physica status solidi (RRL) - Rapid Research Letters

Cover image for Vol. 7 Issue 11

November 2013

Volume 7, Issue 11

Pages 927–1031

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      Cover Picture: Harvesting piezoelectric potential from zinc oxide nanoflowers grown on textile fabric substrate (Phys. Status Solidi RRL 11/2013)

      Azam Khan, Mazhar Ali Abbasi, Jonas Wissting, Omer Nur and Magnus Willander

      Article first published online: 14 NOV 2013 | DOI: 10.1002/pssr.201370464

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      The fabrication of novel devices for harvesting energy from various resources is emerging as an active area of research. The coupling between electrical and mechanical properties of materials, i.e. piezoelectricity, is one of the approaches with great potential. On the other hand, the use of flexible and nonconventional substrates is a popular approach for the fabrication of nanogenerators relying on the piezoelectric property due to the possibility of efficient transfer of mechanical energy. Khan et al. (pp. 980–984) harvest the piezoelectric potential from ZnO nanoflowers grown on a textile fabric substrate by applying an external load. Moreover, a review of the literature reveals that the morphology of the ZnO nanostructures can influence the harvested piezoelectric output. In the investigation by Khan et al., the obtained results proved the effect of morphology on the piezoelectric output from ZnO nanostructure. In addition, the development of a ZnO nano- generator on textile fabrics is a useful step towards introducing electronic devices on non-conventional substrates and for new applications, e.g. self-powered nanosensors on textile fabrics.

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      Back Cover: Thermal recrystallization of physical vapor deposition based germanium thin films on bulk silicon (100) (Phys. Status Solidi RRL 11/2013)

      Aftab M. Hussain, Hossain M. Fahad, Galo A. Torres Sevilla and Muhammad M. Hussain

      Article first published online: 14 NOV 2013 | DOI: 10.1002/pssr.201370465

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      Germanium is a historical semiconductor material whose hole mobility is much higher than that in silicon. Its near-term application areas include, but are not limited to, p-type metal oxide semiconductor field effect transistors (p-MOSFETs) in complementary metal oxide semiconductor (CMOS) technology, high speed devices for communications and optoelectronics. One major challenge with its mass-scale production is the expensive nature of the growth process of single-crystalline germanium. Therefore, Hussain et al. (pp. 966–970) show a simple, low-cost, and scalable process for obtaining uniform, smooth surfaced, high quality mono-crystalline germanium (100) thin films on silicon (100). The germanium thin films were deposited on a silicon substrate using plasma-assisted sputtering based physical vapor deposition (PVD). They were crystallized by annealing at various temperatures ranging from 700 °C to 1100 °C. Hussain et al. report that the best quality germanium thin films are obtained above the melting point of germanium (937 °C), thus offering a method for in-situ Czochralski process. The authors also show well behaved high-κ /metal gate Metal–Oxide–Semi-conductor Capacitors (MOSCAPs) using this film.

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      Issue Information: Phys. Status Solidi RRL 11/2013

      Article first published online: 14 NOV 2013 | DOI: 10.1002/pssr.201370466

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      Contents: Phys. Status Solidi RRL 11/2013 (pages 927–934)

      Article first published online: 14 NOV 2013 | DOI: 10.1002/pssr.201370467

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  6. rrl solar

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    1. Silicon surface passivation

      Silicon surface passivation by aluminium oxide studied with electron energy loss spectroscopy (pages 937–941)

      Bram Hoex, Michel Bosman, Naomi Nandakumar and W. M. M. Kessels

      Article first published online: 14 AUG 2013 | DOI: 10.1002/pssr.201308081

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      The origin behind crystalline silicon surface passivation by Al2O3 films is studied in detail by means of spatially-resolved electron energy loss spectroscopy. The results confirm the presence of an interfacial SiO2-like film and demonstrate changes in the ratio between tetrahedrally and octahedrally coordinated Al in the films after annealing. These observations reveal the underlying origin of c-Si surface passivation by Al2O3.

    2. Influence of precursor gas ratio and firing on silicon surface passivation by APCVD aluminium oxide (pages 942–945)

      Kristopher O. Davis, Kaiyun Jiang, Marshall Wilson, Carsten Demberger, Heiko Zunft, Helge Haverkamp, Dirk Habermann and Winston V. Schoenfeld

      Article first published online: 2 SEP 2013 | DOI: 10.1002/pssr.201308092

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      Using in-line atmosphere chemical vapor deposition, the authors have synthesized amorphous aluminum oxide (AlOx) films from precursors of trimethylaluminum (TMA) and O2, yielding a maximum deposition 150 nm·min–1 per wafer. In addition, the APCVD AlOx films described in this Letter have recently been used to create 20.7% efficient 156 mm x 156 mm, p-type CZ rear passivated solar cells with screen-printed contacts (independently confirmed by Fraunhofer ISE CalLab).

    3. Passivation of aluminium–n+ silicon contacts for solar cells by ultrathin Al2O3 and SiO2 dielectric layers (pages 946–949)

      James Bullock, Di Yan and Andrés Cuevas

      Article first published online: 29 AUG 2013 | DOI: 10.1002/pssr.201308115

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      Reducing carrier recombination at the metal—silicon contact interface is one technique to increase solar cell efficiency. The insertion of a thin passivating dielectric film between the metal and silicon can be performed to achieve this, however, reductions in recombination must be considered in conjunction with changes to the resistive behaviour. This Letter investigates the optimum dielectric thickness in terms of contact recombination and resistivity for Al2O3 and SiO2 dielectrics.

    4. Black silicon

      Passivation of black silicon boron emitters with atomic layer deposited aluminum oxide (pages 950–954)

      Päivikki Repo, Jan Benick, Guillaume von Gastrow, Ville Vähänissi, Friedemann D. Heinz, Jonas Schön, Martin C. Schubert and Hele Savin

      Article first published online: 23 AUG 2013 | DOI: 10.1002/pssr.201308096

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      The nanostructured surface – also called black silicon (b-Si) – is a promising texture for solar cells because of its extremely low reflectance combined with efficient surface passivation by atomic layer deposited (ALD) thin films. In this Letter, the authors show how different boron diffusions affect the optical properties of b-Si and demonstrate that also highly boron-doped b-Si emitters can be passivated with atomic layer deposited Al2O3 by reaching J0e values as low as 51 fA/cm2.

    5. Silicon solar cell wafers

      Wafer thickness optimization for silicon solar cells of heterogeneous material quality (pages 955–958)

      Bernhard Michl, Martin Kasemann, Wilhelm Warta and Martin C. Schubert

      Article first published online: 13 AUG 2013 | DOI: 10.1002/pssr.201308090

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      The optimal wafer thickness for multicrystalline silicon solar cells depends on the relation of bulk to surface recombination and the light trapping. For multicrystalline silicon bulk recombination strongly varies laterally and with injection level. A thickness optimization using the “Efficiency Limiting Bulk Recombination Analysis” (ELBA) takes all these effects correctly into account. The optimal thickness for different material types is calculated. The efficiency gain differs strongly for different technologies.

    6. Defects in poly-Si

      Identification of intra-grain and grain boundary defects in polycrystalline Si thin films by electron paramagnetic resonance (pages 959–962)

      Tobias Sontheimer, Alexander Schnegg, Simon Steffens, Florian Ruske, Daniel Amkreutz, Klaus Lips and Bernd Rech

      Article first published online: 28 AUG 2013 | DOI: 10.1002/pssr.201308061

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      Electron paramagnetic resonance analysis of polycrystalline Si films with dissimilar average grain sizes reveals the existence of two distinctive defect signatures at g -values of 2.0055 and 2.0032, which are attributed to grain boundary defects and intra-grain defects, respectively. Additional hydrogenation leads to a reduction of the overall defect concentration, while rapid thermal annealing primarily heals intra-grain defects.

    7. Photovoltaic modules

      In-situ series connection of an amorphous silicon photovoltaic tandem module (pages 963–965)

      Ahmed Garamoun, Rainer Merz, Shinsuke Miyajima and Markus B. Schubert

      Article first published online: 3 SEP 2013 | DOI: 10.1002/pssr.201308016

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      This Letter presents, for the first time, the in-situ series connection of thin film tandem solar cells into a photovoltaic module by sequential local shading of the deposition processes. A module comprising of five amorphous silicon tandem cells with a total area of 12.5 cm2 exhibits a fill factor FFm > 72% and a total area efficiency ηm = 6.2%.

  7. Rapid Research Letters

    1. Top of page
    2. Cover Picture
    3. Back Cover
    4. Issue Information
    5. Contents
    6. NEW IN pss
    7. rrl solar
    8. Rapid Research Letters
    9. Information for authors
    1. Germanium thin films

      Thermal recrystallization of physical vapor deposition based germanium thin films on bulk silicon (100) (pages 966–970)

      Aftab M. Hussain, Hossain M. Fahad, Galo A. Torres Sevilla and Muhammad M. Hussain

      Article first published online: 16 AUG 2013 | DOI: 10.1002/pssr.201308019

      Thumbnail image of graphical abstract

      In this Letter, the formation of high quality monocrystalline germanium (100) thin films on silicon (100) is reported using a simple, scalable and low-cost process. The films are deposited on a silicon substrate by argon plasma sputtering based PVD process, followed by thermal recrystallization of the as-deposited film by annealing at a temperature higher than the melting point of germanium.

    2. MAX phases

      Phase stability of Crn+ 1GaCn MAX phases from first principles and Cr2GaC thin-film synthesis using magnetron sputtering from elemental targets (pages 971–974)

      Andrejs Petruhins, Arni Sigurdur Ingason, Martin Dahlqvist, Aurelija Mockute, Muhammad Junaid, Jens Birch, Jun Lu, Lars Hultman, Per O. Å. Persson and Johanna Rosen

      Article first published online: 19 AUG 2013 | DOI: 10.1002/pssr.201308025

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      In this Letter, for the first time the synthesis of epitaxial Cr2GaC MAX-phase thin films from elemental targets, including liquid Ga, has been performed. Epitaxial growth of the films is confirmed by X-ray diffraction and high-resolution scanning transmission electron microscopy. Ab-initio calculations of different Cr2GaC collinear magnetic configurations suggest that the ground magnetic state is antiferromagnetic.

    3. Semiconductor quantum dots

      Sb2S3 quantum dots: diffusion-controlled growth and characterization (pages 975–979)

      Rakesh K. Mishra, Agnikumar G. Vedeshwar and Ram P. Tandon

      Article first published online: 23 AUG 2013 | DOI: 10.1002/pssr.201308082

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      The antimony trisulphide (Sb2S3) quantum dots have been grown for the first time in borosilicate glass matrix by precipitation of antimony and sulphur with supporting characterizations. The process for dot size control is discussed. Dots exhibit the novel behavior of strong quantum confinement manifested by the blue shift of band gap with inverse square of dot size.

    4. Nanogenerators

      Harvesting piezoelectric potential from zinc oxide nanoflowers grown on textile fabric substrate (pages 980–984)

      Azam Khan, Mazhar Ali Abbasi, Jonas Wissting, Omer Nur and Magnus Willander

      Article first published online: 29 AUG 2013 | DOI: 10.1002/pssr.201308105

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      The fabrication of novel devices for harvesting the energy is of high interest due to the shortage of energy resources. At present, the use of flexible and nonconventional substrates for the fabrication of nanogenerator devices using ZnO nanostructures is more popular among the scientific community. The present Letter demonstrates the development of piezoelectric nanogenerator based on ZnO nanoflowers with improved performance.

    5. Preparation of ZnO nanorods on cellulose fiber paper and their charge-generating application for waste paper recycling (pages 985–988)

      Yeong Hwan Ko and Jae Su Yu

      Article first published online: 12 AUG 2013 | DOI: 10.1002/pssr.201308076

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      Integrated ZnO nanorod arrays (NRAs) on cellulose fibers (CFs) are prepared from waste papers by simple mechanical blending and hydrothermal synthesis, which allows for growing easily the ZnO NRAs on the overall surface of CFs. The fabricated nanogenerators with ZnO NRAs on CFs generate piezoelectric charges under various external pushing forces and their output current densities are comparable with the results of conventional ZnO-based nanogenerators. This fabrication process and application can be an alternative way for the recycling nanotechnology of waste papers.

    6. Semiconductor surface cleaning

      Atomic hydrogen cleaning of In0.53Ga0.47As studied using synchrotron radiation photoelectron spectroscopy (pages 989–992)

      Barry Brennan, Kumar Kumarappan and Greg Hughes

      Article first published online: 6 AUG 2013 | DOI: 10.1002/pssr.201308038

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      The removal of native oxides from the In0.53Ga0.47As surface by exposure to atomic hydrogen has been investigated by synchrotron radiation based photoelectron spectroscopy. It is possible to fully remove the arsenic oxides at low temperatures, while still leaving a low concentration of stable Ga2O and In2O at the surface. The removal of surface carbon contamination is also seen in the absence of prior substrate annealing.

    7. THz spectroscopy

      Terahertz studies of carrier localization in spontaneously forming polar lateral heterostructures (pages 993–996)

      Grace D. Metcalfe, Asako Hirai, Erin C. Young, James S. Speck, Hongen Shen and Michael Wraback

      Article first published online: 26 AUG 2013 | DOI: 10.1002/pssr.201308099

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      In m-plane GaN polar lateral heterostructures, electron–hole pairs are localized in polarization-induced triangular potentials comprised of zincblende quantum well-like regions within a wurtzite matrix. By tuning the pump energy across the wurtzite bandgap and examining the emitted THz radiation, the authors demonstrate the transition from carrier transport in the continuum states to polarized electron–hole pairs in the lowest conduction and highest valence states. Furthermore, they observe an enhancement of the nonlinear susceptibility in the lateral heterostructures by an order of magnitude compared to bulk wurtzite GaN.

    8. Graphene junctions

      Large anisotropic magnetoresistance in graphene-based junctions (pages 997–1000)

      Marek Rataj and Józef Barna´

      Article first published online: 5 SEP 2013 | DOI: 10.1002/pssr.201308052

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      One of the most promising features of graphene is the fact that its properties can be relatively easily tuned by external factors, like for example specific substrates. Moreover, if a single graphene flake spans over two different substrates, the two parts of the flake have different properties and in consequence a junction forms within graphene. Through the analysis of electronic transport the authors show that a special type of anisotropic magnetoresistance can be observed in such systems.

    9. Multiferroics

      Multiferroism in the dielectric function of CuO (pages 1001–1004)

      I. N. Apostolova, A. T. Apostolov, S. G. Bahoosh, J. M. Wesselinowa and S. Trimper

      Article first published online: 2 SEP 2013 | DOI: 10.1002/pssr.201308093

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      Based on a microscopic model including magnetoelectric coupling and frustration within the magnetic part, the authors calculate analytically the dielectric function (DF) as a characterization of multiferroism. The DF offers a pronounced peak at the magnetic phase transition temperature. The peak can be triggered by an external magnetic field (red). Increasing the field the peak is suppressed (green).

    10. Resistive switching memory

      Characteristics and mechanism of nano-polycrystalline La2O3 thin-film resistance switching memory (pages 1005–1008)

      Hongbin Zhao, Hailing Tu, Feng Wei, Yuhua Xiong, Xinqaing Zhang and Jun Du

      Article first published online: 29 AUG 2013 | DOI: 10.1002/pssr.201308068

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      The rare-earth (RE) oxide based RRAM devices are an important class in oxide based RRAMs for its forming-free characteristic. This Letter reports the application of La2O3 in RRAM, which is found to have excellent resistive switching behavior and an unusual constituent and mechanism of conducting filaments. The authors believe that this study will be a great contribution for understanding resistive switching characteristics of rare-earth oxides.

    11. Phase-change memory

      Structural and electrical analysis of In–Sb–Te-based PCM cells (pages 1009–1013)

      Roberto Fallica, Toni Stoycheva, Claudia Wiemer and Massimo Longo

      Article first published online: 19 AUG 2013 | DOI: 10.1002/pssr.201308074

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      In this Letter, prototype phase-change memory (PCM) cells are investigated with the cross section of the cells as illustrated here. The devices feature the In–Sb–Te chalcogenide as active area, titanium nitride as top electrode, and a deca-nanometric metal heater capped in a dielectric. The In–Sb–Te-based cells show higher threshold voltage than Ge–Sb–Te-based devices. Furthermore, endurance and the programming window were improved by increasing the Te content.

    12. Optical waveguides

      Femtosecond laser micromachined optical waveguides in LiTaO3 crystal (pages 1014–1017)

      Miaomiao Xu, Ruiyun He, Shuqian Sun, Javier R. Vázquez de Aldana and Feng Chen

      Article first published online: 28 AUG 2013 | DOI: 10.1002/pssr.201308102

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      The depressed cladding and dual-line waveguides in LiTaO3 crystal have been fabricated by femtosecond laser micromachining. The cladding waveguides present good guiding properties for both the no and ne polarizations. Dual-line waveguides only support guidance along ne polarization. The propagation loss of the LiTaO3 cladding waveguide was reduced to 0.38 dB/cm after the annealing treatment at 400 °C.

    13. Multi-wavelength visible laser sources

      Simultaneous generation of violet, blue, and green lasers using Nd:YAl3(BO3)4 channel waveguides under pumping at 815 nm (pages 1018–1021)

      Yang Tan, Qing-Fang Luan, Feng Chen, Daniel Jaque and Javier Rodríguez Vázquez de Aldana

      Article first published online: 9 AUG 2013 | DOI: 10.1002/pssr.201308031

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      In this Letter, the authors report, for the first time, on the observation of visible three color emission from a waveguide with pumping laser under 815 nm. This phenomenon proved the enhanced nonlinear effects by the waveguide structure. This work is interesting for the design of multi-visible laser sources in integrated optics.

    14. Superhard materials

      Deformation-induced bonding evolution of iron tetraboride and its electronic origin (pages 1022–1025)

      Xinyu Zhang, Jiaqian Qin, Yanan Xue, Shiliang Zhang, Qin Jing, Mingzhen Ma and Riping Liu

      Article first published online: 7 AUG 2013 | DOI: 10.1002/pssr.201308086

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      The mechanical and electronic properties of FeB4 are investigated using first-principles calculations. Results of ideal shear strength indicate that FeB4 is a hard material, not a superhard material. The calculated charge density distribution implies that the collapse of the unique corrugated B6 units ring in FeB4 under deformation is responsible for the failure under tensile and shear deformation.

    15. Ultraporous alumina

      Electronic transitions in α, θ and γ polymorphs of ultraporous monolithic alumina (pages 1026–1029)

      L. Museur, M. Bouslama, M. Amamra and A. Kanaev

      Article first published online: 13 AUG 2013 | DOI: 10.1002/pssr.201308040

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      In this Letter, the authors analyze the photoluminescence properties of high-purity transition γ and θ and stable α ultraporous alumina at cryogenic temperatures with excitation by synchrotron radiation. The UV photoluminescence spectra are dominated by optical transitions of self-trapped excitons, while the PL excitation spectra are assigned to free excitons and interband transitions. The analysis of the PL excitation spectra indicates a tendency to fundamental bandgap narrowing.

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