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17 Jan 2011

Volume 98, Issue 3, Articles (03xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 98, 031101 (2011); http://dx.doi.org/10.1063/1.3529469 (3 pages)

Sinan Balci, Askin Kocabas, Coskun Kocabas, and Atilla Aydinli
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Localization of surface plasmon polaritons in hexagonal arrays of Moiré cavities

Sinan Balci, Askin Kocabas, Coskun Kocabas, and Atilla Aydinli

Appl. Phys. Lett. 98, 031101 (2011); http://dx.doi.org/10.1063/1.3529469 (3 pages)

Online Publication Date: 18 January 2011

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In view of the progress on the confinement of light, we report on the dispersion characteristics of surface plasmon polaritons (SPPs) on two-dimensional Moiré surfaces in the visible part of the electromagnetic spectrum. Polarization dependent spectroscopic reflection measurements show omnidirectional confinement of SPPs. The resonance wavelength of SPP cavity modes can be adjusted by tuning the propagation direction of SPPs. The results may have an impact on the control of spontaneous emission and absorption with applications in light emitting diodes and solar cells, as well as in quantum electrodynamics experiments.
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73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)
42.25.Bs Wave propagation, transmission and absorption

Design and theoretical analysis of resonant cavity for second-harmonic generation with high efficiency

Sidong Lei, Yao Yao, Zhaosheng Li, Tao Yu, and Zhigang Zou

Appl. Phys. Lett. 98, 031102 (2011); http://dx.doi.org/10.1063/1.3544056 (3 pages)

Online Publication Date: 19 January 2011

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An improved theoretical model is built to discuss the second-harmonic generation (SHG) with high efficiency in a microcavity. Meanwhile, the configuration of the cavity is optimized according to it. It is found that when the length of the cavity leads to a π phase mismatch between fundamental and second-harmonic wave, the cavity reaches its optimum working condition. The SHG efficiency has been calculated for a 10.6 μm laser in a 106.3 μm 〈111〉 GaAs cavity.
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42.55.Sa Microcavity and microdisk lasers
42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation

Controllable assembly and cycling conversion of various supramolecular aggregates of a cyanine dye

Hongxia Sun, Junfeng Xiang, Qianfan Yang, Qian Shang, Qiuju Zhou, Yanxia Zhang, Guangzhi Xu, and Yalin Tang

Appl. Phys. Lett. 98, 031103 (2011); http://dx.doi.org/10.1063/1.3535980 (3 pages)

Online Publication Date: 19 January 2011

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Constructing dye supramolecular aggregates and regulating their structures have been very important tasks in recent years due to their excellent properties and promising applications in many fields. In this paper, four kinds of aggregates have been constructed by using a cyanine dye under controllable conditions, and a simple method to realize a cycling conversion around these aggregates has been developed. To construct and regulate these aggregates were easily manipulated and identified, and could be directly observed with unaided eye.
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81.20.-n Methods of materials synthesis and materials processing

Strong pulse asymmetry in quantum-dot mode-locked semiconductor lasers

Mindaugas Radziunas, Andrei G. Vladimirov, Evgeny A. Viktorov, Gerrit Fiol, Holger Schmeckebier, and Dieter Bimberg

Appl. Phys. Lett. 98, 031104 (2011); http://dx.doi.org/10.1063/1.3544579 (3 pages) | Cited 1 time

Online Publication Date: 20 January 2011

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We describe the formation of a strong pulse asymmetry in mode-locked quantum-dot edge-emitting two-section semiconductor lasers. A mode decomposition technique reveals the role of the superposition of different modal groups. The results of theoretical analysis are supported by the experimental data.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Fc Modulation, tuning, and mode locking

Strain distribution in bent ZnO microwires

C. P. Dietrich, M. Lange, F. J. Klüpfel, H. von Wenckstern, R. Schmidt-Grund, and M. Grundmann

Appl. Phys. Lett. 98, 031105 (2011); http://dx.doi.org/10.1063/1.3544939 (3 pages) | Cited 1 time

Online Publication Date: 20 January 2011

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ZnO microwires grown by carbothermal reduction were mechanically bent and the uniaxial stress state was studied with spatially resolved low-temperature photoluminescence. Inhomogeneous (tensile and compressive) stress (up to ±1 GPa) is visualized by the redshift and blueshift of the wire luminescence. Experimentally determined tensile and compressive strain along the c-axis (wire axis) of up to 1.5 %, symmetrically distributed with respect to the central axis (neutral fiber), is achieved, resulting in maximum energetic shifts of ±30 meV. Within these experiments, we are able to precisely determine the direct relation between energetic shift of the free A-exciton energy and strain to (−2.04±0.02) eV.
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81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
78.55.Et II-VI semiconductors
82.30.Fi Ion-molecule, ion-ion, and charge-transfer reactions
61.46.Km Structure of nanowires and nanorods (long, free or loosely attached, quantum wires and quantum rods, but not gate-isolated embedded quantum wires)
81.16.-c Methods of micro- and nanofabrication and processing

Room temperature photoluminescence of Ge multiple quantum wells with Ge-rich barriers

E. Gatti, E. Grilli, M. Guzzi, D. Chrastina, G. Isella, and H. von Känel

Appl. Phys. Lett. 98, 031106 (2011); http://dx.doi.org/10.1063/1.3541782 (3 pages) | Cited 10 times

Online Publication Date: 20 January 2011

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We report on the observation of room temperature direct band gap photoluminescence in compressively strained-Ge multiple quantum wells with Ge-rich SiGe barriers. A detailed experimental study of the temperature dependence of the photoluminescence is carried out from 5 K up to room temperature. We find that the direct gap photoluminescence at room temperature is due to the thermal excitation of carriers from L-type to Γ-type confined states. Room temperature photoluminescence shows that Ge/SiGe multiple quantum wells are promising candidates for efficient light emitting devices monolithically integrated on Si.
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81.05.Cy Elemental semiconductors
81.07.St Quantum wells
78.67.De Quantum wells
78.55.Ap Elemental semiconductors
73.21.Fg Quantum wells

On the role of evanescent modes and group index tapering in slow light photonic crystal waveguide coupling efficiency

Amir Hosseini, Xiaochuan Xu, David N. Kwong, Harish Subbaraman, Wei Jiang, and Ray T. Chen

Appl. Phys. Lett. 98, 031107 (2011); http://dx.doi.org/10.1063/1.3548557 (3 pages) | Cited 1 time

Online Publication Date: 21 January 2011

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We investigate effects of different mechanisms on coupling efficiency between strip waveguides and the slow light mode in photonic crystal waveguides (PCWs). Both numerical simulations and experimental results show that group index (ng) tapering improves strip-PCW butt-coupling efficiency when compared to a direct coupling between a strip waveguide and a high-ng PCW. However, coupling efficiency is even higher when an intermediate low-ng PCW is used to couple from a strip waveguide to a high-ng PCW without an ng tapering. Our results suggest that the role of evanescent mode is more dominant in efficient coupling between two PCWs with large ng mismatch.
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84.40.Az Waveguides, transmission lines, striplines
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
42.70.Qs Photonic bandgap materials
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Making a geometrically asymmetric capacitive rf discharge electrically symmetric

Julian Schulze, Edmund Schüngel, Uwe Czarnetzki, Markus Gebhardt, Ralf Peter Brinkmann, and Thomas Mussenbrock

Appl. Phys. Lett. 98, 031501 (2011); http://dx.doi.org/10.1063/1.3544541 (3 pages) | Cited 3 times

Online Publication Date: 21 January 2011

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The electrical asymmetry effect in a spherical, geometrically asymmetric capacitive argon discharge driven by two consecutive harmonics is investigated using particle in cell simulations and analytical modeling. We find that the discharge asymmetry can be reduced electrically by tuning the phase shift between the driving frequencies, i.e., the absolute value of the dc self-bias voltage can be completely reduced and the mean ion energies at both electrodes can be adapted.
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52.80.Pi High-frequency and RF discharges
52.65.Rr Particle-in-cell method
52.50.Dg Plasma sources
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Atomic packing in Mg61Cu28Gd11 bulk metallic glass

X. D. Wang, H. B. Lou, S. G. Wang, J. Xu, and J. Z. Jiang

Appl. Phys. Lett. 98, 031901 (2011); http://dx.doi.org/10.1063/1.3544049 (3 pages)

Online Publication Date: 19 January 2011

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Atomic configurations of an Mg61Cu28Gd11 bulk metallic glass and its molten state have been investigated. The supercooled liquid and melt have a volume expansion coefficient only two times as large as that below glass transition temperature. Although the dominant polyhedra are 12- and 13-coordinated, the melt has slightly more polyhedra of low coordinated and less of high coordinated than in the as-cast. By Gd addition, half-octahedra with more volume accommodated are likely formed in the polyhedra, causing the local atomic environments of Mg in the melt quite different from the competing crystalline phase, thereby suppressing crystallization upon quenching.
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61.43.Fs Glasses
64.70.pe Metallic glasses
81.40.Gh Other heat and thermomechanical treatments

Nonlinear absorption of InN/InGaN multiple-quantum-well structures at optical telecommunication wavelengths

F. B. Naranjo, P. K. Kandaswamy, S. Valdueza-Felip, V. Calvo, M. González-Herráez, S. Martín-López, P. Corredera, J. A. Méndez, G. R. Mutta, B. Lacroix, P. Ruterana, and E. Monroy

Appl. Phys. Lett. 98, 031902 (2011); http://dx.doi.org/10.1063/1.3535609 (3 pages) | Cited 1 time

Online Publication Date: 19 January 2011

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We report on the nonlinear optical absorption of InN/InxGa1−xN (x = 0.8,0.9) multiple-quantum-well structures characterized at 1.55 μm by the Z-scan method in order to obtain the effective nonlinear absorption coefficient (α2) of the samples at high repetition rate. Saturable absorption is observed for the sample with x = 0.9, with an effective α2 ∼ −9×103 cm/GW for the studied optical regime. For lower In content in the barrier, reverse saturable absorption is observed, which is attributed to two-photon absorption.
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78.66.Fd III-V semiconductors
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
42.65.-k Nonlinear optics

Strong in-plane anisotropy of magneto-optical Kerr effect in corrugated cobalt films deposited on highly ordered two-dimensional colloidal crystals

Z. L. Han, J. H. Ai, P. Zhan, J. Du, H. F. Ding, and Z. L. Wang

Appl. Phys. Lett. 98, 031903 (2011); http://dx.doi.org/10.1063/1.3544582 (3 pages)

Online Publication Date: 19 January 2011

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The corrugated cobalt films are investigated by magneto-optical Kerr effect and vibrating sample magnetometer (VSM). The films are fabricated by depositing thin cobalt layers on a large area single-domain two-dimensional (2D) hexagonal close-packing colloidal crystal. Strong in-plane anisotropy of the Kerr rotation hysteresis loop is found in sharp contrast to isotropic hysteresis loops obtained by the VSM. The anisotropy of such magneto-optical Kerr rotation disappears when randomly distributed colloidal spheres were used as the substrate. Our observations show that the magneto-optical effect does not completely correspond with the average magnetization state in such a 2D periodic magnetic network.
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78.20.Ls Magneto-optical effects
78.66.Bz Metals and metallic alloys
75.30.Gw Magnetic anisotropy
78.20.Ek Optical activity
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.70.Ak Magnetic properties of monolayers and thin films

Probing the atomic structure of amorphous Ta2O5 coatings

R. Bassiri, K. B. Borisenko, D. J. H. Cockayne, J. Hough, I. MacLaren, and S. Rowan

Appl. Phys. Lett. 98, 031904 (2011); http://dx.doi.org/10.1063/1.3535982 (3 pages) | Cited 1 time

Online Publication Date: 19 January 2011

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Low optical and mechanical loss Ta2O5 amorphous coatings have a growing number of applications in precision optical measurements systems. Transmission electron microscopy is a promising way to probe the atomic structure of these coatings in an effort to better understand the causes of the observed mechanical and optical losses. Analysis of the experimental reduced density functions using a combination of reverse Monte Carlo refinements and density functional theory molecular dynamics simulations reveals that the structure of amorphous Ta2O5 consists of clusters with increased contribution from a Ta2O2 ring fragment.
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61.43.Er Other amorphous solids
61.43.Bn Structural modeling: serial-addition models, computer simulation

Enhanced optical constants of nanocrystalline yttrium oxide thin films

C. V. Ramana, V. H. Mudavakkat, K. Kamala Bharathi, V. V. Atuchin, L. D. Pokrovsky, and V. N. Kruchinin

Appl. Phys. Lett. 98, 031905 (2011); http://dx.doi.org/10.1063/1.3524202 (3 pages)

Online Publication Date: 19 January 2011

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Yttrium oxide (Y2O3) films with an average crystallite-size (L) ranging from 5 to 40 nm were grown by sputter-deposition onto Si(100) substrates. The optical properties of grown Y2O3 films were evaluated using spectroscopic ellipsometry measurements. The size-effects were significant on the optical constants and their dispersion profiles of Y2O3 films. A significant enhancement in the index of refraction (n) is observed in well-defined Y2O3 nanocrystalline films compared to that of amorphous Y2O3. A direct, linear L-n relationship found for Y2O3 films suggests that tuning optical properties for desired applications can be achieved by controlling the size at the nanoscale dimensions.
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78.66.Nk Insulators
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
68.55.aj Insulators
81.15.Cd Deposition by sputtering

Thermal annealing and grain boundary effects on ferromagnetism in Y2O3:Co diluted magnetic oxide nanocrystals

Y. L. Soo, T. S. Wu, C. S. Wang, S. L. Chang, H. Y. Lee, P. P. Chu, C. Y. Chen, L. J. Chou, T. S. Chan, C. A. Hsieh, J. F. Lee, J. Kwo, and M. Hong

Appl. Phys. Lett. 98, 031906 (2011); http://dx.doi.org/10.1063/1.3544059 (3 pages) | Cited 3 times

Online Publication Date: 21 January 2011

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Structures and magnetic properties of Y2O3:Co nanocrystals were investigated using high resolution transmission electron microscopy, x-ray diffraction, x-ray absorption fine structures, and superconducting quantum interference device. Cobalt atoms were found to be driven by thermal annealing from interstitial locations inside the Y2O3 nanoparticles toward particle surface, where increased O vacancies surrounding Co atoms led to increased saturation magnetization. Our results strongly support a bound magnetic polaron model for ferromagnetism in diluted magnetic oxides mostly due to magnetic dopants located on the grain boundaries.
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81.40.Gh Other heat and thermomechanical treatments
61.72.Mm Grain and twin boundaries
75.50.Dd Nonmetallic ferromagnetic materials
75.50.Tt Fine-particle systems; nanocrystalline materials
78.70.Dm X-ray absorption spectra
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Extreme low-temperature molecular beam epitaxy of ZnO-based quantum structures

S. Blumstengel, S. Sadofev, H. Kirmse, and F. Henneberger

Appl. Phys. Lett. 98, 031907 (2011); http://dx.doi.org/10.1063/1.3544575 (3 pages)

Online Publication Date: 21 January 2011

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We report on extreme low-temperature growth of ZnO by plasma-assisted molecular beam epitaxy. Epilayers and quantum well (QW) structures with very good structural and optical properties are prepared at substrate temperatures as low as 50 °C. The growth proceeds in a single crystalline layer-by-layer mode. ZnO QWs prepared on a-plane sapphire show bright excitonic luminescence with a very narrow linewidth of only 6 meV at 5 K. High-resolution transmission electron micrographs confirm that low-temperature single crystalline growth is not restricted to a particular surface termination of ZnO but works also for crystal growth along a nonpolar direction.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
73.21.Fg Quantum wells
78.67.De Quantum wells
78.55.Et II-VI semiconductors
78.66.Hf II-VI semiconductors
68.55.ag Semiconductors

Vacancy-mediated diffusion in biaxially strained Si

Damien Caliste, Konstantin Z. Rushchanskii, and Pascal Pochet

Appl. Phys. Lett. 98, 031908 (2011); http://dx.doi.org/10.1063/1.3548547 (3 pages) | Cited 4 times

Online Publication Date: 21 January 2011

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We present an analysis of stress-enhanced vacancy-mediated diffusion in biaxially deformed Si (100) films as measured by the strain derivative (Q′) of the activation energy. The strain dependence of Q′ is demonstrated by means of a reanalysis of previously published experimental data, which both take into account the temperature dependence of and highlight the differences between tensile and compressive stress. Based on ab initio calculations, we predict that Q′ in pure silicon is higher under compressive conditions due to a broken degeneracy of the split-vacancy configuration.
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66.30.Lw Diffusion of other defects
81.05.Cy Elemental semiconductors
61.72.jd Vacancies
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity

Ductility of bulk metallic glass composites: Microstructural effects

F. Abdeljawad, M. Fontus, and M. Haataja

Appl. Phys. Lett. 98, 031909 (2011); http://dx.doi.org/10.1063/1.3531660 (3 pages)

Online Publication Date: 21 January 2011

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Recent experimental findings suggest that the problem of catastrophic failure by shear band propagation in monolithic bulk metallic glasses (BMGs) can be mitigated by forming two-phase composites consisting of a glassy metal matrix phase and a soft crystalline reinforcement phase. Here, we employ a recently introduced phase-field model in two spatial dimensions, capable of capturing shear banding in BMG systems, to address the effects of microstructure on the mechanical properties of BMG composites. We identify an important geometric length scale associated with the dendritic particles and demonstrate that it controls the overall ductility and ultimate strength of such BMG composites.
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81.40.Lm Deformation, plasticity, and creep
62.20.fk Ductility, malleability
61.43.Fs Glasses
68.70.+w Whiskers and dendrites (growth, structure, and nonelectronic properties)

Uniaxial strain-modulated conductivity in manganite superlattice (LaMnO3/SrMnO3)

Dan Cao, Meng-Qiu Cai, Wang-Yu Hu, Jun Peng, Yue Zheng, and Hai-Tao Huang

Appl. Phys. Lett. 98, 031910 (2011); http://dx.doi.org/10.1063/1.3548675 (3 pages)

Online Publication Date: 21 January 2011

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We have investigated the magnetic ordering and electrical conductivity transitions of (LaMnO3)2/(SrMnO3)2 superlattices grown on SrTiO3 substrate based on density-functional theory. It is found that the uniaxial tensile strain along the z axis of about 1.4% induced a magnetic transition from antiferromagnetic to ferromagnetic ordering. At the interface the orbital order changes from a combination of x2−y2 and 3z2−r2 to x2−y2 as strain becomes more compressive; as a result the electrical transport is transformed from three-dimensions to two-dimensions at the high uniaxial compressive strain. Our results suggest that the out-of-plane electrical conductivity can be modulated and controlled by uniaxial strain.
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75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
73.63.-b Electronic transport in nanoscale materials and structures
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Creation of charged excitons with two-color excitation method and initialization of electron spin qubit in quantum dots

Hideki Gotoh, Haruki Sanada, Hidehiko Kamada, Hiroshi Yamaguchi, and Tetsuomi Sogawa

Appl. Phys. Lett. 98, 032101 (2011); http://dx.doi.org/10.1063/1.3543841 (3 pages)

Online Publication Date: 18 January 2011

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An optical pumping method for creating charged excitons in semiconductor quantum dots is demonstrated using a two-color excitation method. This method employs two laser sources whose energies are in the resonant and barrier excitation conditions, respectively. The photoluminescence (PL) spectra of a single quantum dot clearly vary from exciton-originated PL to charged exciton-originated PL as the excitation conditions are changed. This method is applied to the initialization process of an electron spin qubit without a magnetic field, which provides a simple and effective way of implementing quantum computing with spin qubits.
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73.21.La Quantum dots
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
71.35.Pq Charged excitons (trions)
78.67.Hc Quantum dots
78.55.Cr III-V semiconductors
73.22.Lp Collective excitations

Correlation between structure and electrical transport in ion-irradiated graphene grown on Cu foils

Grant Buchowicz, Peter R. Stone, Jeremy T. Robinson, Cory D. Cress, Jeffrey W. Beeman, and Oscar D. Dubon

Appl. Phys. Lett. 98, 032102 (2011); http://dx.doi.org/10.1063/1.3536529 (3 pages) | Cited 2 times

Online Publication Date: 18 January 2011

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Graphene grown by chemical vapor deposition and supported on SiO2 and sapphire substrates was studied following the controlled introduction of defects induced by 35 keV carbon ion irradiation. Changes in Raman spectra for fluences ranging from 1012 to 1015 cm−2 indicate that the structure of graphene evolves from a highly ordered layer, to a patchwork of disordered domains, to an essentially amorphous film. These structural changes result in a dramatic decrease in the Hall mobility by orders of magnitude while, remarkably, the Hall concentration remains almost unchanged, suggesting that the Fermi level is pinned at a hole concentration near 1×1013 cm−2. A model for scattering by resonant scatterers is in good agreement with mobility measurements up to an ion fluence of 1×1014 cm−2.
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61.48.Gh Structure of graphene
73.22.Pr Electronic structure of graphene
78.67.Wj Optical properties of graphene
78.30.Na Fullerenes and related materials
61.80.Jh Ion radiation effects
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Anisotropic transport of two-dimensional electron gas modulated by embedded elongated GaSb/GaAs quantum dots

Guodong Li, Chao Jiang, Qinsheng Zhu, and Hiroyuki Sakaki

Appl. Phys. Lett. 98, 032103 (2011); http://dx.doi.org/10.1063/1.3541882 (3 pages) | Cited 2 times

Online Publication Date: 19 January 2011

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Geometrically anisotropic GaSb/GaAs quantum dots (QDs) that are elongated along the [110] direction are embedded in the vicinity of a modulation-doped AlGaAs/GaAs heterointerface. At 4.2 K, the electron mobilities μ∥ and μ⊥, which are parallel and perpendicular to the QD elongation axis, respectively, are systematically investigated as a function of the electron concentration NS by both experimental measurements and theoretical simulations. In the experiments, the mobility ratio μ∥/μ⊥ increased with increasing NS. The mobility anisotropy, attributed to the anisotropic scattering potential of the elongated GaSb QDs, is calculated under the theoretical model of a rectangular scattering potential of GaSb QDs.
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73.21.La Quantum dots
73.63.Kv Quantum dots
72.20.Fr Low-field transport and mobility; piezoresistance
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Bandstructure line-up of epitaxial Fe/MgO/Ge heterostructures: A combined x-ray photoelectron spectroscopy and transport study

M. Cantoni, D. Petti, C. Rinaldi, and R. Bertacco

Appl. Phys. Lett. 98, 032104 (2011); http://dx.doi.org/10.1063/1.3543851 (3 pages) | Cited 3 times

Online Publication Date: 19 January 2011

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The bandstructure line-up of Fe/MgO/Ge heterostructures with various Ge doping has been determined by x-ray photoemission spectroscopy. The MgO layer causes a sizable depinning of the Fermi level in Ge for light n-(1015 cm−3) and moderate p-doping (1018 cm−3), but not for heavy n-doping (1020 cm−3). The Fermi level instead stays essentially in the middle of the MgO gap for all the investigated doping. This picture agrees with transport measurements only for moderate n- or p-doping, while we demonstrate that for heavy n-doping the analysis of the conductance versus temperature fails in predicting the Schottky barrier height.
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73.20.At Surface states, band structure, electron density of states
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.30.+y Surface double layers, Schottky barriers, and work functions
61.72.U- Doping and impurity implantation
79.60.Jv Interfaces; heterostructures; nanostructures

Nonvolatile resistive switching in Pr0.7Ca0.3MnO3 devices using multilayer graphene electrodes

Wootae Lee, Gunho Jo, Sangchul Lee, Jubong Park, Minseok Jo, Joonmyoung Lee, Seungjae Jung, Seonghyun Kim, Jungho Shin, Sangsu Park, Takhee Lee, and Hyunsang Hwang

Appl. Phys. Lett. 98, 032105 (2011); http://dx.doi.org/10.1063/1.3544051 (3 pages) | Cited 1 time

Online Publication Date: 20 January 2011

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We report resistive switching in Pr0.7Ca0.3MnO3 (PCMO) devices using multilayer graphene (MLG) for nonvolatile memory applications. When MLG was used as a conducting electrode, PCMO device exhibited resistive switching with an on/off ratio of over two orders of magnitude and stable retention characteristics for over 104 s at 85 °C. Raman spectroscopy in both resistance states revealed increases in D and D′ peaks associated with defects and large shift in G peak position for high-resistance state. This was attributed to formation and dissolution of oxygenated graphene at the MLG/PCMO interface, resulting in resistive switching.
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84.30.Sk Pulse and digital circuits

Spin current generation by adiabatic pumping in monolayer graphene

Qingtian Zhang, K. S. Chan, and Zijing Lin

Appl. Phys. Lett. 98, 032106 (2011); http://dx.doi.org/10.1063/1.3544581 (3 pages) | Cited 6 times

Online Publication Date: 20 January 2011

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We propose a method of generating spin currents in monolayer graphene through adiabatic quantum pumping by two oscillating potentials. Spin splitting is induced in the graphene layer by ferromagnetic proximity. The pumped charge and spin currents are sensitive functions of the Fermi energy, which can thus be used to control the degree of polarization. The predicted pumped currents are measurable using the current technology. The proposed method is useful in the development of graphene spintronics.
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73.61.Wp Fullerenes and related materials
72.25.-b Spin polarized transport
68.47.Pe Langmuir-Blodgett films on solids; polymers on surfaces; biological molecules on surfaces
73.22.Pr Electronic structure of graphene

Direct observation of the 1/E dependence of time dependent dielectric breakdown in the presence of copper

Larry Zhao, Zsolt Tőkei, Kristof Croes, Christopher J. Wilson, Mikhail Baklanov, Gerald P. Beyer, and Cor Claeys

Appl. Phys. Lett. 98, 032107 (2011); http://dx.doi.org/10.1063/1.3543850 (3 pages) | Cited 2 times

Online Publication Date: 20 January 2011

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Time dependent dielectric breakdown (TDDB) lifetime model study has been performed on a metal-insulator-semiconductor capacitor structure with copper directly deposited on silicon dioxide without a barrier material. The structure generates a low electric field acceleration of time-to-failure, which makes it possible to measure TDDB over a wide range of electric fields from 3.5 to 10 MV/cm and experimentally validate TDDB lifetime model without any assumption and data extrapolation. The experimental results are in good agreement with the so called 1/E model and do not support the E, √E, or power-law model.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
77.22.Jp Dielectric breakdown and space-charge effects
84.32.Tt Capacitors
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