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  • 3551.
    Zhang, Hanmin
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Johansson, Lars
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Electronic structure of PTCDA on Sn/Si(111)-2√3×2√32014In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 439, 71-78 p.Article in journal (Refereed)
    Abstract [en]

    The electronic structures of PTCDA on the Sn/Si(111)-2√3×2√3 surface have been thoroughly studied by high-resolution photoelectron spectroscopy and near-edge X-ray absorption fine structure (NEXAFS). Upon deposition of PTCDA, there is an unusual charge transfer from the Sn/Si(111)-2√3×2√3 surface to the molecules. This is clearly shown by a new component in the Sn 4d core-level spectra that shifts towards higher binding energy. In contrast to the literature, the charge provided by Sn is donated to the carbonyl C instead of the O atoms. This is revealed by a new component in the C 1s core-level spectra that shifts towards lower binding energy. The charge transfer causes a splitting of the HOMO level in the valence band spectra. As indicated in the NEXAFS spectra, it also induces a splitting of the LUMO level of the molecules. For thick films the NEXAFS results suggest a layer by layer growth mode.

  • 3552.
    Zhang, Huaeli
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Punkkinen, Marko Patrick John
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Johansson, Börje
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Vitos, Levente
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Elastic parameters of paramagnetic iron-based alloys from first-principles calculations2012In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 85, no 5, 054107- p.Article in journal (Refereed)
    Abstract [en]

    The elastic properties of paramagnetic (PM) Fe1-xMx (M = Al, Si, V, Cr, Mn, Co, Ni, and Rh; 0 <= x <= 0.1) solid solutions in the body-centered-cubic (bcc) and face-centered-cubic (fcc) structures are investigated using the exact muffin-tin orbital density functional method in combination with the coherent-potential approximation and disordered local-magnetic-moment model. All impurities considered here enlarge or leave nearly constant the equilibrium volume of PM Fe but at the same time produce both positive and negative changes in the elastic parameters. Some of the alloying elements induce opposite effects on shear elastic parameters C' and C-44 of PM bcc and fcc Fe, which is discussed. With a few exceptions, we find that the alloying effects on PM bcc Fe are smaller than on PM fcc Fe. The trends in the tetragonal elastic constant C' show a general correlation with the trends obtained for the bcc-fcc lattice energy difference.

  • 3553.
    Zhang, Hualei
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Johansson, Börje
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Ahuja, Rajeev
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Vitos, Levente
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    First-principles study of solid-solution hardening in steel alloys2012In: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 55, 269-272 p.Article in journal (Refereed)
    Abstract [en]

    Materials with excellent mechanical properties, such as light mass combined with remarkable hardness and toughness, are technologically important not least for automotive and other transport applications. Solid solution strengthening, due to dislocation pinning by impurities, is an effective route to enhance the intrinsic hardness of alloys. In the present work, we use advanced quantum theory to reveal the mechanical characteristics of iron alloys within and beyond their thermodynamic stability fields. Among the considered alloying elements, magnesium strongly reduces the density of the host alloys and significantly enhances the hardness. Our findings suggest that stainless steel grades containing a few percent of magnesium are promising engineering materials for high-strength and light-weight designs.

  • 3554.
    Zhang, Hualei
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Johansson, Börje
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Vitos, Levente
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Density-functional study of paramagnetic iron2011In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 84, no 14, 140411- p.Article in journal (Refereed)
    Abstract [en]

    By using density-functional theory in combination with the coherent-potential approximation and the disordered local magnetic moment picture, we demonstrate that the competing high-temperature cubic phases of paramagnetic Fe correspond to two distinct total energy minima in the tetragonal (Bain) configurational space. Both the face-centered-cubic (fcc) and the body-centered-cubic (bcc) lattices are dynamically stable, and at static conditions the fcc structure is found to be the thermodynamically stable phase. The theoretical bcc and fcc bulk parameters are in agreement with the experimental data. Due to the shallow energy minimum around the bcc structure, increasing temperature is predicted to stabilize the bcc (δ) phase against the fcc (γ) one.

  • 3555. Zhang, Hualei
    et al.
    Li, Xiaoqing
    Schonecker, Stephan
    Jesperson, Henrik
    Johansson, Börje
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Vitos, Levente
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Anomalous elastic hardening in Fe-Co alloys at high temperature2014In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 89, no 18, 184107- p.Article in journal (Refereed)
    Abstract [en]

    The elastic moduli of Fe1-cCoc (c <= 0.2) alloys are found to decrease strongly with increasing temperature, but show very weak alloying effects for both low-temperature ferromagnetic and high-temperature paramagnetic states. For temperatures slightly below and around the Curie temperature of Fe, Co addition significantly increases the elastic moduli. The variation of the tetragonal shear elastic constant upon 20% Co addition increases from a small negative value to more than 135% as the temperature rises from 0 to 1200 K. The expected elastic softening in the case of Al doping is not confirmed. Both anomalous trends are ascribed to the interplay between intrinsic chemical effects, magnetism, and temperature.

  • 3556.
    Zhang, Hualei
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Punkkinen, Marko P. J.
    Johansson, Börje
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Vitos, Levente
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Theoretical elastic moduli of ferromagnetic bcc Fe alloys2010In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 22, no 27, 275402- p.Article in journal (Refereed)
    Abstract [en]

    The polycrystalline elastic parameters of ferromagnetic Fe1-xMx (M = Al, Si, V, Cr, Mn, Co, Ni, Rh; 0 <= x <= 0.1) random alloys in the body centered cubic (bcc) crystallographic phase have been calculated using first-principles alloy theory in combination with statistical averaging methods. With a few exceptions, the agreement between the calculated and the available experimental data for the polycrystalline aggregates is satisfactory. All additions considered here decrease the bulk modulus (B) and Poisson's ratio (nu) of bcc Fe. The complex composition dependence of the C-44 single-crystal elastic constant is reflected in the polycrystalline shear modulus (G), Young's modulus (E), and Debye temperature (Theta). The polycrystalline anisotropy of bcc Fe is increased by all additions, and Al, Si, Ni, and Rh yield the largest alloying effects.

  • 3557. Zhang, J
    et al.
    Ellison, A
    Henry, A
    Linnarsson, M K
    KTH, School of Information and Communication Technology (ICT).
    Janzen, E
    Nitrogen impurity incorporation behavior in a chimney HTCVD process: pressure and temperature dependence1999In: Materials Science & Engineering: B. Solid-state Materials for Advanced Technology, ISSN 0921-5107, E-ISSN 1873-4944, Vol. 61-2, 151-154 p.Article in journal (Refereed)
    Abstract [en]

    Experimental results are presented for residual nitrogen incorporation in both Si and C face 4H SiC epilayers using the high temperature chemical vapor deposition (HTCVD) process in a chimney reactor. The influence of total pressure, process temperature and input C/Si ratio on the residual nitrogen doping is studied. The results are further confirmed by intentional nitrogen doping experiments. Activation energies of 200 kcal/mol for Si face and 108 kcal/mol for C face samples are obtained for nitrogen incorporation. Possible incorporation mechanisms related to both surface and gas phase kinetics are discussed. (C) 1999 Elsevier Science S.A. All rights reserved.

  • 3558.
    Zhang, Jiang
    et al.
    Department of Physics, Shandong University, Jinan, China.
    Kyaw, Thi Ha
    Centre for Quantum Technologies, NUS, Singapore.
    Tong, Dianmin
    Department of Physics, Shandong University, Jinan, China.
    Sjöqvist, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala universitet.
    Kwek, Leong Chuan
    Centre for Quantum Technologies, NUS, Singapore.
    Fast non-Abelian geometric gates via transitionless quantum driving2015In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 5, 18414Article in journal (Refereed)
    Abstract [en]

    A practical quantum computer must be capable of performing high fidelity quantum gates on a set of quantum bits (qubits). In the presence of noise, the realization of such gates poses daunting challenges. Geometric phases, which possess intrinsic noise-tolerant features, hold the promise for performing robust quantum computation. In particular, quantum holonomies, i.e., non-Abelian geometric phases, naturally lead to universal quantum computation due to their non-commutativity. Although quantum gates based on adiabatic holonomies have already been proposed, the slow evolution eventually compromises qubit coher- ence and computational power. Here, we propose a general approach to speed up an implementation of adiabatic holonomic gates by using transitionless driving techniques and show how such a universal set of fast geometric quantum gates in a superconducting circuit architecture can be obtained in an all geometric approach. Compared with standard non-adiabatic holonomic quantum computation, the holonomies ob- tained in our approach tends asymptotically to those of the adiabatic approach in the long run-time limit and thus might open up a new horizon for realizing a practical quantum computer. 

  • 3559.
    Zhang, Jie
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Ellison, Alexandre
    Okmetic AB, Linköping, Sweden.
    Danielsson, Örjan
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Linnarsson, M. K.
    Royal Institute of Technology ( KTH), Stockholm, Sweden.
    Henry, Anne
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Epitaxial growth of 4H SiC in a vertical hot-wall CVD reactor: Comparison between up- and down-flow orientations2002In: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 241, no 4, 421-430 p.Article in journal (Refereed)
    Abstract [en]

    The CVD growth of 4H SiC is investigated in a vertical hot-wall reactor in both up-flow (the chimney reactor) and down-flow (the inverted chimney) orientations. The growth rate and the nitrogen doping are studied for comparison. Under the investigated process conditions the growth mechanism is shown to be similar in these two reactor orientations. Only slight difference is observed in the temperature effect depending on the flow direction. Both reactor types have produced epilayers with high growth rates (10–35 μm/h) and low residual n-type doping (low 1016 down to mid 1013 cm−3) with comparable morphology. Dimensionless flow numbers are used to provide a qualitative analysis of the flow and heat transfer mechanisms in the vertical hot-wall system. Two-dimensional numerical simulation in a cylindrical geometry is conducted to demonstrate the flow and temperature profile with selected process parameters. Comparison of the experimental results in the chimney and the inverted chimney is performed to give insight into the fast epitaxial hot-wall growth.

  • 3560.
    Zhang, L.
    et al.
    Lawrence Berkeley Natl Lab, Adv Light Source, Berkeley, CA 94720 USA..
    Li, X.
    Univ Sci & Technol China, Hefei Natl Lab Phys Sci Microscale, Hefei 230026, Anhui, Peoples R China..
    Augustsson, A.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Lee, C. M.
    Lawrence Berkeley Natl Lab, Div Mat Sci, Berkeley, CA 94720 USA..
    Rubensson, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Nordgren, Joseph
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Ross, P. N., Jr.
    Lawrence Berkeley Natl Lab, Div Mat Sci, Berkeley, CA 94720 USA..
    Guo, J. -H
    Revealing the electronic structure of LiC6 by soft X-ray spectroscopy2017In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 110, no 10, 104106Article in journal (Refereed)
    Abstract [en]

    The electronic structure of LiC6 has been investigated by soft X-ray absorption and emission spectroscopies. The results reveal that upon full lithiation of graphite, the Li 2s electrons are transferred into the carbon pi* states in a near rigid-band behavior, resulting in the increased density of states near E-F and the shift of sigma* states to lower energies. In addition, the resonant inelastic X-ray scattering spectra of LiC6 do not show strong dispersive features as that of graphite, indicating that the crystal momentum is not conserved during the scattering process due to the delocalization of electrons in the intermediate state.

  • 3561.
    Zhang, Renyun
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Alecrim, Viviane
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Hummelgård, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Andres, Britta
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Forsberg, Sven
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Andersson, Mattias
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Thermally reduced kaolin-graphene oxide nanocomposites for gas sensing2015In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 5, Art. no. 7676- p.Article in journal (Refereed)
    Abstract [en]

    Highly sensitive graphene-based gas sensors can be made using large-area single layer graphene, but the cost of large-area pure graphene is high, making the simpler reduced graphene oxide (rGO) an attractive alternative. To use rGO for gas sensing, however, require a high active surface area and slightly different approach is needed. Here, we report on a simple method to produce kaolin-graphene oxide (GO) nanocomposites and an application of this nanocomposite as a gas sensor. The nanocomposite was made by binding the GO flakes to kaolin with the help of 3-Aminopropyltriethoxysilane (APTES). The GO flakes in the nanocomposite were contacting neighboring GO flakes as observed by electron microscopy. After thermal annealing, the nanocomposite become conductive as showed by sheet resistance measurements. Based on the conductance changes of the nanocomposite films, electrical gas sensing devices were made for detecting NH3 and HNO3. These devices had a higher sensitivity than thermally annealed multilayer GO films. This kaolin-GO nanocomposite might be useful in applications that require a low-cost material with large conductive surface area including the demonstrated gas sensors.

  • 3562.
    Zhang, Renyun
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Andersson, Henrik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Andersson, Mattias
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Andres, Britta
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Edlund, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Edström, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Edvardsson, Sverker
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Forsberg, Sven
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Hummelgård, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Johansson, Niklas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Karlsson, Kristoffer
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Nilsson, Hans-Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Norgren, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Olsen, Martin
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Uesaka, Tetsu
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Öhlund, Thomas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Soap-film coating: High-speed deposition of multilayer nanofilms2013In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 3, Art. no. 1477- p.Article in journal (Refereed)
    Abstract [en]

    The coating of thin films is applied in numerous fields and many methods are employed for the deposition of these films. Some coating techniques may deposit films at high speed; for example, ordinary printing paper is coated with micrometre-thick layers of clay at a speed of tens of meters per second. However, to coat nanometre thin films at high speed, vacuum techniques are typically required, which increases the complexity of the process. Here, we report a simple wet chemical method for the high-speed coating of films with thicknesses at the nanometre level. This soap-film coating technique is based on forcing a substrate through a soap film that contains nanomaterials. Molecules and nanomaterials can be deposited at a thickness ranging from less than a monolayer to several layers at speeds up to meters per second. We believe that the soap-film coating method is potentially important for industrial-scale nanotechnology.

  • 3563.
    Zhang, Renyun
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Andersson, Henrik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Olsen, Martin
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Hummelgård, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Edvardsson, Sverker
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Nilsson, Hans-Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Piezoelectric gated ZnO nanowire diode studied by in situ TEM probing2014In: Nano Energy, ISSN 2211-2855, Vol. 3, 10-15 p.Article in journal (Refereed)
    Abstract [en]

    The piezoelectricity of ZnO nanowires has shown rising interests during the last few years and fields such as piezotronics and piezophotonics are emerging with a number of applications and devices. One such device is the piezoelectric gated ZnO nanowire diode, where the p–n junction is replaced by a dynamically created potential barrier created simply by bending the otherwise homogeneously doped nanowire. To further study this type of diode we used in situ transmission electron microscope (TEM) probing, where one electrode was fixed at the end of a ZnO nanowire and another moveable electrode was used both for bending and contacting the wire. Thereby we were able to further characterise this diode and found that the diode characteristics depended on whether the contact was made to the stretched (p-type) surface or to the compressed (n-type) surface of the wire. When the neutral line of the wire contacted, between the stretched and the compressed side, the I–V characteristics were independent on the current direction. The performance of the diodes upon different bending intensity showed a rectifying ratio up to the high value of 60:1. The diode ideality factor was found to be about 5. Moreover, the reverse breakdown voltages of the diode were measured and a local but permanent damage to the diode action was found when the voltage went over the reverse breakdown voltage. 

  • 3564.
    Zhang, Renyun
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Hummelgård, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    A facile one-step method for synthesising a parallelogram-shaped single-crystalline ZnO nanosheet2014In: Materials Science and Engineering: B, ISSN 0921-5107, Vol. 184, 1-6 p.Article in journal (Refereed)
    Abstract [en]

    ZnO nanosheets are found to be useful in many fields such as sensors and electronics. Non-uniform- shaped ZnO nanosheets are synthesised using several methods; moreover, uniformly shaped ones are less studied. Here, we report on a simple one-step method to synthesise parallelogram-shaped single- crystalline ZnO nanosheets. By controlling the reaction of Zn(NO3 )2 and hexamethylenetetramine (HMT) in ethanol, average 30 nm-thick nanosheets with a high aspect ratio of 1:100 were obtained. The par- allelogram angles were between 97◦ and 99◦. Transmission electron microscopy (TEM) diffraction and X-ray diffraction (XRD) showed that the nanosheets were wurtzite-structured single-crystalline ZnO. Moreover, a growth mechanism of these parallelogram nanosheets is suggested based on the experi- mental results. These results suggest a new simple solution process to synthesise uniformly shaped ZnO nanosheets allowing large-scale production to be employed. 

  • 3565.
    Zhang, Renyun
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Hummelgård, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Graphite-carbon nanotube flexible electrodes for dye-sensitized solar cells2014Conference paper (Refereed)
    Abstract [en]

    Dye-sensitized solar cell (DSSC) is a low cost and efficient way to transform solar radiation to electricity. Indium tin oxide (ITO) and fluorine doped tin oxide (FTO) coated glass are two kinds of transparent electrodes that are mostly used to fabricate DSSCs. However, these two kinds electrodes lack flexibility, limiting their development. [1] Flexible electrodes are desired in DSSC because of they are lightweight, low cost and ro田l-to-roll compatible. There are attempts to replace both [1] or one [2] of the two electrodes in DSSC. However, the efficiencies are relatively low. Here we reported a simple method to fabricate graphite-carbon nanotube (G-CNT) composited flexible electrode for using as counter electrode in DSSC. The electrodes are simple fabricated by reverse filtration and flash sintering, leading to highly flexible (360 °C) and conductive (sheet resistance, 100 Ohm/sq) electrodes that can be used as both catalyzer and current collector. The energy conversion efficiency of such electrode based DSSC can reach 2.02% with fill factor of 0.56 (Figure 1).

     

    Figure 1. Photograph of the G-CNT composited flexible electrode, and the J-V characterization of the fabricated DSSC.

     

     

    References:

     

    [1]    W. Wang, Q. Zhang, H. Li, G. W. Wu, D. C. Zou, D. P. Yu, Adv. Funct. Mater. 2012, 22, 2775-2782.

    [2]    B. Wang, L. L. Kerr, Sol. Energy Mater. Sol. Cells. 2011, 95, 2531-2535.

  • 3566.
    Zhang, Renyun
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Hummelgård, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Simple Fabrication of Gold Nanobelts and Patterns2012In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 7, no 1, Art. no. e30469- p.Article in journal (Refereed)
    Abstract [en]

    Gold nanobelts are of interest in several areas; however, there are only few methods available to produce these belts. We report here on a simple evaporation induced self-assembly (EISA) method to produce porous gold nanobelts with dimensions that scale across nanometer (thickness ~80 nm) and micrometer (width ~20 μm), to decimeter (length ~0.15 m). The gold nanobelts are well packed on the beaker wall and can be easily made to float on the surface of the solution for depositing onto other substrates. Microscopy showed that gold nanobelts had a different structure on the two sides of the belt; the density of gold nanowires on one side was greater than on the other side. Electrical measurements showed that these nanobelts were sensitive to compressive or tensile forces, indicating a potential use as a strain sensor. The patterned nanobelts were further used as a template to grow ZnO nanowires for potential use in applications such as piezo-electronics. © 2012 Zhang et al.

  • 3567.
    Zhang, Renyun
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Hummelgård, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Size and concentration controlled growth of porous gold nanofilm2012In: Physica status solidi. A, Applied research, ISSN 0031-8965, E-ISSN 1521-396X, Vol. 209, no 3, 519-523 p.Article in journal (Refereed)
    Abstract [en]

    At an air/water interface, diffusion-limited aggregation (DLA) of gold nanoparticles can form porous gold thin films. This porous film roughly consists of a network of irregular nanowires. For this air–water system, external parameters like temperature are well studied, while the influence of internal parameters, e.g., the size and concentration of the nanoparticles, have not been studied in detail. Here, we report on the growth of porous gold nanofilms for different nanoparticle sizes and concentrations to get a relationship between the morphology of the films and the internal parameters. The gold nanoparticles were synthesized by reducing HAuCl4 using sodium citrate. Transmission electron microscopy (TEM) characterization

    showed a linear relation between the formed gold nanowires and the concentration of HAuCl4 if the concentration of sodium citrate is unchanged. A linear dependency was also found between the wire diameter and the gold nanoparticle concen- tration, and between the wire diameter and volume fraction of the nanoparticles. The electrical resistance of the films was measured, showing a linear relation between resistance and the inverse of the cross-sectional area of the nanowires. This study shows the relation between the morphology and resistance of the grown porous films and the controllable internal parameters that will be useful in further exploration of this thin-film growth method.

  • 3568.
    Zhang, Renyun
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Hummelgård, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Olsen, Martin
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Örtegren, Jonas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Nanogenerator made of ZnO nanosheet networks2017In: Semiconductor Science and Technology, ISSN 0268-1242, E-ISSN 1361-6641, Vol. 32, no 5, 054002Article in journal (Refereed)
    Abstract [en]

    The piezoelectricity of nanomaterials attracts a great deal of attention due to its broad application, including the harvesting of ambient mechanical energy to power small electronics devices. We report here a simple method to fabricate piezoelectric nanogenerators consisting of networks of ZnO nanosheets grown on aluminum (Al) foils, where the Al acts as both a substrate for growth and as an electrode contacting the ZnO network. A second, top electrode was tapped, rolled, or rubbed against the ZnO to generate piezoelectricity. This second electrode was either a copper foil or fluorine doped tin oxide (FTO) glass. A piezo voltage of up to 0.924 V was detected during rolling and 6 μA was the highest current observed when rubbing the ZnO film with a FTO glass. Due to its simplicity, this nanogenerator fabrication method has the potential to be scaled up for the industrial production of piezoelectric energy harvesting devices.

  • 3569.
    Zhang, Renyun
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Magnetic Nanoparticles in Biomedical Applications2011In: OMICS: Biomedical Perspectives and Applications / [ed] Debmalya Barh, Kenneth Blum, Margaret A. Madigan, CRC Press, 2011, 1Chapter in book (Refereed)
  • 3570.
    Zhang, Renyun
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Porous Gold Films: A Short Review on Recent Progress2014In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 7, 3834-3854 p.Article, review/survey (Refereed)
    Abstract [en]

    Porous gold films have attracted increasing interest over the last ten years due to the unique properties of high specific surface area and electrical conductivity combined with chemical stability and ability to alter the surface chemistry. Several methods have been developed to synthesize porous gold films such as de-alloying, templating, electrochemical, and self-assembling. These porous gold films are used in diverse fields, for example, as electrochemical and Raman sensors or for chemical catalysis. Here, we provide a short review on the progress of porous gold films over the past ten years, including the synthesis and applications of such films.

  • 3571. Zhang, Shang-Zhou
    et al.
    Cui, Hao
    Li, Ming-Man
    Yu, Hui
    Vitos, Levente
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Yang, Rui
    Hu, Qing-Miao
    First-principles study of phase stability and elastic properties of binary Ti-xTM (TM = V,Cr,Nb,Mo) and ternary Ti-15TH-yAl alloys2016In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 110, 80-89 p.Article in journal (Refereed)
    Abstract [en]

    The phase stability and elastic property of binary Ti-chi TM (TM=V, Cr, Nb, Mo) and ternary Ti-15TH-yAl alloys are investigated systematically by using a first-principles method. The coherent potential approximation is employed to describe the random distribution of the alloying atoms in the alloys. We show that the transition metal (TM) elements V, Cr, Nb, Mo increase the elastic stability of the beta phase but decreases that of the a phase. The polycrystalline bulk modulus of the a phase increases with the concentration of the TM alloying elements whereas the Young's modulus and shear modulus are weakened. For the beta phase, all the polycrystalline elastic moduli hardens with the addition of the TM alloying elements. The influence of the simple metal (SM) element Al on the elastic properties is much weaker than the TM ones. The TM alloying elements increase the stability of the beta relative to the alpha and omega phases. Al stabilizes significantly the beta phase over the omega phase. Our calculations suggest that the d electron density dominates the elastic modulus but not the relative phase stability. The interaction between the TM and SM alloying elements in titanium alloys matters to the relative stability.

  • 3572.
    Zhang, Teng
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Synchrotron radiation study of free and adsorbed organic molecules2016Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    In this licentiate thesis, organic molecules, namely Cobalt Phthalocyanine (CoPc) and Biphenylene, have been studied by means of synchrotron radiation-based spectroscopic methods (Photoemission Spectroscopy (PES) and X-ray Absorption Spectroscopy (XAS) in combination with Density Functional Theory (DFT) calculations.

    Paper I is a combined experimental and theoretical investigation of electronic structure of CoPc. addressing the atomic character of the Highest Occupied Molecular Orbital (HOMO) and the electronic configuration of the molecular ground state. Both these aspects are still under discussion since different experimental and theoretical studies have given controversial results. Previous works have indicated the CoPc ground state to either be described by the 2A1g or 2Eg, or by a mix of the two electronic configurations. Regrading the debated the atomic character of the HOMO of CoPc, it has been suggested to be either metal 3d-like and localized on the central Co atom or originating in the organic ligand of the molecule. In this thesis the valence photoemission results for CoPc in gas phase and as adsorbed films on Au(111) together with the DFT simulations, consistently indicate that the HOMO is derived only by the organic ligand, with mainly contribution from the carbon atoms with no metal character. Moreover, the good agreement between the experimental and theoretical results, confirms that the ground state of CoPc is correctly described by the 2A1g configuration.

    In Paper II, PES and XAS have been used to investigate the occupied and empty density of states of biphenylene films of different thicknesses, deposited onto a Cu(111) crystal. The results have been compared to previous gas phase spectra and single molecule Density Functional Theory (DFT) calculations to get insights into the possible modification of the molecular electronic structure in the film induced by the adsorption on a surface. Furthermore, XAS measurements allowed the characterizion of the variation of the molecular arrangement with the film thickness and helped to clarify the substrate-molecule interaction.

  • 3573.
    Zhang, Wenhua
    KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).
    First Principles Studies on Chemical and Electronic Structures of Adsorbates2009Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In this thesis, we focus on theoretical study of adsorbates on metal and oxide surfaces that are important for surface chemistry and catalysis. Based on first principles calculations, the adsorption ofCO, NO, NO2, C4H6S2, C22H27SH and other molecules or radicals on nobel metal surfaces (gold and silver) are investigated. Also, NO oxidation on oxygen pre-covered Au(111)surface and CO oxidation on water-oxygen covered Au(111)surface aretheoretically studied. A new mechanism of water-enhanced COoxidation is proposed. As for oxide surfaces, we first investigatethe geometric, electronic and magnetic structures of FeO ultrathin film on Pt(111) surface. The experimentally observed scanning tunneling microscopy images are well reproduced for the first timewith our model. The adsorption and dissociation of water on rutileTiO2(110) surface are investigated by quantum molecular dynamics.By theoretical X-ray photoemission spectroscopy (XPS) calculations,the surface species are properly assigned. The same strategy has applied to the study of the phase transition of water covered reconstructed anatase TiO2(001) surface, from which two different phases are theoretically identified. The structure of graphene oxideis also studied by comparing experimental and theoretical XPS spectra. Based on the novel structures identified, a new cutmechanism of graphene oxide is proposed.

  • 3574.
    Zhang, Xiaoli
    et al.
    South Univ Sci & Technol China, Dept Elect & Elect Engn, Shenzhen 518055, Peoples R China.;Wuhan Univ, Sch Power & Mech Engn, Wuhan 430072, Peoples R China.;Nanyang Technol Univ, Sch Elect & Elect Engn, 50 Nanyang Ave, Singapore 639798, Singapore..
    Xu, Bing
    South Univ Sci & Technol China, Dept Elect & Elect Engn, Shenzhen 518055, Peoples R China.;Wuhan Univ, Sch Power & Mech Engn, Wuhan 430072, Peoples R China..
    Zhang, Jinbao
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Gao, Yuan
    Nanyang Technol Univ, Sch Elect & Elect Engn, 50 Nanyang Ave, Singapore 639798, Singapore..
    Zheng, Yuanjin
    Nanyang Technol Univ, Sch Elect & Elect Engn, 50 Nanyang Ave, Singapore 639798, Singapore..
    Wang, Kai
    South Univ Sci & Technol China, Dept Elect & Elect Engn, Shenzhen 518055, Peoples R China..
    Sun, Xiao Wei
    South Univ Sci & Technol China, Dept Elect & Elect Engn, Shenzhen 518055, Peoples R China.;Nanyang Technol Univ, Sch Elect & Elect Engn, 50 Nanyang Ave, Singapore 639798, Singapore..
    All-Inorganic Perovskite Nanocrystals for High-Efficiency Light Emitting Diodes: Dual-Phase CsPbBr3-CsPb2Br5 Composites2016In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 26, no 25, 4595-4600 p.Article in journal (Refereed)
    Abstract [en]

    A dual-phase all-inorganic composite CsPbBr3-CsPb2Br5 is developed and applied as the emitting layer in LEDs, which exhibited a maximum luminance of 3853 cd m(-2), with current density (CE) of approximate to 8.98 cd A(-1) and external quantum efficiency (EQE) of approximate to 2.21%, respectively. The parasite of secondary phase CsPb2Br5 nanoparticles on the cubic CsPbBr3 nanocrystals could enhance the current efficiency by reducing diffusion length of excitons on one side, and decrease the trap density in the band gap on the other side. In addition, the introduction of CsPb2Br5 nanoparticles could increase the ionic conductivity by reducing the barrier against the electronic and ionic transport, and improve emission lifetime by decreasing nonradiative energy transfer to the trap states via controlling the trap density. The dual-phase all-inorganic CsPbBr3-CsPb2Br5 composite nanocrystals present a new route of perovskite material for advanced light emission applications.

  • 3575.
    Zhang, Xiaoliang
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Santra, Pralay Kanti
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Tian, Lei
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Johansson, Malin B.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Johansson, Erik M.J.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Highly Efficient Flexible Quantum Dot Solar Cells with Improved Electron Extraction Using MgZnO Nanocrystals2017In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 11, no 8, 8478-8487 p.Article in journal (Refereed)
    Abstract [en]

    Colloidal quantum dot (CQD) solar cells have high potential for realizing an efficient and lightweight energy supply for flexible or wearable electronic devices. To achieve highly efficient and flexible CQD solar cells, the electron transport layer (ETL), extracting electrons from the CQD solid layer, needs to be processed at a low-temperature and should also suppress interfacial recombination. Herein, a highly stable MgZnO nanocrystal (MZO-NC) layer is reported for efficient flexible PbS CQD solar cells. Solar cells fabricated with MZONC ETL give a high power conversion efficiency (PCE) of 10.4% and 9.4%, on glass and flexible plastic substrates, respectively. The reported flexible CQD solar cell has the record efficiency to date of flexible CQD solar cells. Detailed theoretical simulations and extensive characterizations reveal that the MZO-NCs significantly enhance charge extraction from CQD solids and diminish the charge accumulation at the ETL/CQD interface, suppressing charge interfacial recombination. These important results suggest that the low-temperature processed MZO-NCs are very promising for use in efficient flexible solar cells or other flexible optoelectronic devices.

  • 3576.
    Zhang, Yi-Qi
    et al.
    Technical University of Munich, Germany.
    Björk, Jonas
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Chemistry. Linköping University, Faculty of Science & Engineering.
    Barth, Johannes V.
    Technical University of Munich, Germany.
    Klappenberger, Florian
    Technical University of Munich, Germany.
    Intermolecular Hybridization Creating Nanopore Orbital in a Supramolecular Hydrocarbon Sheet2016In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 16, no 7, 4274-4281 p.Article in journal (Refereed)
    Abstract [en]

    Molecular orbital engineering is a key ingredient for the design of organic devices. Intermolecular hybridization promises efficient charge carrier transport but usually requires dense packing for significant wave function overlap. Here we use scanning tunneling spectroscopy to spatially resolve the electronic structure of a surface-confined nanoporous supramolecular sheet of a prototypical hydrocarbon compound featuring terminal alkyne (CCH) groups. Surprisingly, localized nanopore orbitals are observed, with their electron density centered in the cavities surrounded by the functional moieties. Density functional theory calculations reveal that these new electronic states originate from the intermolecular hybridization of six in-plane x-orbitals of the carbon carbon triple bonds, exhibiting significant electronic splitting and an energy downshift of approximately 1 eV. Importantly, these nanopore states are distinct from previously reported interfacial states. We unravel the underlying connection between the formation of nanopore orbital and geometric arrangements of functional groups, thus demonstrating the generality of applying related orbital engineering concepts in various types of porous organic structures.

  • 3577.
    Zhang, Zhenzhong
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Epitaxial growth optimization for 1.3-um InGaAs/GaAs Vertical-Cavity Surface-Emitting lasers2008Licentiate thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Long-wavelength (1.3-μm) vertical-cavity surface-emitting lasers (VCSELs) are of great interest as low-cost, high performance light sources for fiber-optic metro and access networks. During recent years the main development effort in this field has been directed towards all epitaxial GaAs-based structures by employing novel active materials. Different active region candidates for GaAs-based 1.3-μm VCSELs such as GaInNAs/GaAs QWs, GaAsSb QWs or InAs/InGaAs QDs have been investigated. However, the difficult growth and materials properties of these systems have so far hampered any real deployment of the technology. More recently, a new variety of VCSELs have been developed at KTH as based on highly strained InGaAs QWs and negative gain cavity detuning to reach the 1.3-μm wavelength window. The great benefit of this approach is that it is fully compatible with standard materials and processing methods.

    The aim of this thesis is to investigate long-wavelength (1.3-μm) VCSELs using ~1.2-μm In0.4GaAs/GaAs Multiple Quantum Wells (MQWs). A series of QW structures, DBR structures and laser structures, including VCSELs and Broad Area lasers (BALs) were grown by metal-organic vapor phase epitaxy (MOVPE) and characterized by various techniques: Photoluminescence (PL), high-resolution x-ray diffraction (XRD), atomic force microscopy (AFM), high accuracy reflectance measurements as well as static and dynamic device characterization. The work can be divided into three parts. The first part is dedicated to the optimization and characterization of InGaAs/GaAs QWs growth for long wavelength and strong luminescence. A strong sensitivity to the detailed growth conditions, such as V/III ratio and substrate misorientation is noted. Dislocations in highly strained InGaAs QW structure and Sb as surfactant assisted in InGaAs QW growth are also discussed here. The second part is related to the AlGaAs/GaAs DBR structures. It is shown that the InGaAs VCSELs with doped bottom DBRs have significantly lower slope efficiency, output power and higher threshold current. By a direct study of buried AlGaAs/GaAs interfaces, this is suggested to be due to doping-enhanced Al-Ga hetero-interdiffusion. In the third part, singlemode, high-performance 1.3-μm VCSELs based on highly strained InGaAs QWs are demonstrated. Temperature stable singlemode performance, including mW-range output power and 10 Gbps data transmission, is obtained by an inverted surface relief technique.

  • 3578.
    Zhang, Zhenzhong
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Marcks von Würtemberg, Rickard
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Berggren, Jesper
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Hammar, Mattias
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Optical loss and interface morphology in AlGaAs/GaAs distributed Bragg reflectors2007In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 91, no 10, 101101- p.Article in journal (Refereed)
    Abstract [en]

    It is shown that n-type doping of AlGaAs/GaAs distributed Bragg reflectors (DBRs) grown by metal-organic vapor-phase epitaxy has a profound negative impact on the performance of vertical-cavity surface-emitting lasers (VCSELs) based on such mirrors. Using an intracavity contact scheme, 1.3-mu m-range InGaAs VCSELs with and without doping in the bottom DBR are directly compared. Doped mirrors lead to lower slope efficiency, lower output power, and higher threshold current. From x-ray diffraction, high-accuracy reflectance measurements, and atomic force microscopy studies, it is suggested that this performance degradation is due to the doping-enhanced Al-Ga interdiffusion, leading to interface roughening and increased scattering loss.

  • 3579.
    Zhang, Zhibin
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP. KTH, School of Information and Communication Technology (ICT), Centres, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    Li, Jiantong
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Cabezas, Ana Lopez
    KTH, School of Information and Communication Technology (ICT), Centres, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK. KTH, School of Information and Communication Technology (ICT), Electronic, Computer and Software Systems, ECS.
    Zhang, Shi-Li
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP. KTH, School of Information and Communication Technology (ICT), Centres, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    Characterization of acid-treated carbon nanotube thin films by means of Raman spectroscopy and field-effect response2009In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 476, no 4-6, 258-261 p.Article in journal (Refereed)
    Abstract [en]

    By combining Raman spectroscopy with transistor transfer characteristics, acid treatment of single-walled carbon nanotubes (SWCNTs) in a mixture of concentrated HNO3/H2SO4 has been characterized. The acid treatment results in a sharp decrease in the Raman resonant signals of the metallic SWCNTs but no observable change in those of the semiconducting SWCNTs. However, the acid treatment causes disappearing gate modulation of the thin-film transistors made of the SWCNTs, contrary to what would be expected referring to the Raman results. These experimental results suggest that the energy band of the semiconducting SWCNTs is significantly affected by absorbates induced by the acid treatment.

  • 3580.
    Zhang, Zhibin
    et al.
    KTH, School of Information and Communication Technology (ICT), Centres, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    Li, Jiantong
    KTH, School of Information and Communication Technology (ICT), Centres, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    Qu, Minni
    Cabezas, Ana Lopez
    KTH, School of Information and Communication Technology (ICT), Centres, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK. KTH, School of Information and Communication Technology (ICT), Electronic, Computer and Software Systems, ECS.
    Zhang, Shi-Li
    Photo-Activated Interaction Between P3HT and Single-Walled Carbon Nanotubes Studied by Means of Field-Effect Response2009In: IEEE Electron Device Letters, ISSN 0741-3106, E-ISSN 1558-0563, Vol. 30, no 12, 1302-1304 p.Article in journal (Refereed)
    Abstract [en]

    It is shown in this letter that the field-effect electrical response of transistors with their channel made of networks of single-walled carbon nanotubes (SWNTs) embedded in a poly(3-hexylthiophene) (P3HT) matrix can be significantly altered by light illumination. The experimental results indicate a photo-activated electron transfer from P3HT selectively to the semiconducting SWNTs. This finding points to a potential optoelectronic application of such a field-effect device as a photo-triggered electronic switch.

  • 3581.
    Zhang, Zhigang
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Condensed Matter Theory.
    Grishini, Alex M.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Condensed Matter Theory.
    Characterization of piezoelectric shear mode inkjet actuator2005In: Integrated Ferroelectrics, ISSN 1058-4587, E-ISSN 1607-8489, Vol. 69, 401-+ p.Article in journal (Refereed)
    Abstract [en]

    Impedance analysis was used to characterize the properties of Piezoelectric Shear Mode Inkjet Actuators. Ceramic actuators poled parallel to the channel walls exhibit good performance. Applying high voltage the actuators can be depolarized at high temperature or even re-poled perpendicular to the channel walls. This limits the drive pulse and the bias voltage below the coercive voltage. The leakage current also has been studied with various conditions. For the ferroelectric ceramic materials, the Schottky barrier also can be measured at definite voltage and temperature ranges, the corresponding Barrier for the Al/PZT contact is 0.98 eV. A pronounced low-temperature dielectric relaxation process was observed between 100-150 K; the relaxation rate fellows the Arrhenius law, the fitted activation energy is 0.194 eV. The resonance frequency increases as decreasing the temperature because of increasing for the stiffness coefficient at low temperature.

  • 3582.
    Zhao, Baodan
    et al.
    Cavendish Laboratory, University of Cambridge, Cambridge, UK.
    Abdi-Jalebi, Mojtaba
    Cavendish Laboratory, University of Cambridge, Cambridge, UK.
    Tabachnyk, Maxim
    Cavendish Laboratory, University of Cambridge, Cambridge, UK.
    Glass, Hugh
    Cavendish Laboratory, University of Cambridge, Cambridge, UK.
    Kamboj, Varun S.
    Cavendish Laboratory, University of Cambridge, Cambridge, UK.
    Nie, Wanyi
    Los Alamos National Laboratory, Los Alamos, NM, USA.
    Pearson, Andrew J.
    Cavendish Laboratory, University of Cambridge, Cambridge, UK.
    Puttisong, Yuttapoom
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering. Cavendish Laboratory, University of Cambridge, Cambridge, UK.
    Gödel, Karl C.
    Cavendish Laboratory, University of Cambridge, Cambridge, UK.
    Beere, Harvey E.
    Cavendish Laboratory, University of Cambridge, Cambridge, UK.
    Ritchie, David A.
    Cavendish Laboratory, University of Cambridge, Cambridge, UK.
    Mohite, Aditya D.
    Los Alamos National Laboratory, Los Alamos, NM, USA.
    Dutton, Siân E.
    Cavendish Laboratory, University of Cambridge, Cambridge, UK.
    Friend, Richard H.
    Cavendish Laboratory, University of Cambridge, Cambridge, UK.
    Sadhanala, Aditya
    Cavendish Laboratory, University of Cambridge, Cambridge, UK.
    High Open-Circuit Voltages in Tin-Rich Low-Bandgap Perovskite-Based Planar Heterojunction Photovoltaics2017In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 29, 1604744Article in journal (Refereed)
    Abstract [en]

    Low-bandgap CH3NH3(PbxSn1–x)I3 (0 ≤ x ≤ 1) hybrid perovskites (e.g., ≈1.5–1.1 eV) demonstrating high surface coverage and superior optoelectronic properties are fabricated. State-of-the-art photovoltaic (PV) performance is reported with power conversion efficiencies approaching 10% in planar heterojunction architecture with small (<450 meV) energy loss compared to the bandgap and high (>100 cm2 V−1s−1) intrinsic carrier mobilities.

  • 3583.
    Zhao, Dan
    et al.
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Fabiano, Simone
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Berggren, Magnus
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Crispin, Xavier
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Ionic thermoelectric gating organic transistors2017In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 8, 14214Article in journal (Refereed)
    Abstract [en]

    Temperature is one of the most important environmental stimuli to record and amplify. While traditional thermoelectric materials are attractive for temperature/heat flow sensing applications, their sensitivity is limited by their low Seebeck coefficient (similar to 100 mu V K-1). Here we take advantage of the large ionic thermoelectric Seebeck coefficient found in polymer electrolytes (similar to 10,000 mu V K-1) to introduce the concept of ionic thermoelectric gating a low-voltage organic transistor. The temperature sensing amplification of such ionic thermoelectric-gated devices is thousands of times superior to that of a single thermoelectric leg in traditional thermopiles. This suggests that ionic thermoelectric sensors offer a way to go beyond the limitations of traditional thermopiles and pyroelectric detectors. These findings pave the way for new infrared-gated electronic circuits with potential applications in photonics, thermography and electronic-skins.

  • 3584.
    Zhao, Zhe
    et al.
    Department of Physical Inorganic and Structural Chemistry, Stockholm University.
    Buscaglia, V.
    Viviani, M.
    Buscaglia, M. T.
    Mitoseriu, L.
    Testino, A.
    Nygren, M.
    Johnsson, M.
    Nanni, P.
    Grain-size effects on the ferroelectric behavior of dense nanocrystalline BaTiO3 ceramics2004In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 70, no 2Article in journal (Refereed)
    Abstract [en]

    A progressive reduction of tetragonal distortion, heat of transition, Curie temperature, and relative dielectric constant has been observed on dense BaTiO3 ceramics with grain size decreasing from 1200 to 50 nm. The correlations between grain size, extent of tetragonal distortion, and ferroelectric properties strongly support the existence of an intrinsic size effect. From the experimental trends the critical size for disappearance of ferroelectricity has been evaluated to be 10-30 nm. The strong depression of the relative permittivity observed for the nanocrystalline ceramics can be ascribed to the combination of the intrinsic size effect and of the size-dependent "dilution" effect of a grain boundary "dead" layer.

  • 3585.
    Zhaunerchyk, Vitali
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Univ Gothenburg, Dept Phys, Gothenburg, Sweden..
    Kaminska, Magdalena
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Stockholm Univ, Dept Phys, S-10691 Stockholm, Sweden.;Jan Kochanowski Univ Humanities & Sci, Inst Phys, Kielce, Poland..
    Mucke, Melanie
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Squibb, R. J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Univ Gothenburg, Dept Phys, Gothenburg, Sweden.;Univ London Imperial Coll Sci Technol & Med, Blackett Lab, London, England..
    Eland, John H. D.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Univ Gothenburg, Dept Phys, Gothenburg, Sweden.;Univ Oxford, Dept Chem, Oxford OX1 3QZ, England..
    Piancastelli, Maria Novella
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics. UPMC, LCPMR, Paris, France.;CNRS, Paris, France..
    Frasinski, L. J.
    Univ London Imperial Coll Sci Technol & Med, Blackett Lab, London, England..
    Grilj, J.
    SLAC Natl Accelerator Lab, Menlo Pk, CA USA..
    Koch, M.
    SLAC Natl Accelerator Lab, Menlo Pk, CA USA.;Graz Univ Technol, Inst Expt Phys, A-8010 Graz, Austria..
    McFarland, B. K.
    SLAC Natl Accelerator Lab, Menlo Pk, CA USA..
    Sistrunk, E.
    SLAC Natl Accelerator Lab, Menlo Pk, CA USA..
    Guehr, M.
    SLAC Natl Accelerator Lab, Menlo Pk, CA USA..
    Coffee, R. N.
    SLAC Natl Accelerator Lab, Menlo Pk, CA USA..
    Bostedt, C.
    SLAC Natl Accelerator Lab, Menlo Pk, CA USA..
    Bozek, J. D.
    SLAC Natl Accelerator Lab, Menlo Pk, CA USA..
    Salen, P.
    Stockholm Univ, Dept Phys, S-10691 Stockholm, Sweden..
    Meulen, P. V. D.
    Stockholm Univ, Dept Phys, S-10691 Stockholm, Sweden..
    Linusson, P.
    Stockholm Univ, Dept Phys, S-10691 Stockholm, Sweden..
    Thomas, R. D.
    Stockholm Univ, Dept Phys, S-10691 Stockholm, Sweden..
    Larsson, M.
    Stockholm Univ, Dept Phys, S-10691 Stockholm, Sweden..
    Foucar, L.
    Max Planck Inst Med Res, D-69120 Heidelberg 1, Germany..
    Ullrich, J.
    Max Planck Inst Kernphys, D-69117 Heidelberg, Germany.;Phys Tech Bundesanstalt, Bundesallee 100, Braunschweig, Germany..
    Motomura, K.
    Tohoku Univ, Inst Multidisciplinary Res Adv Mat, Sendai, Miyagi 980, Japan..
    Mondal, S.
    Tohoku Univ, Inst Multidisciplinary Res Adv Mat, Sendai, Miyagi 980, Japan..
    Ueda, K.
    Tohoku Univ, Inst Multidisciplinary Res Adv Mat, Sendai, Miyagi 980, Japan..
    Richter, R.
    Elettra Sincrotrone Trieste, Trieste, Italy. Hiroshima Univ, Dept Chem, Hiroshima 730, Japan..
    Prince, K. C.
    Elettra Sincrotrone Trieste, Trieste, Italy. Hiroshima Univ, Dept Chem, Hiroshima 730, Japan..
    Takahashi, O.
    Elettra Sincrotrone Trieste, Trieste, Italy. Hiroshima Univ, Dept Chem, Hiroshima 730, Japan..
    Osipov, T.
    Western Michigan Univ, Dept Phys, Kalamazoo, MI 49008 USA..
    Fang, L.
    Western Michigan Univ, Dept Phys, Kalamazoo, MI 49008 USA..
    Murphy, B. F.
    Western Michigan Univ, Dept Phys, Kalamazoo, MI 49008 USA..
    Berrah, N.
    Western Michigan Univ, Dept Phys, Kalamazoo, MI 49008 USA.;Univ Connecticut, Dept Phys, Storrs, CT USA..
    Feifel, Raimund
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Univ Gothenburg, Dept Phys, Gothenburg, Sweden..
    Disentangling formation of multiple-core holes in aminophenol molecules exposed to bright X-FEL radiation2015In: Journal of Physics B: Atomic, Molecular and Optical Physics, ISSN 0953-4075, E-ISSN 1361-6455, Vol. 48, no 24, 244003Article in journal (Refereed)
    Abstract [en]

    Competing multi-photon ionization processes, some leading to the formation of double core hole states, have been examined in 4-aminophenol. The experiments used the linac coherent light source (LCLS) x-ray free electron laser, in combination with a time-of-flight magnetic bottle electron spectrometer and the correlation analysis method of covariance mapping. The results imply that 4-aminophenol molecules exposed to the focused x-ray pulses of the LCLS sequentially absorb more than two x-ray photons, resulting in the formation of multiple core holes as well as in the sequential removal of photoelectrons and Auger electrons (so-called PAPA sequences).

  • 3586.
    Zheltukhin, Alexandr A.
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita). Kharkov Institute of Physics and Technology, Ukraine.
    Laplace-Beltrami operator and exact solutions for branes2013In: Nuclear Physics B, ISSN 0550-3213, E-ISSN 1873-1562, Vol. 867, no 3, 763-778 p.Article in journal (Refereed)
    Abstract [en]

    Proposed is a new approach to finding exact solutions of nonlinear p-brane equations in D-dimensional Minkowski space based on the use of various initial value constraints. It is shown that the constraints Delta((p))(x) over right arrow =0 and Delta((p))(x) over right arrow = -Lambda(t, sigma(r))(x) over right arrow give two sets of exact solutions.

  • 3587.
    Zheng, Li-Rong
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Duo, Xinzhong
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Nejad, Majid B.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Rodriguez Duenas, Saul
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Ismail, Muhammed
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Tenhunen, Hannu
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    On-chip versus off-chip passives in radio and mixed-signal system-on-package design2006In: ESTC 2006 - 1st Electronics Systemintegration Technology Conference, New York: IEEE , 2006, 221-232 p.Conference paper (Refereed)
    Abstract [en]

    Optimal total solution for new radio architecture and implementation requires accurate trade-offs for off-chip versus off-chip passives. In this paper, a complete and systematic design methodology for RF blocks in SoP (system-on-package) versus SoC (system-on-chip) is presented. This methodology explores trade-offs between Performance and cost when different on-chip or off-chip passives are used. For a better presentation, the method and design techniques are demonstrated through four multi-band/multi-standard radio design examples with various technologies and different circuit topologies. Our study reveals that, in order to obtain cost benefits in RF-SoPs, small RF chips should be merged as larger chips and the integration density of each RF chip should be high enough. Our study also indicates that in a complex chip like a multi-band radio, moving passives off chip could achieve further cost savings and significant performance improvements. These are general conclusions but, our method offers a detailed analysis which can give quantitative measurements of cost savings and performance improvements in off-chip versus off-chip passives in RF SoP design.

  • 3588.
    Zheng, Qiye
    et al.
    University of Illinois, USA.
    Mei, Antonio B.
    University of Illinois, USA.
    Tuteja, Mohit
    University of Illinois, USA.
    Sangiovanni, Davide
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. Ruhr University of Bochum, Germany.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. University of Illinois, USA.
    Greene, Joseph E
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. University of Illinois, USA.
    Cahill, David G.
    University of Illinois, IL 61801 USA.
    Phonon and electron contributions to the thermal conductivity of VNx epitaxial layers2017In: PHYSICAL REVIEW MATERIALS, ISSN 2475-9953, Vol. 1, no 6, 065002Article in journal (Refereed)
    Abstract [en]

    Thermal conductivities of VNx/MgO(001) (0.76 amp;lt;= x amp;lt;= 1.00) epitaxial layers, grown by reactive magnetron sputter deposition, are measured in the temperature range 300 amp;lt; T amp;lt; 1000 K using time-domain thermore-flectance (TDTR). Data for the total thermal conductivity are compared to the electronic contribution to the thermal conductivity calculated from the measured electrical conductivity, the Wiedemann-Franz law, and an estimate of the temperature dependence of the Lorenz number L(T). The total thermal conductivity is dominated by electron contribution and varies between 13 W m(-1) K-1 at x = 0.76 and 20 W m(-1) K-1 at x = 1.00 for T = 300 K and between 25 and 35 W m(-1) K-1 for T = 1000 K. The lattice thermal conductivity vs x ranges from 5 to 7 W m(-1) K-1 at 300 K and decreases by 20% at 500 K. The low magnitude and weak temperature dependence of the lattice thermal conductivity are attributed to strong electron-phonon coupling in VN.

  • 3589.
    Zheng, Wenhao
    et al.
    Jinan University, Peoples R China.
    Lin, Yuanbao
    Jinan University, Peoples R China.
    Zhang, Yangdong
    Jinan University, Peoples R China.
    Yang, Junyu
    Jinan University, Peoples R China.
    Peng, Zuosheng
    Jinan University, Peoples R China.
    Liu, Alei
    Jinan University, Peoples R China.
    Zhang, Fengling
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering. Jinan University, Peoples R China.
    Hou, Lintao
    Jinan University, Peoples R China.
    Dual Function of UV/Ozone Plasma-Treated Polymer in Polymer/Metal Hybrid Electrodes and Semitransparent Polymer Solar Cells2017In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 9, no 51, 44656-44666 p.Article in journal (Refereed)
    Abstract [en]

    In this work, high-performance inverted indium tin oxide (ITO)-free semitransparent polymer solar cells are comprehensively investigated using a novel polymer/metal hybrid transparent electrode. The electrical and optical characteristics of hybrid electrodes are significantly enhanced by introducing UV/ozone plasma treatment on the polymer poly[(9,9-bis(3-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PFN), which is functioned as both a seed layer for ultrathin Ag metal electrode and an optical spacer for transparent devices. The optimized sheet resistance of PFN/Ag (12 nm) hybrid electrode is only half of the commercial ITO (9.4 vs 20.0 Omega sq(-1)) and the high wavelength-dependent reflectance of hybrid electrode helps to increase the ITO-free device short-circuit current density. Furthermore, the interface property between PFN and ultrathin Ag is analyzed in detail and the optical field distribution is calculated for comparison. A high power conversion efficiency of 5.02%, which is increased by 35% compared to that of the ITO-based device, is achieved in the ITO-free semitransparent device in conjunction with an excellent average visible transmittance above 28% that is higher than the benchmark of 25% for power-generating window, indicating its great potential in building integrated photovoltaic systems in the future. Furthermore, the strategy is successfully developed for other polymer systems, suggesting the universal applicability for plastic electronics.

  • 3590.
    Zhou, Yan
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Spin momentum transfer effects for spintronic device applications2009Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The recent discovery that a spin-polarized current can exert a large torque on a ferromagnet, through direct transfer of spin angular momentum, offers the possibility of electrical current controlled manipulation of magnetic moment in nanoscale magnetic device structures. This so-called spin torque effect holds great promise for two applications, namely, spin torque oscillators (STOs) for wireless communication and radar communication, and spin transfer torque RAM (STT-RAM) for data/information storage.

     

    The STO is a nanosized spintronic device capable of microwave generation at frequencies in the 1-65 GHz range with high quality factors. Although the STO is very promising for future telecommunication, two major shortcomings have to be addressed before it can truly find practical use as a radio-frequency device. Firstly, its very limited output power has to be significantly improved. One possibility is the synchronization of two or more STOs to both increase the microwave power and further increase the signal quality. Synchronization of serially connected STOs has been suggested in this thesis. In this configuration, synchronization relies on phase locking between the STOs and their self-generated alternating current. While this locking mechanism is intrinsically quite weak, we find that the locking range of two serially connected spin-valve STOs can be enhanced by over two orders of magnitude by adjusting the circuit I-V phase to that of an intrinsic preferred phase shift between the STO and an alternating current. More recently, we have also studied the phase-locking of STOs based on magnetic tunnel junctions (MTJ-STO) to meet the power specifications of actual application where the rf output levels should be above 0 dBm (1 mW). In addition to the spin torque terms present in GMR spin valves, MTJs also exhibit a significant perpendicular spin torque component with a quite complex dependence on both material choices and applied junction bias. We find that the perpendicular torque component modifies the intrinsic preferred I-V phase shift in single MTJ-STOs in such a way that serially connected STOs synchronize much more readily without the need for additional circuitry to change the I-V phase.

     

    Secondly, equal attention has been focused on removing the applied magnetic field for STO operation, which requires bulky components and will limit the miniaturization of STO-based devices. Various attempts have been made to realize STOs operating in zero magnetic field. By using a tilted (oblique angle) polarizer (fixed layer) instead of an in-plane polarizer (standard STO), we show zero field operation over a very wide polarizer angle range without sacrificing output signal. In addition, the polarizer angle introduces an entirely new degree of freedom to any spin torque device and opens up for a wide range of additional phenomena.

     

    The STT-RAM has advantages over other types of memories including conventional MRAM in terms of power consumption, speed, and scalability. We use a set of simulation tools to carry out a systematic study on the subject of micromagnetic switching processes of a device for STT-RAM application. We find that the non-zero k spin wave modes play an important role in the experimentally measured switching phase boundary. These may result in telegraph transitions among different spin-wave states, and be related to the back-hopping phenomena where the switching probability will decrease with increasing bias in tunnel junctions.

  • 3591.
    Zhou, Yan
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Bonetti, Stefano
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Persson, Johan
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Åkerman, Johan
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Capacitance Enhanced Synchronization of Pairs of Spin-Transfer Oscillators2009In: IEEE transactions on magnetics, ISSN 0018-9464, E-ISSN 1941-0069, Vol. 45, no 6, 2421-2423 p.Article in journal (Refereed)
    Abstract [en]

    Macro-spin simulations have been performed to study the synchronization of pairs of serially connected spin torque oscillators in parallel with a capacitor. The sensitivity to the STO process variation, which is modeled by the anisotropy field distribution for different STO samples, can be dramatically decreased by the coupling of a capacitor in the circuit. There exists an optimum capacitance where the multi-STO synchronized state develops the highest robustness.

  • 3592.
    Zhou, Yan
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Bonetti, Stefano
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Zha, Chaolin
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Åkerman, Johan
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Zero field precession and hysteretic critical currents in spin torque oscillators with tilted polarizerIn: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630Article in journal (Other academic)
  • 3593.
    Zhou, Yan
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Persson, Johan
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Bonetti, Stefano
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Åkerman, Johan
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Tunable intrinsic phase of a spin torque oscillator2008In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 92, no 9, 092505- p.Article in journal (Refereed)
    Abstract [en]

    We show analytically why a spin torque oscillator (STO) locks to an alternating current (I-ac), having the same frequency as the STO, at a nontrivial, intrinsic, phase value Delta phi(0). We determine both the stability and the exact phase of the locked state and explain the recently observed phase jump by about 180 degrees at the in-plane-to-out-of-plane precession boundary. Delta phi(0) depends on the STO material parameters and is tunable through both the applied field and the dc current, which provides an additional control of the exact I-V phase in an STO driven radio frequency circuit.

  • 3594.
    Zhou, Yan
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Åkerman, Johan
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Perpendicular spin torque promotes synchronization of magnetic tunnel junction based spin torque oscillators2009In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 94, no 11, 112503- p.Article in journal (Refereed)
    Abstract [en]

    We study how the perpendicular spin transfer torque term (b(j)), present in magnetic tunneling junctions (MTJs), affects the synchronization of serially connected MTJ-based spin torque oscillators (MTJ-STOs). We find that b(j) modifies the intrinsic preferred I-V phase shift in single MTJ-STO in such a way that serially connected MTJ-STOs synchronize much more readily without the need for additional circuitry to change the I-V phase. This result strongly suggests that synchronization of serially connected MTJ-STOs should be significantly more straightforward than the previously attempted serial synchronization of giant magnetoresistance based STOs (GMR-STOs).

  • 3595.
    Zhou, Yan
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Åkerman, Johan
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Sun, Jonathan Z
    Micromagnetic study of switching boundary of a ferromagnetic nanodeviceManuscript (preprint) (Other academic)
  • 3596.
    Zhou, Yan
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Åkerman, Johan
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Sun, Jonathan Z.
    Micromagnetic study of switching boundary of a spin torque nanodevice2011In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 98, no 10, 102501- p.Article in journal (Refereed)
    Abstract [en]

    We report on a numerical study of the micromagnetic switching process of a nanostructured spin torque device. We show that incoherent spin waves can be excited over a wide range of current and field even at zero temperature. These large amplitude, incoherent, and nonzero k spin wave modes are shown to alter the switching phase boundary from that calculated within a macrospin model. The presence of telegraphic transitions between different spin wave modes may also contribute to the so-called back-hopping phenomenon where the switching probability varies nonmonotonically with increasing bias current.

  • 3597.
    Zhu, Bin
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology. Faculty of Physics and Electronic Science, Hubei University, Wuhan, Hubei, China.
    Huang, Yizhong
    Fan, L.
    Ma, Y.
    Wang, Baoyuan
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology. Faculty of Physics and Electronic Science, Hubei University, Wuhan, Hubei, China.
    Xia, Chen
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Afzal, Muhammad
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Zhang, B.
    Dong, W.
    Wang, H.
    Lund, P. D.
    Novel fuel cell with nanocomposite functional layer designed by perovskite solar cell principle2016In: Nano Energy, ISSN 2211-2855, Vol. 19, 156-164 p.Article in journal (Refereed)
    Abstract [en]

    A novel fuel-to-electricity conversion technology resembling a fuel cell has been developed based on the perovskite solar cell principle using a perovskite, e.g. La0.6Sr0.4Co0.2Fe0.8O3-δ and an ionic nanocomposite material as a core functional layer, sandwiched between n- and p-conducting layers. The conversion process makes use of semiconductor energy bands and junctions properties. The physical properties of the junction and alignment of the semiconductor energy band allow for direct ion transport and prevent internal electronic short-circuiting, while at the same time avoiding losses at distinct electrolyte/electrode interfaces typical to conventional fuel cells. The new device achieved a stable power output of 1080mWcm-2 at 550°C in converting hydrogen fuel into electricity.

  • 3598.
    Zhu, Hong
    et al.
    Massachusetts Institute of Technology, Cambridge, USA.
    Sun, Wenhao
    Massachusetts Institute of Technology, Cambridge, USA.
    Armiento, Rickard
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Lazić, Predrag
    Rudjer Boskovic Institute, Zagreb, Croatia.
    Ceder, Gerbrand
    Massachusetts Institute of Technology, Cambridge, USA.
    Band structure engineering through orbital interaction for enhanced thermoelectric power factor2014In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 104, 082107-1-082107-5 p.Article in journal (Refereed)
    Abstract [en]

    Band structure engineering for specific electronic or optical properties is essential for the further development of many important technologies including thermoelectrics, optoelectronics, and microelectronics. In this work, we report orbital interaction as a powerful tool to finetune the band structure and the transport properties of charge carriers in bulk crystalline semiconductors. The proposed mechanism of orbital interaction on band structure is demonstrated for IV-VI thermoelectric semiconductors. For IV-VI materials, we find that the convergence of multiple carrier pockets not only displays a strong correlation with the s-p and spin-orbit coupling but also coincides with the enhancement of power factor. Our results suggest a useful path to engineer the band structure and an enticing solid-solution design principle to enhance thermoelectric performance.

  • 3599.
    Zhu, Q.
    et al.
    Laboratory of Physics and Nanostructures, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland.
    Ganière, J. D.
    Laboratory of Quantum Optoelectronics, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland.
    He, Z. B.
    Laboratory of Physics and Nanostructures, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland.
    Karlsson, K Fredrik
    Laboratory of Physics and Nanostructures, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland.
    Byszewski, M.
    Laboratory of Physics and Nanostructures, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland.
    Pelucchi, E.
    Laboratory of Physics and Nanostructures, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland.
    Rudra, A.
    Laboratory of Physics and Nanostructures, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland.
    Kapon, E.
    Laboratory of Physics and Nanostructures, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland.
    Pyramidal GaAs/AlzGa1-zAs quantum wire/dot systems with controlled heterostructure potential2010In: Phys. Rev. B, Vol. 82, 165315Article in journal (Refereed)
    Abstract [en]

    The structural and optical properties of controlled-heterostructure-potential, low-dimensional GaAs/AlGaAs nanostructures self-formed during organometallic chemical vapor deposition in tetrahedral pyramids etched in (111)B-GaAs substrates, are investigated using electron microscopy, cathodoluminescence, photoluminescence (PL), photon correlation spectroscopy, and theoretical modeling. Quantum wires/dots with AlGaAs cores with growth-controlled dimensions are formed, with a system of well-defined, low-dimensional nanostructure barriers around them. Transitions between carrier states confined in the AlGaAs quantum wires and dots are identified in the PL spectra, with features in good agreement with model calculations. Emission of single-photons and bunched-photon pairs is observed using temporal photon correlation spectroscopy. This self-formed nanostructure system provides new ways for shaping low-dimensional quantum structures and their heterostructure environment.

  • 3600.
    Zhu, Xiaomei
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Brändström, Erik
    Umeå University, Faculty of Science and Technology, Physics.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Physics.
    Mechanical measurement of the transverse force on the moving vortices in superconductors1996In: Czechoslovak Journal of Physics volume 46, Supplement S3: Proceedings of the 21st International Conference on Low Temperature Physics (LT 21), Prague 1996, part S3: Superconductivity 2, Praha: CZECHOSLOVAK JOURNAL OF PHYSICS , 1996, 1727-1728 p.Conference paper (Refereed)
    Abstract [en]

    We have designed a mechanical experiment to measure the total transverse force on moving vortices in a type II superconductor. The transverse force is measured by monitoring the motion of the superconductor while the vortices are driven into motion by a moving magnet. The advantage of this direct force measurement is that it is free from complications due to vortex interactions.

6970717273 3551 - 3600 of 3631
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