physica status solidi (RRL) - Rapid Research Letters

Cover image for Vol. 6 Issue 8

August 2012

Volume 6, Issue 8

Pages A83–A92, 327–357

  1. Cover Picture

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      Cover Picture: Host structure dependence of light yield and proportionality in scintillators in terms of hot and thermalized carrier transport (Phys. Status Solidi RRL 8/2012)

      Qi Li, Joel Q. Grim, K. B. Ucer, A. Burger, G. A. Bizarri, W. W. Moses and R. T. Williams

      Version of Record online: 16 AUG 2012 | DOI: 10.1002/pssr.201290019

      Thumbnail image of graphical abstract

      Energy resolving radiation detectors are used in security scanning, medical molecular imaging, and high-energy physics applications. Critical performance improvement in scintillation detectors depends on understanding what controls light yield and the proportionality of light emission to particle energy within a track of very high excitation density and radial gradients. Hot and thermalized electron transport and hole self-trapping are found to be three important controlling phenomena. The cover illustration, pointing to the Letter by Qi Li et al. (pp. 346–348), shows the conduction band structure of NaI from which hot electron group velocity was calculated. The group velocity along with thermalization time governs the hot electron range illustrated by the shaded circular area, which in turn affects the number of trapping centers encountered on the path to recombination with less mobile holes. Such considerations offer insight into the dramatic and previously unexplained difference of light yield and proportionality between the classes of complex halide scintillators exemplified by SrI2:Eu2+ and simple monovalent halide scintillators like NaI:Tl+.

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  3. Back Cover

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      Back Cover: Transmission electron microscopy of single wall carbon nanotube/polymer nanocomposites: A first-principles study (Phys. Status Solidi RRL 8/2012)

      F. Solá, Z. H. Xia, M. Lebrón-Colón and M. A. Meador

      Version of Record online: 16 AUG 2012 | DOI: 10.1002/pssr.201290021

      Thumbnail image of graphical abstract

      Polymer nanocomposites filled with single wall carbon nanotubes (SWCNTs) are promising materials for aerospace applications. The control of homogeneous dispersion of the nanotubes in the polymeric matrix is important, e.g., for an optimum mechanical response of the nanocomposite. Furthermore, identification of the metallic or semiconducting nature of the nanotubes through chirality is needed. However, imaging SWCNTs in a polymer matrix is challenging both due to the small size and because the contrast is covered by scattering from the polymer matrix. Solá et al. (pp. 349–351) theoretically investigate the high-resolution transmission electron microscopy (HRTEM) images and electron diffraction (ED) of nanovolumes composed of polyethylene filled with SWCNTs using multislice theory and the optics of an FEG TEM at 80 kV. If the electron beam is oriented perpendicular to the nanotube walls, the results strongly depend on the nanocomposite thickness, HRTEM features of the nanofiller can even completely disappear, although chirality (and hence diameter) may be extracted by reflections of the ED pattern. The authors discuss the new limits set up for TEM investigation of dispersion and chirality.

  4. Contents

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  6. Rapid Research Letters

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    1. Transparent bulk metals

      A route to transparent bulk metals (pages 327–330)

      U. Schwingenschlögl, C. Schuster and R. Frésard

      Version of Record online: 23 JUL 2012 | DOI: 10.1002/pssr.201206275

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      By electronic band structure calculations, e.g. for Ag-Al2O3, hypothetical sapphire based M-Al2O3 compounds with a quarter of the Al atoms replaced by 4d transition metal M ions are found to be energetically stable. Metallicity is achieved if the electronic bands of the M dopant are close to half-filling. Transparency results from a huge optical band gap reminiscent of the sapphire host.

    2. Silicon solar cells

      On the mechanism of potential-induced degradation in crystalline silicon solar cells (pages 331–333)

      J. Bauer, V. Naumann, S. Großer, C. Hagendorf, M. Schütze and O. Breitenstein

      Version of Record online: 10 JUL 2012 | DOI: 10.1002/pssr.201206276

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      The microscopic structure of crystalline silicon solar cells causing potential-induced degradation is investigated. Electron-beam-induced current measurements reveal a high density of ohmic shunts in the solar cell. Secondary ion mass spectroscopy maps show a strong correlation of the positions of the shunts with locally increased sodium concentration. A model is presented proposing an inverted emitter causing the ohmic shunts.

    3. A glass thinning and texturing method for light incoupling in thin-film polycrystalline silicon solar cells application (pages 334–336)

      Hongtao Cui and Patrick R. Campbell

      Version of Record online: 19 JUL 2012 | DOI: 10.1002/pssr.201206266

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      For 2° cm2 size poly-Si thin-film solar cells on glass superstrates, glass thinning and texturing improves light incoupling. In this Letter, a labour-free wet etching method is developed to texture and thin the glass at the same time in contrast to conventionally separated labour-intensive glass thinning and texturing processes. Also, the wet etching enhances Jsc by 6.3% which is better than the value of 4.6% found in the literature.

    4. Impact of nongeminate recombination on the performance of pristine and annealed P3HT:PCBM solar cells (pages 337–339)

      Markus Gluecker, Alexander Foertig, Vladimir Dyakonov and Carsten Deibel

      Version of Record online: 10 JUL 2012 | DOI: 10.1002/pssr.201206248

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      Markus Gluecker et al. employed the experimental methods of transient photovoltage (TPV) and charge extraction (CE) to analyze the impact of recombination losses on the J–V behavior of poly(3-hexylthiophene) (P3HT): [6,6]-phenyl-C61 butyric acid methyl ester (PCBM) blend systems. The authors found that nongeminate recombination is the major loss process in both annealed and pristine (as-prepared) devices for temperatures down to 200 K. Moreover, they deduced from their results that photogeneration is independent of electric field.

    5. Spin Hall effect

      Intrinsic spin Hall effect in silicene: transition from spin Hall to normal insulator (pages 340–342)

      A. Dyrdał and J. Barnaś

      Version of Record online: 29 JUN 2012 | DOI: 10.1002/pssr.201206202

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      This Letter presents theoretical results indicating a phase transition between the spin Hall and classical band insulator phases in two-dimensional silicene. Such a transition occurs in an external electric field normal to the silicene plane and manifests itself by changes in the spin Hall conductivity for the Fermi level inside the spin–orbit gap, which reaches a universal quantized value for the spin Hall phase and zero for the band insulator phase.

    6. Spin relaxation nanowires

      Spin relaxation in nanowires by hyperfine coupling (pages 343–345)

      C. Echeverría-Arrondo and E. Ya. Sherman

      Version of Record online: 9 AUG 2012 | DOI: 10.1002/pssr.201206257

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      Echeverría-Arrondo and Sherman investigate spin dynamics due to hyperfine coupling of disorder-localized electrons in doped GaAs nanowires. The calculated spin relaxation times, of the order of 10 ns, depend on the electron energy, the impurity content, and the wire cross section area. The obtained results show that the dopant concentration and the wire width are the key factors for efficient spin-based operation with one-dimensional semiconductors.

    7. Hot electrons

      Host structure dependence of light yield and proportionality in scintillators in terms of hot and thermalized carrier transport (pages 346–348)

      Qi Li, Joel Q. Grim, K. B. Ucer, A. Burger, G. A. Bizarri, W. W. Moses and R. T. Williams

      Version of Record online: 6 JUL 2012 | DOI: 10.1002/pssr.201206258

      Thumbnail image of graphical abstract

      Starting from the conduction band structure of scintillator hosts such as NaI (shown), the group velocity of hot electrons is derived and shown to influence light yield and proportionality through interaction of electron and hole separation achieved during thermalization with traps encountered in diffusion back toward recombination. This helps answer a puzzling question of why more complex halides like SrI2 have much better light yield and energy resolution than conventional alkali halides.

    8. Polymer nanocomposites

      Transmission electron microscopy of single wall carbon nanotube/polymer nanocomposites: A first-principles study (pages 349–351)

      F. Solá, Z. H. Xia, M. Lebrón-Colón and M. A. Meador

      Version of Record online: 8 AUG 2012 | DOI: 10.1002/pssr.201206271

      Thumbnail image of graphical abstract

      One key issue for obtaining optimum nanocomposite properties is the ability to homogeneously disperse nanotubes into a polymeric material. In the case of electrical properties major control has to be focused on a reliable method to identify abundance of metallic/semiconducting type of SWCNTs through chirality. In this Letter Solá and coworkers set up new limits for TEM investigations of dispersion and chirality of SWCNT in polyethylene matrices.

    9. Titania–polymer composites

      Effect of TiO2 crystalline composition on the dielectric properties of TiO2/P(VDF-TrFE) composites (pages 352–354)

      Shuang Lin, Xiwen Kuang, Fanghui Wang and Hong Zhu

      Version of Record online: 2 JUL 2012 | DOI: 10.1002/pssr.201206245

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      A mixture of rutile and anatase TiO2 combines the benefits of both crystalline compositions. The incorporation of TiO2 particles with certain proportions of the two crystals into the P(VDF-TrFE) copolymer leads to a large improvement in dielectric properties over those of the neat ferroelectric copolymer. The influence of the proportions of both crystals has been studied.

    10. ZnO nanostructures

      Facile fabrication of forest-like ZnO hierarchical structures on conductive fabric substrate (pages 355–357)

      Yeong Hwan Ko, Sunkook Kim, Wook Park and Jae Su Yu

      Version of Record online: 23 JUL 2012 | DOI: 10.1002/pssr.201206265

      Thumbnail image of graphical abstract

      Ko and Yu found a convenient fabrication method for synthesizing dense forest-like ZnO hierarchical structures on conductive fabric substrate by using the electrochemical deposition method under high external cathodic voltage.

      At –3 V, the deposition current density was kept at ∼9.25–10.4 mA/cm2. The complex ZnO hierarchical structures were readily formed by subsequent creation and growth of branches. These results are very promising for the realization of flexible ZnO based nanodevices.

  7. Information for authors

    1. Top of page
    2. Cover Picture
    3. Issue Information
    4. Back Cover
    5. Contents
    6. NEW IN pss
    7. Rapid Research Letters
    8. Information for authors
    1. You have free access to this content

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