physica status solidi (RRL) - Rapid Research Letters

Cover image for Vol. 6 Issue 11

November 2012

Volume 6, Issue 11

Pages A107–A116, 415–456

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      Cover Picture: Epitaxial phase-change materials (Phys. Status Solidi RRL 11/2012)

      Peter Rodenbach, Raffaella Calarco, Karthick Perumal, Ferhat Katmis, Michael Hanke, André Proessdorf, Wolfgang Braun, Alessandro Giussani, Achim Trampert, Henning Riechert, Paul Fons and Alexander V. Kolobov

      Article first published online: 13 NOV 2012 | DOI: 10.1002/pssr.201290025

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      Ge–Sb–Te (GST) alloys lying along the GeTe–Sb2Te3 pseudo-binary tie line have proven to be among the most auspicious classes of materials for storage applications. Their success is related to the rapid and reversible phase-change from the crystalline to the amorphous state, whose strongly different optical and electrical properties can be used to encode information. The main technique used to produce phase-change material (PCM) thin films, both in academia and in industry, is physical vapor deposition (PVD). The layers fabricated by PVD are polycrystalline in the crystalline state. In their Rapid Research Letter on pp. 415–417, Peter Rodenbach et al. demonstrate the successful molecular beam epitaxy (MBE) of PCM thin films in the quasi-binary GeTe–Sb2Te3 system on slightly (GaSb) as well as largely (Si) lattice-mismatched substrates with (111) orientation. MBE growth is anticipated to allow the control of the alloy composition at the atomic level of the different chemical species. The perfect spatial order of epitaxial layers opens new horizons for investigation of the unique properties of PCMs, that may lead to the development of conceptually new memory devices.

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      Back Cover: A facile method for flexible GaN-based light-emitting diodes (Phys. Status Solidi RRL 11/2012)

      Younghun Jung, Xiaotie Wang, Sung Hyun Kim, Fan Ren, Jihyun Kim and Stephen J. Pearton

      Article first published online: 13 NOV 2012 | DOI: 10.1002/pssr.201290026

      Thumbnail image of graphical abstract

      Flexible GaN-based light-emitting diodes (LEDs) on polyethylene terephthalate (PET) substrates are demonstrated by Younghun Jung et al. in their Letter on pp. 421–423. The process uses commercial LEDs on patterned sapphire substrates, laser lift-off (LLO), wet etching for additional surface roughening, and mounting of the freestanding LED on a PET substrate. Electrical and optical properties from the free-standing LLO-LEDs mounted on the flexible PET substrates were characterized. This process, illustrated on the back cover, is highly practical and can be easily implemented in a manufacturing process to fabricate large-scale flexible GaN-based LEDs.

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      Contents: Phys. Status Solidi RRL 11/2012 (pages A107–A112)

      Article first published online: 13 NOV 2012 | DOI: 10.1002/pssr.201250431

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  5. Rapid Research Letters

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    3. Back Cover
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    1. Phase-change materials

      Epitaxial phase-change materials (pages 415–417)

      Peter Rodenbach, Raffaella Calarco, Karthick Perumal, Ferhat Katmis, Michael Hanke, André Proessdorf, Wolfgang Braun, Alessandro Giussani, Achim Trampert, Henning Riechert, Paul Fons and Alexander V. Kolobov

      Article first published online: 22 OCT 2012 | DOI: 10.1002/pssr.201206387

      Thumbnail image of graphical abstract

      Rodenbach, Calarco and co-workers report the successful epitaxial growth of the phase-change material Ge2Sb2Te5 (GST) on GaSb(001), GaSb(111), and Si(111) using molecular beam epitaxy. The structural properties are investigated by reflection high energy electron diffraction, synchrotron X-ray diffraction and transmission electron microscopy. The films exhibit a superior quality if grown on (111) surfaces, independent of the lattice mismatch. This is attributed to the tendency of this material to form layered structures as well as to the nature of distortion in the metastable cubic phase.

    2. LED efficiency droop

      Auger carrier leakage in III-nitride quantum-well light emitting diodes (pages 418–420)

      Marcus Deppner, Friedhard Römer and Bernd Witzigmann

      Article first published online: 22 OCT 2012 | DOI: 10.1002/pssr.201206367

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      This Letter reports on an Auger leakage model as an intrinsic side effect of the Auger process. It has a significant impact on the internal quantum efficiency versus current characteristics of wide band gap III-nitride quantum-well light emitting diodes (LEDs). Compared to a standard Auger model, Auger leakage reduces the Auger coefficient needed to explain experimental data by 50%, with all other parameters kept constant.

    3. Flexible LEDs

      A facile method for flexible GaN-based light-emitting diodes (pages 421–423)

      Younghun Jung, Xiaotie Wang, Sung Hyun Kim, Fan Ren, Jihyun Kim and Stephen J. Pearton

      Article first published online: 4 OCT 2012 | DOI: 10.1002/pssr.201206374

      Thumbnail image of graphical abstract

      GaN-based flexible light-emitting diodes (LEDs) on polyethylene terephthalate (PET) substrates are demonstrated. The process uses commercial LEDs on patterned sapphire substrates, laser lift-off, wet etching for additional surface roughening, and mounting of the freestanding LED on a PET substrate. Bright electroluminescence was observed under strain.

    4. Dye-sensitized solar cells

      Improved performance of silicon-nanoparticle film-coated dye-sensitized solar cells (pages 424–426)

      Ravindra Kumar Gupta, Idriss M. Bedja and Abdullah Saleh Aldwayyan

      Article first published online: 22 OCT 2012 | DOI: 10.1002/pssr.201206273

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      The present study shows for the first time that coating of a Si-nanoparticle film on top of a dye-sensitized solar cell serves as an ultraviolet to visible light convertor as well as an anti-reflector, resulting in improved cell efficiency. The coating extends the spectral region along with the homogeneous irradiation.

    5. Graphane allotropes

      Structure, stability and electronic properties of tricycle type graphane (pages 427–429)

      Chaoyu He, C. X. Zhang, L. Z. Sun, N. Jiao, K. W. Zhang and Jianxin Zhong

      Article first published online: 27 SEP 2012 | DOI: 10.1002/pssr.201206358

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      A new graphane allotrope with a 4up/2down configuration is proposed and named as tricycle, which can be considered as the combination of the 3up/3down chair and stirrup graphanes. Tricycle graphane possesses remarkable stability comparable to the most stable chair indicating its high probability to coexist with chair graphane in the process of graphene hydrogenation.

    6. Superhydrophobicity

      Facile one-step fabrication of highly transparent and flexible superhydrophobic substrate by room-temperature ion irradiation method (pages 430–432)

      Pradip Ghosh, Shunsaku Satou, Hiroaki Nakamori, Takuto Noda, Ishii Daisuke and Masaki Tanemura

      Article first published online: 22 OCT 2012 | DOI: 10.1002/pssr.201206418

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      A nanocone-based highly transparent and flexible superhydrophobic surface with water contact angle greater than 150º has been fabricated at room temperature by applying the ion irradiation method. This novel one-step strategy might be very promising to fabricate transparent and flexible superhydrophobic surfaces at large scale for potential applications in various fields.

    7. Pulsed laser deposition of ZnO

      Persistent layer-by-layer growth for pulsed-laser homoepitaxy of equation image ZnO (pages 433–435)

      Jan Zippel, Michael Lorenz, Gabriele Benndorf and Marius Grundmann

      Article first published online: 27 SEP 2012 | DOI: 10.1002/pssr.201206305

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      An enhanced interlayer mass transport by adopting an interval pulsed-laser deposition (PLD) process results in a persistent layer-by-layer growth as demonstrated for homoepitaxial equation image ZnO thin films. The surface roughness is considerably reduced for the interval PLD approach as compared with a conventional PLD. In this Letter, Zippel and coworkers compare carefully the properties of homoepitaxial ZnO thin films deposited under identical growth conditions by interval and by conventional PLD.

    8. Surface acoustic wave devices

      Effects of Mn-doping on surface acoustic wave properties of ZnO films (pages 436–438)

      J. T. Luo, P. Fan, F. Pan, F. Zeng, D. P. Zhang, Z. H. Zheng, G. X. Liang and X. M. Cai

      Article first published online: 15 OCT 2012 | DOI: 10.1002/pssr.201206381

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      The piezoelectric coefficient d33 of ZnO:Mn films is a key factor determining the performance of ZnO:Mn/Si surface acoustic wave (SAW) devices, and the SAW properties can be improved by doping with an appropriate Mn concentration. The absolute value of the insertion loss is inversely proportional to d33, while the electromechanical coupling coefficient and bandwidth are both proportional to d33. A Mn–ZnO/Si multilayer structure with large d33 is promising for high frequency, wide-band and low-loss SAW applications.

    9. High-k dielectrics

      Reduction of charge trapping in HfO2 film on a Ge substrate by trimethylaluminum pretreatment (pages 439–441)

      Jae Jin Lee, Yunsang Shin, Juyun Choi, Hyoungsub Kim, Sangjin Hyun, Siyoung Choi, Byung Jin Cho and Seok-Hee Lee

      Article first published online: 4 OCT 2012 | DOI: 10.1002/pssr.201206315

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      Trimethylaluminum (TMA) pretreatment prior to atomic layer deposition of HfO2 on a Ge substrate is introduced. Secondary ion mass spectroscopy reveals less Ge diffusion into the HfO2 film after TMA pretreatment because the germanium native oxide is converted to aluminum oxide, resulting in a capacitance–voltage hysteresis reduction and improved device reliability.

    10. TiO2 UV photodetectors

      Au/TiO2 nanorod-based Schottky-type UV photodetectors (pages 442–444)

      Hakan Karaagac, Levent Erdal Aygun, Mehmet Parlak, Mohammad Ghaffari, Necmi Biyikli and Ali Kemal Okyay

      Article first published online: 12 OCT 2012 | DOI: 10.1002/pssr.201206379

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      Today, ultraviolet (UV) photodetectors are drawing a considerable attention due to their importance in many applications including space communication, environmental monitoring, military and civil applications. In this Letter, the fabrication and characterization of highly sensitive Schottky-type UV photodetectors based on Au/TiO2 nanorods are demonstrated. The fabricated devices function as highly sensitive UV photodetectors with a peak responsivity of 134.8 A/W at a wavelength of 350 nm under reverse bias of 3 V.

    11. Quantum dots

      The effect of post-growth thermal annealing on the emission spectra of GaAs/AlGaAs quantum dots grown by droplet epitaxy (pages 445–447)

      Pilkyung Moon, J. D. Lee, S. K. Ha, E. H. Lee, W. J. Choi, J. D. Song, J. S. Kim and L. S. Dang

      Article first published online: 5 OCT 2012 | DOI: 10.1002/pssr.201206369

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      Pilkyung Moon et al. investigated the effects of post-growth thermal annealing on the optical properties of quantum dots by using (i) the etched micro-mesa to identify the emission signal from the dots, (ii) the superlattice with the same material composition as the dot to make a quantitative estimation of the diffusion length, and (iii) a numerical simulation to provide the diffusion length dependence of the emission energies of the dots.

    12. Exchange bias in shape memory alloys

      Tuning exchange bias through zero field cooling from different remanent states above blocking temperature in Ni50Mn36Sb14 alloy (pages 448–450)

      R. L. Wang, L. S. Xu, Z. G. Sun, V. V. Marchenkov, H. B. Xiao, L. F. Xu, J. C. A. Huang and C. P. Yang

      Article first published online: 25 SEP 2012 | DOI: 10.1002/pssr.201206355

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      Wang et al. report that the value and sign of the exchange bias field can be tuned effectively through zero field cooling from different remanent states above the blocking temperature in Ni50Mn36Sb14 alloy, in addition to the field cooling method. This gives the opportunity to tune the exchange bias even after device fabrication and may be interesting for novel types of magnetoelectronic devices.

    13. Electrostrictive ceramics

      Switching of morphotropic phase boundary and large electrostrictive effect in lead-free BNT–BKT–KNN ceramics (pages 451–453)

      Jigong Hao, Jinwen Wang, Wangfeng Bai, Bo Shen and Jiwei Zhai

      Article first published online: 24 SEP 2012 | DOI: 10.1002/pssr.201206270

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      In this Letter, the phase diagram of the ternary (Bi0.5Na0.5)TiO3–(Bi0.5K0.5)TiO3–(K0.5Na0.5)NbO3 (BNT–BKT–KNN) system is drawn, and the switching characteristics of the morphotropic phase boundary (MPB) are investigated. An evident MPB switching behavior is found with the addition of KNN as a replacement for BNT–BKT. Near the MPB region, excellent electrostriction with good thermostability comparable with that of traditional Pb-based electrostrictors is achieved.

    14. Resistive switching

      Self-formed Schottky barrier induced selector-less RRAM for cross-point memory applications (pages 454–456)

      Sangsu Park, Seungjae Jung, Manzar Siddik, Minseok Jo, Jubong Park, Seonghyun Kim, Wootae Lee, Jungho Shin, Daeseok Lee, Godeuni Choi, Jiyong Woo, Euijun Cha, Byoung Hun Lee and Hyunsang Hwang

      Article first published online: 15 OCT 2012 | DOI: 10.1002/pssr.201206382

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      As shown in this Letter, Park et al. investigated the characteristics of a simple cross-point resistive-switching random access memory (RRAM) array using a self-formed Schottky barrier fabricated without any additional fabrication steps. The device provides an obvious rectification in the low-resistence state (LRS), so the crosstalk phenomenon can be alleviated without serially connecting a diode. On the basis of the characterization results, the authors demonstrate set, reset, and read operation for high cell efficiency and high density memory applications.

  6. Information for authors

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

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