiyuan 030024 (China); Feng, Xiaoting [Key Laboratory of Interface Science and Engineering in Advanced Materials (Taiyuan University of Technology), Ministry of Education, Taiyuan 030024 (China); College of Chemistry and Chemical Engineering, Taiyuan University of Technology, Taiyuan 030024 (China); Zhang, Feng [Key Laboratory of Interface Science and Engineering in Advanced Materials (Taiyuan University of Technology), Ministry of Education, Taiyuan 030024 (China); Research Center on Advanced Materials Science and Technology, Taiyuan University of Technology, Taiyuan 030024 (China); Yang, Yongzhen, E-mail: yyztyut@126.com [Key Laboratory of Interface Science and Engineering in Advanced Materials (Taiyuan University of Technology), Ministry of Education, Taiyuan 030024 (China); Research Center on Advanced Materials Science and Technology, Taiyuan University of Technology, Taiyuan 030024 (China); Liu, Xuguang, E-mail: liuxuguang@tyut.edu.cn [Key Laboratory of Interface Science and Engineering in Advanced Materials (Taiyuan University of Technology), Ministry of Education, Taiyuan 030024 (China); College of Chemistry and Chemical Engineering, Taiyuan University of Technology, Taiyuan 030024 (China)

2016-11-30

Highlights: • Nitrogen-doped carbon dots (NCDs) from ammonia solution and citric acid were synthesized at different temperatures. • Quantum yield (QY) of NCDs depends largely on the amount of fluorescent polymer chains (FPC), more FPC gives higher QY. • The law of QY of NCDs first increase and then decrease with the reaction temperature increased is found and explained. • Nitrogen doping plays significant role in getting increased UV–vis absorption and QY. - Abstract: To investigate the effect of reaction temperature and nitrogen doping on the structure and fluorescence properties of carbon dots (CDs), six kinds of nitrogen-doped CDs (NCDs) were synthesized at reaction temperatures of 120, 140, 160, 180, 200 and 220 °C, separately, by using citric acid as carbon source and ammonia solution as nitrogen source. Nitrogen-free CDs (N-free CDs-180) was also prepared at 180 °C by using citric acid as the only carbon source for comparison. Results show that reaction temperature has obvious effect on carbonization degree, quantum yield (QY), ultraviolet-visible (UV–vis) absorption and photoluminescence (PL) spectra but less effect on functional groups, nitrogen doping degree and fluorescence lifetime of NCDs. Compared with N-free CDs-180, NCDs-180 possesses enchanced QY and longer fluorescence lifetime. Doping nitrogen has obvious effect on UV–vis absorption and PL spectra but less effect on particles sizes and carbonization degree. The formation mechanism of NCDs is explored: QY of NCDs depends largely on the number of fluorescent polymer chains (FPC), the competition between FPC formation on the surface of NCDs and carbon core growth leads to the change in number of FPC, and consequently to the NCDs with highest QY at appropriate hydrothermal temperature.

Effects of Fe fine powders doping on hot deformed NdFeB magnets

International Nuclear Information System (INIS)

Lin, Min; Wang, Huijie; Zheng, Jingwu; Yan, Aru

2015-01-01

The composite NdFeB magnets with blending melt-spun flakes and Fe fine powders were prepared by the hot-pressed and hot-deformed route. Characterizations of the hot-deformed NdFeB magnets affected by the doped Fe powders were tested. The doped Fe powders decrease the hot-deformed pressure when the strain is between 15 and 50%. XRD patterns show that the doped Fe powders have little influence on the c-axis alignment of hot-deformed NdFeB magnets in the press direction. The B r and the (BH) max get improved when the doped Fe powders are less than 3 wt%. The doped Fe of hot-deformed NdFeB magnets exists in the elongated state and the spherical state surrounded by the Nd-rich phase. With the Fe fraction increasing, the potential of magnet moves to the positive direction and the diameter of the Nyquist arc becomes larger, which indicate that the corrosion resistance improved effectively. The bending strength was enhanced by the elongated α-Fe phase embedded in the matrix 2:14:1 phase. - Highlights: • The doped Fe powders have little influence on the c-axis alignment of magnets. • The elongated Fe powders are more than the spherical Fe powders in the magnets. • The corrosion resistance is improved effectively with the increasing Fe fraction. • The bending strength is enhanced by the elongated α-Fe phase embedded in the matrix

Effects of Fe fine powders doping on hot deformed NdFeB magnets

Energy Technology Data Exchange (ETDEWEB)

Lin, Min, E-mail: linm@nimte.ac.cn [Ningbo Institute of Material Technology & Engineering Chinese Academy of Science, Ningbo 315201 (China); Wang, Huijie [Ningbo Jinji Strong Magnetic Material Company, Ningbo 315041 (China); Zheng, Jingwu [Zhejiang University of Technology, Hangzhou 310014 (China); Yan, Aru [Ningbo Institute of Material Technology & Engineering Chinese Academy of Science, Ningbo 315201 (China)

2015-04-01

The composite NdFeB magnets with blending melt-spun flakes and Fe fine powders were prepared by the hot-pressed and hot-deformed route. Characterizations of the hot-deformed NdFeB magnets affected by the doped Fe powders were tested. The doped Fe powders decrease the hot-deformed pressure when the strain is between 15 and 50%. XRD patterns show that the doped Fe powders have little influence on the c-axis alignment of hot-deformed NdFeB magnets in the press direction. The B{sub r} and the (BH){sub max} get improved when the doped Fe powders are less than 3 wt%. The doped Fe of hot-deformed NdFeB magnets exists in the elongated state and the spherical state surrounded by the Nd-rich phase. With the Fe fraction increasing, the potential of magnet moves to the positive direction and the diameter of the Nyquist arc becomes larger, which indicate that the corrosion resistance improved effectively. The bending strength was enhanced by the elongated α-Fe phase embedded in the matrix 2:14:1 phase. - Highlights: • The doped Fe powders have little influence on the c-axis alignment of magnets. • The elongated Fe powders are more than the spherical Fe powders in the magnets. • The corrosion resistance is improved effectively with the increasing Fe fraction. • The bending strength is enhanced by the elongated α-Fe phase embedded in the matrix.

Raman spectroscopy study of the doping effect of the encapsulated terbium halogenides on single-walled carbon nanotubes

Energy Technology Data Exchange (ETDEWEB)

Kharlamova, M.V.; Kramberger, C.; Mittelberger, A. [University of Vienna, Faculty of Physics, Vienna (Austria)

2017-04-15

In the present work, the doping effect of terbium chloride, terbium bromide, and terbium iodide on single-walled carbon nanotubes (SWCNTs) was compared by Raman spectroscopy. A precise investigation of the doping-induced alterations of the Raman modes of the filled SWCNTs was conducted. The shifts of the components of the Raman modes and modification of their profiles allowed concluding that the inserted terbium halogenides have acceptor doping effect on the SWCNTs, and the doping efficiency increases in the line with terbium iodide, terbium bromide, and terbium chloride. (orig.)

FLUX PINNING EFFECTS IN Ag-DOPED YBCO (123 SUPERCONDUCTOR

Directory of Open Access Journals (Sweden)

Madelen Pérez

2010-07-01

Full Text Available Polycrystalline samples of Ag+-doped YBCO (123 (YBa2 (Cu1-xAgx3O7-δwith 0≤x≤0.3 were produced by solid state reaction method. The Ag- doped YBCO samples showed higher critical current densities (Jc with a Jc maximum for samples doped with x=0.05. This behavior can be assigned to an increase of pinning forces. The irreversibility temperature (Tirr, also increased in doped samples as a function of Ag content, with the highest temperature for the sample doped with x=0.05, wich correlates well with the observed Jc increasing. However, samples doped with x>0.05 displayed a decreasing of electrical properties (less Tirr, less Jc, etc. atributed to an excess of Ag in the grain boundaries which, reduces the grain sizes and increases the number of weak- links.

The effect of Bi3+ and Li+ co-doping on the luminescence characteristics of Eu3+-doped aluminum oxide films

International Nuclear Information System (INIS)

Padilla-Rosales, I.; Martinez-Martinez, R.; Cabañas, G.; Falcony, C.

2015-01-01

The incorporation of Bi 3+ and Li + as co-dopants in Eu 3+ -doped aluminum oxide films deposited by the ultrasonic spray pyrolysis technique and its effect on the luminescence characteristics of this material are described. Both Bi 3+ and Li + do not introduce new luminescence features but affect the luminescence intensity of the Eu 3+ related emission spectra as well as the excitation spectra. The introduction of Bi 3+ generates localized states in the aluminum oxide host that result in a quenching of the luminescence intensity, while Li + and Bi 3+ co-doping increase the luminescence intensity of these films. - Highlights: • Li and Bi co-doping increase the luminescence. • Bi creates localized states in the Al 2 O 3 host. • Li was incorporated as a co-activator

Comparison of potential models through heavy quark effective theory

International Nuclear Information System (INIS)

Amundson, J.F.

1995-01-01

I calculate heavy-light decay constants in a nonrelativistic potential model. The resulting estimate of heavy quark symmetry breaking conflicts with similar estimates from lattice QCD. I show that a semirelativistic potential model eliminates the conflict. Using the results of heavy quark effective theory allows me to identify and compensate for shortcomings in the model calculations in addition to isolating the source of the differences in the two models. The results lead to a rule as to where the nonrelativistic quark model gives misleading predictions

Quantum electrodynamical effects in heavy highly-charged ions

International Nuclear Information System (INIS)

Yerokhin, V.A.; Artemyev, A.N.; Indelicato, P.; Shabaev, V.M.

2003-01-01

The present status of theoretical calculations of QED effects in highly charged ions is reviewed for several important cases: the Lamb shift in heavy H-like ions, the 2p 1/2 -2s transition energy in heavy Li-like ions, and the bound-electron g factor in H-like ions. Theoretical predictions are compared with experimental results. Special attention is paid to the discussion of uncertainties of theoretical predictions

Numerical simulation of the impurity photovoltaic effect in silicon solar cells doped with thallium

International Nuclear Information System (INIS)

Zhao Baoxing; Zhou Jicheng; Chen Yongmin

2010-01-01

Many attempts have been made to increase the efficiency of solar cells by introducing a deep impurity level in the semiconductor band gap. Since Tl may be the most suitable impurity for crystalline Si solar cells, the impurity photovoltaic (IPV) effect in silicon solar cell doped with thallium as impurity was investigated by the numerical solar cell simulator SCAPS. Results show that the IPV effect of thallium extends the spectral sensitivity in the sub-band gap range from 1000 to about 1400 nm. When the Tl concentration (N t ) is lower than the base doping density (N D ), the short-circuit current density and efficiency increase with increasing N t . But they decrease rapidly as the impurity density exceeds the shallow base doping density (N t >N D ). The optimum Tl concentration is about equal to the base doping density. For the Si solar cells with high internal reflection coefficients, the IPV effect becomes appreciable (ΔJ sc ∼9 mA/cm 2 and Δη∼2%).

The Effect of Acceptor and Donor Doping on Oxygen Vacancy Concentrations in Lead Zirconate Titanate (PZT).

Science.gov (United States)

Slouka, Christoph; Kainz, Theresa; Navickas, Edvinas; Walch, Gregor; Hutter, Herbert; Reichmann, Klaus; Fleig, Jürgen

2016-11-22

The different properties of acceptor-doped (hard) and donor-doped (soft) lead zirconate titanate (PZT) ceramics are often attributed to different amounts of oxygen vacancies introduced by the dopant. Acceptor doping is believed to cause high oxygen vacancy concentrations, while donors are expected to strongly suppress their amount. In this study, La 3+ donor-doped, Fe 3+ acceptor-doped and La 3+ /Fe 3+ -co-doped PZT samples were investigated by oxygen tracer exchange and electrochemical impedance spectroscopy in order to analyse the effect of doping on oxygen vacancy concentrations. Relative changes in the tracer diffusion coefficients for different doping and quantitative relations between defect concentrations allowed estimates of oxygen vacancy concentrations. Donor doping does not completely suppress the formation of oxygen vacancies; rather, it concentrates them in the grain boundary region. Acceptor doping enhances the amount of oxygen vacancies but estimates suggest that bulk concentrations are still in the ppm range, even for 1% acceptor doping. Trapped holes might thus considerably contribute to the charge balancing of the acceptor dopants. This could also be of relevance in understanding the properties of hard and soft PZT.

The Effect of Acceptor and Donor Doping on Oxygen Vacancy Concentrations in Lead Zirconate Titanate (PZT

Directory of Open Access Journals (Sweden)

Christoph Slouka

2016-11-01

Full Text Available The different properties of acceptor-doped (hard and donor-doped (soft lead zirconate titanate (PZT ceramics are often attributed to different amounts of oxygen vacancies introduced by the dopant. Acceptor doping is believed to cause high oxygen vacancy concentrations, while donors are expected to strongly suppress their amount. In this study, La3+ donor-doped, Fe3+ acceptor-doped and La3+/Fe3+-co-doped PZT samples were investigated by oxygen tracer exchange and electrochemical impedance spectroscopy in order to analyse the effect of doping on oxygen vacancy concentrations. Relative changes in the tracer diffusion coefficients for different doping and quantitative relations between defect concentrations allowed estimates of oxygen vacancy concentrations. Donor doping does not completely suppress the formation of oxygen vacancies; rather, it concentrates them in the grain boundary region. Acceptor doping enhances the amount of oxygen vacancies but estimates suggest that bulk concentrations are still in the ppm range, even for 1% acceptor doping. Trapped holes might thus considerably contribute to the charge balancing of the acceptor dopants. This could also be of relevance in understanding the properties of hard and soft PZT.

Effect of swift heavy ion (SHI) irradiation on transparent conducting oxide electrodes for dye-sensitized solar cell applications

International Nuclear Information System (INIS)

Singh, Hemant Kr.; Avasthi, D.K.; Aggarwal, Shruti

2015-01-01

Highlights: •The objective is to study the effect of swift heavy ion (SHI) irradiation on photoanode of DSSC for better efficiency. •This work presents the effect of SHI irradiation on various Transparent conducting oxides (TCOs). •Effects are studied in terms of conductivity and transmittance of TCOs. •ITO-PET gives best results in comparison to ITO and FTO for DSSC application under SHI irradiation. -- Abstract: Transparent conducting oxides (TCOs) are used as electrodes in dye-sensitized solar cells (DSSCs) because of their properties such as high transmittance and low resistivity. In the present work, the effects of swift heavy ion (SHI) irradiation on various types of TCOs are presented. The objective of this study is to investigate the effect of SHI on TCOs. For the present study, three different types of TCOs are considered, namely, (a) FTO (fluorine-doped tin oxide, SnO 2 :F) on a Nippon glass substrate, (b) ITO (indium tin oxide, In 2 O 3 :Sn) coated on polyethylene terephthalate (PET) on a Corning glass substrate, and (c) ITO on a Corning glass substrate. These films are irradiated with 120 MeV Ag +9 ions at fluences ranging from 3.0 × 10 11 ions/cm 2 to 3.0 × 10 13 ions/cm 2 . The structural, morphological, optical and electrical properties are studied via X-ray diffraction (XRD), atomic force microscopy (AFM), UV–Vis absorption spectroscopy and four-probe resistivity measurements, respectively. The ITO-PET electrode is found to exhibit superior conductivity and transmittance properties in comparison with the others after irradiation and, therefore, to be the most suitable for solar cell applications

Effect of CdS/Mg-Doped CdSe Cosensitized Photoanode on Quantum Dot Solar Cells

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Yingxiang Guan

2015-01-01

Full Text Available Quantum dots have emerged as a material platform for low-cost high-performance sensitized solar cells. And doping is an effective method to improve the performance of quantum dot sensitized solar cells (QDSSCs. Since Kwak et al. from South Korea proved the incorporation of Mg in the CdSe quantum dots (QDs in 2007, the Mg-doped CdSe QDs have been thoroughly studied. Here we report a new attempt on CdS/Mg-doped CdSe quantum dot cosensitized solar cells (QDCSSC. We analyzed the performance of CdS/Mg-doped CdSe quantum dot cosensitized solar cells via discussing the different doping concentration of Mg and the different SILAR cycles of CdS. And we studied the mechanism of CdS/Mg-doped CdSe QDs in detail for the reason why the energy conversion efficiency had been promoted. It is a significant instruction on the development of Mg-doped CdSe quantum dot sensitized solar cells (QDSSCs.

Photo annealing effect on p-doped inverted organic solar cell

Energy Technology Data Exchange (ETDEWEB)

Lafalce, Evan; Toglia, Patrick; Lewis, Jason E.; Jiang, Xiaomei, E-mail: xjiang@usf.edu [Department of Physics, University of South Florida, Tampa, Florida 33620 (United States)

2014-06-28

We report the transient positive photo annealing effect in which over 600% boost of power conversion efficiency was observed in inverted organic photovoltaic devices (OPV) made from P3HT/PCBM by spray method, after 2 hrs of constant solar AM 1.5 irradiation at low temperature. This is opposite to usual photodegradation of OPV, and cannot be explained by thermal activation alone since the mere temperature effect could only account for 30% of the enhancement. We have investigated the temperature dependence, cell geometry, oxygen influence, and conclude that, for p-doped active layer at room temperature, the predominant mechanism is photo-desorption of O{sub 2}, which eliminates electron traps and reduces space charge screening. As temperature decreases, thermal activation and deep trap-state filling start to show noticeable effect on the enhancement of photocurrent at intermediate low temperature (T = 125 K). At very low temperature, the dominant mechanism for photo annealing is trap-filling, which significantly reduces recombination between free and trapped carriers. At all temperature, photo annealing effect depends on illumination direction from cathode or anode. We also explained the large fluctuation of photocurrent by the capture/reemit of trapped electrons from shallow electron traps of O{sub 2}{sup -} generated by photo-doping. Our study has demonstrated the dynamic process of photo-doping and photo-desorption, and shown that photo annealing in vacuum can be an efficient method to improve OPV device efficiency.

Preparation of Rare Earth Doped Alumina-Siloxane Gel and Its ER Effect

Institute of Scientific and Technical Information of China (English)

李幼荣; 张明; 周兰香; 邱关明; 井上真一; 冈本宏

2002-01-01

Poly(methyl methacrylate) (PMMA) was used to wrap alumina-siloxane sol through emulsion polymerization. A kind of suspensions with notable ER effect was produced by fully mixing the prepared microcapsule with silicon oil. Meanwhile a series of PMMA wrapped alumina-siloxane gel doped with rare earths was obtained and its ER effect was tested, like viscosity of different rare earth ion doped samples in different powder concentrations and at different temperatures, at the same time, leak current density and dielectric constant were measured. Results show that the ER effect of this suspension is remarkable, and its stability is much better. The condition of emulsion polymerization and the mechanism of effect are discussed.

Phosphorus doping and deposition pressure effects on optical and electrical properties of polysilicon

International Nuclear Information System (INIS)

Zaghdoudi, M.; Abdelkrim, M.M.; Fathallah, M.; Mohammed-Brahim, T.; Rogel, R.

2006-01-01

The optical and electrical properties of amorphously deposited and then post-crystallized silicon films are studied as a function of the deposition pressure and the phosphorus doping. Amorphous silicon films are deposited in a high pressure regime by SAPCVD (Sub-Atmospheric Pressure Chemical Vapour Deposition) to study the effect of the deposition pressure. They are also deposited in a low pressure regime by LPCVD (Low Pressure Chemical Vapour Deposition) to study the effect of a low phosphorus doping. Both types of amorphous films are then crystallized in the solid phase at 600 deg. C. Using different optical and electrical characterization techniques, the beneficial effect of a high pressure as well as of a weak phosphorus doping on the decrease of the defect density is highlighted. These results give some ways to improve the quality of polysilicon enough to be used in photovoltaic or in thin film electronic devices

[Doping. High-tech cheating in sport].

Science.gov (United States)

Striegel, H; Simon, P

2007-07-01

Today, doping is no longer limited to the classical drugs with well known effects and side effects. Older generation anabolic steroids are used mainly in fitness and recreational sports. In contrast, due to doping tests, substances used in competitive sports include peptide hormones, medications not yet approved, and even specially developed drugs, such as designer steroids. Of the peptide hormones, particularly growth hormones (human growth hormone), erythropoietin and generics, insulin, and presumably insulin-like growth factor 1 are used. Substance groups potentially relevant for doping are selective androgen receptor modulators and gene therapy drugs. For most of these, there is no knowledge about side effects in healthy individuals, and no adequate doping tests. Therefore, anti-doping measures cannot rely solely on the continual improvement of doping analyses, but should include increased measures for doping prevention. Not only sports organizations, but also governmental agencies should be involved in developing and implementing these measures.

Heavy Metal Pollution from Gold Mines: Environmental Effects and Bacterial Strategies for Resistance.

Science.gov (United States)

Fashola, Muibat Omotola; Ngole-Jeme, Veronica Mpode; Babalola, Olubukola Oluranti

2016-10-26

Mining activities can lead to the generation of large quantities of heavy metal laden wastes which are released in an uncontrolled manner, causing widespread contamination of the ecosystem. Though some heavy metals classified as essential are important for normal life physiological processes, higher concentrations above stipulated levels have deleterious effects on human health and biota. Bacteria able to withstand high concentrations of these heavy metals are found in the environment as a result of various inherent biochemical, physiological, and/or genetic mechanisms. These mechanisms can serve as potential tools for bioremediation of heavy metal polluted sites. This review focuses on the effects of heavy metal wastes generated from gold mining activities on the environment and the various mechanisms used by bacteria to counteract the effect of these heavy metals in their immediate environment.

Doping effects of carbon and titanium on the critical current density of MgB2

International Nuclear Information System (INIS)

Shen, T M; Li, G; Cheng, C H; Zhao, Y

2006-01-01

MgB 2 bulks doped with Ti or/and C were prepared by an in situ solid state reaction method to determine the combined effect of C and Ti doping and to probe the detailed mechanism. The magnetization measurement shows that Mg 0.95 Ti 0.05 B 1.95 C 0.05 sample has significantly improved flux pinning compared to the MgB 1.95 C 0.05 sample at 20 K, indicating that C and Ti are largely cooperative in improving the J c (H) behaviour. No TiC phase was detected in the x-ray diffraction (XRD) patterns. Moreover, the overlap of the (100) peaks of MgB 1.95 C 0.05 and Mg 0.95 Ti 0.05 B 1.95 C 0.05 showed that Ti doping does not reduce the amount of C in MgB 2 . Microstructural analyses revealed that the addition of Ti eliminated the porosity present in the carbon-doped MgB 2 pellet, resulting in an improved intergrain connectivity and an increase of effective current pass. Further, MgB 2 doped with C and Ti, which mainly consists of spherical grains about 200-300 nm in size, shows an higher grain homogeneity than the C-doped sample, suggesting that the Ti doping in MgB 1-x C x has played an important role in obtaining uniform grains

Genetic effects of heavy ion irradiation in maize and soybean

International Nuclear Information System (INIS)

Yatou, Osamu; Amano, Etsuo; Takahashi, Tan.

1992-01-01

Somatic mutation on leaves of maize and soybean were observed to investigate genetic effects of heavy ion irradiation. Maize seeds were irradiated with N, Fe and U ions and soybean seeds were irradiated with N ions. This is a preliminary report of the experiment, 1) to examine the mutagenic effects of the heavy ion irradiation, and 2) to evaluate the genetic effects of cosmic ray exposure in a space ship outside the earth. (author)

Corrosion of conductive polypyrrole: Effects of environmental factors, electrochemical stimulation, and doping anions

International Nuclear Information System (INIS)

Qi Kai; Qiu Yubing; Chen Zhenyu; Guo Xingpeng

2012-01-01

Highlights: ► Corrosive galvanic cells form on PPy film with the electrochemical reduction of O 2. ► Suitable electrochemical stimulation can inhibit the PPy’s corrosion. ► PPy film doped with larger sized anions has better corrosion resistance performance. - Abstract: The effects of environmental factors, electrochemical stimulation, and doping anions on the corrosion behaviour of conductive polypyrrole (PPy) films in alkaline aqueous media were studied with cyclic voltammetry, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. High concentrations of electrolyte, low dissolved oxygen and low temperatures enhance the stability of PPy. Polarising PPy at a negative potential inhibits its corrosion obviously. PPy doped with large counter anions shows better corrosion resistance than PPy doped with small counter ions. The possible mechanism involved in PPy corrosion process is discussed.

Effects of low-level Ag doping on Bi2Sr2CaCu2O8+x

International Nuclear Information System (INIS)

Deis, T.A.; Eror, N.G.; Krishnaraj, P.; Prorok, B.C.; Lelovic, M.; Balachandran, U.

1995-07-01

Bi 2 Sr 2 CaCu 2 O 8 has been doped with silver, up to 10,000 ppm, in three ways: excess additions, substitution of Ag for Bi, and substitution of Ag for Sr. Effects of doping on the c-axis lattice parameter and critical temperature (T c ) were measured. Effects from doing were only observed in slow-cooled [10 degree/hr] oxygen equilibrated samples. Doping by excess additions caused a small decrease in T c and an increase in the c-axis length of the lattice. Doping by substitution, compared to excess Ag additions, caused a larger decrease in T c and higher c-axis values for doping levels up to 1,000 ppm. Doping by substitution at higher levels (1,000--10,000 ppm) caused T c to increase and the c-axis to decrease. Samples with similar substitutional doping levels exhibited comparable T c values and samples with Ag substituted for Sr consistently exhibited higher c-axis values than samples that had equivalent amounts of Ag substituted for Bi

Effect of cobalt doping on the mechanical properties of ZnO nanowires

Energy Technology Data Exchange (ETDEWEB)

Vahtrus, Mikk; Šutka, Andris [Institute of Physics, University of Tartu, W. Ostwaldi 1, 50412 Tartu (Estonia); Polyakov, Boris [Institute of Solid State Physics, University of Latvia, Kengaraga 8, LV-1063 Riga (Latvia); Oras, Sven; Antsov, Mikk [Institute of Physics, University of Tartu, W. Ostwaldi 1, 50412 Tartu (Estonia); Doebelin, Nicola [RMS Foundation, Bischmattstrasse 12, Bettlach 2544 (Switzerland); Institute of Geological Sciences, University of Bern, Baltzerstrasse 1–3, Bern 3012 (Switzerland); Lõhmus, Rünno; Nõmmiste, Ergo [Institute of Physics, University of Tartu, W. Ostwaldi 1, 50412 Tartu (Estonia); Vlassov, Sergei, E-mail: vlassovs@ut.ee [Institute of Physics, University of Tartu, W. Ostwaldi 1, 50412 Tartu (Estonia)

2016-11-15

In this work, we investigate the influence of doping on the mechanical properties of ZnO nanowires (NWs) by comparing the mechanical properties of pure and Co-doped ZnO NWs grown in similar conditions and having the same crystallographic orientation [0001]. The mechanical characterization included three-point bending tests made with atomic force microscopy and cantilever beam bending tests performed inside scanning electron microscopy. It was found that the Young's modulus of ZnO NWs containing 5% of Co was approximately a third lower than that of the pure ZnO NWs. Bending strength values were comparable for both materials and in both cases were close to theoretical strength indicating high quality of NWs. Dependence of mechanical properties on NW diameter was found for both doped and undoped ZnO NWs. - Highlights: •Effect of Co doping on the mechanical properties of ZnO nanowires is studied. •Co substitutes Zn atoms in ZnO crystal lattice. •Co addition affects crystal lattice parameters. •Co addition results in significantly decreased Young's modulus of ZnO. •Bending strength for doped and undoped wires is close to the theoretical strength.

Arsenic Removal from Aqueous Solution Using Pure and Metal-Doped Titania Nanoparticles Coated on Glass Beads: Adsorption and Column Studies

Directory of Open Access Journals (Sweden)

M. Ihsan Danish

2013-01-01

Full Text Available Nanosized metal oxide, Titania, provides high surface area and specific affinity for the adsorption of heavy metals, including arsenic (As, which is posing a great threat to the world population due to its carcinogenic nature. In this study, As(III adsorption was studied on pure and metal- (Ag- and Fe- doped Titania nanoparticles. The nanoparticles were synthesized by liquid impregnation method with some modifications, with crystallite size in the range of 30 to 40 nm. Band gap analysis, using Kubelka-Munk function showed a shift of absorption band from UV to visible region for the metal-doped Titania. Effect of operational parameters like dose of nanoparticles, initial As(III concentration, and pH was evaluated at 25°C. The data obtained gave a good fit with Langmuir and Freundlich isotherms and the adsorption was found to conform to pseudo-second-order kinetics. In batch studies, over 90% of arsenic removal was observed for both types of metal-doped Titania nanoparticles from a solution containing up to 2 ppm of the heavy metal. Fixed bed columns of nanoparticles, coated on glass beads, were used for As(III removal under different operating conditions. Thomas and Yoon-Nelson models were applied to predict the breakthrough curves and to find the characteristic column parameters useful for process design. The columns were regenerated using 10% NaOH solution.

Mg doping and its effect on the semipolar GaN(1122) growth kinetics

International Nuclear Information System (INIS)

Lahourcade, L.; Wirthmueller, A.; Monroy, E.; Pernot, J.; Chauvat, M. P.; Ruterana, P.; Laufer, A.; Eickhoff, M.

2009-01-01

We report the effect of Mg doping on the growth kinetics of semipolar GaN(1122) synthesized by plasma-assisted molecular-beam epitaxy. Mg tends to segregate on the surface, inhibiting the formation of the self-regulated Ga film which is used as a surfactant for the growth of undoped and Si-doped GaN(1122). We observe an enhancement of Mg incorporation in GaN(1122) compared to GaN(0001). Typical structural defects or polarity inversion domains found in Mg-doped GaN(0001) were not observed for the semipolar films investigated in the present study.

Designing a Qualitative Model of Doping Phenomenon Effect on Sport Marketing in Iran

Directory of Open Access Journals (Sweden)

Jasem Manouchehri

2016-10-01

Full Text Available There a number of factors effecting consumers' purchase behavior. It is believed that celebrities can effect selling positively by transferring their popular image to the endorsed product. But, it is heard lots about excommunicate behaviors in the sport world today. Disclosure of the recent doping affairs relating to Lance Armstrong's seven wins in Tour De France is just one among many spectacular and also negative cases. The main aim of the present paper was to explore the effect of doping phenomenon on sport marketing. Depth interviews data were analyzed in three phases: open coding, axial coding, and selective coding. 297 open codes were achieved by 18 interviews. Grouping axial codes in each case and comparing, all gained codes can be divided in five groups: brand image (athlete and endorsed product brands images, moral reasoning (moral coupling, moral decoupling, and moral rationalization, consumer behavioral consequences (word of mouth, purchasing intention, and brand loyalty, attitude change (attitudes change toward athlete and brand, and moral emotions (moral evaluation, contempt, anger, disgust, and sympathy. The proposed qualitative model for the effect of doping phenomenon on sport marketing in Iran illustrated that moral emotions and product brand image affected by the doped athlete brand image and it resulted in attitudes change toward endorser athlete and endorsed brand and negative consumer behavioral consequences, however, moral reasoning strategies emerged by cognitive dissonance might protect consumers behavior from negative effects.

Nitrogen-doped graphene: effect of graphite oxide precursors and nitrogen content on the electrochemical sensing properties.

Science.gov (United States)

Megawati, Monica; Chua, Chun Kiang; Sofer, Zdenek; Klímová, Kateřina; Pumera, Martin

2017-06-21

Graphene, produced via chemical methods, has been widely applied for electrochemical sensing due to its structural and electrochemical properties as well as its ease of production in large quantity. While nitrogen-doped graphenes are widely studied materials, the literature showing an effect of graphene oxide preparation methods on nitrogen quantity and chemical states as well as on defects and, in turn, on electrochemical sensing is non-existent. In this study, the properties of nitrogen-doped graphene materials, prepared via hydrothermal synthesis using graphite oxide produced by various classical methods using permanganate or chlorate oxidants Staudenmaier, Hummers, Hofmann and Brodie oxidation methods, were studied; the resulting nitrogen-doped graphene oxides were labeled as ST-GO, HU-GO, HO-GO and BR-GO, respectively. The electrochemical oxidation of biomolecules, such as ascorbic acid, uric acid, dopamine, nicotinamide adenine nucleotide and DNA free bases, was carried out using cyclic voltammetry and differential pulse voltammetry techniques. The nitrogen content in doped graphene oxides increased in the order ST-GO graphene followed this trend, as shown in the cyclic voltammograms. This is a very important finding that provides insight into the electrocatalytic effect of N-doped graphene. The nitrogen-doped graphene materials exhibited improved sensitivity over bare glassy carbon for ascorbic acid, uric acid and dopamine detection. These studies will enhance our understanding of the effects of graphite oxide precursors on the electrochemical sensing properties of nitrogen-doped graphene materials.

The effect of a period of intense exercise on the marker approach to detect growth hormone doping in sports.

Science.gov (United States)

Voss, Sven Christian; Robinson, Neil; Alsayrafi, Mohammed; Bourdon, Pitre C; Schumacher, Yorck Olaf; Saugy, Martial; Giraud, Sylvain

2014-06-01

The major objective of this study was to investigate the effects of several days of intense exercise on the growth hormone marker approach to detect doping with human growth hormone (hGH). In addition we investigated the effect of changes in plasma volume on the test. Fifteen male athletes performed a simulated nine-day cycling stage race. Blood samples were collected twice daily over a period of 15 days (stage race + three days before and after). Plasma volumes were estimated by the optimized CO Rebreathing method. IGF-1 and P-III-NP were analyzed by Siemens Immulite and Cisbio Assays, respectively. All measured GH 2000 scores were far below the published decision limits for an adverse analytical finding. The period of exercise did not increase the GH-scores; however the accompanying effect of the increase in Plasma Volume yielded in essentially lower GH-scores. We could demonstrate that a period of heavy, long-term exercise with changes in plasma volume does not interfere with the decision limits for an adverse analytical finding. Copyright © 2014 John Wiley & Sons, Ltd.

Effect of transition metal-doped Ni(211) for CO dissociation: Insights from DFT calculations

Energy Technology Data Exchange (ETDEWEB)

Yang, Kuiwei; Zhang, Minhua [Key Laboratory for Green Chemical Technology of Ministry of Education, R& D Center for Petrochemical Technology, Tianjin University, Tianjin 300072 (China); Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin 300072 (China); Yu, Yingzhe, E-mail: yzhyu@tju.edu.cn [Key Laboratory for Green Chemical Technology of Ministry of Education, R& D Center for Petrochemical Technology, Tianjin University, Tianjin 300072 (China)

2017-03-31

Highlights: • Doping the step edge of Ni(211) with Fe or Ru observably enhances CO dissociation. • Rh doping is unfavorable for CO activation both kinetically and thermodynamically. • Two neat linear relations are proposed besides the Brønsted–Evans–Polanyi relation. • The differences of CO adsorption are rationalized via the Blyholder model. - Abstract: Density functional theory slab calculations were performed to investigate the adsorption and dissociation of CO over pure and M-doped Ni(211) (M = Fe, Co, Ru and Rh) with the aim to elucidate the effect of transition metal doping for CO activation. Doping the step edge of Ni(211) with Fe, Co and Ru is found to enhance the binding of CO in the initial state (IS) (in the sequence by the improvement degree: Fe > Ru > Co) as well as the co-adsorption of C and O in the final state (FS) (Ru > Fe > Co). In contrast, Rh doping is unfavorable both in the IS and in the FS. Analysis of the overall potential energy surfaces (PES) suggests CO dissociation is facilitated by Fe, Ru and Co doping both kinetically and thermodynamically, wherein Fe and Ru behave extraordinary. Interestingly, Fe substitute is slightly superior to Ru in kinetics whereas the contrary is the case in thermodynamics. Rh doping elevates the energy height from 0.97 eV on Ni(211) to 1.32 eV and releases 0.39 eV less heat relative to Ni(211), again manifesting a negative effect. Besides the classical Brønsted–Evans–Polanyi relationship, we put forward another two neat linear relations, which can well describe the feature of CO dissociation. The differences of CO adsorption and activation in the IS over pure and doped Ni(211) surfaces are rationalized via electronic structure analysis. The findings presented herein are expected to provide theoretical guidance for catalyst design and optimization in relevant processes.

Effect of Gallium Doping on the Characteristic Properties of Polycrystalline Cadmium Telluride Thin Film

Science.gov (United States)

Ojo, A. A.; Dharmadasa, I. M.

2017-08-01

Ga-doped CdTe polycrystalline thin films were successfully electrodeposited on glass/fluorine doped tin oxide substrates from aqueous electrolytes containing cadmium nitrate (Cd(NO3)2·4H2O) and tellurium oxide (TeO2). The effects of different Ga-doping concentrations on the CdTe:Ga coupled with different post-growth treatments were studied by analysing the structural, optical, morphological and electronic properties of the deposited layers using x-ray diffraction (XRD), ultraviolet-visible spectrophotometry, scanning electron microscopy, photoelectrochemical cell measurement and direct-current conductivity test respectively. XRD results show diminishing (111)C CdTe peak above 20 ppm Ga-doping and the appearance of (301)M GaTe diffraction above 50 ppm Ga-doping indicating the formation of two phases; CdTe and GaTe. Although, reductions in the absorption edge slopes were observed above 20 ppm Ga-doping for the as-deposited CdTe:Ga layer, no obvious influence on the energy gap of CdTe films with Ga-doping were detected. Morphologically, reductions in grain size were observed at 50 ppm Ga-doping and above with high pinhole density within the layer. For the as-deposited CdTe:Ga layers, conduction type change from n- to p- were observed at 50 ppm, while the n-type conductivity were retained after post-growth treatment. Highest conductivity was observed at 20 ppm Ga-doping of CdTe. These results are systematically reported in this paper.

[Mapping Critical Loads of Heavy Metals for Soil Based on Different Environmental Effects].

Science.gov (United States)

Shi, Ya-xing; Wu, Shao-hua; Zhou, Sheng-lu; Wang, Chun-hui; Chen, Hao

2015-12-01

China's rapid development of industrialization and urbanization causes the growing problem of heavy metal pollution of soil, threatening environment and human health. Therefore, prevention and management of heavy metal pollution become particularly important. Critical loads of heavy metals are an important management tool that can be utilized to prevent the occurrence of heavy metal pollution. Our study was based on three cases: status balance, water environmental effects and health risks. We used the steady-state mass balance equation to calculate the critical loads of Cd, Cu, Pb, Zn at different effect levels and analyze the values and spatial variation of critical loads. In addition, we used the annual input fluxes of heavy metals of the agro-ecosystem in the Yangtze River delta and China to estimate the proportion of area with exceedance of critical loads. The results demonstrated that the critical load value of Cd was the minimum, and the values of Cu and Zn were lager. There were spatial differences among the critical loads of four elements in the study area, lower critical loads areas mainly occurred in woodland and high value areas distributed in the east and southwest of the study area, while median values and the medium high areas mainly occurred in farmland. Comparing the input fluxes of heavy metals, we found that Pb and Zn in more than 90% of the area exceeded the critical loads under different environmental effects in the study area. The critical load exceedance of Cd mainly occurred under the status balance and the water environmental effect, while Cu under the status balance and water environmental effect with a higher proportion of exceeded areas. Critical loads of heavy metals at different effect levels in this study could serve as a reference from effective control of the emissions of heavy metals and to prevent the occurrence of heavy metal pollution.

Effect of H, O intentionally doping on photoelectric properties in MOVPE-growth GaN layers

KAUST Repository

Ohkawa, Kazuhiro

2017-10-24

GaN crystal growth requires higher purity of materials. Some contaminants in NH3 gas could be the causal factor of defects in GaN crystals. These atoms act as donor or acceptor. In order to clearly demonstrate the effect of gaseous impurities such as H2O on the properties of undoped-GaN layer, high purity NH3 (N70) was used as NH3 source. The concentration of H2O in NH3 was varied at 32, 49, 75, 142, 266, 489, and 899 ppb, respectively. Under the same recipe, we deposited undoped-GaN epitaxial layer with purifier, and H2O-doped GaN series layers. As similar to the results of CO and CO2-doped GaN series, the increase tendency of carrier density changing with increasing H2O concentration. The FWHMs of XRC around (0002) remain stable, witnessing that the crystal quality of GaN layer remain good. LT (15K) PL of undoped-GaN and H2O-doped GaN were measured, the D0X emission peak intensity of all H2O-doped GaN are decreased drastically compared with undoped-GaN. H2O impurity was doped into GaN layer, which not only effects electrical properties and but also effects the radiative emission and furthermore effects PL intensity, its mechanism is discussed.

Effect of Stepwise Doping on Lifetime and Efficiency of Blue and White Phosphorescent Organic Light Emitting Diodes.

Science.gov (United States)

Lee, Song Eun; Lee, Ho Won; Lee, Seok Jae; Koo, Ja-ryong; Lee, Dong Hyung; Yang, Hyung Jin; Kim, Hye Jeong; Yoon, Seung Soo; Kim, Young Kwan

2015-02-01

We investigated a light emission mechanism of blue phosphorescent organic light emitting diodes (PHOLEDs), using a stepwise doping profile of 2, 8, and 14 wt.% within the emitting layer (EML). We fabricated several blue PHOLEDs with phosphorescent blue emitter iridium(III) bis[(4,6-difluorophenyl)-pyridinato-N,C2]picolinate doped in N,N'-dicarbazolyl-3,5-benzene as a p-type host material. A blue PHOLED with the highest doping concentration as part of the EML close to an electron transporting layer showed a maximum luminous efficiency of 20.74 cd/A, and a maximum external quantum efficiency of 10.52%. This can be explained by effective electron injection through a highly doped EML side. Additionally, a white OLED based on the doping profile was fabricated with two thin red EMLs within a blue EML maintaining a thickness of 30 nm for the entire EML. Keywords: Blue Phosphorescent Organic Light Emitting Diodes, Stepwise Doping Structure, Charge Trapping Effect.

Photoreflectance study of InAs ultrathin layer embedded in Si-delta-doped GaAs/AlGaAs quantum wells

Energy Technology Data Exchange (ETDEWEB)

Dhifallah, I., E-mail: ines.dhifallah@gmail.co [Laboratoire de Photovoltaique, des Semiconducteurs et des Nanostructures, Centre de Recherche et des Technologies de l' energie, BP 95 Hammam-Lif 2050 (Tunisia); Daoudi, M.; Bardaoui, A. [Laboratoire de Photovoltaique, des Semiconducteurs et des Nanostructures, Centre de Recherche et des Technologies de l' energie, BP 95 Hammam-Lif 2050 (Tunisia); Eljani, B. [Unite de recherche sur les Hetero-Epitaxie et Applications, Faculte des Sciences de Monastir (Tunisia); Ouerghi, A. [Laboratoire de Photonique et de Nanostructures, CNRS Route de Nozay 91 46a0, Marcoussis (France); Chtourou, R. [Laboratoire de Photovoltaique, des Semiconducteurs et des Nanostructures, Centre de Recherche et des Technologies de l' energie, BP 95 Hammam-Lif 2050 (Tunisia)

2011-05-15

Photoreflectance and photoluminescence studies were performed to characterize InAs ultrathin layer embedded in Si-delta-doped GaAs/AlGaAs high electron mobility transistors. These structures were grown by Molecular Beam Epitaxy on (1 0 0) oriented GaAs substrates with different silicon-delta-doped layer densities. Interband energy transitions in the InAs ultrathin layer quantum well were observed below the GaAs band gap in the photoreflectance spectra, and assigned to electron-heavy-hole (E{sub e-hh}) and electron-light-hole (E{sub e-lh}) fundamental transitions. These transitions were shifted to lower energy with increasing silicon-{delta}-doping density. This effect is in good agreement with our theoretical results based on a self-consistent solution of the coupled Schroedinger and Poisson equations and was explained by increased escape of photogenerated carriers and enhanced Quantum Confined Stark Effect in the Si-delta-doped InAs/GaAs QW. In the photoreflectance spectra, not only the channel well interband energy transitions were observed, but also features associated with the GaAs and AlGaAs bulk layers located at about 1.427 and 1.8 eV, respectively. By analyzing the Franz-Keldysh Oscillations observed in the spectral characteristics of Si-{delta}-doped samples, we have determined the internal electric field introduced by ionized Si-{delta}-doped centers. We have observed an increase in the electric field in the InAs ultrathin layer with increasing silicon content. The results are explained in terms of doping dependent ionized impurities densities and surface charges. - Research highlights: {yields} Studying HEMTs structures with different silicon doping content. {yields} An increase of the electric field in the InAs layer with increasing Si content. {yields} The interband energy transitions in the HEMTs structures have been obtained from PR. {yields} Experimental and theoretical values of transitions energies were in good agreement.

Photoreflectance study of InAs ultrathin layer embedded in Si-delta-doped GaAs/AlGaAs quantum wells

International Nuclear Information System (INIS)

Dhifallah, I.; Daoudi, M.; Bardaoui, A.; Eljani, B.; Ouerghi, A.; Chtourou, R.

2011-01-01

Photoreflectance and photoluminescence studies were performed to characterize InAs ultrathin layer embedded in Si-delta-doped GaAs/AlGaAs high electron mobility transistors. These structures were grown by Molecular Beam Epitaxy on (1 0 0) oriented GaAs substrates with different silicon-delta-doped layer densities. Interband energy transitions in the InAs ultrathin layer quantum well were observed below the GaAs band gap in the photoreflectance spectra, and assigned to electron-heavy-hole (E e-hh ) and electron-light-hole (E e-lh ) fundamental transitions. These transitions were shifted to lower energy with increasing silicon-δ-doping density. This effect is in good agreement with our theoretical results based on a self-consistent solution of the coupled Schroedinger and Poisson equations and was explained by increased escape of photogenerated carriers and enhanced Quantum Confined Stark Effect in the Si-delta-doped InAs/GaAs QW. In the photoreflectance spectra, not only the channel well interband energy transitions were observed, but also features associated with the GaAs and AlGaAs bulk layers located at about 1.427 and 1.8 eV, respectively. By analyzing the Franz-Keldysh Oscillations observed in the spectral characteristics of Si-δ-doped samples, we have determined the internal electric field introduced by ionized Si-δ-doped centers. We have observed an increase in the electric field in the InAs ultrathin layer with increasing silicon content. The results are explained in terms of doping dependent ionized impurities densities and surface charges. - Research highlights: → Studying HEMTs structures with different silicon doping content. → An increase of the electric field in the InAs layer with increasing Si content. → The interband energy transitions in the HEMTs structures have been obtained from PR. → Experimental and theoretical values of transitions energies were in good agreement.

Effect of Sr doping on LaTiO3 thin films

International Nuclear Information System (INIS)

Vilquin, B.; Kanki, T.; Yanagida, T.; Tanaka, H.; Kawai, T.

2005-01-01

We report on the electric properties of La 1-x Sr x TiO 3 (0 ≤ x ≤ 0.5) thin films fabricated by pulsed laser deposition method. Crystallographic measurement of the thin films showed the epitaxial c-axis perovskite structure. The electric property of LaTiO 3 thin film, which is a typical Mott insulative material in bulk, showed insulative behaviour, while the Sr-doped films showed metallic conduction suffering electron-electron scattering. Below x = 0.1, the major carrier type was identified to be hole, and switched to electron with further increasing Sr-doping above x = 0.15. In fact, the switching from p-type to n-type for La 1-x Sr x TiO 3 thin films is first demonstrated in this study. The transition suggests that effective Coulomb gap vanishes due to over-additional Sr doping

The Effects of Doping Copper and Mesoporous Structure on Photocatalytic Properties of TiO2

Directory of Open Access Journals (Sweden)

Yang Wang

2014-01-01

Full Text Available This paper describes a system for the synthesis of Cu-doped mesoporous TiO2 nanoparticles by a hydrothermal method at relatively low temperatures. The technique used is to dope the as-prepared mesoporous TiO2 system with copper. In this method, the copper species with the form of Cu1+, which was attributed to the reduction effect of dehydroxylation and evidenced by X-ray photoelectron spectroscopy (XPS and X-ray diffraction (XRD, was well dispersed in the optimal concentration 1 wt.% Cu-doped mesoporous TiO2. In this as-prepared mesoporous TiO2 system, original particles with a size of approximately 20 nm are aggregated together to shapes of approximately 1100 nm, which resulted in the porous aggregate structure. More importantly, the enhancement of the photocatalytic activity was discussed as effects due to the formation of stable Cu(I and the mesoporous structure in the Cu-doped mesoporous TiO2. Among them, Cu-doped mesoporous TiO2 shows the highest degradation rate of methyl orange (MO. In addition, the effects of initial solution pH on degradation of MO had also been investigated. As a result, the optimum values of initial solution pH were found to be 3.

Effect of low level doping of boron and phosphorus on the properties of amorphous silicon films

International Nuclear Information System (INIS)

Tran, N.T.; Epstein, K.A.; Grimmer, D.P.; Vernstrom, G.D.

1987-01-01

Effect of the low level doping of boron and phosphorus on the properties of amorphous silicon films (a-Si:H) were studied. Doping level of both boron and phosphorus was in the range of 10/sup 17/ atoms/cm/sup 3/. Apparent improvement in the stability of dark and photoconductivity of a-Si: films upon low level doping does not result from the elimination of light-induced defects. The stability of the dark and photoconductivity upon doping is an indication of pinning of the Fermi level

Concurrent doping effect of Ti and nano-diamond on flux pinning of MgB2

International Nuclear Information System (INIS)

Zhao, Y.; Ke, C.; Cheng, C.H.; Feng, Y.; Yang, Y.; Munroe, P.

2010-01-01

Nano-diamond and titanium concurrently doped MgB 2 nanocomposites have been prepared by solid state reaction method. The effects of carbon and Ti concurrent doping on J c -H behavior and pinning force scaling features of MgB 2 have been investigated. Although T c was slightly depressed, J c of MgB 2 have been significantly improved by the nano-diamond doping, especially in the high field region. In the mean time, the J c value in low field region is sustained though concurrent Ti doping. Microstructure analysis reveals that when nano-diamond was concurrently doped with titanium in MgB 2 , a unique nanocomposite in which TiB 2 forms a thin layer surrounding MgB 2 grains whereas nano-diamond particles were wrapped inside the MgB 2 grains. Besides, nano-diamond doping results in a high density stress field in the MgB 2 samples, which may take responsibility for the Δκ pinning behavior in the carbon-doped MgB 2 system.

Heavy Quark Effective Theory

Science.gov (United States)

Manohar, A. V.

2003-02-01

These lecture notes present some of the basic ideas of heavy quark effective theory. The topics covered include the classification of states, the derivation of the HQET Lagrangian at tree level, hadron masses, meson form factors, Luke's theorem, reparameterization invariance and inclusive decays. Radiative corrections are discussed in some detail, including an explicit computation of a matching correction for HQET. Borel summability, renormalons, and their connection with the QCD perturbation series is covered, as well as the use of the upsilon expansion to improve the convergence of the perturbation series.

QCD Effective Field Theories for Heavy Quarkonium

International Nuclear Information System (INIS)

Brambilla, Nora

2006-01-01

QCD nonrelativistic effective field theories (NREFT) are the modern and most suitable frame to describe heavy quarkonium properties. Here I summarize few relevant concepts and some of the interesting physical applications (spectrum, decays, production) of NREFT

Hybrid Doping of Few-Layer Graphene via a Combination of Intercalation and Surface Doping

KAUST Repository

Mansour, Ahmed

2017-05-23

Surface molecular doping of graphene has been shown to modify its work function and increase its conductivity. However, the associated shifts in work function and increases in carrier concentration are highly coupled and limited by the surface coverage of dopant molecules on graphene. Here we show that few-layer graphene (FLG) can be doped using a hybrid approach, effectively combining surface doping by larger (metal-)organic molecules, while smaller molecules, such as Br2 and FeCl3, intercalate into the bulk. Intercalation tunes the carrier concentration more effectively, whereas surface doping of intercalated FLG can be used to tune its work function without reducing the carrier mobility. This multi-modal doping approach yields a very high carrier density and tunable work function for FLG, demonstrating a new versatile platform for fabricating graphene-based contacts for electronic, optoelectronic and photovoltaic applications.

Hybrid Doping of Few-Layer Graphene via a Combination of Intercalation and Surface Doping

KAUST Repository

Mansour, Ahmed; Kirmani, Ahmad R.; Barlow, Stephen; Marder, Seth R.; Amassian, Aram

2017-01-01

Surface molecular doping of graphene has been shown to modify its work function and increase its conductivity. However, the associated shifts in work function and increases in carrier concentration are highly coupled and limited by the surface coverage of dopant molecules on graphene. Here we show that few-layer graphene (FLG) can be doped using a hybrid approach, effectively combining surface doping by larger (metal-)organic molecules, while smaller molecules, such as Br2 and FeCl3, intercalate into the bulk. Intercalation tunes the carrier concentration more effectively, whereas surface doping of intercalated FLG can be used to tune its work function without reducing the carrier mobility. This multi-modal doping approach yields a very high carrier density and tunable work function for FLG, demonstrating a new versatile platform for fabricating graphene-based contacts for electronic, optoelectronic and photovoltaic applications.

Effect of Thermal Annealing on Light-Induced Minority Carrier Lifetime Enhancement in Boron-Doped Czochralski Silicon

International Nuclear Information System (INIS)

Wang Hong-Zhe; Zheng Song-Sheng; Chen Chao

2015-01-01

The effect of thermal annealing on the light-induced effective minority carrier lifetime enhancement (LIE) phenomenon is investigated on the p-type Czochralski silicon (Cz-Si) wafer passivated by a phosphorus-doped silicon nitride (P-doped SiN_x) thin film. The experimental results show that low temperature annealing (below 300°C) can not only increase the effective minority carrier lifetime of P-doped SiN_x passivated boron-doped Cz-Si, but also improve the LIE phenomenon. The optimum annealing temperature is 180°C, and its corresponding effective minority carrier lifetime can be increased from initial 7.5 μs to maximum 57.7 μs by light soaking within 15 min after annealing. The analysis results of high-frequency dark capacitance-voltage characteristics reveal that the mechanism of the increase of effective minority carrier lifetime after low temperature annealing is due to the sharp enhancement of field effect passivation induced by the negative fixed charge density, while the mechanism of the LIE phenomenon after low temperature annealing is attributed to the enhancement of both field effect passivation and chemical passivation. (paper)

Effects of manganese doping on the structure evolution of small-sized boron clusters

Science.gov (United States)

Zhao, Lingquan; Qu, Xin; Wang, Yanchao; Lv, Jian; Zhang, Lijun; Hu, Ziyu; Gu, Guangrui; Ma, Yanming

2017-07-01

Atomic doping of clusters is known as an effective approach to stabilize or modify the structures and properties of resulting doped clusters. We herein report the effect of manganese (Mn) doping on the structure evolution of small-sized boron (B) clusters. The global minimum structures of both neutral and charged Mn doped B cluster \\text{MnB}nQ (n  =  10-20 and Q  =  0, ±1) have been proposed through extensive first-principles swarm-intelligence based structure searches. It is found that Mn doping has significantly modified the grow behaviors of B clusters, leading to two novel structural transitions from planar to tubular and then to cage-like B structures in both neutral and charged species. Half-sandwich-type structures are most favorable for small \\text{MnB}n-/0/+ (n  ⩽  13) clusters and gradually transform to Mn-centered double-ring tubular structures at \\text{MnB}16-/0/+ clusters with superior thermodynamic stabilities compared with their neighbors. Most strikingly, endohedral cages become the ground-state structures for larger \\text{MnB}n-/0/+ (n  ⩾  19) clusters, among which \\text{MnB}20+ adopts a highly symmetric structure with superior thermodynamic stability and a large HOMO-LUMO gap of 4.53 eV. The unique stability of the endohedral \\text{MnB}\\text{20}+ cage is attributed to the geometric fit and formation of 18-electron closed-shell configuration. The results significantly advance our understanding about the structure and bonding of B-based clusters and strongly suggest transition-metal doping as a viable route to synthesize intriguing B-based nanomaterials.

The Development of the World Anti-Doping Code.

Science.gov (United States)

Young, Richard

2017-01-01

This chapter addresses both the development and substance of the World Anti-Doping Code, which came into effect in 2003, as well as the subsequent Code amendments, which came into effect in 2009 and 2015. Through an extensive process of stakeholder input and collaboration, the World Anti-Doping Code has transformed the hodgepodge of inconsistent and competing pre-2003 anti-doping rules into a harmonized and effective approach to anti-doping. The Code, as amended, is now widely recognized worldwide as the gold standard in anti-doping. The World Anti-Doping Code originally went into effect on January 1, 2004. The first amendments to the Code went into effect on January 1, 2009, and the second amendments on January 1, 2015. The Code and the related international standards are the product of a long and collaborative process designed to make the fight against doping more effective through the adoption and implementation of worldwide harmonized rules and best practices. © 2017 S. Karger AG, Basel.

Effect of yttrium chromite doping on its resistance to high-temperature salt and gas corrosions

International Nuclear Information System (INIS)

Oryshich, I.V.; Poryadchenko, N.E.; Rakitskij, A.N.; Bega, N.D.

1996-01-01

Effect of yttrium chromite doping with 2-4 group metal oxides on the corrosion resistance in the air at 1300 C during 5 hours and in sodium chloride and sulfate melts at 900 C during 20 hours is investigated. A notable increase of corrosion resistance is achieved under complex doping with zirconium and magnesium oxides in a quantity, close to solubility in yttrium oxide and solubility by aluminium oxide. Doping with calcium and strontium oxides in the quantities, dose to solubility in yttrium oxide does not produce any notable effect, and at higher concentrations it reduces the corrosion resistance in media indicated. Refs. 8, refs. 2, tabs. 1

Effective Opacity for Gold-Doped Foam Plasmas

International Nuclear Information System (INIS)

Huang Cheng-Wu; Song Tian-Ming; Zhao Yang; Zhu Tuo; Shang Wan-Li; Xiong Gang; Zhang Ji-Yan; Yang Jia-Min; Jiang Shao-En

2012-01-01

Radiation flow through gold-doped hydrocarbon foam is investigated and a model is presented to calculate effective opacity for an inhomogeneous, pressure-equilibrated gold/foam mixture based on the Levermore—Pomraning method for binary stochastic media. The effective opacity dependance on the size of the gold particles and the foam temperature are studied. The results suggest that when the mixture temperature is lower than 250 eV, the opacity difference between the 5 μm particle mix case and the atomic mix case is large enough to induce a significant discrepancy in radiation transport, which is confirmed by the hydrodynamic simulation

Effect of La doping on crystalline orientation, microstructure and dielectric properties of PZT thin films

Energy Technology Data Exchange (ETDEWEB)

Xu, Wencai; Li, Qi; Wang, Xing [Dalian Univ. of Technology, Dalian (China). School of Mechanical Engineering; Yin, Zhifu [Jilin Univ., Changchun (China). Faculty of the School of Mechanical Science and Engineering; Zou, Helin [Dalian Univ. of Technology, Dalian (China). Key Lab. for Micro/Nano Systems and Technology

2017-11-01

Lanthanum (La)-modified lead zirconate titanate (PLZT) thin films with doping concentration from 0 to 5 at.-% have been fabricated by sol-gel methods to investigate the effects of La doping on crystalline orientation, microstructure and dielectric properties of the modified films. The characterization of PLZT thin films were performed by X-ray diffractometry (XRD), scanning electron microscopy (SEM) and precision impedance analysis. XRD analysis showed that PLZT films with La doping concentration below 4 at.-% exhibited (100) preferred orientation. SEM results indicated that PLZT films presented dense and columnar microstructures when La doping concentration was less than 3 at.-%, while the others showed columnar microstructures only at the bottom of the cross section. The maximum dielectric constant (1502.59 at 100 Hz) was obtained in a 2 at.-% La-doped film, which increased by 53.9 % compared with undoped film. Without introducing a seed layer, (100) oriented PLZT thin films were prepared by using conventional heat treatment process and adjusting La doping concentration.

The effect of C60 doping on the electroluminescent performance of organic light-emitting devices

International Nuclear Information System (INIS)

Xu Denghui; Deng Zhenbo; Xiao Jing; Guo Dong; Hao Jingang; Zhang Yuanyuan; Gao Yinhao; Liang Chunjun

2007-01-01

Organic light-emitting devices (OLEDs) with the PVK hole transport layer were fabricated. The effect of C 60 doping in the hole transport PVK layer on the performance of the devices was investigated by changing the C 60 content from 0 to 3.0 wt%. The OLEDs had a structure of ITO/PEDOT:PSS/PVK:C 60 (0, 0.5, 1.0, 2.0, 3.0 wt%)/AlQ/LiF/Al. The doping led to a higher conductivity in C 60 -doped PVK layer and the hole mobility of PVK was improved from 4.5x10 -7 to 2.6x10 -6 cm 2 /Vs with the doping concentration of C 60 changing from 0 to 3.0 wt%. Moreover, the doping led to a high density of equilibrium charges carriers, which facilitated hole injection and transport. Doping of C 60 in PVK resulted in efficient hole injection and low drive voltage at high luminance

Density functional investigation of mercury and arsenic adsorption on nitrogen doped graphene decorated with palladium clusters: A promising heavy metal sensing material in farmland

International Nuclear Information System (INIS)

Zhao, Chunjiang; Wu, Huarui

2017-01-01

Highlights: • PNG can be acted as micro-sensor for monitoring heavy metal in agriculture. • The most favorable adsorption site of Pd atom or cluster on PNG is the vacancy site. • The Pd atom or cluster enhance the reactivity of PNG toward Hg and AsH_3 adsorption. • The efficiency of a sorbent can be tuned by tailoring the ε_d of adsorbed metals. - Abstract: Density functional theory calculations are carried out to study the adsorption of mercury and arsenic on Pd_n (n = 1–6) supported on pyridine-like nitrogen doped graphene (PNG). Owing to the promising sensitivity in trace amounts of atoms or molecules, PNG can be acted as micro-sensor for sensing heavy metals in agriculture soils. Through the analyses of structural and electronic properties of pristine PNG and Pd atom decorated PNG, we find that the most favorable adsorption site for Pd atom is the vacancy site. The analyses of structural and electronic properties reveal that the Pd atom or clusters can enhance the reactivity for Hg and AsH_3 adsorption on PNG. The adsorption ability of Hg on Pd_n decorated PNG is found to be related to the d-band center (ε_d) of the Pd_n, in which the closer ε_d of Pd_n to the Fermi level, the higher adsorption strength for Hg on Pd_n decorated PNG. Moreover, the charge transfer between Pd_n and arsenic may constitute arsenic adsorption on Pd_n decorated PNG. Further design of highly efficient carbon based sorbents for heavy metals removal should be focused on tailoring ε_d of adsorbed metals.

Fe-Doping Effect on Thermoelectric Properties of p-Type Bi0.48Sb1.52Te3

Directory of Open Access Journals (Sweden)

Hyeona Mun

2015-03-01

Full Text Available The substitutional doping approach has been shown to be an effective strategy to improve ZT of Bi2Te3-based thermoelectric raw materials. We herein report the Fe-doping effects on electronic and thermal transport properties of polycrystalline bulks of p-type Bi0.48Sb1.52Te3. After a small amount of Fe-doping on Bi/Sb-sites, the power factor could be enhanced due to the optimization of carrier concentration. Additionally, lattice thermal conductivity was reduced by the intensified point-defect phonon scattering originating from the mass difference between the host atoms (Bi/Sb and dopants (Fe. An enhanced ZT of 1.09 at 300 K was obtained in 1.0 at% Fe-doped Bi0.48Sb1.52Te3 by these synergetic effects.

The effect of intentional potassium co-doping on the luminescent properties of Yb3+ and Tm3+ doped α-NaYF4 core and core–shell nanoparticles

International Nuclear Information System (INIS)

Misiak, Małgorzata; Stręk, Wiesław; Arabasz, Sebastian; Bednarkiewicz, Artur

2016-01-01

Simple and effective ways to circumvent limited luminescence efficiency of up-converting nanoparticles (UCNPs) are sought. One of the methods relays on distorting the crystallographic structure of host material by co-doping the nanocrystals with optically inactive co-dopants. Here we study the influence of K + doping and surface passivation on the up-converting properties of the α-NaYF 4 nanocrystals co-doped with 20% Yb 3+ and 0.1 or 2% Tm 3+ . The intentionally chosen concentrations of K + ions, which were meant to replaced sodium ions were fixed to 0, 5, 10, 20 to 30%. Potassium ions modified the spectroscopic properties of both core and core–shell NPs, but the differences were noticed between samples doped with 0.1% Tm 3+ and 2% Tm 3+ ions. Replacement of sodium by potassium ions decreased up-conversion luminescence intensity as well as shortened thulium excited states lifetimes in the samples doped with 0.1% Tm 3+ , while the opposite behavior was found in the samples co-doped with higher 2% thulium concentration. - Highlights: • We studied the influence of K + doping on luminescent properties of α-NaYF 4 :YbTm. • The 0.1 and 2% Tm doped core and core–shell samples were investigated. • K + -doping influence on UC properties was different in low and highly Tm doped NPs. • The explanations of the observed variations were proposed.

Synthesis of Doped and non-Doped Nano MgO Ceramic Membranes

Directory of Open Access Journals (Sweden)

Shiraz Labib

2013-12-01

Full Text Available Doped and non-doped MgO coated thin films on alumina substrates were prepared using a chelating sol-gel method under controlled conditions to prepare nanomaterials with unprecedented properties. The effect of doping of ZnO on thermal, surface and structural properties was investigated using DTA-TG, BET and XRD respectively. Also microstructural studies and coating thickness measurements of MgO thin film were conducted using SEM. An increase in the thermal stability of MgO with increasing ZnO doping percent was observed. The increase of ZnO doping percent showed a marked decrease in the average particle size of MgO powder as a result of the replacement of some Mg2+ by Zn2+ which has similar ionic radius as Mg2+. This decrease in particle size of MgO was also related to the decrease of the degree of MgO crystalinity. The increase of ZnO doping also showed a marked decrease in coating thickness values of the prepared membranes. This decrease was related to the  mechanism of ZnO doping into a MgO crystal lattice.

Thermal conductivity of bulk GaN—Effects of oxygen, magnesium doping, and strain field compensation

International Nuclear Information System (INIS)

Simon, Roland B.; Anaya, Julian; Kuball, Martin

2014-01-01

The effect of oxygen doping (n-type) and oxygen (O)-magnesium (Mg) co-doping (semi-insulating) on the thermal conductivity of ammonothermal bulk GaN was studied via 3-omega measurements and a modified Callaway model. Oxygen doping was shown to significantly reduce thermal conductivity, whereas O-Mg co-doped GaN exhibited a thermal conductivity close to that of undoped GaN. The latter was attributed to a decreased phonon scattering rate due the compensation of impurity-generated strain fields as a result of dopant-complex formation. The results have great implications for GaN electronic and optoelectronic device applications on bulk GaN substrates

Effects of Mn doping on the ferroelectric properties of PZT thin films

International Nuclear Information System (INIS)

Zhang Qi

2004-01-01

The effects of Mn doping on the ferroelectric properties of Pb(Zr 0.3 Ti 0.7 )O 3 (PZT) thin films on Pt/Ti/SiO 2 /Si substrates have been investigated. The composition of the PZT and Mn doping level are Pb(Zr 0.3 Ti 0.7 ) 1-x Mn x O 3 (x = 0,0.2,0.5,1,2,4 mol%). The PZT thin films doped with a small amount of Mn 2+ (x ≤ 1) showed almost no hysteretic fatigue up to 10 10 switching bipolar pulse cycles, coupled with excellent retention properties. However, excessive additions of manganese made the fatigue behaviour worse. We propose that the addition of small amounts of Mn is able to reduce the oxygen vacancy concentration due to the combination of Mn 2+ and oxygen vacancies in PZT films, forming Mn 4+ ions. The interfacial layer between the Pt electrode and PZT films and Mn-doped PZT (x = 4) was detected by measuring the dielectric constant of thin films of different thickness. However, this interfacial layer was not detected in Mn-doped PZT (x = 1). These observations support the concept of the preferential electromigration of oxygen vacancies into sites in planes parallel to the electrodes, which is probably responsible for the hysteretic fatigue

Fingerprints of heavy scales in electroweak effective Lagrangians

Science.gov (United States)

Pich, Antonio; Rosell, Ignasi; Santos, Joaquín; Sanz-Cillero, Juan José

2017-04-01

The couplings of the electroweak effective theory contain information on the heavy-mass scales which are no-longer present in the low-energy Lagrangian. We build a general effective Lagrangian, implementing the electroweak chiral symmetry breaking SU(2) L ⊗ SU(2) R → SU(2) L+ R , which couples the known particle fields to heavier states with bosonic quantum numbers J P = 0± and 1±. We consider colour-singlet heavy fields that are in singlet or triplet representations of the electroweak group. Integrating out these heavy scales, we analyze the pattern of low-energy couplings among the light fields which are generated by the massive states. We adopt a generic non-linear realization of the electroweak symmetry breaking with a singlet Higgs, without making any assumption about its possible doublet structure. Special attention is given to the different possible descriptions of massive spin-1 fields and the differences arising from naive implementations of these formalisms, showing their full equivalence once a proper short-distance behaviour is required.

Fingerprints of heavy scales in electroweak effective Lagrangians

Energy Technology Data Exchange (ETDEWEB)

Pich, Antonio [Departament de Física Teòrica, IFIC, Universitat de València - CSIC,Apt. Correus 22085, E-46071 València (Spain); Rosell, Ignasi [Departamento de Matemáticas, Física y Ciencias Tecnológicas,Universidad CEU Cardenal Herrera, E-46115 Alfara del Patriarca, València (Spain); Santos, Joaquín [Departament de Física Teòrica, IFIC, Universitat de València - CSIC,Apt. Correus 22085, E-46071 València (Spain); Sanz-Cillero, Juan José [Departamento de Física Teórica I, Universidad Complutense de Madrid,E-28040 Madrid (Spain)

2017-04-04

The couplings of the electroweak effective theory contain information on the heavy-mass scales which are no-longer present in the low-energy Lagrangian. We build a general effective Lagrangian, implementing the electroweak chiral symmetry breaking SU(2){sub L}⊗SU(2){sub R}→SU(2){sub L+R}, which couples the known particle fields to heavier states with bosonic quantum numbers J{sup P}=0{sup ±} and 1{sup ±}. We consider colour-singlet heavy fields that are in singlet or triplet representations of the electroweak group. Integrating out these heavy scales, we analyze the pattern of low-energy couplings among the light fields which are generated by the massive states. We adopt a generic non-linear realization of the electroweak symmetry breaking with a singlet Higgs, without making any assumption about its possible doublet structure. Special attention is given to the different possible descriptions of massive spin-1 fields and the differences arising from naive implementations of these formalisms, showing their full equivalence once a proper short-distance behaviour is required.

Effect of temperature on the active properties of erbium-doped optical fibres

Energy Technology Data Exchange (ETDEWEB)

Kotov, L V [Moscow Institute of Physics and Technology (State University), Dolgoprudnyi, Moscow Region (Russian Federation); Ignat' ev, A D [FORC - Photonics group, Moscow (Russian Federation); Bubnov, M M; Likhachev, M E [Fiber Optics Research Center, Russian Academy of Sciences, Moscow (Russian Federation)

2016-03-31

We have studied the effect of heating on the performance of erbium-doped fibre based devices and determined temperaturedependent absorption and emission cross sections of the erbium ion in silica glass. The results demonstrate that heating of fibres in claddingpumped high-power (∼100 W) erbium-doped fibre lasers causes no significant decrease in their efficiency. In contrast, superluminescent sources operating in the long-wavelength region (1565 – 1610 nm) are extremely sensitive to temperature changes. (fiber optics)

Radiation Effects on Ytterbium-doped Optical Fibers

Science.gov (United States)

2014-06-02

conducted on Er- doped fiber amplifiers (Lezius, et al., 2012; Ahrens, et al., 1999; Ahrens, Jaques , LuValle, DiGiovanni, & Windeler, 2001; Ott, 2004...Ahrens, R. G., Abate, J. A., Jaques , J. J., Presby, H. M., Fields, A. B., DiGiovanni, D. J., LuValle, M. J. (1999). Radiation reliability of rare... Jaques , J. J., LuValle, M. J., DiGiovanni, D. J., & Windeler, R. S. (2001). Radiation effects on optical fibers and amplifiers. Testing, Reliability

Effect of additionally introduced Zn and Eu dopants on the photoluminescence spectra of Er-doped GaN crystals

International Nuclear Information System (INIS)

Mezdrogina, M.M.; Krivolapchuk, V.V.; Petrov, V.N.; Rodin, S.N.; Cherenkov, A.V.

2006-01-01

It is shown that the effect of dopants on the photoluminescence spectrum depends on the conductivity type of the initial GaN crystals. The sensitizing effect of emission is observed in wurtzite p-GaN crystals doped with Er. The same effect was previously observed in such crystals doped with Eu and Zn. In n-type GaN crystals sequentially doped with Eu, Zn, and Er, the emission is observed in visible and infrared ranges of the photoluminescence spectrum [ru

Effect of heavy metals on nitrification performance in different activated sludge processes

International Nuclear Information System (INIS)

You, Sheng-Jie; Tsai, Yung-Pin; Huang, Ru-Yi

2009-01-01

To understand the toxic effect of heavy metals on the nitrification mechanisms of activated sludge, this study identified the specific ammonia utilization rate (SAUR) inhibited by Pb, Ni and/or Cd shock loadings. Seven different heavy metal combinations (Pb, Ni, Cd, Pb + Ni, Ni + Cd, Pb + Cd, and Pb + Ni + Cd) with seven different heavy metal concentrations (0, 2, 5, 10, 15, 25, and 40 ppm, respectively) were examined by batch experiments, where the activated sludge was taken from either sequencing batch reactor (SBR) or anaerobic-anoxic-oxic (A 2 O) processes. The experimental results showed the SAUR inhibition rate was Ni > Cd > Pb. No significant inhibition in the nitrification reaction of the activated sludge was observed even when as much as 40 ppm Pb was added. In addition, no synergistic effect was found when different heavy metals were simultaneously added in different concentrations, and the overall inhibition effect depended on the heavy metal with the highest toxicity. Further, first order kinetic reaction could model the behavior of SAUR inhibition on activated sludge when adding heavy metals, and the SAUR inhibition formula was derived as SAUR=(SAUR max -SAUR min )xe -r i c +SAUR min . On the other hand, the heavy metal adsorption ability in both the activated sludge system was Pb = Cd > Ni. The specific adsorption capacity of activated sludge on heavy metal increased as the heavy metal concentration increased or the mixed liquid volatile suspended solid (MLVSS) decreased. The batch experiments also showed the heavy metal adsorption capacity of the SBR sludge was larger than the A 2 O sludge. Finally, the most predominant bacteria in the phylogenetic trees of SBR and A 2 O activated sludges were proteobacteria, which contributed to 42.1% and 42.8% of the total clones.

Doping droops.

Science.gov (United States)

Chaturvedi, Aditi; Chaturvedi, Harish; Kalra, Juhi; Kalra, Sudhanshu

2007-01-01

Drug abuse is a major concern in the athletic world. The misconception among athletes and their coaches is that when an athlete breaks a record it is due to some "magic ingredient" and not because of training, hard work, mental attitude and championship performance. The personal motivation to win in competitive sports has been intensified by national, political, professional and economic incentives. Under this increased pressure athletes have turned to finding this "magic ingredient". Athlete turns to mechanical (exercise, massage), nutritional (vitamins, minerals), pharmacological (medicines) or gene therapies to have an edge over other players. The World Anti-Doping Agency (WADA) has already asked scientists to help find ways to prevent gene therapy from becoming the newest form of doping. The safety of the life of athletes is compromised with all forms of doping techniques, be it a side effect of a drug or a new technique of gene doping.

Effect of Ga doping and point defect on magnetism of ZnO

Energy Technology Data Exchange (ETDEWEB)

Hou, Qingyu [College of Science, Inner Mongolia University of Technology, 010051 Hohhot (China); Zhao, Chunwang, E-mail: cwzhao@shmtu.edu.cn [College of Arts and Sciences, Shanghai Maritime University, 201306 Shanghai (China); Jia, Xiaofang; Qu, Lingfeng [College of Science, Inner Mongolia University of Technology, 010051 Hohhot (China)

2017-02-01

The combined influence mechanism of Ga doping and Zn vacancy or O vacancy on magnetism of ZnO is studied using the first-principle calculation. The coexistence of Ga doping and Zn vacancy can achieve a Curie temperature higher than room temperature and the Ga doped ZnO system is a p-type diluted degenerate semiconductor with metalized ferromagnetism. The magnetism of the doping system of Ga doping and Zn vacancy is mainly contributed by double-exchange interaction through the holes of Zn vacancy taking carrier as medium. However, the system of Ga doping and O vacancy is non-magnetic. In the coexistence of Ga doping and Zn vacancy or O vacancy, a close relative distance between doping and vacancy will reduce the formation energy of the doping system but increase the easiness of doping and vacancy, as well as enhance the stability of the doping system.

Effect of swift heavy ion (SHI) irradiation on transparent conducting oxide electrodes for dye-sensitized solar cell applications

Energy Technology Data Exchange (ETDEWEB)

Singh, Hemant Kr. [University School of Basic and Applied Sciences, Guru Gobind Singh Indraprastha University, New Delhi (India); Avasthi, D.K. [Inter University Accelerator Center, Post Box 10502, New Delhi (India); Aggarwal, Shruti, E-mail: shruti.al@gmail.com [University School of Basic and Applied Sciences, Guru Gobind Singh Indraprastha University, New Delhi (India)

2015-06-15

Highlights: •The objective is to study the effect of swift heavy ion (SHI) irradiation on photoanode of DSSC for better efficiency. •This work presents the effect of SHI irradiation on various Transparent conducting oxides (TCOs). •Effects are studied in terms of conductivity and transmittance of TCOs. •ITO-PET gives best results in comparison to ITO and FTO for DSSC application under SHI irradiation. -- Abstract: Transparent conducting oxides (TCOs) are used as electrodes in dye-sensitized solar cells (DSSCs) because of their properties such as high transmittance and low resistivity. In the present work, the effects of swift heavy ion (SHI) irradiation on various types of TCOs are presented. The objective of this study is to investigate the effect of SHI on TCOs. For the present study, three different types of TCOs are considered, namely, (a) FTO (fluorine-doped tin oxide, SnO{sub 2}:F) on a Nippon glass substrate, (b) ITO (indium tin oxide, In{sub 2}O{sub 3}:Sn) coated on polyethylene terephthalate (PET) on a Corning glass substrate, and (c) ITO on a Corning glass substrate. These films are irradiated with 120 MeV Ag{sup +9} ions at fluences ranging from 3.0 × 10{sup 11} ions/cm{sup 2} to 3.0 × 10{sup 13} ions/cm{sup 2}. The structural, morphological, optical and electrical properties are studied via X-ray diffraction (XRD), atomic force microscopy (AFM), UV–Vis absorption spectroscopy and four-probe resistivity measurements, respectively. The ITO-PET electrode is found to exhibit superior conductivity and transmittance properties in comparison with the others after irradiation and, therefore, to be the most suitable for solar cell applications.

Renormalons and the heavy quark effective theory

CERN Document Server

Martinelli, G; Martinelli, G; Sachrajda, C T

1995-01-01

We propose a non-perturbative method for defining the higher dimensional operators which appear in the Heavy Quark Effective Theory (HQET), such that their matrix elements are free of renormalon singularities, and diverge at most logarithmically with the ultra-violet cut-off. Matrix elements of these operators can be computed numerically in lattice simulations of the HQET. We illustrate our procedures by presenting physical definitions of the binding energy (\\lb) and of the kinetic energy (-\\lambda_1/2m_Q) of the heavy quark in a hadron. This allows us to define a ``subtracted pole mass", whose inverse can be used as the expansion parameter in applications of the HQET.

Relation between film thickness and surface doping of MoS2 based field effect transistors

Science.gov (United States)

Lockhart de la Rosa, César J.; Arutchelvan, Goutham; Leonhardt, Alessandra; Huyghebaert, Cedric; Radu, Iuliana; Heyns, Marc; De Gendt, Stefan

2018-05-01

Ultra-thin MoS2 film doping through surface functionalization with physically adsorbed species is of great interest due to its ability to dope the film without reduction in the carrier mobility. However, there is a need for understanding how the thickness of the MoS2 film is related to the induced surface doping for improved electrical performance. In this work, we report on the relation of MoS2 film thickness with the doping effect induced by the n-dopant adsorbate poly(vinyl-alcohol). Field effect transistors built using MoS2 films of different thicknesses were electrically characterized, and it was observed that the ION/OFF ratio after doping in thin films is more than four orders of magnitudes greater when compared with thick films. Additionally, a semi-classical model tuned with the experimental devices was used to understand the spatial distribution of charge in the channel and explain the observed behavior. From the simulation results, it was revealed that the two-dimensional carrier density induced by the adsorbate is distributed rather uniformly along the complete channel for thin films (<5.2 nm) contrary to what happens for thicker films.

Effects of doping and bias voltage on the screening in AAA-stacked trilayer graphene

Science.gov (United States)

Mohammadi, Yawar; Moradian, Rostam; Shirzadi Tabar, Farzad

2014-09-01

We calculate the static polarization of AAA-stacked trilayer graphene (TLG) and study its screening properties within the random phase approximation (RPA) in all undoped, doped and biased regimes. We find that the static polarization of undoped AAA-stacked TLG is a combination of the doped and undoped single-layer graphene static polarization. This leads to an enhancement of the dielectric background constant along a Thomas-Fermi screening with the Thomas-Fermi wave vector which is independent of carrier concentrations and a 1/r3 power law decay for the long-distance behavior of the screened Coulomb potential. We show that effects of a bias voltage can be taken into account by a renormalization of the interlayer hopping energy to a new bias-voltage-dependent value, indicating screening properties of AAA-stacked TLG can be tuned electrically. We also find that screening properties of doped AAA-stacked TLG, when μ exceeds √{2}γ, are similar to that of doped SLG only depending on doping. While for μ<√{2}γ, its screening properties are combination of SLG and AA-stacked bilayer graphene screening properties and they are determined by doping and the interlayer hopping energy.

Heavy particle effects

International Nuclear Information System (INIS)

Yao, Y.P.

1981-01-01

There are two problems discussed, both of which have to do with dissimilar magnitudes in mass. Theoretically, we can devise the large difference in mass as observed by decreeing some vev, v/sub i/ to be much bigger than the other; or, we can assume that some couplings g/sub i/ are much stronger. These two different assumptions give rise to entirely different patterns of interaction in the resulting theory. The first way to generate a mass hierarchy can be called the soft way, because in the zeroth order, the large mass scale leaves its foot print merely in a few effective parameters of the residual theory. The effective theory is renormalizable, sans anomaly. In this limit, the heavy particles decouple. The second assumption (g/sub j/ much greater than g/sub j'/) to create mass hierarchy does a lot of violence to a theory. Effects of the large mass scale will be felt by the system left behind in many ways. An infinite number of parameters are needed to summarize the effects in this limit. This is called the hard limit. It follows that the resulting effective Lagrangian, if in fact it makes sense to construct one at all, will be non-polynomial and apparently non-renormalizable

Doping Attitudes and Covariates of Potential Doping Behaviour in High-Level Team-Sport Athletes; Gender Specific Analysis

Science.gov (United States)

Sekulic, Damir; Tahiraj, Enver; Zvan, Milan; Zenic, Natasa; Uljevic, Ognjen; Lesnik, Blaz

2016-01-01

Team sports are rarely studied with regard to doping behaviour and doping-related factors regardless of their global popularity. This study aimed to investigate doping factors and covariates of potential doping behaviour in high-level team-sport athletes. The subjects were 457 high-performing, national- and international-level athletes (21.9 ± 3.4 years of age; 179 females) involved in volleyball (n = 77), soccer (n = 163), basketball (n = 114) and handball (n = 103). Previously validated self-administered questionnaires aimed at evidencing sport factors, doping-related factors, knowledge on sport nutrition and doping, and attitudes to performance enhancement were used. The results indicated a higher doping likelihood in male athletes, with a significant gender difference for basketball and handball. In males, a higher doping likelihood is found for athletes who had achieved better results at junior-age level, those who regularly consume dietary supplements, and who perceive their sport as being contaminated by doping. A higher sport achievement at senior-age level is protective against potential doping behaviour in males. In females, a higher likelihood of doping is evidenced in those athletes involved in binge drinking, while a lower tendency for doping is evidenced in female athletes who possess better knowledge on sport nutrition. Knowledge about doping is very low and thus education about doping is urgently needed. An improvement of knowledge on sport nutrition might be a potentially effective method for reducing the tendency for doping in females. Future studies should consider other approaches and theories, such as theory of planned behaviour and/or social-cognitive theory, in studying the problem of doping behaviour in team-sports. Key points The doping knowledge among Kosovar team-sport athletes is very low and systematic anti-doping education is urgently needed. The highest risk of doping behaviour in males is found for those athletes who had been

Attitudes and doping: a structural equation analysis of the relationship between athletes' attitudes, sport orientation and doping behaviour

Directory of Open Access Journals (Sweden)

Petróczi Andrea

2007-11-01

Full Text Available Abstract Background For effective deterrence methods, individual, systemic and situational factors that make an athlete or athlete group more susceptible to doping than others should be fully investigated. Traditional behavioural models assume that the behaviour in question is the ultimate end. However, growing evidence suggests that in doping situations, the doping behaviour is not the end but a means to an end, which is gaining competitive advantage. Therefore, models of doping should include and anti-doping policies should consider attitudes or orientations toward the specific target end, in addition to the attitude toward the 'tool' itself. Objectives The aim of this study was to empirically test doping related dispositions and attitudes of competitive athletes with the view of informing anti-doping policy developments and deterrence methods. To this end, the paper focused on the individual element of the drug availability – athlete's personality – situation triangle. Methods Data were collected by questionnaires containing a battery of psychological tests among competitive US male college athletes (n = 199. Outcome measures included sport orientation (win and goal orientation and competitiveness, doping attitude, beliefs and self-reported past or current use of doping. A structural equation model was developed based on the strength of relationships between these outcome measures. Results Whilst the doping model showed satisfactory fit, the results suggested that athletes' win and goal orientation and competitiveness do not play a statistically significant role in doping behaviour, but win orientation has an effect on doping attitude. The SEM analysis provided empirical evidence that sport orientation and doping behaviour is not directly related. Conclusion The considerable proportion of doping behaviour unexplained by the model suggests that other factors play an influential role in athletes' decisions regarding prohibited methods

Knowledge of pharmacy students about doping, and the need for doping education: a questionnaire survey.

Science.gov (United States)

Shibata, Keita; Ichikawa, Koichi; Kurata, Naomi

2017-08-11

Anti-doping activities are carried out on a global scale. Based on these activities, the specialty of "sports pharmacist," which entails a deeper comprehension of doping, use of supplements, and appropriate drug use for athletes, was established in 2009 in Japan. It is difficult to say whether the education on doping is adequate for pharmacy students who will be eligible to become sports pharmacists. It is also unclear how well these students understand doping. Therefore, the aim of this study was to investigate pharmacy students' current knowledge of appropriate drug use, doping and use of supplements, and to explore the need for further education on these topics. A questionnaire survey was conducted from July 3rd to August 2nd in 2014 at Showa University in Japan. A total of 406 respondents (2nd- to 6th-year students) were assessed as eligible. Group comparison was used to compare those who had attended a lecture about doping and those who had not. Most of the students only knew the word doping and had not attended a lecture on the subject, but 72% of them expressed a desire to attend one. Over half did not know that the most common doping violation in Japan is unintentional doping, and were unfamiliar with certain past cases of doping. In addition, 41% did not know that over-the-counter medicines and dietary supplements might contain prohibited substances, and 87% were unaware that names of prohibited substances might not appear on the ingredient labels of dietary supplements. In contrast, attending a lecture on doping was effective in facilitating the acquisition of all these types of knowledge. It is important to provide more opportunities for appropriate education of pharmacy students on the topic of doping, given that interest exists and attending a lecture on the topic appears to be useful. More education about doping for pharmacy students would be as effective for anti-doping activities as is education of athletes.

Effect of co-doping of sodium on the thermoluminescence dosimetry properties of copper-doped zinc lithium borate glass system

International Nuclear Information System (INIS)

Saidu, A.; Wagiran, H.; Saeed, M.A.; Alajerami, Y.S.M.; Kadir, A.B.A.

2016-01-01

The effect of sodium as a co-dopant on the thermoluminescence (TL) properties of copper-doped zinc lithium borate (ZLB: Cu) subjected to Co-60 gamma radiation is reported in this study. TL intensity is enhanced with the introduction of sodium in ZLB: Cu. The obtained glow curve is simple with a single peak. The annealing procedure and the best heating rate for the proposed thermoluminescent dosimeter (TLD) are established, and the phosphor is reusable. The TL response within the dose range of 0.5–1000 Gy is investigated. The results show that the thermal fading behaviour is improved significantly. - Highlights: • Dosimetry properties of an improved TL dosimeter. • The dosimeter is made of lithium borate, modified with ZnO, doped with CuO and co-doped with Na 2 O. • With addition of Na to Cu in the ZLB host, TL yield and sensitivity has significantly enhanced. • The fading behaviour has also been minimized significantly. • The new material is also characterized with the linear dose response, and good reproducibility behaviour.

First-Principles Study of Antimony Doping Effects on the Iron-Based Superconductor CaFe(SbxAs1-x)2

Science.gov (United States)

Nagai, Yuki; Nakamura, Hiroki; Machida, Masahiko; Kuroki, Kazuhiko

2015-09-01

We study antimony doping effects on the iron-based superconductor CaFe(SbxAs1-x)2 by using the first-principles calculation. The calculations reveal that the substitution of a doped antimony atom into As of the chainlike As layers is more stable than that into FeAs layers. This prediction can be checked by experiments. Our results suggest that doping homologous elements into the chainlike As layers, which only exist in the novel 112 system, is responsible for rising up the critical temperature. We discuss antimony doping effects on the electronic structure. It is found that the calculated band structures with and without the antimony doping are similar to each other within our framework.

Synthesis and pressure effects on the La doped CaFe{sub 2}As{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Shin, Soo Hyun; Park, Tuson [Dept. of physics, Sungkyunkwan University, Suwon (Korea, Republic of); Shang, T.; Yuan, H. Q. [Dept. of physics, Zhejiang University, Hangzhou (China)

2014-09-15

We have synthesized La doped CaFe2As{sub 2} single crystals with Sn flux in an evacuated quartz ampule. Doping and pressure effects on the magnetic and superconducting properties of the under-doped Ca{sub 1-x}La{sub x}Fe{sub 2}As{sub 2} (x=0.08, 0.1) were studied by measuring electrical resistivity under quasi-hydrostatic pressure up to 21 kbar. Magnetic transition temperatures for all studied concentrations were sharply suppressed with slight amplitude of pressure, less than 3 kbar, while superconducting transition temperatures were robust against pressure. In this communication, we report temperature-pressure phase diagram for the La-doped CaFe{sub 2}As{sub 2} single crystals.

Effective technical service in the life cycle of heavy dumpers

Directory of Open Access Journals (Sweden)

Михайло Валерійович Помазков

2016-11-01

Full Text Available A comparative analysis of the known systems of technical reliability of heavy dumpers functionality has been made. It has been stated that the previously proposed methods to determine the optimal service life of heavy-duty dumpers are not effective enough and do not take into account the whole range of factors specific to the operation of heavy dumpers in the current economic realities of industrial enterprises. Based on the analysis results, a mechanism of determining the optimal service life of heavy-duty dumpers and their constituent technical systems ensuring the operational reliability of heavy-duty dumpers has been offered. The article takes into account the analysis of resource factors, general description of system logistic tasks, the main provisions of serviceability, the resource forming in route charts at ore mining and metallurgical enterprises, the use of theoretical developments in practice. Heavy dumpers generalized description modelling shown in the article, the principle of resource use by using interchangable work at different intensity routes has received confirmation in the dumpers’ work schedule

Effect of heavy metals on growth and heavy metal content of Allium porrum L. and Pisum sativum L

Energy Technology Data Exchange (ETDEWEB)

Gruenhage, L.; Jaeger, H.J.

1985-01-01

The effects of cadmium, lead, zinc and copper, singly and in combination, on yield, heavy metal content and the mineral composition of Allium porrum L. and Pisum sativum L. have been investigated. The Cd, Pb, Zn and Cu concentrations of shoots and roots of Allium porrum increased with increasing heavy metal contamination of soil. However, no visible symptoms of heavy metal toxicity were recognized. The dry matter production was reduced as a function of heavy metal concentration and combination. The mechanisms of combinations were mostly synergistic. The correlation between pollutant contents (nmol/shoot) and yield was higher than the correlation between heavy metal concentrations of soil or shoots (ppm) and yield. Results of regression analyses showed that the inhibition of copper translocation caused by Cd, Pb and Zn was responsible for the yield depressions. The antagonism between Cd and N-deficiency showed that the level of N-supply was without negative effects on yield depressions of Pisum sativum caused by Cd. In contrast to this, the N-form played an important role in Cd-toxicity as the synergism between Cd and NH4 illustrated. K-deficiency as well as acidic nutrient solution (pH=4) diminished the root/shoot-barrier for Cd and therefore Cd-translocation from roots to shoots increased. Concerning calcium, magnesium and iron the decrease of ion uptake caused by Cd was statistically significant higher than yield depression.

Effect of Bi doping on morphotropic phase boundary and dielectric properties of PZT

Energy Technology Data Exchange (ETDEWEB)

Joshi, Shraddha; Acharya, Smita, E-mail: saha275@yahoo.com [Advanced Materials Research Laboratory, Department of Physics, Rashtrasant Tukadoji Maharaj Nagpur University, Nagpur-440033, M.S. India (India)

2016-05-23

In our present attempt, Pb{sub (1-x)}Bi{sub x}Zr{sub 0.52}Ti{sub 0.48}O{sub 3} [PBZT] {where x = 0, 0.05, 0.1} is synthesized by sol-gel route. Effect of Bi addition on structure, sinterability and dielectric properties are observed. The presence of morphotropic phase boundary (coexistence of tetragonal and rhombohedral symmetry) is confirmed by X-ray diffraction. Enhancement of sinterability after Bi doping is observed through a systematic sintering program. Frequency and temperature dependent dielectric constant are studied. Bi doping in PZT is found to enhance room temperature dielectric constant. However, at high temperature the dielectric constant of pure PZT is more than that of doped PZT.

Preparation and Characterization of Rare Earth Doped Fluoride Nanoparticles

Directory of Open Access Journals (Sweden)

Timothy A. DeVol

2010-03-01

Full Text Available This paper reviews the synthesis, structure and applications of metal fluoride nanoparticles, with particular focus on rare earth (RE doped fluoride nanoparticles obtained by our research group. Nanoparticles were produced by precipitation methods using the ligand ammonium di-n-octadecyldithiophosphate (ADDP that allows the growth of shells around a core particle while simultaneously avoiding particle aggregation. Nanoparticles were characterized on their structure, morphology, and luminescent properties. We discuss the synthesis, properties, and application of heavy metal fluorides; specifically LaF3:RE and PbF2, and group IIA fluorides. Particular attention is given to the synthesis of core/shell nanoparticles, including selectively RE-doped LaF3/LaF3, and CaF2/CaF2 core/(multi-shell nanoparticles, and the CaF2-LaF3 system.

Effect of heavy metal on survival of certain groups of indigenous soil ...

African Journals Online (AJOL)

Heavy metal pollution of soil is known to adversely effect microbial activities at elevated concentration. However, response of indigenous soil bacterial population to added heavy metal and metal combinations is poorly understood. In the present study salts of heavy metals like Cu, Cd, Cr, Hg, Mn, Ni, Pb and Zn were added ...

Epigenetic Analysis of Heavy-ion Radiation Induced Bystander Effects in Mice

Science.gov (United States)

Zhang, Meng; Sun, Yeqing; Cui, Changna; Xue, Bei

Abstract: Radiation-induced bystander effect was defined as the induction of damage in neighboring non-hit cells by signals released from directly-irradiated cells. Recently, low dose of high LET radiation induced bystander effects in vivo have been reported more and more. It has been indicated that radiation induced bystander effect was localized not only in bystander tissues but also in distant organs. Genomic, epigenetic and proteomics plays significant roles in regulating heavy-ion radiation stress responses in mice. To identify the molecular mechanism that underlies bystander effects of heavy-ion radiation, the male Balb/c and C57BL mice were exposed head-only to 40, 200, 2000mGy dose of (12) C heavy-ion radiation, while the rest of the animal body was shielded. Directly radiation organ ear and the distant organ liver were detected on 1h, 6h, 12h and 24h after radiation, respectively. Methylation-sensitive amplification polymorphism (MSAP) was used to monitor the level of polymorphic genomic DNA methylation changed with dose and time effects. The results show that heavy-ion irradiated mouse head could induce genomic DNA methylation changes significantly in both the directly radiation organ ear and the distant organ liver. The percent of DNA methylation changes were time-dependent and tissue-specific. Demethylation polymorphism rate was highest separately at 1 h in 200 mGy and 6 h in 2000 mGy after irradiation. The global DNA methylation changes tended to occur in the CG sites. The results illustrated that genomic methylation changes of heavy ion radiation-induced bystander effect in liver could be obvious 1 h after radiation and achieved the maximum at 6 h, while the changes could recover gradually at 12 h. The results suggest that mice head exposed to heavy-ion radiation can induce damage and methylation pattern changed in both directly radiation organ ear and distant organ liver. Moreover, our findings are important to understand the molecular mechanism of

Microscopic effects of Dy doping in the topological insulator Bi2Te3

Science.gov (United States)

Duffy, L. B.; Steinke, N.-J.; Krieger, J. A.; Figueroa, A. I.; Kummer, K.; Lancaster, T.; Giblin, S. R.; Pratt, F. L.; Blundell, S. J.; Prokscha, T.; Suter, A.; Langridge, S.; Strocov, V. N.; Salman, Z.; van der Laan, G.; Hesjedal, T.

2018-05-01

Magnetic doping with transition metal ions is the most widely used approach to break time-reversal symmetry in a topological insulator (TI)—a prerequisite for unlocking the TI's exotic potential. Recently, we reported the doping of Bi2Te3 thin films with rare-earth ions, which, owing to their large magnetic moments, promise commensurately large magnetic gap openings in the topological surface states. However, only when doping with Dy has a sizable gap been observed in angle-resolved photoemission spectroscopy, which persists up to room temperature. Although disorder alone could be ruled out as a cause of the topological phase transition, a fundamental understanding of the magnetic and electronic properties of Dy-doped Bi2Te3 remained elusive. Here, we present an x-ray magnetic circular dichroism, polarized neutron reflectometry, muon-spin rotation, and resonant photoemission study of the microscopic magnetic and electronic properties. We find that the films are not simply paramagnetic but that instead the observed behavior can be well explained by the assumption of slowly fluctuating, inhomogeneous, magnetic patches with increasing volume fraction as the temperature decreases. At liquid helium temperatures, a large effective magnetization can be easily introduced by the application of moderate magnetic fields, implying that this material is very suitable for proximity coupling to an underlying ferromagnetic insulator or in a heterostructure with transition-metal-doped layers. However, the introduction of some charge carriers by the Dy dopants cannot be excluded at least in these highly doped samples. Nevertheless, we find that the magnetic order is not mediated via the conduction channel in these samples and therefore magnetic order and carrier concentration are expected to be independently controllable. This is not generally the case for transition-metal-doped topological insulators, and Dy doping should thus allow for improved TI quantum devices.

Luminescence of Ce doped oxygen crystalline compounds based on Hf and Ba

CERN Document Server

Borisevich, A E; Lecoq, P

2003-01-01

The luminescence properties of the Ce-doped hafnium and barium compounds have been investigated to determine their potential as heavy scintillation materials. Compounds have been prepared by solid state synthesis. All of them have shown a bright luminescence attributed to trivalent cerium. Emission bands are peaked in the 425-475nm spectral region at room temperature.

The effect of grain size and phosphorous-doping of polycrystalline 3C–SiC on infrared reflectance spectra

International Nuclear Information System (INIS)

Rooyen, I.J. van; Engelbrecht, J.A.A.; Henry, A.; Janzén, E.; Neethling, J.H.; Rooyen, P.M. van

2012-01-01

Highlights: ► IR is investigated as a technique to measure grain size and P-doping of polycrystalline SiC. ► Infrared plasma minima can be used to determine doping levels in 3C–SiC for doping levels greater than 5 × 10 17 cm −3 . ► A linear relationship is found between FWHM and the inverse of grain size of 3C–SiC irrespective of P-doping level. ► It is further found that ω p is not influenced by the grain size. ► P-doping level has no significant effect on the linear relationship between grain size and surface roughness. - Abstract: The effect of P-doping and grain size of polycrystalline 3C–SiC on the infrared reflectance spectra is reported. The relationship between grain size and full width at half maximum (FWHM) suggest that the behavior of the 3C–SiC with the highest phosphorous doping level (of 1.2 × 10 19 at. cm −3 ) is different from those with lower doping levels ( 18 at. cm −3 ). It is also further demonstrated that the plasma resonance frequency (ω p ) is not influenced by the grain size.

Effects of time-temperature profiles on glow curves of germanium-doped optical fibre

Science.gov (United States)

Lam, S. E.; Alawiah, A.; Bradley, D. A.; Mohd Noor, N.

2017-08-01

The Germanium (Ge) doped silica optical fibres have demonstrated the great potential to be developed as a thermoluminescent (TL) dosimeter that can be used in various applications in radiotherapy, diagnostic radiology, UV dosimetry system and food irradiation industry. Different time-temperature profile (TTP) parameters of the TL reader have been employed by many researchers in various of TL studies. Nevertheless, none of those studies adequately addressed the effects of the reader's preheat temperature and heating rate on the kinetic parameters of the TL glow curve specifically, the Ge-doped silica optical fibres. This research addresses the issue of TTP parameters with special attention to the determination of the kinetic parameters of the glow curve. The glow curve responses were explored and the kinetic parameters were analyzed by the WinGCF software, to show the effect of the preheat temperature and heating rate of the reader on Ge-doped fibre irradiated with 18 Gy of 6 MV photons radiation. The effect of TTP parameters was discussed and compared against the commercial fibre and tailored made fibre of 6 mol% Ge-doped of flat and cylindrical shape. The deconvolution of glow peaks and the kinetic parameters were obtained by the WinGCF software. This enables to fit accurately (1.5%doped silica optical fibres.

Hall effect of K-doped superconducting thin films

Energy Technology Data Exchange (ETDEWEB)

Son, Eunseon; Lee, Nam Hoon; Kang, Won Nam [Dept. of physics, Sungkyunkwan University, Suwon (Korea, Republic of); Hwang, Tae Jong; Kim, Dong Ho [Dept. of physics, Yeungnam University, Gyeongsan(Korea, Republic of)

2013-09-15

We have studied Hall effect for potassium (K)-doped BaFe{sub 2}As{sub 2}superconducting thin films by analyzing the relation between the longitudinal resistivity (ρ{sub xy}) and the Hall resistivity (ρ{sub xy}). The thin films used in this study were fabricated on Al{sub O3} (000l) substrates by using an ex-situ pulsed laser deposition (PLD) technique under a high-vacuum condition of ∼10{sup -6} Torr. The samples showed the high superconducting transition temperatures (T{sub C}) of ∼40 K. The ρ{sub xx} and ρ{sub xy}the for K-doped BaFeAs{sub 2} thin films were measured by using a physical property measurement system (PPMS) with a temperature sweep (T-sweep) mode at an applied current density of 100 A/cm{sup 2} and at magnetic fields from 0 up to 9 T. We report the T-sweep results of the ρ{sub xx} and the ρ{sub xy} to investigate Hall scaling behavior on the basis of the relation of ρ{sub xy} = A(ρ{sub xy}){sup β}. The ρ{sub xx} values are 3.0 ± 0.2 in the c-axis-oriented K-doped BaFeAs{sub 2} thin films, whereas the thin films with various oriented-directions like a polycrystal showed slightly lower β than that of c-axis-oriented thin films. Interestingly, the β value is decreased with increasing magnetic fields.

The effect of a period of intensive exercise on the isoform test to detect growth hormone doping in sports.

Science.gov (United States)

Voss, S C; Giraud, S; Alsayrafi, M; Bourdon, P C; Schumacher, Y O; Saugy, M; Robinson, N

2013-08-01

The major objective of this study was to investigate the effects of several days of intense exercise on growth hormone (hGH) testing using the World Anti-Doping Agencies hGH isoform differential immunoassays. Additionally the effects of circadian variation and exercise type on the isoform ratios were also investigated. 15 male athletes performed a simulated nine day cycling stage race. Blood samples were collected twice daily over a period of 15 days (stage race+three days before and after). hGH isoforms were analysed by the official WADA immunoassays (CMZ Assay GmbH). All measured isoform ratios were far below the WADA decision limits for an adverse analytical finding. Changes in the isoform ratios could not be clearly connected to circadian variation, exercise duration or intensity. The present study demonstrates that the hGH isoform ratios are not significantly affected by exercise or circadian variation. We demonstrated that heavy, long term exercise does not interfere with the decision limits for an adverse analytical finding. Copyright © 2013 Elsevier Ltd. All rights reserved.

Effect of heavy metals ondecolorization of reactive brilliant red by newly isolated microorganisms

International Nuclear Information System (INIS)

Nosheen, S.; Arshad, M.

2011-01-01

This study involves aerobic decolorisation of reactive azo dye reactive brilliant red 2KBP by newly isolated microbial strains (two bacterial and one fungal strain) in presence of heavy metals including cobalt chloride, ferric chloride, zinc sulphate, copper sulphate and nickel chloride. Many heavy metals are necessary for microbial growth and are required in very small amounts however at higher levels they become toxic. So was the objective of present work to check the effect of concentration of heavy metals on the potential of microbial strains to decolorize azo dyes. All the heavy metals under consideration were added in range of 0.5 gl-1-2.5gl/sup -1/. All heavy metals showed inhibitory effect on decolorization capacity of bacterial as well as fungal strain .At optimum conditions bacterial strains named as B1 and B2 removed 84% and 78% while fungal strain decolorized 90.4% of dye. Cobalt and nickel showed greater inhibitors on% decolorization of dyes than Zinc and iron. Fungal strain showed greater negative effect. Heavy metals might affect enzyme activities and thus reducing removal of dye. (author)

Concurrent doping effect of Ti and nano-diamond on flux pinning of MgB{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Zhao, Y., E-mail: yzhao@swjtu.edu.c [Key Laboratory of Magnetic Levitation and Maglev Trains (Ministry of Education of China), Superconductivity R and D Center (SRDC), Mail Stop 165, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China); Superconductivity Research Group, School of Materials Science and Engineering, University of New South Wales, Sydney, 2052 NSW (Australia); Ke, C. [Key Laboratory of Magnetic Levitation and Maglev Trains (Ministry of Education of China), Superconductivity R and D Center (SRDC), Mail Stop 165, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China); Cheng, C.H. [Superconductivity Research Group, School of Materials Science and Engineering, University of New South Wales, Sydney, 2052 NSW (Australia); Feng, Y. [Northwest Institute for Nonferrous Metal Research, P.O. Box 51, Xian, Shaanxi 710016 (China); Western Superconductivity Technology Company, Xian (China); Yang, Y. [Key Laboratory of Magnetic Levitation and Maglev Trains (Ministry of Education of China), Superconductivity R and D Center (SRDC), Mail Stop 165, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China); Munroe, P. [Superconductivity Research Group, School of Materials Science and Engineering, University of New South Wales, Sydney, 2052 NSW (Australia)

2010-11-01

Nano-diamond and titanium concurrently doped MgB{sub 2} nanocomposites have been prepared by solid state reaction method. The effects of carbon and Ti concurrent doping on J{sub c}-H behavior and pinning force scaling features of MgB{sub 2} have been investigated. Although T{sub c} was slightly depressed, J{sub c} of MgB{sub 2} have been significantly improved by the nano-diamond doping, especially in the high field region. In the mean time, the J{sub c} value in low field region is sustained though concurrent Ti doping. Microstructure analysis reveals that when nano-diamond was concurrently doped with titanium in MgB{sub 2}, a unique nanocomposite in which TiB{sub 2} forms a thin layer surrounding MgB{sub 2} grains whereas nano-diamond particles were wrapped inside the MgB{sub 2} grains. Besides, nano-diamond doping results in a high density stress field in the MgB{sub 2} samples, which may take responsibility for the {Delta}{kappa} pinning behavior in the carbon-doped MgB{sub 2} system.

Magnesium Oxide Embedded Nitrogen Self-Doped Biochar Composites: Fast and High-Efficiency Adsorption of Heavy Metals in an Aqueous Solution.

Science.gov (United States)

Ling, Li-Li; Liu, Wu-Jun; Zhang, Shun; Jiang, Hong

2017-09-05

Lead (Pb) pollution in natural water bodies is an environmental concern due to toxic effects on aquatic ecosystems and human health, while adsorption is an effective approach to remove Pb from the water. Surface interactions between adsorbents and adsorbates play a dominant role in the adsorption process, and properly engineering a material's surface property is critical to the improvement of adsorption performance. In this study, the magnesium oxide (MgO) nanoparticles stabilized on the N-doped biochar (MgO@N-biochar) were synthesized by one-pot fast pyrolysis of an MgCl 2 -loaded N-enriched hydrophyte biomass as a way to increase the exchangeable ions and N-containing functional groups and facilitate the adsorption of Pb 2+ . The as-synthesized MgO@N-biochar has a high performance with Pb in an aqueous solution with a large adsorption capacity (893 mg/g), a very short equilibrium time (adsorption performance can be maintained with various environmentally relevant interferences including pH, natural organic matter, and other metal ions, suggesting that the material may be suitable for the treatment of wastewater, natural bodies of water, and even drinking water. In addition, MgO@N-biochar quickly and efficiently removed Cd 2+ and tetracycline. Multiple characterizations and comparative tests have been performed to demonstrate the surface adsorption and ion exchange contributed to partial Pb adsorption, and it can be inferred from these results that the high performance of MgO@N-biochar is mainly due to the surface coordination of Pb 2+ and C═O or O═C-O, pyridinic, pyridonic, and pyrrolic N. This work suggests that engineering surface functional groups of biochar may be crucial for the development of high performance heavy metal adsorbents.

Effect of zinc doping on the bandgap and photoluminescence of Zn2+-doped TiO2 nanowires

Science.gov (United States)

Loan, Trinh Thi; Huong, Vu Hoang; Tham, Vu Thi; Long, Nguyen Ngoc

2018-03-01

This study was focused on the effect of Zn2+ dopant concentration on the absorption edge and photoluminescence of anatase TiO2 nanowires synthesized by hydrothermal technique. For the undoped anatase TiO2 nanowires, the indirect band gap of 3.26 eV and the direct band gap of 3.58 eV are assigned to the indirect Γ3 → X1b and direct X2b → X1b transitions, respectively. The Zn2+-doping makes the absorption edge of TiO2:Zn2+ nanowires shift towards the lower energy side (red shift). On the other hand, the replacing Ti4+ ions with Zn2+ ions creates oxygen vacancies (VO) and shallow defects associated with VO. Just these defects are responsible for the enhanced luminescence of Zn2+-doped TiO2 nanowires.

Investigation of structural materials of reactors using high-energy heavy-ion irradiations

International Nuclear Information System (INIS)

Wang Zhiguang

2007-01-01

Radiation damage in structural materials of fission/fusion reactors is mainly attributed to the evolution of intensive atom displacement damage induced by energetic particles (n, α and/or fission fragments) and high-rate helium doping by direct α particle bombardments and/or (n, α) reactions. It can cause severe degradation of reactor structural materials such as surface blistering, bulk void swelling, deformation, fatigue, embrittlement, stress erosion corrosion and so on that will significantly affect the operation safety of reactors. However, up to now, behavior of structural materials at the end of their service can hardly be fully tested in a real reactor. In the present work, damage process in reactor structural materials is briefly introduced, then the advantages of energetic ion implantation/irradiation especially high-energy heavy ion irradiation are discussed, and several typical examples on simulation of radiation effects in reactor candidate structural materials using high-energy heavy ion irradiations are pronounced. Experimental results and theoretical analysis suggested that irradiation with energetic particles especially high-energy heavy ions is very useful technique for simulating the evolution of microstructures and macro-properties of reactor structural materials. Furthermore, an on-going plan of material irradiation experiments using high energy H- and He-ions based on the Heavy Ion Research Facilities in Lanzhou (HIRFL) is also briefly interpreted. (authors)

Effect of V-Nd co-doping on phase transformation and grain growth process of TiO2

Science.gov (United States)

Khatun, Nasima; Amin, Ruhul; Anita, Sen, Somaditya

2018-05-01

The pure and V-Nd co-doped TiO2 samples are prepared by the modified sol-gel process. The phase formation is confirmed by XRD spectrum. Phase transformation is delayed in V-Nd co-doped TiO2 (TVN) samples compared to pure TiO2. The particle size is comparatively small in TVN samples at both the temperature 450 °C and 900 °C. Hence the effect of Nd doping is dominated over V doping in both phase transformation and grain growth process of TiO2.

Effect of microstructural anisotropy on the mechanical properties of K-doped tungsten rods for plasma facing components

Energy Technology Data Exchange (ETDEWEB)

Nogami, Shuhei, E-mail: shuhei.nogami@qse.tohoku.ac.jp; Guan, Wenhai, E-mail: wenhai.guan@jupiter.qse.tohoku.ac.jp; Fukuda, Makoto, E-mail: fukuda@jupiter.qse.tohoku.ac.jp; Hasegawa, Akira, E-mail: akira.hasegawa@qse.tohoku.ac.jp

2016-11-01

Highlights: • K-doping led to improve the tensile strength regardless of the test direction and temperature. • K-doping did not alter the elongation regardless of the test direction in the ductile fracture temperature range. • The ductility at lower temperature range was improved by the K-doping. • The lowest temperature of ductile fracture along both axial and radial directions decreased because of K-doping. • K-doping could suppress the influence of microstructural anisotropy on tensile properties, especially ductility, in large diameter W rods. - Abstract: The effect of microstructural anisotropy in pure tungsten (W) and potassium (K) doped W rods (20 mm in diameter) on their mechanical properties was investigated by tensile tests along the axial and radial directions at temperatures from 473 K to 1573 K and fracture analysis. K-doping led to improved tensile strength regardless of the test direction and temperature. K-doping did not alter the elongation regardless of the test direction in the temperature range showing ductile fracture. The ductility at lower temperature range was improved by the K-doping, especially in tensile tests along the radial direction. The lowest temperature of ductile fracture along both axial and radial directions decreased from 1373 K to 973 K because of K-doping. Thus, K-doping could suppress the influence of microstructural anisotropy on tensile properties, especially ductility, in large diameter W rods.

Density functional investigation of mercury and arsenic adsorption on nitrogen doped graphene decorated with palladium clusters: A promising heavy metal sensing material in farmland

Energy Technology Data Exchange (ETDEWEB)

Zhao, Chunjiang, E-mail: zhaocj_nercita@163.com [National Engineering Research Center for Information Technology in Agriculture, Beijing 100097 (China); Beijing Research Center for Information Technology in Agriculture, Beijing Academy of Agriculture and Forestry Sciences, Beijing 100097 (China); Key Laboratory for Information Technologies in Agriculture, Ministry of Agriculture, Beijing100097 (China); Wu, Huarui, E-mail: wuhrnercita@163.com [National Engineering Research Center for Information Technology in Agriculture, Beijing 100097 (China); Beijing Research Center for Information Technology in Agriculture, Beijing Academy of Agriculture and Forestry Sciences, Beijing 100097 (China); Key Laboratory for Information Technologies in Agriculture, Ministry of Agriculture, Beijing100097 (China)

2017-03-31

Highlights: • PNG can be acted as micro-sensor for monitoring heavy metal in agriculture. • The most favorable adsorption site of Pd atom or cluster on PNG is the vacancy site. • The Pd atom or cluster enhance the reactivity of PNG toward Hg and AsH{sub 3} adsorption. • The efficiency of a sorbent can be tuned by tailoring the ε{sub d} of adsorbed metals. - Abstract: Density functional theory calculations are carried out to study the adsorption of mercury and arsenic on Pd{sub n} (n = 1–6) supported on pyridine-like nitrogen doped graphene (PNG). Owing to the promising sensitivity in trace amounts of atoms or molecules, PNG can be acted as micro-sensor for sensing heavy metals in agriculture soils. Through the analyses of structural and electronic properties of pristine PNG and Pd atom decorated PNG, we find that the most favorable adsorption site for Pd atom is the vacancy site. The analyses of structural and electronic properties reveal that the Pd atom or clusters can enhance the reactivity for Hg and AsH{sub 3} adsorption on PNG. The adsorption ability of Hg on Pd{sub n} decorated PNG is found to be related to the d-band center (ε{sub d}) of the Pd{sub n}, in which the closer ε{sub d} of Pd{sub n} to the Fermi level, the higher adsorption strength for Hg on Pd{sub n} decorated PNG. Moreover, the charge transfer between Pd{sub n} and arsenic may constitute arsenic adsorption on Pd{sub n} decorated PNG. Further design of highly efficient carbon based sorbents for heavy metals removal should be focused on tailoring ε{sub d} of adsorbed metals.

Impurity doping effects on the orbital thermodynamic properties of hydrogenated graphene, graphane, in Harrison model

Science.gov (United States)

Yarmohammadi, Mohsen

2016-12-01

Using the Harrison model and Green's function technique, impurity doping effects on the orbital density of states (DOS), electronic heat capacity (EHC) and magnetic susceptibility (MS) of a monolayer hydrogenated graphene, chair-like graphane, are investigated. The effect of scattering between electrons and dilute charged impurities is discussed in terms of the self-consistent Born approximation. Our results show that the graphane is a semiconductor and its band gap decreases with impurity. As a remarkable point, comparatively EHC reaches almost linearly to Schottky anomaly and does not change at low temperatures in the presence of impurity. Generally, EHC and MS increases with impurity doping. Surprisingly, impurity doping only affects the salient behavior of py orbital contribution of carbon atoms due to the symmetry breaking.

Doping kinetics of organic semiconductors investigated by field-effect transistors

NARCIS (Netherlands)

Maddalena, F.; Meijer, E.J.; Asadi, K.; Leeuw, D.M. de; Blom, P.W.M.

2010-01-01

The kinetics of acid doping of the semiconductor regioregular poly-3-hexylthiophene with vaporized chlorosilane have been investigated using field-effect transistors. The dopant density has been derived as a function of temperature and exposure time from the shift in the pinch-off voltage, being the

Effects of heavy ion temperature on low-frequency kinetic Alfven waves

International Nuclear Information System (INIS)

Yang, L.; Wu, D. J.

2011-01-01

Heavy ion-electron (or proton) temperature ratio varies in a wide range in the solar and space environment. In this paper, proton and heavy ion temperatures are included in a three-fluid plasma model. For the specified parameters, low-frequency (<< heavy ion gyrofrequency) kinetic Alfven waves (KAWs) with sub- and super-Alfvenic speeds are found to coexist in the same plasma environment. Our results show that the temperature ratio of heavy ions to electrons can considerably affect the dispersion, propagation, and electromagnetic polarizations of the KAWs. In particular, the temperature ratio can increase the ratio of parallel to perpendicular electric fields and the normalized electric to magnetic field ratio, the variations of which are greatly different in regions with a high heavy ion temperature and with a low one. The results may help to understand the physical mechanism of some energization processes of heavy ions in the solar and space plasma environment. Effects of the ratio of electron thermal to Alfven speeds and the heavy ion abundance on these parameters are also discussed.

Effects of shape, size, and pyrene doping on electronic properties of graphene nanoflakes.

Science.gov (United States)

Kuamit, Thanawit; Ratanasak, Manussada; Rungnim, Chompoonut; Parasuk, Vudhichai

2017-11-25

Effects of size, shape, and pyrene doping on electronic properties of graphene nanoflakes (GNFs) were theoretically investigated using density functional theory method with PBE, B3PW91, and M06-2X functionals and cc-pVDZ basis set. Two shapes of zigzag GNFs, hexagonal (HGN) and rhomboidal (RGN), were considered. The energy band gap of GNF depends on shape and decreases with size. The HGN has larger band gap energy (1.23-3.96 eV) than the RGN (0.13-2.12 eV). The doping of pyrene and pyrene derivatives on both HGN and RGN was also studied. The adsorption energy of pyrene and pyrene derivatives on GNF does not depend on the shape of GNFs with energies between 21 and 27 kcal mol -1 . The substituent on pyrene enhances the binding to GNF but the strength does not depend on electron withdrawing or donating capability. The doping by pyrene and pyrene derivatives also shifts the HOMO and LUMO energies of GNFs. Both positive (destabilizing) and negative (stabilizing) shifts on HOMO and LUMO of GNFs were seen. The direction and magnitude of the shift do not follow the electron withdrawing and donating capability of pyrene substituents. However, only a slight shift was observed for doped RGN. A shift of 0.19 eV was noticed for HOMO of HGN doped with 1-aminopyrene (pyNH 2 ) and of 0.04 eV for LUMO of HGN doped with 1-pyrenecarboxylic acid (pyCOOH). Graphical Abstract HOMO and LUMO Energies of pyrene/pyrene derivatives doped Graphene Nanoflakes.

Heavy baryons

International Nuclear Information System (INIS)

Koerner, J.G.

1994-06-01

We review the experimental and theoretical status of baryons containing one heavy quark. The charm and bottom baryon states are classified and their mass spectra are listed. The appropriate theoretical framework for the description of heavy baryons is the Heavy Quark Effective Theory, whose general ideas and methods are introduced and illustrated in specific examples. We present simple covariant expressions for the spin wave functions of heavy baryons including p-wave baryons. The covariant spin wave functions are used to determine the Heavy Quark Symmetry structure of flavour-changing current-induced transitions between heavy baryons as well as one-pion and one-photon transitions between heavy baryons of the same flavour. We discuss 1/m Q corrections to the current-induced transitions as well as the structure of heavy to light baryon transitions. Whenever possible we attempt to present numbers to compare with experiment by making use of further model-dependent assumptions as e.g. the constituent picture for light quarks. We highlight recent advances in the theoretical understanding of the inclusive decays of hadrons containing one heavy quark including polarization. For exclusive semileptonic decays we discuss rates, angular decay distributions and polarization effects. We provide an update of the experimental and theoretical status of lifetimes of heavy baryons and of exclusive nonleptonic two body decays of charm baryons. (orig.)

380 keV proton irradiation effects on photoluminescence of Eu-doped GaN

International Nuclear Information System (INIS)

Okada, Hiroshi; Nakanishi, Yasuo; Wakahara, Akihiro; Yoshida, Akira; Ohshima, Takeshi

2008-01-01

The effect of 380 keV proton irradiation on the photoluminescence (PL) properties has been investigated for undoped and Eu-doped GaN. As the proton irradiation exceeds 1x10 13 cm -2 , a drastic decrease of PL intensity of the near band-edge emission of undoped GaN was observed. On the other hand, for Eu-doped GaN, the PL emission corresponding to the 5 D 0 → 7 F 2 transition in Eu 3+ kept the initial PL intensity after the proton irradiation up to 1x10 14 cm -2 . Present results, together with our previous report on electron irradiation results, suggest that Eu-doped GaN is a strong candidate for light emitting devices in high irradiation environment

The effect of grain size and phosphorous-doping of polycrystalline 3C-SiC on infrared reflectance spectra

Energy Technology Data Exchange (ETDEWEB)

Rooyen, I.J. van, E-mail: Isabella.vanRooyen@inl.gov [Fuel Performance and Design Department, Idaho National Laboratory, Idaho Falls, ID 83415-6188 (United States); Department of Physics, Nelson Mandela Metropolitan University, Port Elizabeth (South Africa); Engelbrecht, J.A.A. [Department of Physics, Nelson Mandela Metropolitan University, Port Elizabeth (South Africa); Henry, A.; Janzen, E. [Department of Physics, Chemistry and Biology, Semiconductor Materials, Linkoeping University, Linkoeping 58183 (Sweden); Neethling, J.H. [Department of Physics, Nelson Mandela Metropolitan University, Port Elizabeth (South Africa); Rooyen, P.M. van [Philip M van Rooyen Network Consultants, Midlands Estates (South Africa)

2012-03-15

Highlights: Black-Right-Pointing-Pointer IR is investigated as a technique to measure grain size and P-doping of polycrystalline SiC. Black-Right-Pointing-Pointer Infrared plasma minima can be used to determine doping levels in 3C-SiC for doping levels greater than 5 Multiplication-Sign 10{sup 17} cm{sup -3}. Black-Right-Pointing-Pointer A linear relationship is found between FWHM and the inverse of grain size of 3C-SiC irrespective of P-doping level. Black-Right-Pointing-Pointer It is further found that {omega}{sub p} is not influenced by the grain size. Black-Right-Pointing-Pointer P-doping level has no significant effect on the linear relationship between grain size and surface roughness. - Abstract: The effect of P-doping and grain size of polycrystalline 3C-SiC on the infrared reflectance spectra is reported. The relationship between grain size and full width at half maximum (FWHM) suggest that the behavior of the 3C-SiC with the highest phosphorous doping level (of 1.2 Multiplication-Sign 10{sup 19} at. cm{sup -3}) is different from those with lower doping levels (<6.6 Multiplication-Sign 10{sup 18} at. cm{sup -3}). It is also further demonstrated that the plasma resonance frequency ({omega}{sub p}) is not influenced by the grain size.

Effects of irradiation of sewage sludge on heavy metal bioavailability

International Nuclear Information System (INIS)

Sheppard, S.C.; Mayoh, K.R.

1986-10-01

Sewage sludges are a valuable resource to agriculture, but their use is limited by the hazards of pathogens, toxic chemicals and heavy metals. Irradiation can control the pathogens and deactivate some of the toxic chemicals. The relative cost of industrial-scale irradiation using accelerators has decreased progressively. This, coupled with the increasing necessity to recycle wastes, has led to renewed interest in irradiation of sludges. In response to this renewed interest, this report examines what is known about the effects of irradiation on the bioavailability of heavy metals. Very few studies have addressed this topic, although workers in the U.S. have claimed decreased solubility of metals in irradiated sludges. We have also briefly reviewed the general literature on sludge to gain indirect evidence on the likely effects. The scant data, often based on less than ideal experimental methodologies, show no major consistent effects of irradiation on the availability of heavy metals from sludge. The data are not sufficient to rule out such effects entirely, but the effects appear to be fairly subtle and not likely to persist beyond one growth season. 85 refs

Borazino-Doped Polyphenylenes.

Science.gov (United States)

Marinelli, Davide; Fasano, Francesco; Najjari, Btissam; Demitri, Nicola; Bonifazi, Davide

2017-04-19

The divergent synthesis of two series of borazino-doped polyphenylenes, in which one or more aryl units are replaced by borazine rings, is reported for the first time, taking advantage of the decarbonylative [4 + 2] Diels-Alder cycloaddition reaction between ethynyl and tetraphenylcyclopentadienone derivatives. Because of the possibility of functionalizing the borazine core with different groups on the aryl substituents at the N and B atoms of the borazino core, we have prepared borazino-doped polyphenylenes featuring different doping dosages and orientations. To achieve this, two molecular modules were prepared: a core and a branching unit. Depending on the chemical natures of the central aromatic module and the reactive group, each covalent combination of the modules yields one exclusive doping pattern. By means of this approach, three- and hexa-branched hybrid polyphenylenes featuring controlled orientations and dosages of the doping B 3 N 3 rings have been prepared. Detailed photophysical investigations showed that as the doping dosage is increased, the strong luminescent signal is progressively reduced. This suggests that the presence of the B 3 N 3 rings engages additional deactivation pathways, possibly involving excited states with an increasing charge-separated character that are restricted in the full-carbon analogues. Notably, a strong effect of the orientational doping on the fluorescence quantum yield was observed for those hybrid polyphenylene structures featuring low doping dosages. Finally, we showed that Cu-catalyzed 1,3-dipolar cycloaddition is also chemically compatible with the BN core, further endorsing the inorganic benzene as a versatile aromatic scaffold for engineering of molecular materials with tailored and exploitable optoelectronic properties.

Soil heavy metals

Energy Technology Data Exchange (ETDEWEB)

Sherameti, Irena [Jena Univ. (Germany). Inst. fuer Allgemeine Botanik und Pflanzenphysiologie; Varma, Ajit (eds.) [Amity Univ., Uttar Pradesh (India). Amity Inst. of Microbial Technology; Amity Science, Technology and Innovation Foundation, Noida, UP (India)

2010-07-01

Human activities have dramatically changed the composition and organisation of soils. Industrial and urban wastes, agricultural application and also mining activities resulted in an increased concentration of heavy metals in soils. How plants and soil microorganisms cope with this situation and the sophisticated techniques developed for survival in contaminated soils is discussed in this volume. The topics presented include: the general role of heavy metals in biological soil systems; the relation of inorganic and organic pollutions; heavy metal, salt tolerance and combined effects with salinity; effects on abuscular mycorrhizal and on saprophytic soil fungi; heavy metal resistance by streptomycetes; trace element determination of environmental samples; the use of microbiological communities as indicators; phytostabilization of lead polluted sites by native plants; effects of soil earthworms on removal of heavy metals and the remediation of heavy metal contaminated tropical land. (orig.)

[Doping, sport and addiction--any links?].

Science.gov (United States)

Foucart, J; Verbanck, P; Lebrun, P

2015-01-01

Sport is widely encouraged as it is beneficial for health. However, high-performance sport is more and more associated to rather suspicious practices; doping is one of the best example. From a physician point of view, the use of doping agents is obviously a major concern because taking such products often induce serious adverse effects on health. The present manuscript aims to inform physicians about the most frequent doping practices. It also points out that intensive sport can generate an "addictive" behavior sharing with "common"addictions a loss of practice control, a lack of interest in other activities and even a sport's practice detrimental to athlete's health. Analysis of the doping issue needs to take this reality into account as some doping products display an established " addictive" effect.

Investigation of the effect of Mg doping for improvements of optical and electrical properties

Energy Technology Data Exchange (ETDEWEB)

Caglar, Mujdat, E-mail: mcaglar@anadolu.edu.tr; Caglar, Yasemin; Ilican, Saliha

2016-03-15

Sol–gel spin coating method was used for the deposition of nanostructured undoped and Mg doped ZnO films. The effects of magnesium incorporation on the crystalline structure were investigated by XRD measurements and the structural deterioration was observed in the crystalline quality of the films with respect to increasing in Mg doping. All the samples exhibited a wurtzite structure. From the scanning electron microscopy (SEM) images obtained to investigate the surface morphology it was detected that an increase in Mg doping caused an improvement on the surface roughness and a reduction in the number of voids on the surface. To evaluate the absorption edges of the produced samples depending on the Mg, different methods were used and according to the obtained results, a shifting towards to high energies for the optical band gap was observed in each method. By using the single oscillator model, developed by DiDomenico and Wemple, the refractive index dispersion of the films was analyzed. E{sub o} and E{sub d} values of the 5% Mg doped film were found to be 5.76 eV and 11.80 eV, respectively. Within the scope of electrical properties, from Hall effect measurements, it was determined that all the films exhibited n-type behavior and the carrier concentration increased from 1.49×10{sup 16} to 1.20×10{sup 17} cm{sup −3} with increasing Mg doping.

First-principles study of antimony doping effects on the iron-based superconductor CaFe(SbxAs1−x)2

International Nuclear Information System (INIS)

Nagai, Yuki; Nakamura, Hiroki; Machida, Masahiko; Kuroki, Kazuhiko

2015-01-01

We study antimony doping effects on the iron-based superconductor CaFe(Sb x As 1−x ) 2 by using the first-principles calculation. The calculations reveal that the substitution of a doped antimony atom into As of the chainlike As layers is more stable than that into FeAs layers. This prediction can be checked by experiments. Our results suggest that doping homologous elements into the chainlike As layers, which only exist in the novel 112 system, is responsible for rising up the critical temperature. We discuss antimony doping effects on the electronic structure. It is found that the calculated band structures with and without the antimony doping are similar to each other within our framework. (author)

Substrate and Mg doping effects in GaAs nanowires

Directory of Open Access Journals (Sweden)

Perumal Kannappan

2017-10-01

Full Text Available Mg doping of GaAs nanowires has been established as a viable alternative to Be doping in order to achieve p-type electrical conductivity. Although reports on the optical properties are available, few reports exist about the physical properties of intermediate-to-high Mg doping in GaAs nanowires grown by molecular beam epitaxy (MBE on GaAs(111B and Si(111 substrates. In this work, we address this topic and present further understanding on the fundamental aspects. As the Mg doping was increased, structural and optical investigations revealed: i a lower influence of the polytypic nature of the GaAs nanowires on their electronic structure; ii a considerable reduction of the density of vertical nanowires, which is almost null for growth on Si(111; iii the occurrence of a higher WZ phase fraction, in particular for growth on Si(111; iv an increase of the activation energy to release the less bound carrier in the radiative state from nanowires grown on GaAs(111B; and v a higher influence of defects on the activation of nonradiative de-excitation channels in the case of nanowires only grown on Si(111. Back-gate field effect transistors were fabricated with individual nanowires and the p-type electrical conductivity was measured with free hole concentration ranging from 2.7 × 1016 cm−3 to 1.4 × 1017 cm−3. The estimated electrical mobility was in the range ≈0.3–39 cm2/Vs and the dominant scattering mechanism is ascribed to the WZ/ZB interfaces. Electrical and optical measurements showed a lower influence of the polytypic structure of the nanowires on their electronic structure. The involvement of Mg in one of the radiative transitions observed for growth on the Si(111 substrate is suggested.

Stabilization of Fermi level via electronic excitation in Sn doped CdO thin films

Science.gov (United States)

Das, Arkaprava; Singh, Fouran

2018-04-01

Pure and Sn doped CdO sol-gel derived thin films were deposited on corning glass substrate and further irradiated by swift heavy ion (SHI) (Ag and O) with fluence upto 3×1013 ions/cm2. The observed tensile stress from X-ray diffraction pattern at higher fluence for Ag ions can be corroborated to the imbrications of cylindrical tracks due to multiple impacts. The anomalous band gap enhancement after irradiation may be attributed to the consolidated effect of Burstein-Moss shift (BMS) and impurity induced virtual gap states (ViGs). At higher excitation density as Fermi stabilization level (EFS) tends to coincide with charge neutrality level (CNL), band gap enhancement saturates as further creation of additional defects inside the lattice becomes unsustainable. Raman spectroscopy divulges an intensity enhancement of 478 cm-1 LO phonon mode with Sn doping and irradiation induces further asymmetric peak broadening due to damage and disordering inside the lattice. However for 3% Sn doped thin film irradiated with Ag ions having 3×1013 fluence shows a drastic change in structural properties and reduction in band gap which might be attributed to the generation of localized energy levels between conduction and valance band due to high density of defects.

Comparison of the Thermal Degradation of Heavily Nb-Doped and Normal PZT Thin Films.

Science.gov (United States)

Yang, Jeong-Suong; Kang, YunSung; Kang, Inyoung; Lim, SeungMo; Shin, Seung-Joo; Lee, JungWon; Hur, Kang Heon

2017-03-01

The degradation of niobium-doped lead zirconate titanate (PZT) and two types of PZT thin films were investigated. Undoped PZT, two-step PZT, and heavily Nb-doped PZT (PNZT) around the morphotropic phase boundary were in situ deposited under optimum condition by RF-magnetron sputtering. All 2- [Formula: see text]-thick films had dense perovskite columnar grain structure and self-polarized (100) dominant orientation. PZT thin films were deposited on Pt/TiO x bottom electrode on Si wafer, and PNZT thin film was on Ir/TiW electrode with the help of orientation control. Sputtered PZT films formed on microelectromechanical system (MEMS) gyroscope and the degradation rates were compared at different temperatures. PNZT showed the best resistance to the thermal degradation, followed by two-step PZT. To clarify the effect of oxygen vacancies on the degradation of the film at high temperature, photoluminescence measurement was conducted, which confirmed that oxygen vacancy rate was the lowest in heavy PNZT. Nb-doping PZT thin films suppressed the oxygen deficit and made high imprint with self-polarization. This defect distribution and high internal field allowed PNZT thin film to make the piezoelectric sensors more stable and reliable at high temperature, such as reflow process of MEMS packaging.

Synergistic effect of non-covalent interaction in colloidal nematic liquid crystal doped with magnetic functionalized single-walled carbon nanotubes

Science.gov (United States)

Dalir, Nima; Javadian, Soheila

2018-03-01

Single-walled carbon nanotubes (SWCNTs), CNT@Fe3O4, and Fe3O4 nanocomposites were doped to eutectic uniaxial nematic liquid crystal (NLC's) (E5CN7) to improve physiochemical properties such as phase transition temperature, activation energy (Ea), dielectric anisotropy, and electro-optical properties. The thermal study of nematic phase shows a decrease in the nematic to isotropic phase transition temperature as CNT is doped. However, higher doping concentration of CNTs leads to the further increase in transition temperature. The anchoring effect or π-π interaction plays a key role in N-I phase transition. The functionalization of SWCNTs with Fe3O4 diminishes the CNT aggregation while the magnetic susceptibility is increased. The functionalized CNT doping to NLC's decrease significantly the phase transition temperature compared to doping of non-functionalized CNTs. Attractive interaction between guest and host molecules by magnetic and geometry effect increased the enthalpy and entropy of phase transition in the SWCNT@Fe3O4 sample compared to non-functionalized CNT doped system. Also, the Ea values are decreased as SWCNT@Fe3O4 is doped to pure E5CN7. The difference of N-I phase transition temperature was observed in Fe3O4 and CNT@Fe3O4 compared to SWCNT doped systems. Finally, dielectric anisotropy was increased in the doped system compared to pure NLC.

Effects of (Al,Ge) double doping on the thermoelectric properties of higher manganese silicides

Energy Technology Data Exchange (ETDEWEB)

Chen, Xi; Salta, Daniel; Zhang, Libin [Materials Science and Engineering Program, Texas Materials Institute, The University of Texas at Austin, Austin, Texas 78712 (United States); Weathers, Annie [Department of Mechanical Engineering, The University of Texas at Austin, Austin, Texas 78712 (United States); Zhou, Jianshi; Goodenough, John B.; Shi, Li [Materials Science and Engineering Program, Texas Materials Institute, The University of Texas at Austin, Austin, Texas 78712 (United States); Department of Mechanical Engineering, The University of Texas at Austin, Austin, Texas 78712 (United States)

2013-11-07

Experiments and analysis have been carried out to investigate the effects of Al and (Al,Ge) doping on the microstructure and thermoelectric properties of polycrystalline higher manganese silicide (HMS) samples, which were prepared by solid-state reaction, ball milling, and followed by spark plasma sintering. It has been found that Al doping effectively increases the hole concentration, which leads to an increase in the electrical conductivity and power factor. By introducing the second dopant Ge into Al-doped HMS, the electrical conductivity is increased, and the Seebeck coefficient is decreased as a result of further increased hole concentration. The peak power factor is found to occur at a hole concentration between 1.8 × 10{sup 21} and 2.2 × 10{sup 21} cm{sup −3} measured at room temperature. The (Al,Ge)-doped HMS samples show lower power factors owing to their higher hole concentrations. The mobility of Mn(Al{sub 0.0035}Ge{sub y}Si{sub 0.9965-y}){sub 1.8} with y = 0.035 varies approximately as T{sup −3/2} above 200 K, suggesting acoustic phonon scattering is the dominant scattering mechanism. The thermal conductivity of HMS does not change appreciably by Al or (Al,Ge) doping. The maximum ZT of (Al,Ge)-doped HMS is 0.57 at 823 K, which is similar to the highest value found in the Al-doped HMS samples. The ZT values were reduced in the Mn(Al{sub 0.0035}Ge{sub y}Si{sub 0.9965-y}){sub 1.8} samples with high Ge concentration of y = 0.025 and 0.035, because of reduced power factor. In addition, a two-band model was employed to show that the hole contribution to the thermal conductivity dominates the bipolar and electron contributions for all samples from 300 to 823 K and accounts for about 12% of the total thermal conductivity at about 800 K.

Effects of (Al,Ge) double doping on the thermoelectric properties of higher manganese silicides

International Nuclear Information System (INIS)

Chen, Xi; Salta, Daniel; Zhang, Libin; Weathers, Annie; Zhou, Jianshi; Goodenough, John B.; Shi, Li

2013-01-01

Experiments and analysis have been carried out to investigate the effects of Al and (Al,Ge) doping on the microstructure and thermoelectric properties of polycrystalline higher manganese silicide (HMS) samples, which were prepared by solid-state reaction, ball milling, and followed by spark plasma sintering. It has been found that Al doping effectively increases the hole concentration, which leads to an increase in the electrical conductivity and power factor. By introducing the second dopant Ge into Al-doped HMS, the electrical conductivity is increased, and the Seebeck coefficient is decreased as a result of further increased hole concentration. The peak power factor is found to occur at a hole concentration between 1.8 × 10 21 and 2.2 × 10 21  cm −3 measured at room temperature. The (Al,Ge)-doped HMS samples show lower power factors owing to their higher hole concentrations. The mobility of Mn(Al 0.0035 Ge y Si 0.9965-y ) 1.8 with y = 0.035 varies approximately as T −3/2 above 200 K, suggesting acoustic phonon scattering is the dominant scattering mechanism. The thermal conductivity of HMS does not change appreciably by Al or (Al,Ge) doping. The maximum ZT of (Al,Ge)-doped HMS is 0.57 at 823 K, which is similar to the highest value found in the Al-doped HMS samples. The ZT values were reduced in the Mn(Al 0.0035 Ge y Si 0.9965-y ) 1.8 samples with high Ge concentration of y = 0.025 and 0.035, because of reduced power factor. In addition, a two-band model was employed to show that the hole contribution to the thermal conductivity dominates the bipolar and electron contributions for all samples from 300 to 823 K and accounts for about 12% of the total thermal conductivity at about 800 K

Electronic structure of p type Delta doped systems

International Nuclear Information System (INIS)

Gaggero S, L.M.; Perez A, R.

1998-01-01

We summarize of the results obtained for the electronic structure of quantum wells that consist in an atomic layer doped with impurities of p type. The calculations are made within the frame worth of the wrapper function approach to independent bands and with potentials of Hartree. We study the cases reported experimentally (Be in GaAs and B in Si). We present the levels of energy, the wave functions and the rate of the electronic population between the different subbands, as well as the dependence of these magnitudes with the density of impurities in the layer. The participation of the bans of heavy holes is analysed, light and split-off band in the total electronic population. The effect of the temperature is discussed and we give a possible qualitative explanation of the experimental optical properties. (Author)

Electronic structures and three-dimensional effects of boron-doped carbon nanotubes

International Nuclear Information System (INIS)

Koretsune, Takashi; Saito, Susumu

2008-01-01

We study boron-doped carbon nanotubes by first-principles methods based on the density functional theory. To discuss the possibility of superconductivity, we calculate the electronic band structure and the density of states (DOS) of boron-doped (10,0) nanotubes by changing the boron density. It is found that the Fermi level density of states D(ε F ) increases upon lowering the boron density. This can be understood in terms of the rigid band picture where the one-dimensional van Hove singularity lies at the edge of the valence band in the DOS of the pristine nanotube. The effect of three-dimensionality is also considered by performing the calculations for bundled (10,0) nanotubes and boron-doped double-walled carbon nanotubes (10,0)/(19,0). From the calculation of the bundled nanotubes, it is found that interwall dispersion is sufficiently large to broaden the peaks of the van Hove singularity in the DOS. Thus, to achieve the high D(ε F ) using the bundle of nanotubes with single chirality, we should take into account the distance from each nanotube. In the case of double-walled carbon nanotubes, we find that the holes introduced to the inner tube by boron doping spread also on the outer tube, while the band structure of each tube remains almost unchanged.

Effect of additionally introduced Zn and Eu dopants on the photoluminescence spectra of Er-Doped GaN crystals

International Nuclear Information System (INIS)

Mezdrogina, M. M.; Krivolapchuk, V. V.; Petrov, V. N.; Rodin, S. N.; Cherenkov, A. V.

2006-01-01

It is shown that the effect of dopants on the photoluminescence spectrum depends on the conductivity type of the initial GaN crystals. Sensitization of emission is observed in wurtzite p-GaN crystals doped with Er. The same effect was previously observed in such crystals doped with Eu and Zn. In n-type GaN crystals sequentially doped with Eu, Zn, and Er, emission is observed in the visible (λ = 360-440 and 530-560 nm) and IR (λ = 1.54 μm) spectral regions

Effect of doping concentration on the structural, morphological, optical and electrical properties of Mn-doped CdO thin films

Directory of Open Access Journals (Sweden)

Manjula N.

2015-12-01

Full Text Available Thin films of manganese-doped cadmium oxide (CdO:Mn with different Mn-doping levels (0, 1, 2, 3 and 4 at.% were deposited on glass substrates by employing an inexpensive, simplified spray technique using a perfume atomizer at 375 °C. The influence of Mn incorporation on the structural, morphological, optical and electrical properties of CdO films has been studied. All the films exhibit cubic crystal structure with a (1 1 1 preferential orientation. Mn-doping causes a slight shift of the (1 1 1 diffraction peak towards higher angle. The crystallite size of the films is found to decrease from 34.63 nm to 17.68 nm with an increase in Mn doping concentration. The CdO:Mn film coated with 1 at.% Mn exhibit a high transparency of nearly 90 % which decreases for higher doping concentration. The optical band gap decreases with an increase in Mn doping concentration. All the films have electrical resistivity of the order of 10−4 Ω·cm.

Carbon doped GaN buffer layer using propane for high electron mobility transistor applications: Growth and device results

Energy Technology Data Exchange (ETDEWEB)

Li, X.; Nilsson, D.; Danielsson, Ö.; Pedersen, H.; Janzén, E.; Forsberg, U. [Department of Physics, Chemistry, and Biology (IFM), Linköping University, Linköping 58183 (Sweden); Bergsten, J.; Rorsman, N. [Microwave Electronics Laboratory, Department of Microtechnology and Nanoscience, Chalmers University of Technology, Göteborg 41296 (Sweden)

2015-12-28

The creation of a semi insulating (SI) buffer layer in AlGaN/GaN High Electron Mobility Transistor (HEMT) devices is crucial for preventing a current path beneath the two-dimensional electron gas (2DEG). In this investigation, we evaluate the use of a gaseous carbon gas precursor, propane, for creating a SI GaN buffer layer in a HEMT structure. The carbon doped profile, using propane gas, is a two stepped profile with a high carbon doping (1.5 × 10{sup 18 }cm{sup −3}) epitaxial layer closest to the substrate and a lower doped layer (3 × 10{sup 16 }cm{sup −3}) closest to the 2DEG channel. Secondary Ion Mass Spectrometry measurement shows a uniform incorporation versus depth, and no memory effect from carbon doping can be seen. The high carbon doping (1.5 × 10{sup 18 }cm{sup −3}) does not influence the surface morphology, and a roughness root-mean-square value of 0.43 nm is obtained from Atomic Force Microscopy. High resolution X-ray diffraction measurements show very sharp peaks and no structural degradation can be seen related to the heavy carbon doped layer. HEMTs are fabricated and show an extremely low drain induced barrier lowering value of 0.1 mV/V, demonstrating an excellent buffer isolation. The carbon doped GaN buffer layer using propane gas is compared to samples using carbon from the trimethylgallium molecule, showing equally low leakage currents, demonstrating the capability of growing highly resistive buffer layers using a gaseous carbon source.

Selected bibliography on deuterium isotope effects and heavy water

International Nuclear Information System (INIS)

Dave, S.M.; Donde, M.M.

1983-01-01

In recent years, there has been a great deal of interest in using deuterium and heavy water not only in nuclear industry but also in various fields of basic as well as applied research in physics, chemistry and biology. As a result, the literature is being enriched with a large number of research papers and technical reports published each year. Thus, to enable the scientists to have an easy reference to these works, an endeavour has been made in this selected bibliography, to enlist the publications related to these fields. Since the interest is concerned mainly with heavy water production processes, deuterium isotope effects etc., several aspects (e.g. nuclear) of deuterium have not been covered here. The material in this bibliography which cites 2388 references has been classified under six broad headings, viz. (1) Production of heavy water, (2) Study of deuterium isotope effects, (3) Analysis and Properties of heavy water, (4) Laser Separation of deuterium, (5) Isotopic exchange reactions, and (6) Miscellaneous. The sources of information used for this compilation are chemical abstracts, nuclear science abstracts, INIS Atomindex and also some scattered search through journals and reports available in the B.A.R.C. library. However, in spite of sincere attempts for a wide coverage, no claim is being made towards the exhaustiveness of this bibliography. (author)

DFT study of stabilization effects on N-doped graphene for ORR catalysis

DEFF Research Database (Denmark)

Reda, Mateusz; Hansen, Heine Anton; Vegge, Tejs

2018-01-01

Noble metal free catalysts, such as N-doped graphene, have drawn a lot of attention as a promising replacement for platinum in low temperature fuel cells. Computational prediction of catalytic activity requires accurate description of the oxygen reduction reaction (ORR) intermediates adsorption...... energies. Two stabilizing effects, immanently present in experimental ORR setups with basal plane N-doped graphene catalyst, are studied systematically by means of density functional theory. Distant nitrogen with no adsorbates on neighboring carbon atoms selectively stabilizes *O and *O2 adsorbates. Water...... solvation stabilizes all ORR intermediates, having a greater impact on *O and *O2, than on *OH and *OOH, in contrast to metal and oxide catalysts. Synergistic stabilization of *O caused by both effects reaches remarkably a high value of 1.5 eV for nitrogen concentrations above 4.2% N. Such a strong effect...

Doping effects in high-Tc superconductors

International Nuclear Information System (INIS)

Hessel Andersen, N.

1996-11-01

The purpose of the project has been to study how the superconducting and magnetic properties of the high temperature superconductors change as function of oxygen stoichiometry and cation doping. The primary system of investigation has been YBa 2 Cu 3 O 6+x , which has been studied as function of oxygen stoichiometry, 0 2 planes, that is necessary for superconductivity, is strongly depending on structural ordering. The static properties and the kinetics of the structural ordering process have been studied experimentally by neutron and high energy synchrotron x-ray diffraction, by Raman scattering, and by computer simulation technique. Not only the oxygen stoichiometry but also the cation doping has been shown to influence the magnetic phases, in some cases in an unexpected manner. Thus, by neutron diffraction experiments it has been shown that doping with non-magnetic Al gives rise to a new magnetic phase. A theoretical model, has been developed. The magnetic phases of the Cu and Nd ordering in NdBa 2 Cu 3 O 6+x , and of the Cu and Pr ordering in PrBa 2 Cu 3 O 6+x have been studied by neutron diffraction with the main purpose of understanding why PrBa 2 Cu 3 O 6+x is magnetic and non-superconducting for all oxygen stoichiometries. In NdBa:2Cu 3 O 6+x studies of the magnetic flux lattice have been carried out by Small Angle Neutron Scattering. Additional structural studies of the superconducting and magnetic phases of related materials, of RENi 2 B 2 C (RE = rare earth), and of oxidized and cation doped materials based on La 2 CuO 4+δ have been carried out. Methods for structural studies and analyses, and equipment for electrical and magnetic characterization have been developed. (EG) 5 tabs., 46 ills., 35 refs

Negative differential resistance in BN co-doped coaxial carbon nanotube field effect transistor

Science.gov (United States)

Shah, Khurshed A.; Parvaiz, M. Shunaid

2016-12-01

The CNTFETs are the most promising advanced alternatives to the conventional FETs due to their outstanding structure and electrical properties. In this paper, we report the I-V characteristics of zig-zag (4, 0) semiconducting coaxial carbon nanotube field effect transistor (CNTFET) using the non-equilibrium Green's function formalism. The CNTFET is co-doped with two, four and six boron-nitrogen (BN) atoms separately near the electrodes using the substitutional doping method and the I-V characteristics were calculated for each model using Atomistic Tool Kit software (version 13.8.1) and its virtual interface. The results reveal that all models show negative differential resistance (NDR) behavior with the maximum peak to valley current ratio (PVCR) of 3.2 at 300 K for the four atom doped model. The NDR behavior is due to the band to band tunneling (BTBT) in semiconducting CNTFET and decreases as the doping in the channel increases. The results are beneficial for next generation designing of nano devices and their potential applications in electronic industry.

Aluminum and carbon substitution in MgB2. Electron doping and scattering effects

International Nuclear Information System (INIS)

Samuely, P.; Szabo, P.; Pribulova, Z.; Angst, M.; Bud'ko, S.L.; Canfield, P.C.; Klein, T.; Lyard, L.; Marcus, J.; Marcenat, C.; Kang, B.W.; Kim, H.-J.; Lee, H.-S.; Lee, H.-K.; Lee, S.I.

2007-01-01

The point-contact spectroscopy is used to address the evolution of two superconducting energy gaps in the Al- and C-doped magnesium diboride polycrystals and single crystals with T c 's from 39 to 22 K prepared by different techniques. The obtained evolution of two gaps does not show any anomalous behavior but can be consistently described by the combination of the (prevailing) band filling effect and a (minor) increased interband scattering as proposed by Kortus et al. [Kortus et al., Phys. Rev. Lett. 94 (2005) 027002]. The approaching of two gaps is stronger in the Al-doped systems but interband scattering is still not large enough to merge two gaps. The full merging can expected only for higher dopings with T c 's below 10-15 K. In-magnetic-field measurements are used to analyze the intraband scatterings introduced by these two substitutions. It is shown that the carbon doping introduces significant disorder mainly by decreasing the diffusion coefficient in the π band while the Al substitution leaves the samples in the clean limit

Effective meson lagrangian with chiral and heavy quark symmetries from quark flavor dynamics

International Nuclear Information System (INIS)

Ebert, D.; Feldmann, T.; Friedrich, R.; Reinhardt, H.

1994-06-01

By bosonization of an extended NJL model we derive an effective meson theory which describes the interplay between chiral symmetry and heavy quark dynamics. This effective theory is worked out in the low-energy regime using the gradient expansion. The resulting effective lagrangian describes strong and weak interactions of heavy B and D mesons with pseudoscalar Goldstone bosons and light vector and axial-vector mesons. Heavy meson weak decay constants, coupling constants and the Isgur-Wise function are predicted in terms of the model parameters partially fixed from the light quark sector. Explicit SU(3) F symmetry breaking effects are estimated and, if possible, confronted with experiment. (orig.)

The effect of boron doping on crystal structure, magnetic properties and magnetocaloric effect of DyCo{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Wang, C.L., E-mail: wangchaolun2004@163.com [The Ames Laboratory U.S. Department of Energy, Iowa State University, Ames, IA 50011-3020 (United States); School of Materials Science and Engineering, University of Science and Technology of Beijing, Beijing 100083 (China); Liu, J. [The Ames Laboratory U.S. Department of Energy, Iowa State University, Ames, IA 50011-3020 (United States); Department of Materials Science and Engineering, Iowa State University, Ames, IA 50011-2300 (United States); Mudryk, Y.; Gschneidner, K.A. [The Ames Laboratory U.S. Department of Energy, Iowa State University, Ames, IA 50011-3020 (United States); Long, Y. [School of Materials Science and Engineering, University of Science and Technology of Beijing, Beijing 100083 (China); Pecharsky, V.K. [The Ames Laboratory U.S. Department of Energy, Iowa State University, Ames, IA 50011-3020 (United States); Department of Materials Science and Engineering, Iowa State University, Ames, IA 50011-2300 (United States)

2016-05-01

The magnetic properties and magnetic entropy changes of DyCo{sub 2}B{sub x} (x=0, 0.05, 0.1, and 0.2) alloys were investigated. The Curie temperature (T{sub C}) increases with increasing B concentration. The frequency dependence of ac magnetic susceptibility of DyCo{sub 2} caused by the narrow domain wall pinning effect is depressed by B doping, but the coercivity and the magnetic viscosity are prominently increased in the B doped alloys. The magnetic transition nature of DyCo{sub 2}B{sub x} changes from the first-order to the second-order with increasing x, which leads to the decrease of the maximum magnetic entropy change. However, the relative cooling power (RCP) of DyCo{sub 2} and the B doped alloys remains nearly constant. - Highlights: • The discrepancy between the ZFC and FCC curves of DyCo{sub 2}B{sub x} is enhanced in the B doped samples, while the frequency dependence of the ac magnetic susceptibility is depressed. • The Curie temperature, coercivity and viscosity of DyCo{sub 2}B{sub x} are increased by B doping • The magnetic transition nature of the B doped samples is changed from first order to second order, leading to the decrease of magnetic entropy change. However, the relative cooling power of DyCo{sub 2}B{sub 0.05} is increased about 18%.

The effect of meson wave function on heavy-quark fragmentation function

Energy Technology Data Exchange (ETDEWEB)

Moosavi Nejad, S.M. [Yazd University, Faculty of Physics (Iran, Islamic Republic of); Institute for Research in Fundamental Sciences (IPM), School of Particles and Accelerators, Tehran (Iran, Islamic Republic of)

2016-05-15

We calculate the process-independent fragmentation functions (FFs) for a heavy quark to fragment into heavy mesons considering the effects of meson wave function. In all previous works, where the FFs of heavy mesons or heavy baryons were calculated, a delta function form was approximated for the wave function of hadrons. Here, for the first time, we consider a typical mesonic wave function which is different from the delta function and is the nonrelativistic limit of the solution of Bethe-Salpeter equation with the QCD kernel. We present our numerical results for the heavy FFs and show how the proposed wave function improves the previous results. As an example, we focus on the fragmentation function for c-quark to split into S-wave D{sup 0} -meson and compare our results with experimental data from BELLE and CLEO. (orig.)

Characterization of solution processed, p-doped films using hole-only devices and organic field-effect transistors

Energy Technology Data Exchange (ETDEWEB)

Swensen, James S.; Wang, Liang (Frank); Rainbolt, James E.; Koech, Phillip K.; Polikarpov, Evgueni; Gaspar, Daniel J.; Padmaperuma, Asanga B.

2012-12-01

We report a solution-processed approach for a p-type doped hole transport layer in organic light emitting devices (OLEDs). UV-vis-NIR absorption spectra identified the charge transfer between the donor and acceptor in the solution processed doped films. Single carrier device and field-effect transistor were utilized as test vehicles to study the charge transport property and extract important parameters such as bulk mobile carrier concentration and mobility. OLEDs with p-type doped hole transport layer showed significant improvement in power efficiency up to 30% at the optimal doping ratio. This approach has the great potential to reduce the power consumption for OLED solid state lighting while lowering the cost and boosting the throughput of its manufacturing.

Effect of amino acid doping on the growth and ferroelectric properties of triglycine sulphate single crystals

International Nuclear Information System (INIS)

Raghavan, C.M.; Sankar, R.; Mohan Kumar, R.; Jayavel, R.

2008-01-01

Effect of amino acids (L-leucine and isoleucine) doping on the growth aspects and ferroelectric properties of triglycine sulphate crystals has been studied. Pure and doped crystals were grown from aqueous solution by low temperature solution growth technique. The cell parameter values were found to significantly vary for doped crystals. Fourier transform infrared analysis confirmed the presence of functional groups in the grown crystal. Morphology study reveals that amino acid doping induces faster growth rate along b-direction leading to a wide b-plane and hence suitable for pyroelectric detector applications. Ferroelectric domain structure has been studied by atomic force microscopy and hysteresis measurements reveal an increase of coercive field due to the formation of single domain pattern

Effect of nitrogen doping on the thermal conductivity of GeTe thin films

Energy Technology Data Exchange (ETDEWEB)

Fallica, Roberto; Longo, Massimo; Wiemer, Claudia [Laboratorio MDM, IMM-CNR, Agrate Brianza (Italy); Varesi, Enrico; Fumagalli, Luca; Spadoni, Simona [Micron Semiconductor Italia, Agrate Brianza (Italy)

2013-12-15

The 3{omega} method was employed to determine the effect of nitrogen doping (5 at.%) on the thermal conductivity of sputtered thin films of stoichiometric GeTe (a material of interest for phase change memories). It was found that nitrogen doping has a detrimental effect on the thermal conductivity of GeTe in both phases, but less markedly in the amorphous (-25%) than in the crystalline one (-40%). On the opposite, no effect could be detected on the measured thermal boundary resistance between these films and SiO{sub 2}, within the experimental error. Our results agree with those obtained by molecular dynamic simulation of amorphous GeTe. (copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Heavy quark fragmentation into polarized quarkonium in the heavy quark effective theory

International Nuclear Information System (INIS)

Martynenko, A.P.; Saleev, V.A.

1996-01-01

Fragmentation of b-antiquark into polarized B* c -mesons is investigated within the framework of effective theory of heavy quarks. Functions of b fragmentation into longitudinally polarized and transversely polarized S-wave states of b c are calculated with an exact regard tot he first order corrections by 1/m b . Agreement of the results obtained with the corresponding calculations, performed in the quantum chromodynamics, is shown. 17 refs.; 2 figs

Heavy Metal Polluted Soils: Effect on Plants and Bioremediation Methods

Directory of Open Access Journals (Sweden)

G. U. Chibuike

2014-01-01

Full Text Available Soils polluted with heavy metals have become common across the globe due to increase in geologic and anthropogenic activities. Plants growing on these soils show a reduction in growth, performance, and yield. Bioremediation is an effective method of treating heavy metal polluted soils. It is a widely accepted method that is mostly carried out in situ; hence it is suitable for the establishment/reestablishment of crops on treated soils. Microorganisms and plants employ different mechanisms for the bioremediation of polluted soils. Using plants for the treatment of polluted soils is a more common approach in the bioremediation of heavy metal polluted soils. Combining both microorganisms and plants is an approach to bioremediation that ensures a more efficient clean-up of heavy metal polluted soils. However, success of this approach largely depends on the species of organisms involved in the process.

Effect of Mo and Ti doping concentration on the structural and optical properties of ZnS nanoparticles

Science.gov (United States)

Naz, Hina; Ali, Rai Nauman; Zhu, Xingqun; Xiang, Bin

2018-06-01

In this paper, we report the effect of single phase Mo and Ti doping concentration on the structural and optical properties of the ZnS nanoparticles. The structural and optical properties of the as-synthesized samples have been examined by x-ray diffraction, transmission electron microscopy (TEM), UV-visible near infrared absorption spectroscopy and x-ray photoelectron spectroscopy. TEM characterizations reveal a variation in the doped ZnS nanoparticle size distribution by utilizing different dopants of Mo and Ti. In absorption spectra, a clear red shift of 14 nm is observed with increasing Mo concentration as compared to pure ZnS nanoparticles, while by increasing Ti doping concentration, blue shift of 14 nm is obtained. Moreover, it demonstrates that the value of energy band gap decreases from 4.03 eV to 3.89 eV in case of Mo doping. However, the value of energy band gap have shown a remarkable increase from 4.11 eV to 4.27 eV with increasing Ti doping concentration. Our results provide a new pathway to understand the effect of Mo and Ti doping concentrations on the structural and optical properties of ZnS nanoparticles as it could be the key to tune the properties for future optoelectronic devices.

Effect of doping on electronic properties of double-walled carbon and boron nitride hetero-nanotubes

International Nuclear Information System (INIS)

Majidi, R.; Ghafoori Tabrizi, K.; Jalili, S.

2009-01-01

The effect of boron nitride (BN) doping on electronic properties of armchair double-walled carbon and hetero-nanotubes is studied using ab initio molecular dynamics method. The armchair double-walled hetero-nanotubes are predicted to be semiconductor and their electronic structures depend strongly on the electronic properties of the single-walled carbon nanotube. It is found that electronic structures of BN-doped double-walled hetero-nanotubes are intermediate between those of double-walled boron nitride nanotubes and double-walled carbon and boron nitride hetero-nanotubes. Increasing the amount of doping leads to a stronger intertube interaction and also increases the energy gap.

Effect of doping on electronic properties of double-walled carbon and boron nitride hetero-nanotubes

Energy Technology Data Exchange (ETDEWEB)

Majidi, R. [Department of Physics, Shahid Beheshti University, Evin, Tehran 19839-63113 (Iran, Islamic Republic of); Ghafoori Tabrizi, K., E-mail: K-TABRIZI@sbu.ac.i [Department of Physics, Shahid Beheshti University, Evin, Tehran 19839-63113 (Iran, Islamic Republic of); Jalili, S. [Department of Chemistry, K.N. Toosi University of Technology, Tehran 16315-1618 (Iran, Islamic Republic of)

2009-11-01

The effect of boron nitride (BN) doping on electronic properties of armchair double-walled carbon and hetero-nanotubes is studied using ab initio molecular dynamics method. The armchair double-walled hetero-nanotubes are predicted to be semiconductor and their electronic structures depend strongly on the electronic properties of the single-walled carbon nanotube. It is found that electronic structures of BN-doped double-walled hetero-nanotubes are intermediate between those of double-walled boron nitride nanotubes and double-walled carbon and boron nitride hetero-nanotubes. Increasing the amount of doping leads to a stronger intertube interaction and also increases the energy gap.

Positron Lifetimes in Pure and Doped Ice and in Water

DEFF Research Database (Denmark)

Eldrup, Morten Mostgaard; Mogensen, O.; Trumpy, Georg

1972-01-01

for the other components show a complex behavior. The spectra for mono- and polycrystalline light ice and for polycrystalline heavy ice are identical. For water long lifetime components attributed to ortho-Ps are 1.86 nsec, 27% for H2O and 2.01 nsec, 22% for D2O. Theoretical explanations are suggested. Fast......Positron lifetime spectra were measured in mono- and polycrystalline light ice, polycrystalline heavy ice, doped light ice, as well as in light and heavy water. All spectra were resolved into three components. At temperatures between −196° and −100°C the lifetimes and relative intensities...... of the spectra are found by heating above approximately −120°C. Measurements on a number of fast frozen aqueous solutions of acids, bases, and salts are reported, none of them showing as strong influence on the ortho-Ps lifetime as HF. ©1972 The American Institute of Physics...

Effects of ultraviolet light on B-doped CdS thin films prepared by spray pyrolysis method using perfume atomizer

Science.gov (United States)

Novruzov, V. D.; Keskenler, E. F.; Tomakin, M.; Kahraman, S.; Gorur, O.

2013-09-01

Boron doped CdS thin films were deposited by spray pyrolysis method using perfume atomizer. The effects of ultraviolet light on the structural, optical and electrical properties of B-doped CdS thin films were investigated as a function of dopant concentration (B/Cd). X-ray diffraction studies showed that all samples were polycrystalline nature with hexagonal structure. It was determined that the preferred orientation of non-illuminated samples changes from (1 0 1) to (0 0 2) with B concentration. The c lattice constant of films decreases from 6.810 Å to 6.661 Å with boron doping. The XRD peak intensity increased with the illumination for almost all the samples. The lattice parameters of B-doped samples remained nearly constant after illumination. It was found that the optical transmittance, photoluminescence spectra, resistivity and carrier concentration of the B-doped samples are stable after the illumination with UV light. Also the effects of UV light on B-doped CdS/Cu2S solar cell were investigated and it was determined that photoelectrical parameters of B-doped solar cell were more durable against the UV light.

Effects of ultraviolet light on B-doped CdS thin films prepared by spray pyrolysis method using perfume atomizer

Energy Technology Data Exchange (ETDEWEB)

Novruzov, V.D. [Department of Physics, Recep Tayyip Erdogan University, Rize (Turkey); Keskenler, E.F., E-mail: keskenler@gmail.com [Department of Nanotechnology Engineering, Recep Tayyip Erdogan University, Rize (Turkey); Tomakin, M. [Department of Physics, Recep Tayyip Erdogan University, Rize (Turkey); Kahraman, S. [Department of Physics, Mustafa Kemal University, Hatay (Turkey); Gorur, O. [Department of Physics, Abant Izzet Baysal University, Bolu (Turkey)

2013-09-01

Boron doped CdS thin films were deposited by spray pyrolysis method using perfume atomizer. The effects of ultraviolet light on the structural, optical and electrical properties of B-doped CdS thin films were investigated as a function of dopant concentration (B/Cd). X-ray diffraction studies showed that all samples were polycrystalline nature with hexagonal structure. It was determined that the preferred orientation of non-illuminated samples changes from (1 0 1) to (0 0 2) with B concentration. The c lattice constant of films decreases from 6.810 Å to 6.661 Å with boron doping. The XRD peak intensity increased with the illumination for almost all the samples. The lattice parameters of B-doped samples remained nearly constant after illumination. It was found that the optical transmittance, photoluminescence spectra, resistivity and carrier concentration of the B-doped samples are stable after the illumination with UV light. Also the effects of UV light on B-doped CdS/Cu{sub 2}S solar cell were investigated and it was determined that photoelectrical parameters of B-doped solar cell were more durable against the UV light.

Atomistic modeling of La3+ doping segregation effect on nanocrystalline yttria-stabilized zirconia.

Science.gov (United States)

Zhang, Shenli; Sha, Haoyan; Castro, Ricardo H R; Faller, Roland

2018-05-16

The effect of La3+ doping on the structure and ionic conductivity change in nanocrystalline yttria-stabilized zirconia (YSZ) was studied using a combination of Monte Carlo and molecular dynamics simulations. The simulation revealed the segregation of La3+ at eight tilt grain boundary (GB) structures and predicted an average grain boundary (GB) energy decrease of 0.25 J m-2, which is close to the experimental values reported in the literature. Cation stabilization was found to be the main reason for the GB energy decrease, and energy fluctuations near the grain boundary are smoothed out with La3+ segregation. Both dynamic and energetic analysis on the Σ13(510)/[001] GB structure revealed La3+ doping hinders O2- diffusion in the GB region, where the diffusion coefficient monotonically decreases with increasing La3+ doping concentration. The effect was attributed to the increase in the site-dependent migration barriers for O2- hopping caused by segregated La3+, which also leads to anisotropic diffusion at the GB.

Modulation-doped β-(Al0.2Ga0.8)2O3/Ga2O3 field-effect transistor

Science.gov (United States)

Krishnamoorthy, Sriram; Xia, Zhanbo; Joishi, Chandan; Zhang, Yuewei; McGlone, Joe; Johnson, Jared; Brenner, Mark; Arehart, Aaron R.; Hwang, Jinwoo; Lodha, Saurabh; Rajan, Siddharth

2017-07-01

Modulation-doped heterostructures are a key enabler for realizing high mobility and better scaling properties for high performance transistors. We report the realization of a modulation-doped two-dimensional electron gas (2DEG) at the β-(Al0.2Ga0.8)2O3/Ga2O3 heterojunction by silicon delta doping. The formation of a 2DEG was confirmed using capacitance voltage measurements. A modulation-doped 2DEG channel was used to realize a modulation-doped field-effect transistor. The demonstration of modulation doping in the β-(Al0.2Ga0.8)2O3/Ga2O3 material system could enable heterojunction devices for high performance electronics.

Effect of carrier doping and external electric field on the optical properties of graphene quantum dots

Science.gov (United States)

Basak, Tista; Basak, Tushima

2018-02-01

In this paper, we demonstrate that the optical properties of finite-sized graphene quantum dots can be effectively controlled by doping it with different types of charge carriers (electron/hole). In addition, the role played by a suitably directed external electric field on the optical absorption of charge-doped graphene quantum dots have also been elucidated. The computations have been performed on diamond-shaped graphene quantum dot (DQD) within the framework of the Pariser-Parr-Pople (PPP) model Hamiltonian, which takes into account long-range Coulomb interactions. Our results reveal that the energy band-gap increases when the DQD is doped with holes while it decreases on doping it with electrons. Further, the optical absorption spectra of DQD exhibits red/blue-shift on doping with electrons/holes. Our computations also indicate that the application of external transverse electric field results in a substantial blue-shift of the optical spectrum for charge-doped DQD. However, it is observed that the influence of charge-doping is more prominent in tuning the optical properties of finite-sized graphene quantum dots as compared to externally applied electric field. Thus, tailoring the optical properties of finite-sized graphene quantum dots by manipulative doping with charge carriers and suitably aligned external electric field can greatly enhance its potential application in designing nano-photonic devices.

Biological effects of heavy particles

International Nuclear Information System (INIS)

Sabatier, L.; Martins, B.; Dutrillaux, B.

1991-01-01

The usual definitions of biological dose and biological dosimetry do not fit in case of particles with high linear energy transfer (LET). The dose corresponds to an average value which is not representative of the highly localized energy transfer due to heavy ions. Fortunately, up to now, a biological dosimetry following an exposure to high LET particles is necessary only for cosmonauts. In radiotherapy applications, one exactly knows the nature and energy of incident particle beams. The quality requirements for a good biodosimeter include reliable relation between dose and effect, weak sensitivity to individual variations, reliability and stability of acquired informations against the time delay between exposure and measurements. Nothing is better than the human lymphocyte to be used for measurements that fulfil these requirements. In the case of a manned spaceship, the irradiation dose corresponds to a wide range of radiation (protons, neutrons, heavy ions), and making a dosimetry as well as defining it are of current concern. As yet, there exist two possible definitions, which reduce the dose either to a proton or to a neutron equivalent one. However, such an approximation is not a faithful representation of the irradiation effects and in particular, the long-term effects may be quite different. In the future, it is reasonable to expect an evolution towards technics that enable identifying irradiated cells and quantifying precisely their radiation damage in order to reconstruct the spectrum of particles received by a given cosmonaut in a given time. Let us emphasize that the radiation hazards due to a short stay in space are quite minor, but in the case of a travel to Mars, they cannot be neglected [fr

The effect of Gd doping on the electrical and photoelectrical properties of Gd:ZnO/p-Si heterojunctions

Energy Technology Data Exchange (ETDEWEB)

Baturay, Silan [Department of Physics, Faculty of Science, Dicle University, 21280 Diyarbakir (Turkey); Ocak, Yusuf Selim, E-mail: yusufselim@gmail.com [Department of Science, Faculty of Education, Dicle University, 21280 Diyarbakir (Turkey); Science and Technology Application and Research Center, Dicle University, 21280 Diyarbakir (Turkey); Kaya, Derya [Department of Physics, Institute of Natural Applied Sciences, Dicle University, 21280 Diyarbakir (Turkey)

2015-10-05

Highlights: • Undoped and Gd doped ZnO thin films were deposited onto p-Si semiconductor. • The Gd:ZnO/p-Si heterojunctions were compared with undoped ZnO/p-Si heterojunction. • A strong effect of Gd doping on the performance of the devices were reported. - Abstract: Undoped ZnO thin films, as well as 1%, 3% and 5% Gd-doped ZnO films, were deposited on p-type Si using spin coating. The structural properties of these thin films were analysed using X-ray diffraction, and the current–voltage (I–V) and capacitance–voltage (C–V) characteristics of the Gd:ZnO/p-Si heterojunctions were compared with those of the undoped ZnO/p-Si heterojunctions. We found that Gd doping had a strong effect on the performance of the devices, and that the Gd:ZnO/p-Si heterojunctions formed with 1% Gd-doped ZnO were the most strongly rectifying, and had the highest barrier height and the lowest series resistance. Furthermore, the I–V measurements of the 1% Gd-doped ZnO/p-Si heterojunction exhibited the strongest response to light.

Effect of light Si doping on the properties of GaN

International Nuclear Information System (INIS)

Shang, Lin; Zhai, Guangmei; Jia, Zhigang; Mei, Fuhong; Lu, Taiping; Liu, Xuguang; Xu, Bingshe

2016-01-01

An obvious increase in electron mobility and yellow luminescence (YL) band intensity was found in light Si doping GaN. For a series of GaN samples with different doping concentration, the dislocation density is almost the same. It is inferred that the abrupt increase in mobility and YL intensity does not originate from the change of dislocation density. The mobility behavior is attributed to the screening of scattering by dislocation and increase of ionized impurity scattering with the increase of Si doping concentration. At lower doping level, the screening of dislocation scattering is dominant, which results in the increase in carrier mobility. At higher doping level, the increase in ionized impurity scattering leads to the decrease in carrier mobility. Higher mobility causes longer diffusion length of nonequilibrium carrier. More dislocations will participate in the recombination process which induces stronger YL intensity in light Si doping GaN.

Effects of Bi doping on dielectric and ferroelectric properties

Indian Academy of Sciences (India)

[Pb0.95(La1−Bi)0.05][Zr0.53Ti0.47]O3 (PLBZT) ferroelectric thin films have been synthesized on indium tin oxide (ITO)-coated glass by sol–gel processing. PLBZT thin films were annealed at a relatively low temperature of 550 °C in oxygen ambient. Effects of Bi doping on structure, dielectric and ferroelectric properties of ...

Raman and time resolved photoluminescence studies on the effect of temperature on disorder production in SHI irradiated N-doped 6H-SiC crystals

Energy Technology Data Exchange (ETDEWEB)

Sivaji, K., E-mail: sivaji.krishnan@yahoo.com [Materials Science Centre, Department of Nuclear Physics, University of Madras, Guindy Campus, Chennai 600025 (India); Viswanathan, E. [Materials Science Centre, Department of Nuclear Physics, University of Madras, Guindy Campus, Chennai 600025 (India); Selvakumar, S. [Materials Science Centre, Department of Nuclear Physics, University of Madras, Guindy Campus, Chennai 600025 (India); University of Tsukuba Tandem Accelerator Complex, University of Tsukuba, Tennodai 1-1-1, Ibaraki 305-8577 (Japan); Sankar, S. [Department of Physics, MIT Campus, Anna University, Chennai 600044 (India); Kanjilal, D. [Inter-University Accelerator Centre, Aruna Asaf Ali Marg, P.O. Box 10502, New Delhi 110067 (India)

2014-02-25

Highlights: • N doped SiC were irradiated with 150 MeV Ag{sup 12+} (1 × 10{sup 12} to 5 × 10{sup 13} ions/cm{sup 2}). • Local disorder are analyzed by studying the LO Raman mode of the irradiated sample. • The TRPL studies provided evidence of the formation of radiative centers at 80 K. -- Abstract: In this report, the effect of disorder accumulation in Swift Heavy Ion (SHI) irradiated 6H-SiC is distinguished with respect to the irradiation temperature, viz., 80 K and 300 K. The samples were irradiated with 150 MeV Ag{sup 12+} ions with different fluences ranging from 1 × 10{sup 12} to 5 × 10{sup 13} ions/cm{sup 2}. The structural and optical properties of N-doped 6H-SiC in its pristine condition and after SHI irradiation have been studied. The changes observed by Raman spectroscopy and Time resolved photoluminescence (TRPL) spectroscopy were ascribed to the disorder accumulation in 6H-SiC. The local disorder has been analyzed by studying the LO Raman mode of the irradiated sample in comparison to the pristine sample. The TRPL studies have provided evidence of the formation of radiative centers after irradiation at 80 K.

The magnetoviscous effect of micellar solutions doped with water based ferrofluids

Energy Technology Data Exchange (ETDEWEB)

Arantes, Fabiana R., E-mail: farantes@if.usp.br [Institute of Physics, University of Sao Paulo (Brazil); Institute of Fluid Mechanics, Technische Universität Dresden (Germany); Odenbach, Stefan, E-mail: stefan.odenbach@tu-dresden.de [Institute of Fluid Mechanics, Technische Universität Dresden (Germany)

2015-09-15

This work presents a magnetorheological study of micellar solutions of potassium laurate and water doped with magnetite nanoparticles, accompanied by auxiliary dynamic light scattering measurements. An increase in the viscosity of the samples under applied field was observed and, furthermore, a considerable magnetoviscous effect was revealed even at magnetic particles' concentrations as low as 0.005–0.01 vol%. This indicates that the rheological behavior of the micelles is changed by the interaction of the magnetic particles with the applied field, leading to different microscopic arrangements in the micellar solutions. - Highlights: • We study the magnetorheological behavior of micellar solutions doped with ferrofluids. • We observe an increase in the viscosity of the samples under an applied field. • We find a large magnetoviscous effect even at low magnetic particles' concentration. • Interaction of particles with the field changes the micelles' rheological behavior.

Ego involvement increases doping likelihood.

Science.gov (United States)

Ring, Christopher; Kavussanu, Maria

2018-08-01

Achievement goal theory provides a framework to help understand how individuals behave in achievement contexts, such as sport. Evidence concerning the role of motivation in the decision to use banned performance enhancing substances (i.e., doping) is equivocal on this issue. The extant literature shows that dispositional goal orientation has been weakly and inconsistently associated with doping intention and use. It is possible that goal involvement, which describes the situational motivational state, is a stronger determinant of doping intention. Accordingly, the current study used an experimental design to examine the effects of goal involvement, manipulated using direct instructions and reflective writing, on doping likelihood in hypothetical situations in college athletes. The ego-involving goal increased doping likelihood compared to no goal and a task-involving goal. The present findings provide the first evidence that ego involvement can sway the decision to use doping to improve athletic performance.

Hydrogen storage capacity of lithium-doped KOH activated carbons

International Nuclear Information System (INIS)

Minoda, Ai; Oshima, Shinji; Iki, Hideshi; Akiba, Etsuo

2014-01-01

Highlights: • The hydrogen adsorption of lithium-doped KOH activated carbons has been studied. • Lithium doping improves their hydrogen adsorption affinity. • Lithium doping is more effective for materials with micropores of 0.8 nm or smaller. • Lithium reagent can alter the pore structure, depending on the raw material. • Optimizing the pore size and functional group is needed for better hydrogen uptake. - Abstract: The authors have studied the hydrogen adsorption performance of several types of lithium-doped KOH activated carbons. In the case of activated cokes, lithium doping improves their hydrogen adsorption affinity from 5.02 kg/m 3 to 5.86 kg/m 3 at 303 K. Hydrogen adsorption density increases by around 17% after lithium doping, likely due to the fact that lithium doping is more effective for materials with micropores of 0.8 nm or smaller. The effects of lithium on hydrogen storage capacity vary depending on the raw material, because the lithium reagent can react with the material and alter the pore structure, indicating that lithium doping has the effect of plugging or filling the micropores and changing the structures of functional groups, resulting in the formation of mesopores. Despite an observed decrease in hydrogen uptake, lithium doping was found to improve hydrogen adsorption affinity. Lithium doping increases hydrogen uptake by optimizing the pore size and functional group composition

Gene doping: possibilities and practicalities.

Science.gov (United States)

Wells, Dominic J

2009-01-01

Our ever-increasing understanding of the genetic control of cardiovascular and musculoskeletal function together with recent technical improvements in genetic manipulation generates mounting concern over the possibility of such technology being abused by athletes in their quest for improved performance. Genetic manipulation in the context of athletic performance is commonly referred to as gene doping. A review of the literature was performed to identify the genes and methodologies most likely to be used for gene doping and the technologies that might be used to identify such doping. A large number of candidate performance-enhancing genes have been identified from animal studies, many of them using transgenic mice. Only a limited number have been shown to be effective following gene transfer into adults. Those that seem most likely to be abused are genes that exert their effects locally and leave little, if any, trace in blood or urine. There is currently no evidence that gene doping has yet been undertaken in competitive athletes but the anti-doping authorities will need to remain vigilant in reviewing this rapidly emerging technology. The detection of gene doping involves some different challenges from other agents and a number of promising approaches are currently being explored. 2009 S. Karger AG, Basel

A DFT study of arsine adsorption on palladium doped graphene: Effects of palladium cluster size

International Nuclear Information System (INIS)

Kunaseth, Manaschai; Mudchimo, Tanabat; Namuangruk, Supawadee; Kungwan, Nawee; Promarak, Vinich; Jungsuttiwong, Siriporn

2016-01-01

Graphical abstract: The relationship between charge difference and adsorption strength demonstrates that charge migration from Pd_n-SDG to AsH_x significantly enhanced adsorption strength, the Pd_6 clusters doped SDG with a steep slope is recommended as a superior adsorbent material for AsH_3 removal from gas stream. - Highlights: • Pd atom and Pd clusters bind strongly onto the defective graphene surface. • Larger size of Pd cluster adsorbs arsine and its hydrogenated products stronger. • Order of adsorption strength on Pd_n doped graphene: As > AsH > AsH_2 > > AsH_3. • Charge migration characterizes the strong adsorption of AsH_2, AsH, and As. • Pd cluster doped graphene is thermodynamically preferable for arsine removal. - Abstract: In this study, we have investigated the size effects of palladium (Pd) doped single-vacancy defective graphene (SDG) surface to the adsorption of AsH_3 and its dehydrogenated products on Pd using density functional theory calculations. Here, Pd cluster binding study revealed that Pd_6 nanocluster bound strongest to the SDG surface, while adsorption of AsH_x (x = 0–3) on the most stable Pd_n doped SDG showed that dehydrogenated arsine compounds adsorbed onto the surface stronger than the pristine AsH_3 molecule. Charge analysis revealed that considerable amount of charge migration from Pd to dehydrogenated arsine molecules after adsorption may constitute strong adsorption for dehydrogenated arsine. In addition, study of thermodynamic pathways of AsH_3 dehydrogenation on Pd_n doped SDG adsorbents indicated that Pd cluster doping on SDG adsorbent tends to be thermodynamically favorable for AsH_3 decomposition than the single-Pd atom doped SDG. Hence, our study has indicated that Pd_6 clusters doped SDG is more advantageous as adsorbent material for AsH_3 removal.

N-type doping effect of single-walled carbon nanotubes with aromatic amines

Energy Technology Data Exchange (ETDEWEB)

Koizhaiganova, Raushan B.; Hwang, Doo Hee; Lee, Cheol Jin; Dettlaff-Weglikowska, Urszula [School of Electrical Engineering, Korea University, Seoul 136-713 (Korea, Republic of); Roth, Siegmar [School of Electrical Engineering, Korea University, Seoul 136-713 (Korea, Republic of); Sineurop Nanotech GmbH, Nobelstreet15, 70569 Stuttgart (Germany)

2010-12-15

We investigated the chemical doping of the single-walled carbon nanotubes (SWCNTs) networks by a treatment with aromatic amines. Adsorption and intercalation of amine molecules in bundled SWCNTs leads to typical n-type doping observed already for alkali metals. The electron donation to SWCNTs is demonstrated by the X-ray-induced photoelectron spectra (XPS), where the carbon C 1s peak observed at 284.4 eV for the sp{sup 2} carbon in pristine samples is shifted by up to 0.3 eV to higher binding energy upon chemical treatment. The development of a Breit-Wigner-Fano component on the lower energy side of the G{sup -} mode in the Raman spectrum as well as a shift of the G{sup +} to lower frequency provide evidence for charge accumulation in the nanotube {pi} system, and indication for the n-type doping. The spectroscopic changes are accompanied by the modification of the electrical properties of the SWCNTs. A reduction of conductivity depends on the doping level and implies the decreasing concentration of the charge carriers in the naturally p-doped tubes. Comparing the two selected n-type dopants, the tetramethyl-p-phenylenediamine, shows more pronounced changes in the XPS and the Raman spectra than tetramethylpyrazine, indicating that the sp{sup 3} hybridization of nitrogen in the amine groups attached to phenyl ring is much more effective in interaction with the tube {pi} system than the sp{sup 2} hybridization of nitrogen in the aromatic pyrazine ring. (Copyright copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Effects of heavy metals (other than mercury) on marine and estuarine organisms

Energy Technology Data Exchange (ETDEWEB)

Bryan, G W

1971-01-01

Heavy metals such as copper, zinc and lead are normal constituents of marine and estuarine environments. When additional quantities are introduced from industrial wastes or sewage they enter the biogeochemical cycle and, as a result of being potentially toxic, may interfere with the ecology of a particular environment. In different marine organisms, the behavior of heavy metals is described in terms of their absorption, storage, excretion and regulation when different concentrations are available in the environment. At higher concentrations, the detrimental effects of heavy metals become apparent and their different toxic effects and factors affecting them are also described. 78 references, 9 figures, 4 tables.

Synergistic Effect of Fluorinated and N Doped TiO2 Nanoparticles Leading to Different Microstructure and Enhanced Photocatalytic Bacterial Inactivation

Directory of Open Access Journals (Sweden)

Irena Milosevic

2017-11-01

Full Text Available This work focuses on the development of a facile and scalable wet milling method followed by heat treatment to prepare fluorinated and/or N-doped TiO2 nanopowders with improved photocatalytic properties under visible light. The structural and electronic properties of doped particles were investigated by various techniques. The successful doping of TiO2 was confirmed by X-ray photoelectron spectroscopy (XPS, and the atoms appeared to be mainly located in interstitial positions for N whereas the fluorination is located at the TiO2 surface. The formation of intragap states was found to be responsible for the band gap narrowing leading to the faster bacterial inactivation dynamics observed for the fluorinated and N doped TiO2 particles compared to N-doped TiO2. This was attributed to a synergistic effect. The results presented in this study confirmed the suitability of the preparation approach for the large-scale production of cost-efficient doped TiO2 for effective bacterial inactivation.

Multiple quantum phase transitions and superconductivity in Ce-based heavy fermions.

Science.gov (United States)

Weng, Z F; Smidman, M; Jiao, L; Lu, Xin; Yuan, H Q

2016-09-01

Heavy fermions have served as prototype examples of strongly-correlated electron systems. The occurrence of unconventional superconductivity in close proximity to the electronic instabilities associated with various degrees of freedom points to an intricate relationship between superconductivity and other electronic states, which is unique but also shares some common features with high temperature superconductivity. The magnetic order in heavy fermion compounds can be continuously suppressed by tuning external parameters to a quantum critical point, and the role of quantum criticality in determining the properties of heavy fermion systems is an important unresolved issue. Here we review the recent progress of studies on Ce based heavy fermion superconductors, with an emphasis on the superconductivity emerging on the edge of magnetic and charge instabilities as well as the quantum phase transitions which occur by tuning different parameters, such as pressure, magnetic field and doping. We discuss systems where multiple quantum critical points occur and whether they can be classified in a unified manner, in particular in terms of the evolution of the Fermi surface topology.

Effect of annealing on structural and luminescence properties of Eu3+ doped NaYF4 phosphor

Science.gov (United States)

Pathak, Trilok K.; Kumar, Ashwini; Swart, H. C.; Kroon, R. E.

2018-04-01

Eu3+ doped NaYF4 phosphors have been synthesized by the combustion method. The effect of annealing on the structural, morphological and luminescence properties has been investigated. X-ray diffraction analysis revealed that the Eu3+ doped NaYF4 phosphors consisted of mixed phases: α-phase and β-phase which were affected by the annealing of the phosphor. The surface morphology showed a significant change with annealing in the Eu3+ doped NaYF4 phosphors. The elemental mapping and energy dispersive X-ray spectroscopy spectra proved the formation of the desired materials. The photoluminescence spectra illustrated the optical properties of Eu3+ in the as-prepared and annealed Eu3+ doped NaYF4 phosphors. The intensity of the peaks 5D0 → 7F2 and 5D0 → 7F1 varied in as-prepared and annealed samples. The lifetime of the Eu3+ luminescence at 615 nm was also weakly affected by the Eu3+ doping and annealing temperature.

The biological effectiveness of heavy ion radiations in the environment

International Nuclear Information System (INIS)

Craven, P.A.

1996-03-01

Although heavy ions are rarely encountered in the majority of terrestrial environments, the exposure of humans to this fascinating class of ionizing radiation is becoming more frequent. Long-duration spaceflight, new radiotherapeutic procedures and enhanced levels of radon, and other naturally-occurring alpha particle emitters, have all increased concern and stimulated interest recently within the radiological protection and radiobiological communities. Significant data concerning the long-term effects of low levels of heavy ions on mammalian systems are correspondingly scarce, leading to increased emphasis on modelling all aspects of the radiation-organism interaction. Contemporary radiation protection procedures reflect the need for a more fundamental understanding of the mechanisms responsible for the biological actions of such radiations. Major deficiencies exist in the current recommendations for assessment of relative effectiveness, the enhanced severity of the biological consequences instigated by heavy ions, over conventional sparsely ionizing radiations. In an attempt to remedy some of the inadequate concepts and assumptions presently employed and, simultaneously, to gain insight into the fundamental mechanisms behind the notion of radiation quality, a series of algorithms have been developed and executed as computer code, to evaluate the biological effectiveness of heavy ion radiation ''tracks'' according to a number of criteria. These include consideration of the spatial characteristics of physical energy deposition in idealised cellular structures (finite particle range, radial extension of tracks via δ-ray emission) and the likelihood of induction and mis-repair of severe molecular lesions (double-strand breaks, multiply-damaged sites). (author)

On single doping and co-doping of spray pyrolysed ZnO films: Structural, electrical and optical characterisation

International Nuclear Information System (INIS)

Vimalkumar, T.V.; Poornima, N.; Jinesh, K.B.; Kartha, C. Sudha; Vijayakumar, K.P.

2011-01-01

In this paper we present studies on ZnO thin films (prepared using Chemical Spray pyrolysis (CSP) technique) doped in two different ways; in one set, 'single doping' using indium was done while in the second set, 'co-doping' using indium and fluorine was adopted. In the former case, effect of in-situ as well as ex-situ doping using In was analyzed. Structural (XRD studies), electrical (I-V measurements) and optical characterizations (through absorption, transmission and photoluminescence studies) of the films were done. XRD analysis showed that, for spray-deposited ZnO films, ex-situ doping using Indium resulted in preferred (0 0 2) plane orientation, while in-situ doping caused preferred orientation along (1 0 0), (0 0 2), (1 0 1) planes; however for higher percentage of in-situ doping, orientation of grains changed from (0 0 2) plane to (1 0 1) plane. The co-doped films had (0 0 2) and (1 0 1) planes. Lowest resistivity (2 x 10 -3 Ω cm) was achieved for the films, doped with 1% Indium through in-situ method. Photoluminescence (PL) emissions of ex-situ doped and co-doped samples had two peaks; one was the 'near band edge' emission (NBE) and the other was the 'blue-green' emission. But interestingly the PL emission of in-situ doped samples exhibited only the 'near band edge' emission. Optical band gap of the films increased with doping percentage, in all cases of doping.

Large-area uniform electron doping of graphene by Ag nanofilm

Directory of Open Access Journals (Sweden)

Xiaopeng Guo

2017-04-01

Full Text Available Graphene has attracted much attention at various research fields due to its unique optical, electronic and mechanical properties. Up to now, graphene has not been widely used in optoelectronic fields due to the lack of large-area uniform doped graphene (n-doped and p-doped with smooth surface. Therefore, it is rather desired to develop some effective doping methods to extend graphene to optoelectronics. Here we developed a novel doping method to prepare large-area (> centimeter scale uniform doped graphene film with a nanoscale roughness(RMS roughness ∼1.4 nm, the method (nano-metal film doping method is simple but effective. Using this method electron doping (electron-injection may be easily realized by the simple thermal deposition of Ag nano-film on a transferred CVD graphene. The doping effectiveness has been proved by Raman spectroscopy and spectroscopic ellipsometry. Importantly, our method sheds light on some potential applications of graphene in optoelectronic devices such as photodetectors, LEDs, phototransistors, solar cells, lasers etc.

Effects of heavy metal Cd pollution on microbial activities in soil.

Science.gov (United States)

Shi, Weilin; Ma, Xiying

2017-12-23

Heavy metal contamination of soil occurs when heavy metals are introduced to soil through human activities, leading to the gradual deterioration of the ecology and environment. Microorganism activity reflects the intensity of various biochemical reactions in soil, and changes in it reflect the level of heavy metal pollution affecting the soil. The effects were studied of heavy metal Cd on the microbial activity of soil at different concentrations by investigating the respiratory intensity, urease activity, and catalase activity in forest soil and garden soil. The results showed that the respiratory intensity, urease and catalase activities in the garden soil were all higher than in the forest soil. Cd has obvious inhibitory effects on microbial activities. The three parameters exhibited a downward trend with increasing concentrations of Cd. Catalase activity increased when the mass concentration of Cd reached 1.0 mg/kg, indicating that low concentrations of Cd can promote the activity of some microorganisms. Respiratory intensity and urease activity also increased when the concentration reached 10.0 mg/kg, showing that respiratory intensity and urease activity have strong response mechanisms to adverse conditions. The effective state of Cd in soil, as well as inhibition of microbial activity, decreased with incubation time.

Effects of heavy metal Cd pollution on microbial activities in soil

Directory of Open Access Journals (Sweden)

Weilin Shi

2017-12-01

Full Text Available Heavy metal contamination of soil occurs when heavy metals are introduced to soil through human activities, leading to the gradual deterioration of the ecology and environment. Microorganism activity reflects the intensity of various biochemical reactions in soil, and changes in it reflect the level of heavy metal pollution affecting the soil. The effects were studied of heavy metal Cd on the microbial activity of soil at different concentrations by investigating the respiratory intensity, urease activity, and catalase activity in forest soil and garden soil. The results showed that the respiratory intensity, urease and catalase activities in the garden soil were all higher than in the forest soil. Cd has obvious inhibitory effects on microbial activities. The three parameters exhibited a downward trend with increasing concentrations of Cd. Catalase activity increased when the mass concentration of Cd reached 1.0 mg/kg, indicating that low concentrations of Cd can promote the activity of some microorganisms. Respiratory intensity and urease activity also increased when the concentration reached 10.0 mg/kg, showing that respiratory intensity and urease activity have strong response mechanisms to adverse conditions. The effective state of Cd in soil, as well as inhibition of microbial activity, decreased with incubation time.

Heavy Fermion Materials and Quantum Phase Transitions Workshop on Frontiers of the Kondo Effect

Science.gov (United States)

2016-02-12

SECURITY CLASSIFICATION OF: The contemporary studies of the Kondo effect and heavy -fermion materials occur at the intersection of some of the most...magnetism. Electronic systems in this intermediate regime are particularly tunable. Correspondingly, heavy fermions have emerged as a promising setting...materials. Second, heavy -fermion materials typically contain heavy elements, and there is an increasing 1. REPORT DATE (DD-MM-YYYY) 4. TITLE AND

Gene doping.

Science.gov (United States)

Haisma, H J; de Hon, O

2006-04-01

Together with the rapidly increasing knowledge on genetic therapies as a promising new branch of regular medicine, the issue has arisen whether these techniques might be abused in the field of sports. Previous experiences have shown that drugs that are still in the experimental phases of research may find their way into the athletic world. Both the World Anti-Doping Agency (WADA) and the International Olympic Committee (IOC) have expressed concerns about this possibility. As a result, the method of gene doping has been included in the list of prohibited classes of substances and prohibited methods. This review addresses the possible ways in which knowledge gained in the field of genetic therapies may be misused in elite sports. Many genes are readily available which may potentially have an effect on athletic performance. The sporting world will eventually be faced with the phenomena of gene doping to improve athletic performance. A combination of developing detection methods based on gene arrays or proteomics and a clear education program on the associated risks seems to be the most promising preventive method to counteract the possible application of gene doping.

Effect of pressure and doping on lattice structure of zinc oxide

Energy Technology Data Exchange (ETDEWEB)

Zolfaghari, Mahmoud, E-mail: mzolfaghari@phys.usb.ac.ir

2017-01-15

The semiconductor ZnO belongs to the IIb-VI binary compound. It has a high exciton binding energy of 60 meV. The bonding in these materials is covalent with some ionic character. Induced changes on the physical properties of Mn doped ZnO samples due to different dopant concentrations and pressure were evaluated. The results obtained showed higher solubility limit for Mn doped ZnO due to pressure. The trend of XRD results for higher Mn concentration (9 at%) as pressure increases, was towards doping improvement. The XRD, SEM and UV–vis study of the samples also revealed that there were variations in the lattice parameters, nanoparticle size and bandgap energy of the doped and pressurized doped samples. Further, the directions of variation of bandgap energy values and calculated particle size, as well as SEM values of the doped samples due to pressure variation were found to be the same i.e. all of them together either increase or decrease as pressure varies. However, these variations were found to be opposite to that of lattice constants (all a and most c values) variation for both Mn dopant concentrations (3 at% and 9 at%). These physical variations of unpressurized doped samples can be attributed to the change in the polar bonding of the elemental constitutions in the lattice. While for the pressurized doped samples, the variations attributed to repulsion of lone pairs as well as change in the electronegativity of the system.

Study of Sn and Mg doping effects on TiO2/Ge stack structure by combinatorial synthesis

Science.gov (United States)

Nagata, Takahiro; Suzuki, Yoshihisa; Yamashita, Yoshiyuki; Ogura, Atsushi; Chikyow, Toyohiro

2018-04-01

The effects of Sn and Mg doping of a TiO2 film on a Ge substrate were investigated to improve leakage current properties and Ge diffusion into the TiO2 film. For systematic analysis, dopant-composition-spread TiO2 samples with dopant concentrations of up to 20.0 at. % were fabricated by RF sputtering and a combinatorial method. X-ray photoelectron spectroscopy revealed that the instability of Mg doping of TiO2 at dopant concentrations above 10.5 at. %. Both Sn and Mg dopants reduced Ge diffusion into TiO2. Sn doping enhanced the crystallization of the rutile phase, which is a high-dielectric-constant phase, although the Mg-doped TiO2 film indicated an amorphous structure. Sn-doping indicated systematic leakage current reduction with increasing dopant concentration. Doping at Sn concentrations higher than 16.8 at. % improved the leakage properties (˜10-7 A/cm2 at -3.0 V) and capacitance-voltage properties of metal-insulator-semiconductor (MIS) operation. The Sn doping of TiO2 may be useful for interface control and as a dielectric material for Ge-based MIS capacitors.

Parameters of heavy quark effective theory from N{sub f}=2 lattice QCD

Energy Technology Data Exchange (ETDEWEB)

Blossier, Benoit [CNRS, Orsay (France). LPT; Paris-11 Univ., 91 - Orsay (France); Della Morte, Michele [Mainz Univ. (Germany). Inst. fuer Kernphysik; Fritzsch, Patrick [Humboldt-Universitaet, Berlin (Germany). Inst. fuer Physik; Garron, Nicolas [Edinburgh Univ. (United Kingdom). School of Physics and Astronomy; Heitger, Jochen [Muenster Univ. (Germany). Inst. fuer Theoretische Physik 1; Simma, Hubert; Sommer, Rainer [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Tantalo, Nazario [Rome-3 Univ. (Italy). Dipt. di Fisica; INFN, Sezione di Roma (Italy)

2012-07-15

We report on a non-perturbative determination of the parameters of the lattice Heavy Quark Effective Theory (HQET) Lagrangian and of the time component of the heavy-light axial-vector current with N{sub f} = 2 flavors of massless dynamical quarks. The effective theory is considered at the 1/m{sub h} order, and the heavy mass m{sub h} covers a range from slightly above the charm to beyond the beauty region. These HQET parameters are needed to compute, for example, the b-quark mass, the heavy-light spectrum and decay constants in the static approximation and to order 1/m{sub h} in HQET. The determination of the parameters is done non-perturbatively. The computation reported in this paper uses the plaquette gauge action and two different static actions for the heavy quark described by HQET. For the light-quark action we choose non-perturbatively O(a)-improved Wilson fermions.

ZnO and Al doped ZnO thin films deposited by Spray Plasma: Effect of the growth time and Al doping on microstructural, optical and electrical properties

International Nuclear Information System (INIS)

Baba, Kamal; Lazzaroni, Claudia; Nikravech, Mehrdad

2015-01-01

Nanostructured zinc oxide (ZnO) and Al doped ZnO (ZnO:Al) thin films are deposited on glass substrate by the Spray Plasma technique. Zinc nitrate and aluminium nitrate are used as Zn and Al precursors, respectively. The effect of the growth time on structural and optical properties of undoped films is studied by X-ray diffraction, atomic force microscopy, and UV–Vis spectroscopy. The effect of Al doping on microstructural, optical and electrical characteristics of ZnO:Al films is also investigated. The results show that the grain size and the film thickness both increase with the growth time. The band gap of the layers varies from 3.17 to 3.24 eV depending on the thickness. The increase of the Al doping results in the enlargement of the peak (002) and the shift of its position to higher 2θ values. Average optical transmittance decreases from 90 to 65% with the growth time because of the thickness increase while there is no significant influence of the aluminium doping on the transmittance which is above 80% in most of the visible and near-IR range for all ZnO:Al films. The electrical properties characterized by Hall measurements show that all the deposited films exhibit high resistivity, between 4 and 10 4 Ω cm. The carrier concentration decreases from 2.10 19 to 2.10 13 cm −3 when the concentration of Al increases from 1.5 to 5 atm%. - Highlights: • The original Spray Plasma technique is used for ZnO and ZnO:Al thin film deposition. • Investigation of the effect of growth time and Al doping on the structural and optical properties • Increase of grain size and film thickness with the growth time • Optical transmittance decreases from 90 to 65% with the growth time and is above 80% for ZnO:Al films in UV–Vis-NIR range. • The peak position of the (002) plane is shifted to high 2θ values with Al doping.

Doping effects of Fe ion on magnetic anisotropy of YBa2Cu3Oy

International Nuclear Information System (INIS)

Ugawa, T.; Horii, S.; Maeda, T.; Haruta, M.; Shimoyama, J.

2013-01-01

Highlights: •We clarified orientation effects of Fe-doped Y123 in modulated rotating fields. •Y123 showed two different hard magnetic axes due to twin microstructures. •The two hard magnetic axes in Fe-doped Y123 were [1 0 0] and [1 1 0] directions. •Magnetic anisotropy of the [1 1 0] grain was higher than that of the [1 0 0] grain. -- Abstract: We report magnetic alignment of YBa 2 (Cu 1−x Fe x ) 3 O y (Fe-doped Y123, x = 0–0.1) powders under modulated rotation magnetic fields (MRFs) and roles of Fe ion as a determination factor of magnetic anisotropy in Y123. The Fe-free and Fe-doped Y123 powder samples aligned in the MRF of 10 T showed two different orientation types of the hard axis in Y123 grains. From an X-ray rocking curve measurement for the magnetically aligned powder samples of the Fe-doped Y123, inplane magnetic anisotropy for Y123 grains with the hard axis parallel to the [1 1 0] direction was found to be higher than that for Y123 grains with the hard axis parallel to the [0 1 0] direction

Effect of swift heavy ion irradiation on ethylene–chlorotrifluoroethylene copolymer

International Nuclear Information System (INIS)

Singh, Lakhwant; Devgan, Kusum; Samra, Kawaljeet Singh

2012-01-01

The swift heavy irradiation induced changes taking place in ethylene–chlorotrifluoroethylene (E–CTFE) copolymer films were investigated in correlation with the applied doses. Samples were irradiated in vacuum at room temperature by lithium (50 MeV), carbon (85 MeV), nickel (120 MeV) and silver (120 MeV) ions with the fluence in the range of 1×10 11 –3×10 12 ions cm −2 . Structural and thermal properties of the irradiated as well as pristine E–CTFE films were studied using FTIR, UV–visible, TGA, DSC and XRD techniques. Swift heavy ion irradiation was found to induce changes in E–CTFE depending upon the applied doses. - Highlights: ► Effect of swift heavy ion irradiation on E–CTFE films has been studied. ► Different structural changes in the original structure of E–CTFE are observed after irradiation with different ions. ► Swift heavy ion irradiation has made E–CTFE more prone to thermal degradation.

Heavy-ion targets

International Nuclear Information System (INIS)

Adair, H.L.; Kobisk, E.H.

1985-01-01

This chapter examines the characteristics of targets required in heavy-ion accelerator physics experiments. The effects of target parameters on heavy-ion experimental results are reviewed. The target fabrication and characterization techniques used to minimize experimental problems during heavy-ion bombardment are described. Topics considered include target thickness and uniformity, target lifetime, target purity, substrate materials, Doppler shift effects, metal preparations, and target preparation methods

Effect of barium doping on the physical properties of zinc oxide ...

Indian Academy of Sciences (India)

2015-11-27

Home; Journals; Pramana – Journal of Physics; Volume 87; Issue 1. Effect of barium doping on the physical properties of zinc oxide ... Proceedings of the International Workshop/Conference on Computational Condensed Matter Physics and Materials Science (IWCCMP-2015). Posted on November 27, 2015. Guest Editors: ...

Doping Attitudes and Covariates of Potential Doping Behaviour in High-Level Team-Sport Athletes; Gender Specific Analysis

Directory of Open Access Journals (Sweden)

Damir Sekulic, Enver Tahiraj, Milan Zvan, Natasa Zenic, Ognjen Uljevic, Blaz Lesnik

2016-12-01

Full Text Available Team sports are rarely studied with regard to doping behaviour and doping-related factors regardless of their global popularity. This study aimed to investigate doping factors and covariates of potential doping behaviour in high-level team-sport athletes. The subjects were 457 high-performing, national- and international-level athletes (21.9 ± 3.4 years of age; 179 females involved in volleyball (n = 77, soccer (n = 163, basketball (n = 114 and handball (n = 103. Previously validated self-administered questionnaires aimed at evidencing sport factors, doping-related factors, knowledge on sport nutrition and doping, and attitudes to performance enhancement were used. The results indicated a higher doping likelihood in male athletes, with a significant gender difference for basketball and handball. In males, a higher doping likelihood is found for athletes who had achieved better results at junior-age level, those who regularly consume dietary supplements, and who perceive their sport as being contaminated by doping. A higher sport achievement at senior-age level is protective against potential doping behaviour in males. In females, a higher likelihood of doping is evidenced in those athletes involved in binge drinking, while a lower tendency for doping is evidenced in female athletes who possess better knowledge on sport nutrition. Knowledge about doping is very low and thus education about doping is urgently needed. An improvement of knowledge on sport nutrition might be a potentially effective method for reducing the tendency for doping in females. Future studies should consider other approaches and theories, such as theory of planned behaviour and/or social-cognitive theory, in studying the problem of doping behaviour in team-sports.

Thickness-dependent magneto-optical effects in hole-doped GaS and GaSe multilayers: a first-principles study

Science.gov (United States)

Li, Fei; Zhou, Xiaodong; Feng, Wanxiang; Fu, Botao; Yao, Yugui

2018-04-01

Recently, two-dimensional (2D) GaS and GaSe nanosheets were successfully fabricated and the measured electronic, mechanical, and optoelectronic properties are excellent. Here, using the first-principles density functional theory, we investigate the magnetic, optical, and magneto-optical (MO) Kerr and Faraday effects in hole-doped GaS and GaSe multilayers. GaS and GaSe monolayers (MLs) manifest ferromagnetic ground states by introducing even a small amount of hole doping, whereas the magnetism in GaS and GaSe multilayers are significantly different under hole doping. Our results show that ferromagnetic states can be easily established in GaS bilayers and trilayers under proper hole doping, however, most of GaSe multilayers are more favorable to nonmagnetic states. The magnetic moments in GaS multilayers are weakened remarkably with the increasing of thin film thickness and are negligible more than three MLs. This leads to the thickness dependence of MO Kerr and Faraday effects. Furthermore, the MO effects strongly depend on the doping concentration and therefore are electrically controllable by adjusting the number of holes via gate voltage. The substrate effects on the MO properties are also discussed. Combining the unique MO and other interesting physical properties make GaS and GaSe a superior 2D material platform for semiconductor MO and spintronic nanodevices.

Heavy irradiation effects in radiation-resistant optical fibers

Energy Technology Data Exchange (ETDEWEB)

Shikama, Tatsuo [Tohoku Univ., Oarai, Ibaraki (Japan). Oarai Branch, Inst. for Materials Research

1998-07-01

Development of a system for optical measurements in a nuclear reactor has been progressing to investigate dynamic changes in a material caused by heavy irradiation. In such system, transfer of optical signals to out-pile measuring systems is being attempted by the use of optical fibers. In this report, the characteristics of optical fibers in the heavy irradiation field were summarized. It has been known that amorphous silica might produce radiolysis and structural defects by the exposure to ionizing radiation. The effects of heavy irradiation on molten silica were extremely complicated. A large intensity of visible light absorption occurred from an early time during start-up of the reactor. The absorption range was limited below 700 nm for the radiation associating fast neutron and the absorption was mostly attributed to non-bridging oxygen hole center. The depletion of optical transferring capacity under the radiation might be related to the internal stress. Therefore, it seems desirable to use optical fibers in the conditions without leading too much stress. (M.N.)

Effects of heavy metals on enzyme synthesis in substrate-amended river sediments

Energy Technology Data Exchange (ETDEWEB)

Wainwright, M; Duddridge, J E

1982-01-01

The effects of heavy metals in diverse substrate-amended river sediments were studied. Cd/sup 2 +/, Pb/sup 2 +/ and Zn/sup 2 +/ generally had a marked inhibitory effect on the synthesis of amylase, cellulase and urease, on numbers of substrate-hydrolysing bacteria, in all sediments studied. Inhibition increased with increasing metal concentration, and amylase was particularly sensitive. Pb/sup 2 +/ generally had the least effect. We conclude that enzyme synthesis measurements are useful in determining the effects of heavy metals on the degradation of organic pollutants in river sediments.

Morphology and Doping Level of Electropolymerized Biselenophene-Flanked 3,4- Ethylenedioxythiophene Polymer: Effect of Solvents and Electrolytes

International Nuclear Information System (INIS)

Agrawal, Vikash; Shahjad; Bhardwaj, Dinesh; Bhargav, Ranoo; Sharma, Gauri Datt; Bhardwaj, Ramil Kumar; Patra, Asit; Chand, Suresh

2016-01-01

Highlights: • Biselenophene-flanked 3,4-ethylenedioxythiophene polymer films were obtained by electrochemical polymerization. • Supporting electrolyte has significant effect on the doping level, whereas electropolymerized solvent has a major effect on morphology of the polymer films. • Optoelectronic properties and morphology of the electropolymerized films were studied. • Density functional theory (DFT) calculation has been made for optoelectronic properties. - Abstract: Biselenophene-flanked 3,4-ethylenedioxythiophene (EDOT) based polymer films were obtained by electrochemical polymerization. The effects of polymerization conditions such as supporting electrolytes and solvents on doping level, optical property and morphology of the polymer films were systematically studied. Interestingly, we found that polymer prepared by using different supporting electrolytes (TBAPF 6 , TBABF 4 and TBAClO 4 ) has significant effects on the doping level of the polymer films, whereas electropolymerized solvents (acetonitrile and dichloromethane) has no such effects on doping level. The polymer films show reversible dedoping and doping behavior upon treatment with hydrazine hydrate and iodine respectively. Biselenophene-flanked EDOT polymer shows a band gap of about 1.6 eV which is comparable to poly(3,4- ethylenedioxythiophene) (PEDOT) and parent polyselenophene, whereas fine-tuning of HOMO and LUMO energy levels has been found. In contrast, we observed that electropolymerized solvent has a major effect on morphology of the polymer films, while supporting electrolyte has very minor effects on the morphology. The surface morphologies of the polymer films were characterized by scanning electron microscope (SEM) and atomic force microscope (AFM) techniques. We also present an efficient synthesis of bisthiophene-flanked bridged EDOT (ETTE), and biselenophene-flanked bridged EDOT (ESeSeE), and their electrochemical polymerization, characterizations and throughout comparison

The effect of n- and p-type doping on coherent phonons in GaN.

Science.gov (United States)

Ishioka, Kunie; Kato, Keiko; Ohashi, Naoki; Haneda, Hajime; Kitajima, Masahiro; Petek, Hrvoje

2013-05-22

The effect of doping on the carrier-phonon interaction in wurtzite GaN is investigated by pump-probe reflectivity measurements using 3.1 eV light in near resonance with the fundamental band gap of 3.39 eV. Coherent modulations of the reflectivity due to the E2 and A1(LO) modes, as well as the 2A1(LO) overtone are observed. Doping of acceptor and donor atoms enhances the dephasing of the polar A1(LO) phonon via coupling with plasmons, with the effect of donors being stronger. Doping also enhances the relative amplitude of the coherent A1(LO) phonon with respect to that of the high-frequency E2 phonon, though it does not affect the relative intensity in Raman spectroscopic measurements. We attribute this enhanced coherent amplitude to the transient depletion field screening (TDFS) excitation mechanism, which, in addition to impulsive stimulated Raman scattering (ISRS), contributes to the generation of coherent polar phonons even for sub-band gap excitation. Because the TDFS mechanism requires photoexcitation of carriers, we argue that the interband transition is made possible at a surface with photon energies below the bulk band gap through the Franz-Keldysh effect.

Mutation effect of streptomyces kitasatoensis after exposure to heavy ions radiation

International Nuclear Information System (INIS)

Liu Jing; Chen Jihong; Wang Shuyang; Li Wenjian

2011-01-01

To define the optimum dose of heavy ion beams for selecting high productive strains, we should study mortality and mutation effects of Streptomyces kitasatoensis irradiated by heavy ion beams in different doses. In this research, spores of Streptomyces kitasatoensis were irradiated by heavy ion beams with different doses. And survival rate, mortality rate, positive mutation and negative mutation were analyzed statistically. The results showed that high mortality rate appeared from 5 Gy and then the mortality rate curve became gently. Compared the positive and negative mutations in different doses, highest positive mutation was obtained in 40 Gy, while the negative mutation was lower in this dose, and the survival rate was 0.92%. So we defined that optimum dose of heavy ions radiation for Streptomyces kitasatoensis selection was 40 Gy in this experiment. (authors)

Different doping effect on physical properties of non-magnetic Pt and Ga in CaFe4As3

International Nuclear Information System (INIS)

Wu, Dapeng

2015-01-01

Highlights: • CaFe 3.64 Pt 0.36 As 3 and CaFe 3.64 Ga 0.36 As 3 were grown using Sn flux method. • The two magnetic transition temperatures of CaFe 4 As 3 remain untouched upon Pt or Ga doping. • The effects of Pt and Ga doping give a different modification of physical properties and electronic structure in CaFe 4 As 3 . • The magnetic structure of CaFe 4 As 3 is insusceptible to non-magnetic dopants. - Abstract: We have successfully doped Pt and Ga into CaFe 4 As 3 and investigated the structure and physical properties of CaFe 3.64 X 0.36 As 3 (X = Pt, Ga). Two magnetic transition temperatures remain unchanged upon Pt or Ga doping, as confirmed by specific heat, electrical resistivity and magnetic susceptibility. The electrical resistivity of CaFe 4 As 3 is reduced by approximately half with Pt dopant but increases by an order of magnitude with Ga doping, consistent with the changes in their Hall coefficients, which indicates the effects of Pt and Ga doping give us a different modification on physical properties and electronic structure in CaFe 4 As 3

Muon spin relaxation studies of heavy fermion superconductors

International Nuclear Information System (INIS)

Heffner, R.H.

1993-01-01

This talk will focus recent developments in our understanding of heavy fermion (HF) superconductors and the role that positive muon spin relaxation (μSR) studies have played in helping to elucidate their properties. As illustrations two systems will be discussed: (1) UPd 2 Al 3 , one of the most recently discovered HF superconductors, which also displays coexisting magnetic order and (2) UBe 3 doped with small quantities Of Th substituted for U, which displays an interplay between its superconducting and magnetic ground states, leading to multiple superconducting states

The effect of doping titanium dioxide nanoparticles on phase transformation, photocatalytic activity and anti-bacterial properties

Science.gov (United States)

Buzby, Scott Edward

Nanosized titanium dioxide has a variety of important applications in everyday life including a photocatalyst for pollution remediation, photovoltaic devices, sunscreen, etc. This study focuses on the various properties of titanium dioxide nanoparticles doped with various cation and anion species. Samples were produced by various methods including metalorganic chemical vapor deposition (MOCVD), plasma assisted metalorganic chemical vapor deposition (PA-MOCVD) and sol-gel. Numerous techniques such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), electron microscopy both scanning (SEM) and transmission (TEM) were used for physical characterization. Photocatalytic properties were determined by the oxidation of methylene blue dye and 2-chlorophenol in water as well as gaseous formic acid with results analyzed by high performance liquid chromatography (HPLC), Fourier transform infrared spectroscopy (FTIR) and ultra violet - visible spectroscopy (UV-VIS). For the purpose of enhancement of the photocatalytic activity of titanium dioxide nanoparticles, the effect of anion doping and the anatase-rutile phase ratio were studied. Although anatase, rutile and mixed crystallite phases all show some degree of activity in photocatalytic reactions, these results show that anatase is better suited for the degradation of organic compounds in an aqueous medium any advantage in photocatalytic activity gained through the enhancement in optical response from the smaller band gap by addition of rutile was overcome by the negatives associated with the rutile phase. Furthermore substitutional nitrogen doping showed significant improvement in UV photocatalysis as well as allowing for visible light activation of the catalyst. Further studies on the phase transitions in titanium dioxide nanoparticles were carried out by synthesizing various cation doped samples by sol-gel. Analysis of the phases by XRD showed an inverse relationship between dopant size and rutile percentage

Effect of doping of N and B atoms on thermoelectric properties of ...

Indian Academy of Sciences (India)

In this work, the doping effect on the thermoelectric properties of the C60 molecule ... mopower and thermal conductance of atomic sized metallic contacts, 1D wires, single ..... For negative energies, the sign of thermopower is positive while.

Magnetic field effect on pentacene-doped sexithiophene diodes

Science.gov (United States)

Pham, Song-Toan; Fayolle, Marine; Ohto, Tatsuhiko; Tada, Hirokazu

2017-11-01

We studied the effect of impurities on the magnetoresistance of sexithiophene-based diodes using impedance spectroscopy. The impurities were introduced by doping pentacene molecules into a sexithiophene film through a co-evaporation process. The pentacene molecules act as charge-scattering centers, which trigger the negative magnetoresistance of the device. This makes it possible to tune the value of magnetoresistance from positive to negative by increasing the applied voltage. The beneficial properties induced by impurities suggest a potential route to integrate additional functions into organic devices.

Effect of noble metal doping on the structural properties of lanthanum cobaltite

International Nuclear Information System (INIS)

Dharmadhikari, Dipti V.; Athawal, Anjali A.

2016-01-01

Pristine and Noble metal (Ag and Pd) doped lanthanum cobaltite samples have been synthesised by Hydrothermal method. Lanthanum in the A-Site and Co at B-site of Lanthanum cobaltite (LaCoO 3 ) perovskites were partially doped by silver and palladium (4%). Crystal structure analysis revealed that the hydrothermal synthesis led to the formation of pure nanocrystalline perovskite structure. Morphological analysis of the samples shows that the noble metal doping affects the morphology of the samples. Pristine sample shows spherical to oval shaped particles while the doping results in the formation of irregular shaped, spherical and rod shaped particles. Silver doping results in the agglomeration of particles. The particles were observed to be fused with each other to form rod shaped structures in case of palladium doped samples. (author)

General analysis of weak decay form factors in heavy to heavy and heavy to light baryon transitions

International Nuclear Information System (INIS)

Hussain, F.; Liu Dongsheng; Kraemer, M.; Koerner, J.G.; Tawfiq, S.

1992-01-01

We present a complete analysis of the heavy to heavy and heavy to light baryon semi-leptonic decays in the heavy quark effective theory within the framework of a Bethe-Salpeter (BS) approach and demonstrate the equivalence of this approach to other work in the field. We present in a compact form the baryon BS amplitudes which incorporate the symmetries manifest in the heavy quark limit and which also show clearly the light quark dynamics. A similar form of the BS amplitude is presented for light baryons. Using the BS amplitudes, the heavy to heavy and heavy to light semi-leptonic baryon decays are considered. As expected there is a dramatic reduction in the number of form factors. An advantage of our BS approach is demonstrated where the form factors are written as loop integrals which in principle can be calculated. (orig.)

Heavy Metal Polluted Soils: Effect on Plants and Bioremediation Methods

OpenAIRE

Chibuike, G. U.; Obiora, S. C.

2014-01-01

Soils polluted with heavy metals have become common across the globe due to increase in geologic and anthropogenic activities. Plants growing on these soils show a reduction in growth, performance, and yield. Bioremediation is an effective method of treating heavy metal polluted soils. It is a widely accepted method that is mostly carried out in situ; hence it is suitable for the establishment/reestablishment of crops on treated soils. Microorganisms and plants employ different mechanisms for...

The effect of material composition of 3-dimensional graphene oxide and self-doped polyaniline nanocomposites on DNA analytical sensitivity.

Science.gov (United States)

Yang, Tao; Chen, Huaiyin; Yang, Ruirui; Wang, Xinxing; Nan, Fuxin; Jiao, Kui

2015-09-01

Until now, morphology effects of 2-dimensional or 3-dimensional graphene nanocomposites and the effect of material composition on the biosensors have been rarely reported. In this paper, the various nanocomposites based on graphene oxide and self-doped polyaniline nanofibres for studying the effect of morphology and material composition on DNA sensitivity were directly reported. The isolation and dispersion of graphene oxide were realized via intercalated self-doped polyaniline and ultrasonication, where the ultrasonication prompts the aggregates of graphite oxide to break up and self-doped polyaniline to diffuse into the stacked graphene oxide. Significant electrochemical enhancement has been observed due to the existence of self-doped polyaniline, which bridges the defects for electron transfer and, in the mean time, increases the basal spacing between graphene oxide sheets. Different morphologies can result in different ssDNA surface density, which can further influence the hybridization efficiency. Compared with 2-dimensional graphene oxide, self-doped polyaniline and other morphologies of nanocomposites, 3-dimensional graphene oxide-self-doped polyaniline nanowalls exhibited the highest surface density and hybridization efficiency. Furthermore, the fabricated biosensors presented the broad detection range with the low detection limit due to the specific surface area, a large number of electroactive species, and open accessible space supported by nanowalls. Copyright © 2015 Elsevier B.V. All rights reserved.

Doping effects in high-T{sub c} superconductors

Energy Technology Data Exchange (ETDEWEB)

Hessel Andersen, N.

1996-11-01

The purpose of the project has been to study how the superconducting and magnetic properties of the high temperature superconductors change as function of oxygen stoichiometry and cation doping. The primary system of investigation has been YBa{sub 2}Cu{sub 3}O{sub 6+x}, which has been studied as function of oxygen stoichiometry, 0 < x < 1, and cation doping with Al, Co and Fe on the Cu-sites and Nd and Pr on the Y-site. In these materials the hole doping into the CuO{sub 2} planes, that is necessary for superconductivity, is strongly depending on structural ordering. The static properties and the kinetics of the structural ordering process have been studied experimentally by neutron and high energy synchrotron x-ray diffraction, by Raman scattering, and by computer simulation technique. Not only the oxygen stoichiometry but also the cation doping has been shown to influence the magnetic phases, in some cases in an unexpected manner. Thus, by neutron diffraction experiments it has been shown that doping with non-magnetic Al gives rise to a new magnetic phase. A theoretical model, has been developed. The magnetic phases of the Cu and Nd ordering in NdBa{sub 2}Cu{sub 3}O{sub 6+x}, and of the Cu and Pr ordering in PrBa{sub 2}Cu{sub 3}O{sub 6+x} have been studied by neutron diffraction with the main purpose of understanding why PrBa{sub 2}Cu{sub 3}O{sub 6+x} is magnetic and non-superconducting for all oxygen stoichiometries. In NdBa:2Cu{sub 3}O{sub 6+x} studies of the magnetic flux lattice have been carried out by Small Angle Neutron Scattering. Additional structural studies of the superconducting and magnetic phases of related materials, of RENi{sub 2}B{sub 2}C (RE = rare earth), and of oxidized and cation doped materials based on La{sub 2}CuO{sub 4+{delta}} have been carried out. Methods for structural studies and analyses, and equipment for electrical and magnetic characterization have been developed. (EG) 5 tabs., 46 ills., 35 refs.

Effect of bismuth doping on the ZnO nanocomposite material and study of its photocatalytic activity under UV-light

International Nuclear Information System (INIS)

Chandraboss, V.L.; Natanapatham, L.; Karthikeyan, B.; Kamalakkannan, J.; Prabha, S.; Senthilvelan, S.

2013-01-01

Graphical abstract: The hetero-junctions that are formed between the ZnO and the Bi provide an internal electric field that facilitates separation of the electron-hole pairs and induces faster carrier migration. Thus they often enhanced photocatalytic reaction. - Highlights: • Bi-doped ZnO nanocomposite material was prepared by precipitation method. • Characterized by XRD, HR-SEM with EDX, UV–visible DRS and FT-RAMAN analysis. • Bi-doped ZnO nanocomposite material was used to photodegradation of Congo red. • Mechanism and photocatalytic effect of nanocomposite material have been discussed. - Abstract: Bismuth (Bi)-doped ZnO nanocomposite material was prepared by precipitation method with doping precursors of bismuth nitrate pentahydrate and oxalic acid, characterized by X-ray diffraction (XRD), High Resolution-Scanning Electron Microscopy (HR-SEM) with Energy Dispersive X-ray (EDX) analysis, UV–visible Diffuse Reflectance Spectroscopy (UV–visible DRS) and Fourier Transform-Raman (FT-RAMAN) analysis. The enhanced photocatalytic activity of the Bi-doped ZnO is demonstrated through photodegradation of Congo red under UV-light irradiation. The mechanism of photocatalytic effect of Bi-doped ZnO nanocomposite material has been discussed

Antibacterial effects of silver-doped hydroxyapatite thin films sputter deposited on titanium

International Nuclear Information System (INIS)

Trujillo, Nathan A.; Oldinski, Rachael A.; Ma, Hongyan; Bryers, James D.; Williams, John D.; Popat, Ketul C.

2012-01-01

Since many orthopedic implants fail as a result of loosening, wear, and inflammation caused by repeated loading on the joints, coatings such as hydroxyapatite (HAp) on titanium with a unique topography have been shown to improve the interface between the implant and the natural tissue. Another serious problem with long-term or ideally permanent implants is infection. It is important to prevent initial bacterial colonization as existing colonies have the potential to become encased in an extracellular matrix polymer (biofilm) that is resistant to antibacterial agents. In this study, plasma-based ion implantation was used to examine the effects of pre-etching on plain titanium. Topographical changes to the titanium samples were examined and compared via scanning electron microscopy. Hydroxyapatite and silver-doped hydroxyapatite thin films were then sputter deposited on titanium substrates etched at − 700 eV. For silver-doped films, two concentrations of silver (∼ 0.5 wt.% and ∼ 1.5 wt.%) were used. Silver concentrations in the film were determined using energy dispersive X-ray spectroscopy. Hydroxyapatite film thicknesses were determined by measuring the surface profile using contact profilometry. Staphylococcus epidermidis and Pseudomonas aeruginosa adhesion studies were performed on plain titanium, titanium coated with hydroxyapatite, titanium coated with ∼ 0.5 wt.% silver-doped hydroxyapatite, and titanium coated with ∼ 1.5 wt.% silver-doped hydroxyapatite. Results indicate that less bacteria adhered to surfaces containing hydroxyapatite and silver; further, as the hydroxyapatite films delaminated, silver ions were released which killed bacteria in suspension. - Highlights: ► We have developed a combination of plasma-based ion implantation and ion beam sputter deposition technique. ► Silver-doped hydroxyapatite thin films on titanium were developed. ► The thin films showed the ability to control the concentration of silver that is doped within the

Effect of Mg-doping on the degradation of LiNiO2-based cathode materials by combined spectroscopic methods

OpenAIRE

Muto, Shunsuke; Tatsumi, Kazuyoshi; Kojima, Yuji; Oka, Hideaki; Kondo, Hiroki; Horibuchi, Kayo; Ukyo, Yoshio

2012-01-01

The performance of a LiNiO2-based cell has been shown to be significantly improved by Mg-doping of LiNi0.8Co0.15Al0.05O2 (Mg-doped NCA) cathode materials. In the present study, the effects of Mg-doping were examined by electrochemical impedance spectroscopy (EIS) and scanning transmission electron microscopy-electron energy loss spectroscopy. EIS analysis revealed that the activation energy of Mg-doped NCA for the charge-transfer reaction was larger than that of undoped NCA by a factor of ∼10...

Characteristics of Mg-doped and In-Mg co-doped p-type GaN epitaxial layers grown by metal organic chemical vapour deposition

International Nuclear Information System (INIS)

Chung, S J; Lee, Y S; Suh, E-K; Senthil Kumar, M; An, M H

2010-01-01

Mg-doped and In-Mg co-doped p-type GaN epilayers were grown using the metal organic chemical vapour deposition technique. The effect of In co-doping on the physical properties of p-GaN layer was examined by high resolution x-ray diffraction (HRXRD), transmission electron microscopy (TEM), Hall effect, photoluminescence (PL) and persistent photoconductivity (PPC) at room temperature. An improved crystalline quality and a reduction in threading dislocation density are evidenced upon In doping in p-GaN from HRXRD and TEM images. Hole conductivity, mobility and carrier density also significantly improved by In co-doping. PL studies of the In-Mg co-doped sample revealed that the peak position is blue shifted to 3.2 eV from 2.95 eV of conventional p-GaN and the PL intensity is increased by about 25%. In addition, In co-doping significantly reduced the PPC effect in p-type GaN layers. The improved electrical and optical properties are believed to be associated with the active participation of isolated Mg impurities.

Toxic effect of heavy metals on aquatic environment | Baby ...

African Journals Online (AJOL)

Toxic effect of heavy metals on aquatic environment. ... International Journal of Biological and Chemical Sciences ... The indiscriminate discharge of industrial effluents, raw sewage wastes and other waste pollute most of the environments and ...

Fabrication and photovoltaic performance of niobium doped TiO{sub 2} hierarchical microspheres with exposed {001} facets and high specific surface area

Energy Technology Data Exchange (ETDEWEB)

Liu, Yongqiang; Ran, Huili [School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450001 (China); State Centre for International Cooperation on Designer Low-Carbon and Environmental Materials, Zhengzhou University, Zhengzhou 450001 (China); Fan, Jiajie, E-mail: fanjiajie@zzu.edu.cn [School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450001 (China); State Centre for International Cooperation on Designer Low-Carbon and Environmental Materials, Zhengzhou University, Zhengzhou 450001 (China); Zhang, Xiaoli; Mao, Jing [School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450001 (China); State Centre for International Cooperation on Designer Low-Carbon and Environmental Materials, Zhengzhou University, Zhengzhou 450001 (China); Shao, Guosheng [School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450001 (China); State Centre for International Cooperation on Designer Low-Carbon and Environmental Materials, Zhengzhou University, Zhengzhou 450001 (China); Institute for Renewable Energy and Environmental Technologies, University of Bolton, Bolton BL3 5AB (United Kingdom)

2017-07-15

Highlights: • Nb-doped hierarchical TiO{sub 2} microsphere DSSCs show enhanced performance. • Nb{sup 5+} dopant replaces Ti{sup 4+} cation in TiO{sub 2} lattice. • Electrons transport was enhanced due to the down-shifted conduction band minimum. • Exposed (001) facets and high specific surface area allows high dye-loading. - Abstract: The niobium doped hierarchical anatase TiO{sub 2} microspheres, which are consist of a serried nano-thorns and plicate nano-ribbons with exposed {001} facets, were synthesized using hydrothermal method followed by heat treatment. The effects of niobium on the microstructures and photovoltaic performances of the dye-sensitized solar cells (DSSCs) were studied. The results revealed that Nb{sup 5+} doping replaces Ti{sup 4+} cations in TiO{sub 2} lattice, and the bandgap of the films varies with increasing Nb doping concentration because of the downshift of the conduction band minimum (CBM). The niobium-doped TiO{sub 2} DSSCs with moderate loadings show enhanced performance comparing with their pure TiO{sub 2} counterparts. Optimally, the conversion efficiency of the Nb-3.5 (Nb 3.5 mol%) DSSC is 4.99%. This is higher than that (4.39%) of pure TiO{sub 2} cells by 13.7%. This is due to the fact that the Nb-doped solar cells have increased the number of the photo-induced electrons because of their exposed (001) facets and higher specific surface area; and enhanced electrons collection and transport because of the downshifted CBM of the Nb-doped TiO{sub 2}. However, heavy Nb doping results in the decrease of the performance of the niobium-doped cells due to the excessive defects within the Nb-TiO{sub 2} samples resulting in enhanced charge recombination at defects.

Effects of Ba doping on physical properties of La-Ca-Mn-O thin films

CERN Document Server

Hong, N H; Sakai, J; Iwasaki, H

2003-01-01

Transport and magnetic properties of La-Ba-Ca-Mn-O thin films fabricated by the pulsed laser deposition technique had been investigated systematically to see the effects of substitution of the small atom Ca by Ba which is much bigger. The induced insulator-to-metal (IM) transition was obtained not only in compositions near 0.5 and 0.18 which are boundaries between metallic and insulating phases but also in the heavily doped region. In the region of x > 0.5, the Ba doping causes an anomalous response of the system to the magnetic field and a positive magnetoresistance was observed. Besides, our results concerning the vicinity of 0.5 imply the existence of phase separation. As for x < 0.5, the doping enhances remarkably the paramagnetism-ferromagnetism transition and the IM transition temperatures.

The synergetic effect of V and Fe-co-doping in TiO{sub 2} studied from the DFT + U first-principle calculation

Energy Technology Data Exchange (ETDEWEB)

Liu, Baoshun, E-mail: liubaoshun@126.com; Zhao, Xiujian

2017-03-31

Highlights: • The effect of Fe and V doping on TiO{sub 2} structure was studied with DFT + U calculation. • V and Fe co-doping affects the formation energies and electronic structure. • V and Fe co-doping causes the synergetic effect on the optical properties. - Abstract: Based on the density functional theory (DFT + U), a detailed study on the energetic, electronic, and optical properties of Fe-, V-, and Fe & V-co-doping anatase and rutile TiO{sub 2} was performed The synergetic effect of Fe & V bimetal co-doping on the optical absorption was discussed on electronic level. Two kinds of co-dopants were considered, which included edge-shared and corner-shared co-doping. It was shown that Fe and V atoms prefer to replace Ti atom in the O-rich contions than in the Ti-rich conditions. Co-doping in anatase reduces the formation energies in both cases, while the formation energies for rutile cannot be decreased. The Bader charge analysis indicates the +3 of Fe atom and +4 of V atom, and the obvious electron exchange between Fe and V atom in co-doping cases can be identified, which indicates the presence of synergetic effect induced by co-doping. The cooperation of Fe & V co-dopants was also supported by the result of projected density of states and spin charge density differences, as the hybridization of Fe3d with V3d orbitals was seen within the TiO{sub 2} forbidden band. Different from single-dopant systems, the V3d-Fe3d co-interaction leads to the formation of some spin mid-gap states, which have an obvious effect on the optical absorptions.

Nonequilibrium-Plasma-Synthesized ZnO Nanocrystals with Plasmon Resonance Tunable via Al Doping and Quantum Confinement.

Science.gov (United States)

Greenberg, Benjamin L; Ganguly, Shreyashi; Held, Jacob T; Kramer, Nicolaas J; Mkhoyan, K Andre; Aydil, Eray S; Kortshagen, Uwe R

2015-12-09

Metal oxide semiconductor nanocrystals (NCs) exhibit localized surface plasmon resonances (LSPRs) tunable within the infrared (IR) region of the electromagnetic spectrum by vacancy or impurity doping. Although a variety of these NCs have been produced using colloidal synthesis methods, incorporation and activation of dopants in the liquid phase has often been challenging. Herein, using Al-doped ZnO (AZO) NCs as an example, we demonstrate the potential of nonthermal plasma synthesis as an alternative strategy for the production of doped metal oxide NCs. Exploiting unique, thoroughly nonequilibrium synthesis conditions, we obtain NCs in which dopants are not segregated to the NC surfaces and local doping levels are high near the NC centers. Thus, we achieve overall doping levels as high as 2 × 10(20) cm(-3) in NCs with diameters ranging from 12.6 to 3.6 nm, and for the first time experimentally demonstrate a clear quantum confinement blue shift of the LSPR energy in vacancy- and impurity-doped semiconductor NCs. We propose that doping of central cores and heavy doping of small NCs are achievable via nonthermal plasma synthesis, because chemical potential differences between dopant and host atoms-which hinder dopant incorporation in colloidal synthesis-are irrelevant when NC nucleation and growth proceed via irreversible interactions among highly reactive gas-phase ions and radicals and ligand-free NC surfaces. We explore how the distinctive nucleation and growth kinetics occurring in the plasma influences dopant distribution and activation, defect structure, and impurity phase formation.

Effect of light rare earth doping in 123 high temperature supercoductors

Directory of Open Access Journals (Sweden)

M. Mirzadeh

2006-09-01

Full Text Available   We have studied the structural and electrical properties of Gd(Ba2-xLaxCu3O7+δ [Gd(BaLa123], Gd(Ba2-xNdxCu3O7+δ [Gd(BaNd123], and Nd(Ba2-xPrxCu3O7+δ [Nd(BaPr123] compounds with 0.0≤x≤0.8 prepared by the standard solid-state reaction. The XRD patterns show that all of the samples with x≤0.5 are isosructure 123 phase, but in Gd(BaNd123 and Nd(BaPr123 there are several impurity peaks in the XRD patterns for x≥0.6. We estimated the xcsolubility=1.1, 0.6 and 0.55 in Gd(BaLa123, Nd(BaPr123, and Gd(BaNd123, respectively. The resistivity increases with the increase of doping. The decrease of Tc with the increase of Pr doping is faster than Nd and La doping. The normal-state resistivity is fitted for two and three dimensional variable range hopping (2D&amp3D-VRH and Coulomb gap (CG regimes, separately. Our results indicate that the dominant mechanism for x≥xcSIT is 3D-VRH. The broadening of magnetoresistance have been investigated by TAFC and AH models. The pinning energy and Josephson coupling energy, decrease with the increase of applied magnetic field as U~H-β, these values also decrease with doping concentration Pr is more effective than Nd and La.

Photoacoustic study of the effect of doping concentration on the transport properties of GaAs epitaxial layers

NARCIS (Netherlands)

George, S.D.; Dilna, S.; Prasanth, R.; Radhakrishnan, P.; Vallabhan, C.P.G.; Nampoori, V.P.N.

2003-01-01

We report a photoacoustic (PA) study of the thermal and transport properties of a GaAs epitaxial layer doped with Si at varying doping concentration, grown on GaAs substrate by molecular beam epitaxy. The data are analyzed on the basis of Rosencwaig and Gersho's theory of the PA effect. The

Ce-doping effects on electronic structures of Ba0.5Sr0.5TiO3 thin film

International Nuclear Information System (INIS)

Wang, S Y; Cheng, B L; Wang, Can; Button, T W; Dai, S Y; Jin, K J; Lu, H B; Zhou, Y L; Chen, Z H; Yang, G Z

2006-01-01

In order to clarify the basic reason why Ce doping can dramatically decrease the leakage current in Ba 0.5 Sr 0.5 TiO 3 (BST) as reported in our previous work (Wang et al 2005 J. Phys. D: Appl. Phys. 38 2253), we have employed x-ray photoelectron spectroscopy (XPS) and the optical transmittance technique to study the electronic structure of undoped and 1.0 at% Ce-doped BST (CeBST) films fabricated by pulsed laser deposition. XPS results show that Ce doping has a strong influence on the valence band and core levels of BST films, and that the Fermi level is lowered by about 0.35 eV by Ce doping. Optical transmittance measurements demonstrate that the energy gap is expanded with Ce doping. These Ce-doping effects can induce an increase in the barrier height for the thermionic emission and eventually reduce leakage current in CeBST thin films

Factorization of heavy-to-light form factors in soft-collinear effective theory

CERN Document Server

Beneke, Martin; Feldmann, Th.

2004-01-01

Heavy-to-light transition form factors at large recoil energy of the light meson have been conjectured to obey a factorization formula, where the set of form factors is reduced to a smaller number of universal form factors up to hard-scattering corrections. In this paper we extend our previous investigation of heavy-to-light currents in soft-collinear effective theory to final states with invariant mass Lambda^2 as is appropriate to exclusive B meson decays. The effective theory contains soft modes and two collinear modes with virtualities of order m_b*Lambda (`hard-collinear') and Lambda^2. Integrating out the hard-collinear modes results in the hard spectator-scattering contributions to exclusive B decays. We discuss the representation of heavy-to-light currents in the effective theory after integrating out the hard-collinear scale, and show that the previously conjectured factorization formula is valid to all orders in perturbation theory. The naive factorization of matrix elements in the effective theory ...

Effect of Platinum Group Metal Doping in Magnesium Diboride Wires

DEFF Research Database (Denmark)

Grivel, Jean-Claude; Alexiou, Aikaterini; Namazkar, Shahla

2016-01-01

The effect of some platinum group metals(PGM = Rh, Pd, and Pt) on the microstructure and critical current density of Cu/Nb-sheathed MgB2 wires has been studied using Mg1-x PGMxB2 powders with low doping levels. It was found that Pt and Pd do not enter the MgB2 lattice and have only limited influe...

Investigation of the additive induced doping effects in gelcast soft lead zirconate titanate ceramics

International Nuclear Information System (INIS)

Guo Dong; Cai Kai; Li Longtu; Gui Zhilun

2009-01-01

Due to the high sensitivity of the electrical properties of electronic ceramics to various factors, knowledge about the possible influence of the processing procedure on their electrical performance is critical for applying a new technique to the fabrication of the materials. In this study, various electrical parameters, complex impedance spectra, ferroelectric hysteresis loops, and microstructures of soft lead zirconate titanate (PZT) ceramics formed by the gelcasting technique from suspensions with various dispersants were investigated in comparison with those of the conventional dry pressed ones. We found that the sodium ion, which is the main cation in many commercial surfactants, exhibited obvious hard doping effects; thus causing deteriorated performance of the gelcast PZT ceramics. While a certain impurity ion introduced by a dispersant was also found to induce soft doping characteristics and improve the electrical performance of the materials. The results suggest that the doping effects of the metal ions or impurities introduced by the dispersants, or other additives, should be generally considered for applying a wet processing technique to forming multicomponent electronic ceramics.

Negative effects of crystalline-SiC doping on the critical current density in Ti-sheathed MgB2(SiC)y superconducting wires

International Nuclear Information System (INIS)

Liang, G; Fang, H; Luo, Z P; Hoyt, C; Yen, F; Guchhait, S; Lv, B; Markert, J T

2007-01-01

Ti-sheathed MgB 2 wires doped with nanosize crystalline-SiC up to a concentration of 15 wt% SiC have been fabricated, and the effects of the SiC doping on the critical current density (J c ) and other superconducting properties studied. In contrast with the previously reported results that nano-SiC doping with a doping range below 16 wt% usually enhances J c , particularly at higher fields, our measurements show that SiC doping decreases J c over almost the whole field range from 0 to 7.3 T at all temperatures. Furthermore, it is found that the degradation of J c becomes stronger at higher SiC doping levels, which is also in sharp contrast with the reported results that J c is usually optimized at doping levels near 10 wt% SiC. Our results indicate that these negative effects on J c could be attributed to the absence of significant effective pinning centres (mainly Mg 2 Si) due to the high chemical stability of the crystalline-SiC particles

Transport properties for carbon chain sandwiched between heteroatom-doped carbon nanotubes with different doping sites

International Nuclear Information System (INIS)

Liu, Wenjiang; Deng, Xiaoqing; Cai, Shaohong

2016-01-01

The First-principles calculation is used to investigate the transport properties of a carbon chain connected with N-and/or B-doped caped carbon nanotube acting as electrodes. The I-V curves of the carbon chain are affected by the N/B doping sites, and rectifying behavior can be obtained distinctly when the carbon chain is just connected onto two doping atom sites (N- chain-B), and a weak rectification occurs when N (B) doping at other sites. Interestingly, the spin-filtering effects exist in the junction when it is doped at other sites, undoped system, or N-terminal carbon chains. However, no this behavior is found in N-chain-B and B-chain-B systems. The analysis on the transmission spectra, PDOS, LDOS, spin density, and the electron transmission pathways give an insight into the observed results for the system.

Transport properties for carbon chain sandwiched between heteroatom-doped carbon nanotubes with different doping sites

Energy Technology Data Exchange (ETDEWEB)

Liu, Wenjiang [Big Data and Information Engineering College of Guizhou University, Guiyang 550025 (China); Guizhou University of Finance and Economics, Guiyang 550025 (China); Deng, Xiaoqing, E-mail: xq-deng@163.com, E-mail: caish@mail.gufe.edu.cn [School of Physics and Electronic Science, Changsha University of Science and Technology, Changsha 410114 (China); Cai, Shaohong, E-mail: xq-deng@163.com, E-mail: caish@mail.gufe.edu.cn [Guizhou University of Finance and Economics, Guiyang 550025 (China)

2016-07-15

The First-principles calculation is used to investigate the transport properties of a carbon chain connected with N-and/or B-doped caped carbon nanotube acting as electrodes. The I-V curves of the carbon chain are affected by the N/B doping sites, and rectifying behavior can be obtained distinctly when the carbon chain is just connected onto two doping atom sites (N- chain-B), and a weak rectification occurs when N (B) doping at other sites. Interestingly, the spin-filtering effects exist in the junction when it is doped at other sites, undoped system, or N-terminal carbon chains. However, no this behavior is found in N-chain-B and B-chain-B systems. The analysis on the transmission spectra, PDOS, LDOS, spin density, and the electron transmission pathways give an insight into the observed results for the system.

Understanding the doping effects on the structural and electrical properties of ultrathin carbon nanotube networks

International Nuclear Information System (INIS)

Zhou, Ying; Shimada, Satoru; Azumi, Reiko; Saito, Takeshi

2015-01-01

Similar to other semiconductor technology, doping of carbon nanotube (CNT) thin film is of great significance for performance improvement or modification. However, it still remains a challenge to seek a stable and effective dopant. In this paper, we unitize several spectroscopic techniques and electrical characterizations under various conditions to investigate the effects of typical dopants and related methods. Nitric acid (HNO 3 ) solution, I 2 vapor, and CuI nanoparticles are used to modify a series of ultrathin CNT networks. Although efficient charge transfer is achieved initially after doping, HNO 3 is not applicable because it suffers from severe reliability problems in structural and electrical properties, and it also causes a number of undesired structural defects. I 2 vapor doping at 150 °C can form some stable C-I bonding structures, resulting in relatively more stable but less efficient electrical performances. CuI nanoparticles seem to be an ideal dopant. Photonic curing enables the manipulation of CuI, which not only results in the construction of novel CNT-CuI hybrid structures but also encourages the deepest level of charge transfer doping. The excellent reliability as well as processing feasibility identify the bright perspective of CNT-CuI hybrid film for practical applications

Understanding the doping effects on the structural and electrical properties of ultrathin carbon nanotube networks

Energy Technology Data Exchange (ETDEWEB)

Zhou, Ying, E-mail: y-shuu@aist.go.jp; Shimada, Satoru; Azumi, Reiko [Electronics and Photonics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, 305-8565 Tsukuba (Japan); Saito, Takeshi [Nanomaterials Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, 305-8565 Tsukuba (Japan)

2015-12-07

Similar to other semiconductor technology, doping of carbon nanotube (CNT) thin film is of great significance for performance improvement or modification. However, it still remains a challenge to seek a stable and effective dopant. In this paper, we unitize several spectroscopic techniques and electrical characterizations under various conditions to investigate the effects of typical dopants and related methods. Nitric acid (HNO{sub 3}) solution, I{sub 2} vapor, and CuI nanoparticles are used to modify a series of ultrathin CNT networks. Although efficient charge transfer is achieved initially after doping, HNO{sub 3} is not applicable because it suffers from severe reliability problems in structural and electrical properties, and it also causes a number of undesired structural defects. I{sub 2} vapor doping at 150 °C can form some stable C-I bonding structures, resulting in relatively more stable but less efficient electrical performances. CuI nanoparticles seem to be an ideal dopant. Photonic curing enables the manipulation of CuI, which not only results in the construction of novel CNT-CuI hybrid structures but also encourages the deepest level of charge transfer doping. The excellent reliability as well as processing feasibility identify the bright perspective of CNT-CuI hybrid film for practical applications.

Can heavy metal pollution defend seed germination against heat stress? Effect of heavy metals (Cu(2+), Cd(2+) and Hg(2+)) on maize seed germination under high temperature.

Science.gov (United States)

Deng, Benliang; Yang, Kejun; Zhang, Yifei; Li, Zuotong

2016-09-01

Heavy metal pollution, as well as greenhouse effect, has become a serious threat today. Both heavy metal and heat stresses can arrest seed germination. What response can be expected for seed germination under both stress conditions? Here, the effects of heavy metals (Cu(2+), Cd(2+) and Hg(2+)) on maize seed germination were investigated at 20 °C and 40 °C. Compared with 20 °C, heat stress induced thermodormancy. However, this thermodormancy could be significantly alleviated by the addition of a low concentration of heavy metals. Heavy metals, as well as heat stress induced H2O2 accumulation in germinating seeds. Interestingly, this low concentration of heavy metal that promoted seed germination could be partly blocked by DMTU (a specific ROS scavenger), irrespective of temperature. Accordingly, H2O2 addition reinforced this promoting effect on seed germination, which was induced by a low concentration of heavy metal. Furthermore, we found that the NADPH oxidase derived ROS was required for seed germination promoted by the heavy metals. Subsequently, treatment of seeds with fluridone (a specific inhibitor of ABA) or ABA significantly alleviated or aggravated thermodormancy, respectively. However, this alleviation or aggravation could be partly attenuated by a low concentration of heavy metals. In addition, germination that was inhibited by high concentrations of heavy metals was also partly reversed by fluridone. The obtained results support the idea that heavy metal-mediated ROS and hormone interaction can finally affect the thermodormancy release or not. Copyright © 2016 Elsevier Ltd. All rights reserved.

Size effect on the SHG properties of Cu-doped CdI2 nanocrystals

International Nuclear Information System (INIS)

Miah, M. Idrish

2009-01-01

Because the optically induced second harmonic generation (SHG) is prevented by symmetry in a centrosymmetric material, one needs to form noncentrosymmetric processes in order to observe the SHG. However, one of the efficient ways to enhance the noncentrosymmetricity of a material is to dope it with an appropriate impurity and amount. We grow Cu-doped CdI 2 layered nanocrystal structures from the mixture of CdI 2 and CuI using the standard Bridgman-Stockbarger method and investigate the nano-confined effects by studying the second-order optical effect via the measurements of SHG. The second-order susceptibility for the nanocrystals is calculated and the values at liquid helium temperature range from 0.38 to 0.83 pm V -1 for the thicknesses of 10-0.8 nm respectively. The size dependence demonstrates the nano-sized quantum-confined effect with a clear increase in the SHG with decreasing the thickness of the nanocrystal or crystal temperature. Since the local electron-phonon anharmonicity is described by third-order rank tensors in disordered systems, the SHG is very similar to that one introduced for the third-order optical susceptibility. It has been confirmed by observing the large photoluminescent yield of the pure crystals. The Raman scattering spectra taken for thin nanocrystals confirm the phonon modes originating from interlayer phonons crucially responsible for the observed effects. The obtained results show that the Cu-doped CdI 2 layered nanocrystals are promising materials for applications in optoelectronic nano-devices.

A DFT study of arsine adsorption on palladium doped graphene: Effects of palladium cluster size

Energy Technology Data Exchange (ETDEWEB)

Kunaseth, Manaschai, E-mail: manaschai@nanotec.or.th [National Nanotechnology Center (NANOTEC), National Science and Technology Development Agency (NSTDA) , Pathum Thani 12120 (Thailand); Mudchimo, Tanabat [Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Ubon Ratchathani University, Ubon Ratchathani 34190 (Thailand); Namuangruk, Supawadee [National Nanotechnology Center (NANOTEC), National Science and Technology Development Agency (NSTDA) , Pathum Thani 12120 (Thailand); Kungwan, Nawee [Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Promarak, Vinich [Department of Material Science and Engineering, School of Molecular Science and Engineering, Vidyasirimedhi Institute of Science and Technology, Rayong 21201 (Thailand); Jungsuttiwong, Siriporn, E-mail: siriporn.j@ubu.ac.th [Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Ubon Ratchathani University, Ubon Ratchathani 34190 (Thailand)

2016-03-30

Graphical abstract: The relationship between charge difference and adsorption strength demonstrates that charge migration from Pd{sub n}-SDG to AsH{sub x} significantly enhanced adsorption strength, the Pd{sub 6} clusters doped SDG with a steep slope is recommended as a superior adsorbent material for AsH{sub 3} removal from gas stream. - Highlights: • Pd atom and Pd clusters bind strongly onto the defective graphene surface. • Larger size of Pd cluster adsorbs arsine and its hydrogenated products stronger. • Order of adsorption strength on Pd{sub n} doped graphene: As > AsH > AsH{sub 2} > > AsH{sub 3}. • Charge migration characterizes the strong adsorption of AsH{sub 2}, AsH, and As. • Pd cluster doped graphene is thermodynamically preferable for arsine removal. - Abstract: In this study, we have investigated the size effects of palladium (Pd) doped single-vacancy defective graphene (SDG) surface to the adsorption of AsH{sub 3} and its dehydrogenated products on Pd using density functional theory calculations. Here, Pd cluster binding study revealed that Pd{sub 6} nanocluster bound strongest to the SDG surface, while adsorption of AsH{sub x} (x = 0–3) on the most stable Pd{sub n} doped SDG showed that dehydrogenated arsine compounds adsorbed onto the surface stronger than the pristine AsH{sub 3} molecule. Charge analysis revealed that considerable amount of charge migration from Pd to dehydrogenated arsine molecules after adsorption may constitute strong adsorption for dehydrogenated arsine. In addition, study of thermodynamic pathways of AsH{sub 3} dehydrogenation on Pd{sub n} doped SDG adsorbents indicated that Pd cluster doping on SDG adsorbent tends to be thermodynamically favorable for AsH{sub 3} decomposition than the single-Pd atom doped SDG. Hence, our study has indicated that Pd{sub 6} clusters doped SDG is more advantageous as adsorbent material for AsH{sub 3} removal.

Effect of DOPE and cholesterol on the protein adsorption onto lipid nanoparticles

International Nuclear Information System (INIS)

Caracciolo, Giulio; Pozzi, Daniela; Capriotti, Anna Laura; Cavaliere, Chiara; Laganà, Aldo

2013-01-01

Upon administration, nanoparticles (NPs) are exposed to biological fluids from which they adsorb proteins and other biomolecules to form a “protein corona”. NP–protein interactions are still poorly understood and quantitative studies to characterize them remain scarce. Here, we have investigated the effect of neutral dioleoylphosphatidylethanolamine (DOPE) and cholesterol on the adsorption of human plasma proteins onto the surface of 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP)-based cationic liposomes of 100 nm in diameter. Quantitative analysis of the protein corona revealed that replacing cationic DOTAP lipids with neutral lipids, being indifferently DOPE or cholesterol, reduces the affinity of fibrinogen, prothrombin, vitamin K, and vitronectin for the lipid surface. On the other side, DOPE specifically promotes the adsorption of apolipoproteins and serum albumin, while cholesterol induces the preferential binding of immunoglobulins and complement proteins. The results of this study will help to explain why NPs of different lipid compositions have a dramatic difference in their in vivo transfection efficiency and will be useful for design of lipid NPs with optimal circulation profiles.

Effect of DOPE and cholesterol on the protein adsorption onto lipid nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Caracciolo, Giulio, E-mail: giulio.caracciolo@uniroma1.it; Pozzi, Daniela [' Sapienza' University of Rome, Department of Molecular Medicine (Italy); Capriotti, Anna Laura; Cavaliere, Chiara; Lagana, Aldo [' Sapienza' University of Rome, Department of Chemistry (Italy)

2013-03-15

Upon administration, nanoparticles (NPs) are exposed to biological fluids from which they adsorb proteins and other biomolecules to form a 'protein corona'. NP-protein interactions are still poorly understood and quantitative studies to characterize them remain scarce. Here, we have investigated the effect of neutral dioleoylphosphatidylethanolamine (DOPE) and cholesterol on the adsorption of human plasma proteins onto the surface of 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP)-based cationic liposomes of 100 nm in diameter. Quantitative analysis of the protein corona revealed that replacing cationic DOTAP lipids with neutral lipids, being indifferently DOPE or cholesterol, reduces the affinity of fibrinogen, prothrombin, vitamin K, and vitronectin for the lipid surface. On the other side, DOPE specifically promotes the adsorption of apolipoproteins and serum albumin, while cholesterol induces the preferential binding of immunoglobulins and complement proteins. The results of this study will help to explain why NPs of different lipid compositions have a dramatic difference in their in vivo transfection efficiency and will be useful for design of lipid NPs with optimal circulation profiles.

Effect of doping (C or N) and co-doping (C+N) on the photoactive properties of magnetron sputtered titania coatings for the application of solar water-splitting.

Science.gov (United States)

Rahman, M; Dang, B H Q; McDonnell, K; MacElroy, J M D; Dowling, D P

2012-06-01

The photocatalytic splitting of water into hydrogen and oxygen using a photoelectrochemical (PEC) cell containing titanium dioxide (TiO2) photoanode is a potentially renewable source of chemical fuels. However, the size of the band gap (-3.2 eV) of the TiO2 photocatalyst leads to its relatively low photoactivity toward visible light in a PEC cell. The development of materials with smaller band gaps of approximately 2.4 eV is therefore necessary to operate PEC cells efficiently. This study investigates the effect of dopant (C or N) and co-dopant (C+N) on the physical, structural and photoactivity of TiO2 nano thick coating. TiO2 nano-thick coatings were deposited using a closed field DC reactive magnetron sputtering technique, from titanium target in argon plasma with trace addition of oxygen. In order to study the influence of doping such as C, N and C+N inclusions in the TiO2 coatings, trace levels of CO2 or N2 or CO2+N2 gas were introduced into the deposition chamber respectively. The properties of the deposited nano-coatings were determined using Spectroscopic Ellipsometry, SEM, AFM, Optical profilometry, XPS, Raman, X-ray diffraction UV-Vis spectroscopy and tri-electrode potentiostat measurements. Coating growth rate, structure, surface morphology and roughness were found to be significantly influenced by the types and amount of doping. Substitutional type of doping in all doped sample were confirmed by XPS. UV-vis measurement confirmed that doping (especially for C doped sample) facilitate photoactivity of sputtered deposited titania coating toward visible light by reducing bandgap. The photocurrent density (indirect indication of water splitting performance) of the C-doped photoanode was approximately 26% higher in comparison with un-doped photoanode. However, coating doped with nitrogen (N or N+C) does not exhibit good performance in the photoelectrochemical cell due to their higher charge recombination properties.

Photoluminescence Studies of P-type Modulation Doped GaAs/AlGaAs Quantum Wells in the High Doping Regime

Science.gov (United States)

Wongmanerod, S.; Holtz, P. O.; Reginski, K.; Bugaiski, M.; Monemar, B.

The influence of high Be-acceptor doping on the modulation-doped GaAs/Al0.3Ga0.7As quantum wells structures has been optically studied by using the low-temperature photoluminescence (PL) and photoluminescence excitation (PLE) techniques.The modulation doped samples were grown by the molecular-beam epitaxy technique with a varying Be acceptor concentration ranging from 1×1018 to 8×1018cm-3. Several novels physical effects were observed. The main effect is a significant shift of the main emission towards lower energies as the doping concentrations increase. There are two contradictory mechanisms, which determine the peak energy of the main emission; the shrinkage of the effective bandgap due to many body effects and the reduction of the exciton binding energy due to the carrier screening effect. We conclude that the first one is the dominating effect. At a sufficiently high doping concentration (roughly 2×1018cm-3), the lineshape of the main PL emission is modified, and a new feature, the so called Fermi-edge singularity (FES), appears on the high energy side of the PL emission and exhibits a blue-shift as a function of doping concentration. This feature has been found to be very sensitive to a temperature change, already in the range of 4.4-50K. In addition, PLE spectra with a suitable detection energy show that the absorption edge is blue-shifted with respect to the PL main emission. The resulting Stoke shift is due to phase-space-filling of the carriers, in agreement with the FES interpretation. Finally, we have found from the PLE spectra that the exciton quenching is initiated in the same doping regime. Compared to the exciton quenching in other p-type structures, the critical acceptor concentration required to quench the excitons is significantly lower than in the case of 2D structures with acceptor doping within the well, but larger than in the case of 3D bulk.

The effects of heavy metals concentration on some commercial fish ...

African Journals Online (AJOL)

Badmus B S

heavy metals (lead, cadmium, copper and zinc) were analyzed and only copper and zinc were found to be present in the ... contents of essential minerals, vitamins and unsaturated fatty acids .... that the interaction effect is significant. This effect ...

Effect of doping on the modification of polycrystalline silicon by spontaneous reduction of diazonium salts

Science.gov (United States)

Girard, A.; Coulon, N.; Cardinaud, C.; Mohammed-Brahim, T.; Geneste, F.

2014-09-01

The chemical modification of doped polycrystalline silicon materials (N+, N++ and P++) and silicon (1 0 0) and (1 1 1) used as references is investigated by spontaneous reduction of diazonium salts. The effectiveness of the grafting process on all polySi surfaces is shown by AFM and XPS analyses. The effect of substrate doping on the efficiency of the electrografting process is compared by using the thicknesses of the deposited organic films. For a better accuracy, two methods are used to estimate the thicknesses: XPS and the coupling of a O2 plasma etching with AFM measurement. Structural characteristics of the poly-Si films were investigated by Scanning Electron Microscopy and X-ray diffraction to find a correlation between the structure of the material and its reactivity. Different parameters that could have an impact on the efficiency of the grafting procedure are discussed. The observed differences between differently doped silicon surfaces is rather limited, this is in agreement with the radical character of the reacting species.

Competing effects between intrinsic and extrinsic defects in pure and Mn-doped ZnO nanocrystals

Energy Technology Data Exchange (ETDEWEB)

Ruf, Thomas; Repp, Sergej; Urban, Joanna [Albert-Ludwigs-Universität Freiburg, Institut für Physikalische Chemie (Germany); Thomann, Ralf [Albert-Ludwigs-Universität Freiburg, Freiburger Materialforschungszentrum (FMF) (Germany); Erdem, Emre, E-mail: emre.erdem@physchem.uni-freiburg.de [Albert-Ludwigs-Universität Freiburg, Institut für Physikalische Chemie (Germany)

2016-05-15

Nano-sized ZnO doped with transition metals is one of the most promising candidates in the field of diluted magnetic semiconductors unifying ferromagnetic and semiconductor properties. Promising is the exploitation of the magnetic spin of the electron and by that the application in spintronics. As the mechanism of spin coupling is still controversial, insight into the coexistence and interaction of intrinsic and extrinsic effects is vital for further technological progress. We report on the synthesis of a set of nano-sized Zn{sub 1−x}Mn{sub x}O samples with a nominal concentration of x = 0.000005–0.03 and structural (XRD, TEM, and AFM), as well as electronic (PL, UV–Vis, FTIR, and EPR) investigations. In this contribution, possible interaction effects were summarized in terms of Mn doping and size. PL quenching after doping was also discussed as another aspect for the interrelations of the defects.

BDK-doped core microstructured PMMA optical fiber for effective Bragg grating photo-inscription

DEFF Research Database (Denmark)

Hu, Xuehao; Woyessa, Getinet; Kinet, Damien

2017-01-01

An endlessly single-mode doped microstructured poly(methyl methacrylate) (PMMA) optical fiber is produced for effective fiber Bragg grating (FBG) photo-inscription by means of a 400 nm femtosecond pulsed laser and the phase mask technique. The fiber presents a uniform benzyl dimethyl ketal (BDK......) distribution in its core without drastic loss increase. It was produced using the selected center hole doping technique, and the BDK dopant acts as a photoinitiator. In this Letter, we report a rapidly growing process of the grating reflection band. For an 11 mW mean laser power, the FBG reflectivity reaches...

Effect of seeds of heavy charged particles of galactic cosmic radiation

International Nuclear Information System (INIS)

Maksimova, Y.N.

1985-01-01

The experiments were carried out on Lactuca sativa seeds exposed for 20, 66, 123 and 308 days in a biostack also containing physical detectors of heavy charged particles. The yield of aberrant cells and its dependence on the exposure time and the site where particles hit the object were measured. The cytogenetic examination demonstrated a significant difference between the seeds that were or were not hit by heavy charged particles. A significant contribution of galactic cosmic radiation to the radiobiological effect is indicated. The yield of aberrant cells as a function of the localization of heavy charged particles in the seed is established. The most sensitive target is the root meristem

Effect of doping on the modification of polycrystalline silicon by spontaneous reduction of diazonium salts

Energy Technology Data Exchange (ETDEWEB)

Girard, A.; Coulon, N. [UMR-CNRS 6164, Institut d’Electronique et de Télécommunications de Rennes, Université de Rennes 1, Campus de Beaulieu, 35042 Rennes cedex (France); Cardinaud, C. [UMR-CNRS 6502, Institut des Matériaux Jean Rouxel, Université de Nantes, 2 rue de la Houssinière, BP32229, F-44322 Nantes cedex 3 (France); Mohammed-Brahim, T. [UMR-CNRS 6164, Institut d’Electronique et de Télécommunications de Rennes, Université de Rennes 1, Campus de Beaulieu, 35042 Rennes cedex (France); Geneste, F., E-mail: Florence.Geneste@univ-rennes1.fr [UMR-CNRS 6226, Institut des Sciences Chimiques de Rennes, Equipe MaCSE, Université de Rennes 1, Campus de Beaulieu, 35042 Rennes cedex (France)

2014-09-30

Highlights: • Spontaneous grafting of aryl diazonium salts on polycrystalline silicon surfaces. • Effect of the nature and level of doping on the efficiency of the functionalization. • The grafting process was more efficient on PolySi substrates than on monosilicon. • Influence of the crystal structure and grain boundaries on the modification procedure. • Role of the reducing power of the substrate on the grafting procedure. - Abstract: The chemical modification of doped polycrystalline silicon materials (N+, N++ and P++) and silicon (1 0 0) and (1 1 1) used as references is investigated by spontaneous reduction of diazonium salts. The effectiveness of the grafting process on all polySi surfaces is shown by AFM and XPS analyses. The effect of substrate doping on the efficiency of the electrografting process is compared by using the thicknesses of the deposited organic films. For a better accuracy, two methods are used to estimate the thicknesses: XPS and the coupling of a O{sub 2} plasma etching with AFM measurement. Structural characteristics of the poly-Si films were investigated by Scanning Electron Microscopy and X-ray diffraction to find a correlation between the structure of the material and its reactivity. Different parameters that could have an impact on the efficiency of the grafting procedure are discussed. The observed differences between differently doped silicon surfaces is rather limited, this is in agreement with the radical character of the reacting species.

Effect of doping on the modification of polycrystalline silicon by spontaneous reduction of diazonium salts

International Nuclear Information System (INIS)

Girard, A.; Coulon, N.; Cardinaud, C.; Mohammed-Brahim, T.; Geneste, F.

2014-01-01

Highlights: • Spontaneous grafting of aryl diazonium salts on polycrystalline silicon surfaces. • Effect of the nature and level of doping on the efficiency of the functionalization. • The grafting process was more efficient on PolySi substrates than on monosilicon. • Influence of the crystal structure and grain boundaries on the modification procedure. • Role of the reducing power of the substrate on the grafting procedure. - Abstract: The chemical modification of doped polycrystalline silicon materials (N+, N++ and P++) and silicon (1 0 0) and (1 1 1) used as references is investigated by spontaneous reduction of diazonium salts. The effectiveness of the grafting process on all polySi surfaces is shown by AFM and XPS analyses. The effect of substrate doping on the efficiency of the electrografting process is compared by using the thicknesses of the deposited organic films. For a better accuracy, two methods are used to estimate the thicknesses: XPS and the coupling of a O 2 plasma etching with AFM measurement. Structural characteristics of the poly-Si films were investigated by Scanning Electron Microscopy and X-ray diffraction to find a correlation between the structure of the material and its reactivity. Different parameters that could have an impact on the efficiency of the grafting procedure are discussed. The observed differences between differently doped silicon surfaces is rather limited, this is in agreement with the radical character of the reacting species

Energy loss effects on heavy quark production in heavy-ion collisions at sq root s = 5.5 A TeV

CERN Document Server

Lin Zi Wei

1999-01-01

We study the effect of energy loss on charm and bottom quarks in high-energy heavy-ion collisions including hadronization, longitudinal expansion and partial thermalization. We consider in detail the detector geometry and single lepton energy cuts of the ALICE and CMS detectors at the Large Hadron Collider (LHC) to show the large suppression of high P sub T heavy quarks and the consequences on their semileptonic decays.

From heavy nuclei to super-heavy nuclei

International Nuclear Information System (INIS)

Theisen, Ch.

2003-01-01

The existence of super-heavy nuclei has been predicted nearly fifty years ago. Due to the strong coulomb repulsion, the stabilisation of these nuclei is possible only through shell effects. The reasons for this fragile stability, as well as the theoretical predictions concerning the position of the island of stability are presented in the first part of this lecture. In the second part, experiments and experimental techniques which have been used to synthesize or search for super-heavy elements are described. Spectroscopic studies performed in very heavy elements are presented in the following section. We close this lecture with techniques that are currently being developed in order to reach the superheavy island and to study the structure of very-heavy nuclei. (author)

Effect of tin doping on oxygen- and carbon-related defects in Czochralski silicon

International Nuclear Information System (INIS)

Chroneos, A.; Londos, C. A.; Sgourou, E. N.

2011-01-01

Experimental and theoretical techniques are used to investigate the impact of tin doping on the formation and the thermal stability of oxygen- and carbon-related defects in electron-irradiated Czochralski silicon. The results verify previous reports that Sn doping reduces the formation of the VO defect and suppresses its conversion to the VO 2 defect. Within experimental accuracy, a small delay in the growth of the VO 2 defect is observed. Regarding carbon-related defects, it is determined that Sn doping leads to a reduction in the formation of the C i O i , C i C s , and C i O i (Si I ) defects although an increase in their thermal stability is observed. The impact of strain induced in the lattice by the larger tin substitutional atoms, as well as their association with intrinsic defects and carbon impurities, can be considered as an explanation to account for the above observations. The density functional theory calculations are used to study the interaction of tin with lattice vacancies and oxygen- and carbon-related clusters. Both experimental and theoretical results demonstrate that tin co-doping is an efficient defect engineering strategy to suppress detrimental effects because of the presence of oxygen- and carbon-related defect clusters in devices.

Effect of CASP glass doping on sintering and dielectric properties of SBN ceramics

International Nuclear Information System (INIS)

Chen Guohua; Qi Bing

2009-01-01

16CaO-29Al 2 O 3 -34SiO 2 -13PbO-4B 2 O 3 -2ZnO-2P 2 O 5 (CASP) glass doped-Sr 0.5 Ba 0.5 Nb 2 O 6 (SBN50) ceramics have been synthesized by solid-state ceramic route. The effects of CASP glass on the firing, microstructure and dielectric characterization of SBN50 ceramics are investigated. The densities of the ceramic samples firstly increase and then slightly decrease with increasing CASP glass content. The appropriate amount of doping glass is 2%. The SBN50 ceramics doped with CASP glass can be sintered at a relatively low temperature, 1200 deg. C. X-ray diffraction analysis shows the single phase (tetragonal tungsten bronze type structure) is preserved for all the samples. The diffuse character of the ceramic system increases and the dielectric constant at phase transition temperature (T c ) markedly decreases as CASP glass content increases. Interestingly, the CASP glass addition drastically alters the microstructure of the sintered ceramics. The isotropic grains in the pure SBN50 ceramics transform to rod like grains after the addition of CASP glass. The grain size of SBN phase is found to obviously increase with increase in CASP glass doping level

Effects of Sn doping on the morphology, structure, and electrical property of In{sub 2}O{sub 3} nanofiber networks

Energy Technology Data Exchange (ETDEWEB)

Wu, Xu; Wang, Yihua [Zhejiang Sci-Tech University, College of Materials and Textiles, Hangzhou (China); Yang, Bin [Zhejiang Sci-Tech University, Ministry of Education, Key Laboratory of Advanced Textile Materials and Manufacturing Technology, College of Materials and Textiles, Hangzhou (China); Zhejiang Sci-Tech University, College of Materials and Textiles, Hangzhou (China)

2014-11-15

This paper studies the effect of Sn doping on the morphological, structural, and electrical properties of the Sn-doping In{sub 2}O{sub 3} nanofiber networks. In{sub 2}O{sub 3}-based nanofibers with various relative concentration of Sn precursor (0-20 mol%) were fabricated through the electrospinning method. Scanning electron microscopy observations show that, depending on the relative concentration of SnCl{sub 4} in the starting materials, the doped nanofibers with different morphologies, from smooth to corn-like and then to accidented, are fabricated. Transmission electron microscopy and X-ray diffraction analyses reveal that the Sn dopants influence the growth direction of seeds, resulting in doped nanoparticles having diverse shapes and sizes, which are critical for the formation of doped nanofiber with different morphology. From these nanofiber networks, we fabricated several thin sheets to characterize the effect of Sn concentration on the electrical resistivity. The resistivity of thin sheets decreased significantly before the doping concentration up to 12.5 mol%, and then increased slightly at a larger addition. This work will assist further understanding the formation of Sn-doped In{sub 2}O{sub 3} nanofibers and is expected to be extended to other transparent conductive oxides. (orig.)

Effective visible light-active nitrogen and samarium co-doped BiVO4 for the degradation of organic pollutants

International Nuclear Information System (INIS)

Wang, Min; Niu, Chao; Liu, Jun; Wang, Qianwu; Yang, Changxiu; Zheng, Haoyan

2015-01-01

Nitrogen and samarium co-doped BiVO 4 (N–xSm–BiVO 4 ) nanoparticles were synthesized using a sol–gel method with a corn stem template. The physicochemical properties of the resultant N–xSm–BiVO 4 particles were characterized using various methods: XPS, XRD, SEM, BET, and UV–Vis DRS analyses. The visible-light photocatalytic activity was successfully demonstrated by degrading a model dye, namely, methyl orange. The dopant content was optimized, and the nitrogen and samarium co-doped BiVO 4 extended the light absorption spectrum toward the visible region, significantly enhancing the photodegradation of the model dye. The Sm and N co-doped BiVO 4 exhibited the highest photocatalytic activity compared to materials with a single dopant or no dopant. The significantly enhanced photocatalytic activity of the N–Sm co-doped BiVO 4 under visible-light irradiation can be attributed to the synergistic effects of the nitrogen and samarium. - Highlights: • The N–Sm codoped BiVO 4 were synthesized using a sol–gel method with a corn stem template. • The N and Sm codoped BiVO 4 has excellent photocatalytic activity of methyl orange degradation. • The maximum activity was observed when the molar ratio of Sm/Bi was 1.0. • The high photocatalytic activity was caused by the synergistic effects between N doping and Sm doping

Valence band states in Si-based p-type delta-doped field effect transistors

International Nuclear Information System (INIS)

Martinez-Orozco, J C; Vlaev, Stoyan J

2009-01-01

We present tight-binding calculations of the hole level structure of δ-doped Field Effect Transistor in a Si matrix within the first neighbors sp 3 s* semi-empirical tight-binding model including spin. We employ analytical expressions for Schottky barrier potential and the p-type δ-doped well based on a Thomas-Fermi approximation, we consider these potentials as external ones, so in the computations they are added to the diagonal terms of the tight-binding Hamiltonian, by this way we have the possibility to study the energy levels behavior as we vary the backbone parameters in the system: the two-dimensional impurity density (p 2d ) of the p-type δ-doped well and the contact voltage (V c ). The aim of this calculation is to demonstrate that the tight-binding approximation is suitable for device characterization that permits us to propose optimal values for the input parameters involved in the device design.

Doping effect on photoabsorption and charge-separation dynamics in light-harvesting organic molecule

Directory of Open Access Journals (Sweden)

Satoshi Ohmura

2016-01-01

Full Text Available Using ab-initio theoretical methods, we demonstrate possible enhancement of photo-conversion efficiency of an organic solar cell via intentional doping in molecular graphene-fullerene heterojunction [the hexabenzocoronene (HBC-triethylene glycol (TEG–C60 molecule]. Photoabsorption analysis indicates oxygen substitution into HBC leads to an extension of the spectra up to an infrared regime. A quantum-mechanical molecular dynamics simulation incorporating nonadiabatic electronic transitions reveals that a dissociated charge state (D+ and A- in the O-doped system is more stable than the pristine case due to the presence of an effective barrier by the TEG HOMO/LUMO level. We also find that oxygen doping in HBC enhances the intermolecular carrier mobility after charge separation. On the other hand, the pristine molecule undergoes rapid recombination between donor and acceptor charges at the interface. These analyses suggest that the graphene oxidation opens a new window in the application of organic super-molecules to solar cells.

Valence band states in Si-based p-type delta-doped field effect transistors

Energy Technology Data Exchange (ETDEWEB)

Martinez-Orozco, J C; Vlaev, Stoyan J, E-mail: jcmover@correo.unam.m [Unidad Academica de Fisica, Universidad Autonoma de Zacatecas, Calzada Solidaridad esquina con Paseo la Bufa S/N, C.P. 98060, Zacatecas, Zac. (Mexico)

2009-05-01

We present tight-binding calculations of the hole level structure of delta-doped Field Effect Transistor in a Si matrix within the first neighbors sp{sup 3}s* semi-empirical tight-binding model including spin. We employ analytical expressions for Schottky barrier potential and the p-type delta-doped well based on a Thomas-Fermi approximation, we consider these potentials as external ones, so in the computations they are added to the diagonal terms of the tight-binding Hamiltonian, by this way we have the possibility to study the energy levels behavior as we vary the backbone parameters in the system: the two-dimensional impurity density (p{sub 2d}) of the p-type delta-doped well and the contact voltage (V{sub c}). The aim of this calculation is to demonstrate that the tight-binding approximation is suitable for device characterization that permits us to propose optimal values for the input parameters involved in the device design.

Doping effect on photoabsorption and charge-separation dynamics in light-harvesting organic molecule

Energy Technology Data Exchange (ETDEWEB)

Ohmura, Satoshi, E-mail: s.ohmura.m4@cc.it-hiroshima.ac.jp [Research Center for Condensed Matter Physics, Department of Civil Engineering and Urban Design, Hiroshima Institute of Technology, Hiroshima 731-5193 (Japan); Tsuruta, Kenji [Department of Electrical and Electronic Engineering, Okayama University, Okayama 700-8530 (Japan); Shimojo, Fuyuki [Department of Physics, Kumamoto University, Kumamoto 860-8555 Japan (Japan); Nakano, Aiichiro [Collaboratory for Advanced Computing and Simulations, Department of Computer Science, Department of Physics & Astronomy, Department of Chemical Engineering & Materials Science, Department of Biological Sciences, University of Southern California, CA90089-024 (United States)

2016-01-15

Using ab-initio theoretical methods, we demonstrate possible enhancement of photo-conversion efficiency of an organic solar cell via intentional doping in molecular graphene-fullerene heterojunction [the hexabenzocoronene (HBC)-triethylene glycol (TEG)–C{sub 60} molecule]. Photoabsorption analysis indicates oxygen substitution into HBC leads to an extension of the spectra up to an infrared regime. A quantum-mechanical molecular dynamics simulation incorporating nonadiabatic electronic transitions reveals that a dissociated charge state (D{sup +} and A{sup -}) in the O-doped system is more stable than the pristine case due to the presence of an effective barrier by the TEG HOMO/LUMO level. We also find that oxygen doping in HBC enhances the intermolecular carrier mobility after charge separation. On the other hand, the pristine molecule undergoes rapid recombination between donor and acceptor charges at the interface. These analyses suggest that the graphene oxidation opens a new window in the application of organic super-molecules to solar cells.

Effect of Er doping on optical transmission and EL spectra of (Zn, Cd)S:Cu phosphors

International Nuclear Information System (INIS)

Patil, P.K.; Nandgave, J.K.; Lawangar Pawar, R.D.

1991-01-01

Powder phosphors((Znsub(0.4)Cdsub(0.6))S)doped with Cu and Er have been prepared under the inert atmosphere of argon. The optical transmission spectra of Cu doped phosphors have been investigated and explained on the basis of copper associated defect states. The improvement of optical transmission of the phosphors due to Er doping has been reported and explained. The EL emission spectrum of (Znsub(0.4)Cdsub(0.6))S:Cu:Er phosphors exhibits two broad bands characteristic of Cu. The absence of characteristic Er bands has been explained as an effect of thermal quenching of Er donor levels. (author). 9 refs., 2 figs

Study on the Effect of Heavy metals toxicity according to changing Hardness concentration using D.magna

Science.gov (United States)

Chun Sang, H.

2016-12-01

n order to determine and prevent the number of ecological effects of heavy metals in the materials, we have to accurately measure the heavy metals present in the water-based protection ecosystems and may determine the effects to humans. Heavy metals occurred in the industrial effluent which is a state in which the monitor, based on the emission standards are made by the Ministry of Environment and managed and waste water contained Copper, Zinc, lead, etc. These heavy metals are able to express the toxic effects only when present in the free-ions in the aqueous condition, which appears differently affected by the degree to hardness change in accordance with the season, precipitation. Generally changing hardness concentration can not precisely evaluate toxic effects of heavy metals in the water system. Anderson announced a study on bioassay for heavy metals from industrial waste water using Daphnia magna(Anderson, 1944, 1948). Breukelman published study the resitivity difference for the mercury Chloride(HgCl2). Braudouin(1974) compared the zooplankton(Daphnia sp.) acute toxicity of the different heavy metals and confirmed the sensitivity. Shcherban(1979) presented for toxicity evaluation results for the heavy metal of the Daphnia magna according to different temperature conditions. In the United States Environmental Protection Agency(EPA) established a standard test method for water fleas, managed and supervised water ecosystems, and announced the adoption of a bioassay standard method. This study was performed to evaluate acute inhibition using the Daphnia magna for the biological effect of heavy metal ions in water-based toxicity in the hardness change. Evaluation methods were conducted in EPA Water Quality process test criteria. TU(Toxic Unit), NOEC (No Observable Effect Concentration), LOEC (Lowest Observable Effect Concentration), EC50 (Median Effective Concentration) was calculated by Toxcalc 5.0 Program. Keywords : D. magna, Hardness, Toxic Unit, Heavy metal

Effects of Nb and Sr doping on crystal structure of epitaxial BaTiO3 thin films on MgO substrates

International Nuclear Information System (INIS)

Kim, Yongsam; Chen, Chunhua; Saiki, Atsushi; Wakiya, Naoki; Shinozaki, Kazuo; Mizutani, Nobuyasu

2002-01-01

Niobium (Nb) and strontium (Sr) doped barium titanate (BT) films were deposited by radio frequency (RF) magnetron sputtering with Nb and Sr doped BT ceramic targets, respectively. The effect of Nb and Sr doping on the crystal structure of epitaxial BaTiO 3 thin films on MgO substrates was investigated. The crystal structure of the films was examined using the reciprocal space mapping measurement. All the films exhibit a cube-on-cube relation with respect to the substrates. As the amount of doped Sr increased, both of the in-plane and out-of-plane lattice constants of Sr doped BT films slowly approached the BT bulk values. On the other hand, the lattice constants of Nb doped BT films were rapidly coming close to the bulk values. These indicated that the lattices of doped BT films were relaxed as the amount of doped elements increased. In addition, Nb doping had greater influence on the relaxation of the films than Sr doping for the same content of dopant. (author)

Insights on semiconductor-metal transition in indium-doped zinc oxide from x-ray photoelectron spectroscopy, time-of-flight secondary ion mass spectrometry and x-ray diffraction

Energy Technology Data Exchange (ETDEWEB)

Saw, K. G., E-mail: kgsaw@usm.my; Aznan, N. M., E-mail: nanieaz1004@gmail.com [Physics Programme, School of Distance Education, Universiti Sains Malaysia, 11800 Penang (Malaysia); Yam, F. K., E-mail: yamfk@yahoo.com; Ng, S. S., E-mail: shashiong@usm.my [Nano-optoelectronics Research Laboratory, Universiti Sains Malaysia, 11800 Penang (Malaysia); Pung, S. Y., E-mail: sypung@usm.my [School of Materials and Mineral Resources Eng., Universiti Sains Malaysia, 14300 Nibong Tebal (Malaysia)

2016-07-06

ZnO thin films doped with various amounts of In impurities were prepared by magnetron sputtering at a substrate temperature of 150°C. The shift in optical bandgap of the In-doped ZnO films is studied as a function of carrier concentration. Nominally doped ZnO films exhibit an increase in the measured optical band gap known as the Burstein-Moss effect. Dominant band gap narrowing is observed with increased doping. XPS and TOFSIMS analyses confirm that In is incorporated in the ZnO material. The In 3d peaks show that no metallic In is present as a result of heavy doping. The XRD phase analysis shows a preferential c-axis growth but a shift of the ZnO (002) peak to lower 2-theta values with increasing FWHM as the carrier concentration increases indicates the decline in the quality of crystallinity. An elongation of the c lattice constant is also observed and is likely to be caused by intersitital In as the amount of In dopants increases. The incorporation of In induces a semiconductor-metal transition between the carrier concentrations of 3.58 – 5.61×10{sup 19} cm{sup −3} and structural changes in the ZnO host material.

Hole-doping effects on the magnetic properties of the La4Ba2Cu2O10 ferromagnet

International Nuclear Information System (INIS)

Mizuno, F.; Masuda, H.; Hirabayashi, I.; Tanaka, S.; Mochiku, T.; Asano, H.; Izumi, F.

1992-01-01

Hole-doping effects by Ba substitution for La in La 4-x Ba 2+x Cu 2 O 10 (0 ≤ x ≤ 1) have been studied to explore the possibilities of its metal-insulator transition and superconductivity. We have not detected any symptoms for metal-insulator transition, but found certain evidence for the hole-doping effect. We observed the dilution effect of Cu 2+ spin by non-magnetic Cu 3+ on the ferromagnetic transition temperature and the reduction of effective magnetic moment. (orig.)

Soft X-ray angle-resolved photoemission spectroscopy of heavily boron-doped superconducting diamond films

Directory of Open Access Journals (Sweden)

T. Yokoya, T. Nakamura, T. Matushita, T. Muro, H. Okazaki, M. Arita, K. Shimada, H. Namatame, M. Taniguchi, Y. Takano, M. Nagao, T. Takenouchi, H. Kawarada and T. Oguchi

2006-01-01

Full Text Available We have performed soft X-ray angle-resolved photoemission spectroscopy (SXARPES of microwave plasma-assisted chemical vapor deposition diamond films with different B concentrations in order to study the origin of the metallic behavior of superconducting diamond. SXARPES results clearly show valence band dispersions with a bandwidth of ~23 eV and with a top of the valence band at gamma point in the Brillouin zone, which are consistent with the calculated valence band dispersions of pure diamond. Boron concentration-dependent band dispersions near the Fermi level (EF exhibit a systematic shift of EF, indicating depopulation of electrons due to hole doping. These SXARPES results indicate that diamond bands retain for heavy boron doping and holes in the diamond band are responsible for the metallic states leading to superconductivity at low temperature. A high-resolution photoemission spectroscopy spectrum near EF of a heavily boron-doped diamond superconductor is also presented.

Dual field effects in electrolyte-gated spinel ferrite: electrostatic carrier doping and redox reactions.

Science.gov (United States)

Ichimura, Takashi; Fujiwara, Kohei; Tanaka, Hidekazu

2014-07-24

Controlling the electronic properties of functional oxide materials via external electric fields has attracted increasing attention as a key technology for next-generation electronics. For transition-metal oxides with metallic carrier densities, the electric-field effect with ionic liquid electrolytes has been widely used because of the enormous carrier doping capabilities. The gate-induced redox reactions revealed by recent investigations have, however, highlighted the complex nature of the electric-field effect. Here, we use the gate-induced conductance modulation of spinel ZnxFe₃₋xO₄ to demonstrate the dual contributions of volatile and non-volatile field effects arising from electronic carrier doping and redox reactions. These two contributions are found to change in opposite senses depending on the Zn content x; virtual electronic and chemical field effects are observed at appropriate Zn compositions. The tuning of field-effect characteristics via composition engineering should be extremely useful for fabricating high-performance oxide field-effect devices.

Electron-translation effects in heavy-ion scattering

International Nuclear Information System (INIS)

Heinz, U.; Greiner, W.; Mueller, B.

1981-01-01

The origin and importance of electron-translation effects within a molecular description of electronic excitations in heavy-ion collisions is investigated. First, a fully consistent quantum-mechanical description of the scattering process is developed; the electrons are described by relativistic molecular orbitals, while the nuclear motion is approximated nonrelativistically. Leaving the quantum-mechanical level by using the semiclassical approximation for the nuclear motion, a set of coupled differential equations for the occupation amplitudes of the molecular orbitals is derived. In these coupled-channel equations the spurious asymptotic dynamical couplings are corrected for by additional matrix elements stemming from the electron translation. Hence, a molecular description of electronic excitations in heavy-ion scattering has been achieved, which is free from the spurious asymptotic couplings of the conventional perturbated stationary-state approach. The importance of electron-translation effects for continuum electrons and positrons is investigated. To this end an algorithm for the description of continuum electrons is proposed, which for the first time should allow for the calculation of angular distributions for delta electrons. Finally, the practical consequences of electron-translation effects are studied by calculating the corrected coupling matrix elements for the Pb-Cm system and comparing the corresponding K-vacancy probabilities with conventional calculations. We critically discuss conventional methods for cutting off the coupling matrix elements in coupled-channel calculations

Modeling the effect of doping on the catalyst-assisted growth and field emission properties of plasma-grown graphene sheet

International Nuclear Information System (INIS)

Gupta, Neha; Sharma, Suresh C.; Sharma, Rinku

2016-01-01

A theoretical model describing the effect of doping on the plasma-assisted catalytic growth of graphene sheet has been developed. The model accounts the charging rate of the graphene sheet, kinetics of all the plasma species, including the doping species, and the growth rate of graphene nuclei and graphene sheet due to surface diffusion, and accretion of ions on the catalyst nanoparticle. Using the model, it is observed that nitrogen and boron doping can strongly influence the growth and field emission properties of the graphene sheet. The results of the present investigation indicate that nitrogen doping results in reduced thickness and shortened height of the graphene sheet; however, boron doping increases the thickness and height of the graphene sheet. The time evolutions of the charge on the graphene sheet and hydrocarbon number density for nitrogen and boron doped graphene sheet have also been examined. The field emission properties of the graphene sheet have been proposed on the basis of the results obtained. It is concluded that nitrogen doped graphene sheet exhibits better field emission characteristics as compared to undoped and boron doped graphene sheet. The results of the present investigation are consistent with the existing experimental observations.

Modeling the effect of doping on the catalyst-assisted growth and field emission properties of plasma-grown graphene sheet

Energy Technology Data Exchange (ETDEWEB)

Gupta, Neha; Sharma, Suresh C.; Sharma, Rinku [Department of Applied Physics, Delhi Technological University (DTU), Shahbad Daulatpur, Bawana Road, Delhi-110042 (India)

2016-08-15

A theoretical model describing the effect of doping on the plasma-assisted catalytic growth of graphene sheet has been developed. The model accounts the charging rate of the graphene sheet, kinetics of all the plasma species, including the doping species, and the growth rate of graphene nuclei and graphene sheet due to surface diffusion, and accretion of ions on the catalyst nanoparticle. Using the model, it is observed that nitrogen and boron doping can strongly influence the growth and field emission properties of the graphene sheet. The results of the present investigation indicate that nitrogen doping results in reduced thickness and shortened height of the graphene sheet; however, boron doping increases the thickness and height of the graphene sheet. The time evolutions of the charge on the graphene sheet and hydrocarbon number density for nitrogen and boron doped graphene sheet have also been examined. The field emission properties of the graphene sheet have been proposed on the basis of the results obtained. It is concluded that nitrogen doped graphene sheet exhibits better field emission characteristics as compared to undoped and boron doped graphene sheet. The results of the present investigation are consistent with the existing experimental observations.

Viscous fingering effects in solvent displacement of heavy oil

Energy Technology Data Exchange (ETDEWEB)

Cuthiell, D. [Suncor Energy, Fort McMurray, AB (Canada); Kissel, G.; Jackson, C.; Frauenfeld, T.W.J.; Fisher, D. [Alberta Research Council, Devon, AB (Canada); Rispler, K. [Saskatchewan Research Council, Saskatoon, SK (Canada)

2004-07-01

Vapour Extraction (VAPEX) is a solvent-based process that is analogous to steam-assisted gravity drainage (SAGD) for the recovery of heavy oil. A cyclic solvent process is preferred for thin reservoirs, particularly primary-depleted reservoirs. In a cyclic steam stimulation process, a solvent is injected into the reservoir for a period of time before oil is produced from the well. Viscous fingering is a phenomena that characterizes several solvent-based processes for the recovery of heavy oil. A combined experimental and simulation study was conducted to characterize viscous fingering under heavy oil recovery conditions (high ratio of oil to solvent viscosity). Four experiments were conducted in heavy oil-saturated sand packs. Three involved injection of a miscible, liquid solvent at the bottom of the sand pack. The heavy oil in these experiments was displaced upwardly. The fourth experiment involved top-down injection of a gaseous solvent. The miscible liquid displacement was dominated by one solvent finger which broke through to a producing well at the other end of the sand pack. Breakthrough times were similar to that at lower viscosity. The fourth experiment showed fingering along with features of a gravity-driven VAPEX process. Key features of the experiment and realistic fingering patterns were numerically simulated using a commercial reservoir simulator. It was emphasized that accurate modelling of dispersion is necessary in matching the observed phenomena. The simulations should include the capillary effects because of their significance for gaseous fingering and the VAPEX processes. 17 refs., 2 tabs., 20 figs.

Density functional theory calculations on the adsorption of formaldehyde and other harmful gases on pure, Ti-doped, or N-doped graphene sheets

International Nuclear Information System (INIS)

Zhang, Hong-ping; Luo, Xue-gang; Lin, Xiao-yang; Lu, Xiong; Leng, Yang; Song, Hong-tao

2013-01-01

Understanding the interaction mechanisms of CO, NO, SO 2 , and HCHO with graphene are important in developing graphene-based sensors for gas detection and removal. In this study, the effects of doped Ti or N atom on the interaction of these gases with graphene were investigated by density functional theory calculations. Analyses of adsorption energy, electron density difference, and density of states indicated that the doped Ti atom could greatly improve the interaction of gas molecules with graphene. The Ti-doped graphene sheet demonstrated selective gas absorption. The order of interaction between the gas molecules and the Ti-doped graphene sheet was as follows: SO 2 > NO > HCHO > CO. By contrast, the N-doped graphene sheet did not exhibit apparent selective gas absorption. These results imply that the Ti-doped graphene sheet is more effective than the N-doped graphene sheet in detecting and removing gas molecules because of its high selectivity.

Density functional theory calculations on the adsorption of formaldehyde and other harmful gases on pure, Ti-doped, or N-doped graphene sheets

Energy Technology Data Exchange (ETDEWEB)

Zhang, Hong-ping, E-mail: zhp1006@126.com [Engineering Research Center of Biomass Materials, Ministry of Education, School of Materials Science and Engineering, Southwest University of Science and Technology, Mianyang, Sichuan 621010 (China); Luo, Xue-gang, E-mail: lxg@swust.edu.cn [Engineering Research Center of Biomass Materials, Ministry of Education, School of Materials Science and Engineering, Southwest University of Science and Technology, Mianyang, Sichuan 621010 (China); Lin, Xiao-yang, E-mail: xylin-2004@163.com [Engineering Research Center of Biomass Materials, Ministry of Education, School of Materials Science and Engineering, Southwest University of Science and Technology, Mianyang, Sichuan 621010 (China); Lu, Xiong, E-mail: luxiong_2004@163.com [Key Laboratory of Advanced Technologies of Materials, Ministry of Education, School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu 610031, Sichuan (China); Leng, Yang, E-mail: meleng@ust.hk [Department of Mechanical Engineering, Hong Kong University of Science and Technology, Kowloon, Hong Kong (China); Song, Hong-tao, E-mail: yinyishushengsht@163.com [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China)

2013-10-15

Understanding the interaction mechanisms of CO, NO, SO{sub 2}, and HCHO with graphene are important in developing graphene-based sensors for gas detection and removal. In this study, the effects of doped Ti or N atom on the interaction of these gases with graphene were investigated by density functional theory calculations. Analyses of adsorption energy, electron density difference, and density of states indicated that the doped Ti atom could greatly improve the interaction of gas molecules with graphene. The Ti-doped graphene sheet demonstrated selective gas absorption. The order of interaction between the gas molecules and the Ti-doped graphene sheet was as follows: SO{sub 2} > NO > HCHO > CO. By contrast, the N-doped graphene sheet did not exhibit apparent selective gas absorption. These results imply that the Ti-doped graphene sheet is more effective than the N-doped graphene sheet in detecting and removing gas molecules because of its high selectivity.

Effect of Cr doping on the structural, morphological, optical and electrical properties of indium tin oxide films

Science.gov (United States)

Mirzaee, Majid; Dolati, Abolghasem

2015-03-01

We report on the preparation and characterization of high-purity chromium (0.5-2.5 at.%)-doped indium tin oxide (ITO, In:Sn = 90:10) films deposited by sol-gel-mediated dip coating. The effects of different Cr-doping contents on structural, morphological, optical and electrical properties of the films were characterized by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), UV-Vis spectroscopy and four-point probe methods. XRD showed high phase purity cubic In2O3 and indicated a contraction of the lattice with Cr doping. FESEM micrographs show that grain size decreased with increasing the Cr-doping content. A method to determine chromium species in the sample was developed through the decomposition of the Cr 2 p XPS spectrum in Cr6+ and Cr3+ standard spectra. Optical and electrical studies revealed that optimum opto-electronic properties, including minimum sheet resistance of 4,300 Ω/Sq and an average optical transmittance of 85 % in the visible region with a band gap of 3.421 eV, were achieved for the films doped with Cr-doping content of 2 at.%.

The effects of social and health consequence framing on heavy drinking intentions among college students.

Science.gov (United States)

Kingsbury, John H; Gibbons, Frederick X; Gerrard, Meg

2015-02-01

Many interventions targeting college student drinking have focused on negative health effects of drinking heavily; however, some research suggests that social factors may have a stronger influence on the drinking behaviour of young people. Moreover, few studies have examined message framing effects in the context of alcohol consumption. This study investigated the effects of social and health consequence framing on college students' intentions to engage in heavy drinking. This study used a 2 × 2 experimental design with an appended control condition. One hundred and twenty-four college students (74 women; M(age) = 18.9) participated in this study for course credit. Participants read vignettes that were ostensibly written by a recent graduate from the university, who described an episode of drinking in which he or she experienced either social or health consequences. These consequences were framed as either a gain (i.e., positive consequences of not drinking heavily) or a loss (i.e., negative consequences of drinking heavily). After reading the vignette, participants completed a measure of heavy drinking intentions. Regression analyses revealed that social consequences were associated with lower heavy drinking intentions when framed as a loss and that health consequences were associated with lower heavy drinking intentions when framed as a gain. These effects were stronger among those who reported higher (vs. lower) levels of previous drinking. Results suggest that interventions that focus on the negative health effects of heavy drinking may be improved by instead emphasizing the negative social consequences of drinking heavily and the positive health consequences of avoiding this behaviour. Statement of contribution What is already known on this subject? Previous studies have shown that gain frames are more effective than loss frames when highlighting the health consequences of health risk behaviours, such as heavy drinking. The heavy drinking behaviour of young

Heavy-heavy-light quark potential in SU(3) lattice QCD

International Nuclear Information System (INIS)

Yamamoto, Arata; Suganuma, Hideo; Iida, Hideaki

2008-01-01

We perform the first study for the heavy-heavy-light quark (QQq) potential in SU(3) quenched lattice QCD with the Coulomb gauge. The calculations are done with the standard gauge and O(a)-improved Wilson fermion action on the 16 4 lattice at β=6.0. We calculate the energy of QQq systems as the function of the distance R between the two heavy quarks, and find that the QQq potential is well described with a Coulomb plus linear potential form up to the intermediate distance R≤0.8 fm. Compared to the static three-quark case, the effective string tension between the heavy quarks is significantly reduced by the finite-mass valence quark effect. This reduction is considered to be a general property for baryons

Thermal spin filtering effect and giant magnetoresistance of half-metallic graphene nanoribbon co-doped with non-metallic Nitrogen and Boron

Science.gov (United States)

Huang, Hai; Zheng, Anmin; Gao, Guoying; Yao, Kailun

2018-03-01

Ab initio calculations based on density functional theory and non-equilibrium Green's function are performed to investigate the thermal spin transport properties of single-hydrogen-saturated zigzag graphene nanoribbon co-doped with non-metallic Nitrogen and Boron in parallel and anti-parallel spin configurations. The results show that the doped graphene nanoribbon is a full half-metal. The two-probe system based on the doped graphene nanoribbon exhibits various excellent spin transport properties, including the spin-filtering effect, the spin Seebeck effect, the single-spin negative differential thermal resistance effect and the sign-reversible giant magnetoresistance feature. Excellently, the spin-filtering efficiency can reach nearly 100% in the parallel configuration and the magnetoresistance ratio can be up to -1.5 × 1010% by modulating the electrode temperature and temperature gradient. Our findings indicate that the metal-free doped graphene nanoribbon would be a promising candidate for spin caloritronic applications.

Synergistic effects of F and Fe in co-doped TiO{sub 2} nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Zhang, Yufei, E-mail: zhang.yu.fei@stu.xjtu.edu.cn; Shen, Huiyuan; Liu, Yanhua, E-mail: yhliu@mail.xjtu.edu.cn [Xi’an Jiaotong University, Department of Building Environment and Services Engineering, School of Human Settlements and Civil Engineering (China)

2016-03-15

TiO{sub 2} photocatalysts co-doped with F and Fe were synthesized by a sol–gel method. Synergistic effects of F and Fe in the co-doped TiO{sub 2} were verified by NH{sub 3} decomposition, X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and ultraviolet–visible (UV–Vis) absorption spectroscopy, and was analyzed by the simulation based on the density functional theory (DFT). The results from NH{sub 3} decomposition confirmed that the cooperation of F and Fe broadened the optical response of TiO{sub 2} to visible light region and also enhanced the photocatalytic activity of TiO{sub 2} under ultraviolet light. XRD patterns, SEM and HRTEM images showed that the co-doped samples were nanometric anatase with an average particle size of 25 nm. Co-doping with F and Fe inhibited the grain growth of TiO{sub 2} from anatase to rutile and resulted in a larger lattice defect. XPS analysis exhibited that the doped F and Fe atoms were into the TiO{sub 2} lattice. UV–Vis absorption spectra showed that its optical absorption edge was moved up to approximately 617 nm and its ultraviolet absorption was also enhanced. The DFT results indicated that the cooperation of Fe 3d and O 2p orbits narrowed the band gap of TiO{sub 2} and F 2p orbit widened the upper valence bands. The synergistic electron density around F and Fe in co-doped TiO{sub 2} was capable to enhance the photo-chemical stability of TiO{sub 2}.