physica status solidi (RRL) - Rapid Research Letters

Cover image for Vol. 7 Issue 4

April 2013

Volume 7, Issue 4

Pages 235–306

  1. Cover Picture

    1. Top of page
    2. Cover Picture
    3. Issue Information
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    5. Contents
    6. NEW IN pss
    7. Review@RRL
    8. rrl solar
    9. Rapid Research Letters
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      Cover Picture: Screening and interlayer coupling in multilayer MoS2 (Phys. Status Solidi RRL 4/2013)

      Saptarshi Das and Joerg Appenzeller

      Article first published online: 16 APR 2013 | DOI: 10.1002/pssr.201390010

      Thumbnail image of graphical abstract

      After decades of relentless progress, the evolutionary path of silicon CMOS industry is finally approaching an end. Fundamental limitations do not allow silicon to scale beyond 10 nm technology node without compromising severely on the device performance. In order to reinforce the accelerating pace, there is an urgent and immediate need for alternative materials. Low-dimensional materials in general and 2D layered material in particular are extremely interesting in this context, as they not only offer the fundamental study of their unique electrical, optical, mechanical and chemical properties but also their excellent electrostatic integrity and inherent scalability make them attractive from a technological standpoint. Recently the rich family of transition metal di-chalcogenides – comprising of MoS2, WS2, WSe2 and many more – have received a lot of scientific attention as the future of nanoelectronics. In order to harvest the ultimate potential of these novel nano materials it is extremely important to evaluate the core physical enterprises that drive them. In their Letter on pp. 268–273, Saptarshi Das and Joerg Appenzeller experimentally investigated the mobility of multilayer MoS2 field effect transistors with different metal contacts. The authors found a rather interesting trend in the “effective” field effect mobility as a function of the MoS2 layer thickness which could be explained by a unique model based on Thomas–Fermi charge screening and interlayer coupling. The associated cartoon image is a medley of the experimental mobility trend and the corresponding resistor network model that explains the trend.

  2. Issue Information

    1. Top of page
    2. Cover Picture
    3. Issue Information
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    7. Review@RRL
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      Issue Information: Phys. Status Solidi RRL 4/2013

      Article first published online: 16 APR 2013 | DOI: 10.1002/pssr.201390011

  3. Back Cover

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      Back Cover: Au–Ge bonding on a uniformly Au-covered Ge(001) surface (Phys. Status Solidi RRL 4/2013)

      Dana G. Popescu and Marius A. Husanu

      Article first published online: 16 APR 2013 | DOI: 10.1002/pssr.201390012

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      The Rapid Research Letter by Dana G. Popescu and Marius A. Husanu (pp. 274–277) reveals the mechanisms acting at the Au/Ge interface, when one single atomic layer (1 ML) of Au is deposited on heated Ge surface. Understanding the nature of the interactions between the ad-atoms and the substrate plays an important role in the context of newly established dimerized surfaces (Si, Ge) as efficient host for the growth of noble metals chains (Pt, Au, Ag). Employing first principles calculations and correlating photoelectron spectroscopy, in both valence and core level regions, with scanning tunneling microscopy, the authors establish that a uniform coverage regime may occur. The surface is featured by symmetric surface dimers, covalently bonded with Au atoms. The metallic character of the surface is due to the Au5d–Ge3s3p hybridized states. The XPS signature of Ge-dimer-bonded Au is documented for the first time in the Au 4f core-level spectra.

  4. Contents

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      Contents: Phys. Status Solidi RRL 4/2013 (pages 235–240)

      Article first published online: 16 APR 2013 | DOI: 10.1002/pssr.201350511

  5. NEW IN pss

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  6. Review@RRL

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    1. Oxide interfaces

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      Properties of manganite/ruthenate superlattices with ultrathin layers (pages 243–257)

      Michael Ziese and Ionela Vrejoiu

      Article first published online: 6 MAR 2013 | DOI: 10.1002/pssr.201307007

      Thumbnail image of graphical abstract

      High-quality manganite/ruthenate superlattices were grown by pulsed laser deposition and studied by structural techniques as well as magnetization and magnetotransport measurements. Here, the authors review the complex behavior of these systems ranging from structural transitions of the ruthenate layers to antiferromagnetic coupling phenomena, an unprecedented Curie temperature stabilization of the manganite layers and intriguing interfacial magnetotransport effects. These findings highlight that the manganite/ruthenate interface serves as a model system for the study of interfacial reconstruction and charge transfer in highly correlated ferromagnets.

  7. rrl solar

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    1. Quaternary chalcogenides

      Raman scattering and disorder effect in Cu2ZnSnS4 (pages 258–261)

      M. Y. Valakh, O. F. Kolomys, S. S. Ponomaryov, V. O. Yukhymchuk, I. S. Babichuk, V. Izquierdo-Roca, E. Saucedo, A. Perez-Rodriguez, J. R. Morante, S. Schorr and I. V. Bodnar

      Article first published online: 12 MAR 2013 | DOI: 10.1002/pssr.201307073

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      One of the most important challenges for the CZTS-type materials used for solar cells is nonstoichiometry. In this Letter, we investigate the relationship of antisite defects in the cation sublattice of CZTS with the peculiarities of its Raman spectra. The change of CZTS crystal symmetry from kesterite-type I4 to a disordered kesterite-type equation image manifests itself in a change of frequency and bandwidth of the main Raman A peak. This fact is discussed in the connection with disorder of Cu+ and Zn2+-ions on 2c and 2d sites in the crystalline lattice.

    2. Silicon solar cells

      Light-induced degradation in copper-contaminated gallium-doped silicon (pages 262–264)

      Jeanette Lindroos, Marko Yli-Koski, Antti Haarahiltunen, Martin C. Schubert and Hele Savin

      Article first published online: 25 FEB 2013 | DOI: 10.1002/pssr.201307011

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      In standard Czochralski (Cz) silicon solar cells, light-induced degradation (LID) refers to a 1–2% efficiency decrease after one day of solar illumination. As LID does not occur in clean gallium-doped Cz silicon, gallium has been proposed as a replacement for boron in Cz silicon solar cells. However, we see clear light-induced degradation in gallium-doped Cz silicon after intentional copper contamination, emphasizing the importance of controlling contamination in cell manufacturing.

    3. Silicon characterization

      Calibration of excitonic photoluminescence to determine high aluminum concentrations in silicon (pages 265–267)

      Kevin Lauer, Christian Möller, Dirk Schulze, Til Bartel and Fritz Kirscht

      Article first published online: 18 FEB 2013 | DOI: 10.1002/pssr.201307028

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      The photoluminescence intensity ratio of the aluminum bound exciton and the free exciton in silicon is calibrated with respect to the aluminum concentration. Photoluminescence measurements are performed at elevated temperatures around 20 K to assess the aluminum concentration range from 1015 to 1017 atoms/cm3. The obtained results open up the possibility to determine high aluminum concentrations in silicon using photoluminescence spectroscopy. This is in particular important for solar silicon.

  8. Rapid Research Letters

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    1. Charge screening in MoS2

      Screening and interlayer coupling in multilayer MoS2 (pages 268–273)

      Saptarshi Das and Joerg Appenzeller

      Article first published online: 6 MAR 2013 | DOI: 10.1002/pssr.201307015

      Thumbnail image of graphical abstract

      The authors present the first comprehensive experimental study on the dependence of carrier mobility on the layer thickness of multilayer MoS2 field-effect transistors. They also propose a theoretical model based on Thomas–Fermi charge screening and interlayer coupling in order to explain their findings. Their model is extremely generic and can be applied to any two-dimensional layered system.

    2. Ge(001)-bonded Au

      Au–Ge bonding on a uniformly Au-covered Ge(001) surface (pages 274–277)

      Dana G. Popescu and Marius A. Husanu

      Article first published online: 25 FEB 2013 | DOI: 10.1002/pssr.201307029

      Thumbnail image of graphical abstract

      In the context of recently emerging Au/Ge(001) one-dimensional systems, the authors investigate the chemical bonding of 1 ML Au deposited on a dimerized Ge(001) surface. Effects on the covalent bonding of Au on the Ge dimer surface are shown combining photoelectron spectroscopy with first-principles calculations.

    3. Electron–hole liquids

      Control of condensation and evaporation of electron–hole liquid in diamond by femtosecond laser pulses (pages 278–281)

      Martin Kozák, František Trojánek, Tomáš Popelárˇ and Petr Malý

      Article first published online: 28 FEB 2013 | DOI: 10.1002/pssr.201307030

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      The electron–hole liquid in semiconductors has similar properties as the classical liquid, i.e. constant density at a given temperature, spatial distribution in form of droplets and the possibility of induced phase transition (from gas to liquid and vice versa). In this Letter, the authors demonstrate the femtosecond pulse-induced evaporation of electron–hole droplets in monocrystalline CVD diamond. This phenomenon extends the limits of ultrafast phase control in highly excited semiconductors.

    4. Resistive switching memory

      Resistive switching behaviour of a tantalum oxide nanolayer fabricated by plasma oxidation (pages 282–284)

      G. S. Tang, F. Zeng, C. Chen, S. Gao, H. D. Fu, C. Song, G. Y. Wang and F. Pan

      Article first published online: 11 FEB 2013 | DOI: 10.1002/pssr.201206534

      Thumbnail image of graphical abstract

      A tantalum oxide nanolayer-based resistive switching memory device was made by plasma oxidation of TaN films at room temperature. The storage medium layer was about 5 nm, and the Pt/Ta2O5-x/TaN memory device demonstrated a stable bipolar resistive switching behaviour with a memory window beyond 100. A cost-efficient method using complementary metal–oxide–semiconductor (CMOS) technology compatible with resistive switching nonvolatile memory application is proposed.

    5. Thin-film transistors

      Flexible InGaZnO thin film transistors using stacked Y2O3/TiO2/Y2O3 gate dielectrics grown at room temperature (pages 285–288)

      Hsiao-Hsuan Hsu, Chun-Yen Chang and Chun-Hu Cheng

      Article first published online: 13 MAR 2013 | DOI: 10.1002/pssr.201307047

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      Indium gallium zinc oxide (IGZO) thin film transistors (TFTs) have been studied extensively owing to the advantages of a low-temperature growth process and high drive current. The authors demonstrate a high performance flexible IGZO TFT with a low operation voltage of <3 V using a room-temperature processed tri-layer gate dielectric. Such good transistor characteristics can also be attributed to low interface defects improving sub-threshold swing and device mobility.

    6. Half-metallic ferromagnets

      Structural, electronic and magnetic properties of quaternary half-metallic Heusler alloy CoFeCrAl (pages 289–292)

      Jagdish Nehra, V. D. Sudheesh, N. Lakshmi and K. Venugopalan

      Article first published online: 7 MAR 2013 | DOI: 10.1002/pssr.201307057

      Thumbnail image of graphical abstract

      A highly ordered, structurally stable, half-metallic ferromagnetic Heusler alloy CoFeCrAl with high Curie temperature and good magnetic properties is obtained by partial substitution of Co by Fe in Co2CrAl. Phase separation and corresponding deterioration of magnetic properties in Co2CrAl is thus eliminated while retaining the half-metallicity, making it very promising for use in spintronics devices.

    7. Semipolar ZnO films

      Semipolar (11\bar 2\bar 2) ZnO thin films grown on LaAlO3-buffered LSAT (112) single crystals by pulsed laser deposition (pages 293–296)

      Jr-Sheng Tian, Chun-Yen Peng, Wei-Lin Wang, Yue-Han Wu, Yi-Sen Shih, Kun-An Chiu, Yen-Teng Ho, Ying-Hao Chu and Li Chang

      Article first published online: 12 MAR 2013 | DOI: 10.1002/pssr.201307037

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      The growth of semipolar (11\bar 2 \bar 2) ZnO by pulsed laser deposition is demonstrated on LaAlO3-buffered (112) LSAT ((LaAlO3)0.29(Sr2AlTaO6)0.35) substrates. The semipolar ZnO shows an effective reduction of the threading dislocation density with increasing film thickness and a very low basal stacking fault density. These features could pave the way for achieving high-quality (11\bar 2 \bar 2) ZnO films for optoelectronic applications.

    8. Photoluminescence

      Temperature-dependent emission shift and carrier dynamics in deep ultraviolet AlGaN/AlGaN quantum wells (pages 297–300)

      Jianping Zeng, Wei Li, Jianchang Yan, Junxi Wang, Peipei Cong, Jinmin Li, Weiying Wang, Peng Jin and Zhanguo Wang

      Article first published online: 6 FEB 2013 | DOI: 10.1002/pssr.201307004

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      The authors report the temperature-dependent emission shift and carrier dynamics by studying radiative and nonradiative processes in deep ultraviolet (DUV) AlGaN/AlGaN quantum wells (QWs). The peak energy of DUV-AlGaN/AlGaN MQW PL emission exhibits an anti-S-shaped behavior (blueshift-accelerated redshift-decelerated redshift). This temperature-induced PL shift is strongly affected by the change in carrier dynamics with increasing temperature.

    9. Surface optics

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      Optical probe for surface and subsurface defects induced by ion bombardment (pages 301–304)

      L. D. Sun, M. Hohage and P. Zeppenfeld

      Article first published online: 5 MAR 2013 | DOI: 10.1002/pssr.201307088

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      Reflectance difference spectroscopy (RDS) is sensitive to ion bombardment induced defects located either in the topmost layer or the subsurface region of Cu(110). Since the corresponding signatures in the RD spectrum arise from perturbations of different types of electronic states, these two kinds of defects can be spectrally discriminated and thus can be simultaneously monitored in-situ during ion bombardment and thermal annealing.

  9. Information for authors

    1. Top of page
    2. Cover Picture
    3. Issue Information
    4. Back Cover
    5. Contents
    6. NEW IN pss
    7. Review@RRL
    8. rrl solar
    9. Rapid Research Letters
    10. Information for authors
    1. You have free access to this content
      Information for authors: Phys. Status Solidi RRL 4/2013 (pages 305–306)

      Article first published online: 16 APR 2013 | DOI: 10.1002/pssr.201350513

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