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25 Jun 2012

Volume 100, Issue 26, Articles (26xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 100, 261104 (2012); http://dx.doi.org/10.1063/1.4711253 (4 pages)

Marcelo Davanço, Jun Rong Ong, Andrea Bahgat Shehata, Alberto Tosi, Imad Agha, Solomon Assefa, Fengnian Xia, William M. J. Green, Shayan Mookherjea, and Kartik Srinivasan
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Magnetostriction in the vicinity of structural transitions in Ni2MnGa

J. M. Barandiarán, V. A. Chernenko, J. Gutiérrez, I. Orúe, and P. Lázpita

Appl. Phys. Lett. 100, 262410 (2012); http://dx.doi.org/10.1063/1.4732483 (5 pages) | Cited 2 times

Online Publication Date: 29 June 2012

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We report parallel and perpendicular magnetostriction measurements performed in polycrystalline Ni2MnGa to shed light on the magnetoelastic coupling, responsible for the ordinary magnetostriction, and giant magnetic field-induced strains (MFIS). Parallel magnetostriction is negative while its perpendicular component switches from positive to negative at the martensitic transformation. The saturation magnetostriction is negative, takes moderate values and has a large increase in absolute value at both pre- and martensitic temperatures, arising from the lattice softening at the transitions. The reported values are those of the true magnetostriction and can be a starting point for further studies of MFIS.
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75.80.+q Magnetomechanical effects, magnetostriction
81.30.Kf Martensitic transformations
64.70.K- Solid-solid transitions

Light controlled magnetoresistance and magnetic field controlled photoresistance in CoFe film deposited on BiFeO3

B. Kundys, C. Meny, M. R. J. Gibbs, V. Da Costa, M. Viret, M. Acosta, D. Colson, and B. Doudin

Appl. Phys. Lett. 100, 262411 (2012); http://dx.doi.org/10.1063/1.4731201 (4 pages)

Online Publication Date: 29 June 2012

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We present a magnetoresistive—photoresistive device based on the interaction of a piezomagnetic CoFe thin film with a photostrictive BiFeO3 (BFO) substrate that undergoes light-induced strain. The magnitude of the resistance and magnetoresistance in the CoFe film can be controlled by the wavelength of the incident light on the BiFeO3. Moreover, a light-induced decrease in anisotropic magnetoresistance is detected due to an additional magnetoelastic contribution to magnetic anisotropy of the CoFe film. This effect may find applications in photo-sensing systems, wavelength detectors and can possibly open a research development in light-controlled magnetic switching properties for next generation magnetoresistive memory devices.
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75.80.+q Magnetomechanical effects, magnetostriction
72.15.Gd Galvanomagnetic and other magnetotransport effects
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
75.30.Gw Magnetic anisotropy

High propagating velocity of spin waves and temperature dependent damping in a CoFeB thin film

Haiming Yu, R. Huber, T. Schwarze, F. Brandl, T. Rapp, P. Berberich, G. Duerr, and D. Grundler

Appl. Phys. Lett. 100, 262412 (2012); http://dx.doi.org/10.1063/1.4731273 (4 pages) | Cited 1 time

Online Publication Date: 29 June 2012

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Spin wave propagation in a magnetron-sputtered CoFeB thin film is investigated. We apply both in-plane and out-of-plane magnetic fields. At room temperature, we find velocities of up to 25 and 3.5 km/s, respectively. These values are much larger compared to a thin permalloy film. Analyzing the resonance linewidth, we obtain an intrinsic Gilbert damping parameter of about 0.007 at room temperature. It increases to 0.023 at 5 K. CoFeB is a promising material for magnonic devices supporting fast propagating spin waves.
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75.30.Ds Spin waves
75.70.Ak Magnetic properties of monolayers and thin films

Isothermal switching of perpendicular exchange bias by pulsed high magnetic field

Yu Shiratsuchi, Kohei Wakatsu, Tetsuya Nakamura, Hiroto Oikawa, Satoru Maenou, Yasuo Narumi, Kou Tazoe, Chiharu Mitsumata, Toyohiko Kinoshita, Hiroyuki Nojiri, and Ryoichi Nakatani

Appl. Phys. Lett. 100, 262413 (2012); http://dx.doi.org/10.1063/1.4731643 (4 pages) | Cited 1 time

Online Publication Date: 29 June 2012

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Isothermal switching of a perpendicular exchange bias by a strong pulsed magnetic field has been investigated using a Pt/Co/α-Cr2O3 thin film system. The switching of the perpendicular exchange bias is accompanied by the spin reversal of interfacial uncompensated antiferromagnetic Cr spins. We have also demonstrated that the switching of the exchange bias is reversible by changing the pulsed magnetic field direction. The mechanism of the demonstrated switching is discussed from the viewpoint of the spin flop transition of the α-Cr2O3 layer.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
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Probing quasiparticle excitations in a hybrid single electron transistor

H. S. Knowles, V. F. Maisi, and J. P. Pekola

Appl. Phys. Lett. 100, 262601 (2012); http://dx.doi.org/10.1063/1.4730407 (4 pages)

Online Publication Date: 26 June 2012

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We investigate the behavior of quasiparticles in a hybrid electron turnstile with the aim of improving its performance as a metrological current source. The device is used to directly probe the density of quasiparticles and monitor their relaxation into normal metal traps. We compare different trap geometries and reach quasiparticle densities below 3 μm−3 for pumping frequencies of 20 MHz. Our data show that quasiparticles are excited both by the device operation itself and by the electromagnetic environment of the sample. Our observations can be modelled on a quantitative level with a sequential tunneling model and a simple diffusion equation.
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85.35.Gv Single electron devices

Superconductor-insulator transition controlled by annealing in Ga implanted Si

V. Heera, J. Fiedler, M. Voelskow, A. Mücklich, R. Skrotzki, T. Herrmannsdörfer, and W. Skorupa

Appl. Phys. Lett. 100, 262602 (2012); http://dx.doi.org/10.1063/1.4732081 (4 pages) | Cited 1 time

Online Publication Date: 27 June 2012

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Heavily Ga implanted Si nanolayers covered with a thin SiO2 layer exhibit a superconductor-insulator transition in dependence on annealing conditions. The transition characteristics resemble those of ultrathin quench-condensed metal films although the implanted layer differs clearly in composition, width, and nanostructure. This implies a general physical mechanism for the superconductor-insulator transition in thin, disordered layers which is supposed to be a quantum phase transition between dual states—the superconducting and the superinsulating one. There is a resistance criterion for the phase transition closely associated with a critical hole concentration.
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74.62.Yb Other effects
61.72.uf Ge and Si
61.72.Cc Kinetics of defect formation and annealing
74.62.-c Transition temperature variations, phase diagrams

Spatially dependent sensitivity of superconducting meanders as single-photon detectors

G. R. Berdiyorov, M. V. Milošević, and F. M. Peeters

Appl. Phys. Lett. 100, 262603 (2012); http://dx.doi.org/10.1063/1.4731627 (4 pages) | Cited 2 times

Online Publication Date: 28 June 2012

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The photo-response of a thin current-carrying superconducting stripe with a 90° turn is studied within the time-dependent Ginzburg-Landau theory. We show that the photon acting near the inner corner (where the current density is maximal due to the current crowding [J. R. Clem and K. K. Berggren, Phys. Rev. B 84, 174510 (2011)]) triggers the nucleation of superconducting vortices at currents much smaller than the expected critical one, but does not bring the system to a higher resistive state and thus remains undetected. The transition to the resistive state occurs only when the photon hits the stripe away from the corner due to there uniform current distribution across the sample, and dissipation is due to the nucleation of a kinematic vortex-antivortex pair near the photon incidence. We propose strategies to account for this problem in the measurements.
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85.25.-j Superconducting devices

Monolithic high-temperature superconducting heterodyne Josephson frequency down-converter

J. Du, T. Zhang, J. C. Macfarlane, Y. J. Guo, and X. W. Sun

Appl. Phys. Lett. 100, 262604 (2012); http://dx.doi.org/10.1063/1.4731878 (4 pages) | Cited 1 time

Online Publication Date: 29 June 2012

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A monolithic microwave integrated circuit (MMIC) frequency down-converter based on a compact high-Tc superconducting (HTS) device is demonstrated. The on-chip integrated HTS down-converter consists of a 7–9 GHz bandpass filter for RF input, a lowpass filter for intermediate frequency output, and a self-pumped Josephson heterodyne mixer. All the above passive and active components are fabricated on a single 10 mm × 20 mm chip of YBa2Cu3O7−x film on MgO substrate. Characterization of this MMIC HTS down-converter in terms of frequency response, conversion gain, frequency-tuneability, bias dependence, dynamic range, linearity, and intrinsic noise are presented in this paper.
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85.25.Cp Josephson devices
84.30.Qi Modulators and demodulators; discriminators, comparators, mixers, limiters, and compressors
84.30.Vn Filters
84.40.Lj Microwave integrated electronics

Etch induced microwave losses in titanium nitride superconducting resonators

Martin Sandberg, Michael R. Vissers, Jeffrey S. Kline, Martin Weides, Jiansong Gao, David S. Wisbey, and David P. Pappas

Appl. Phys. Lett. 100, 262605 (2012); http://dx.doi.org/10.1063/1.4729623 (4 pages) | Cited 4 times

Online Publication Date: 29 June 2012

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We have investigated the correlation between the microwave loss and patterning method for coplanar waveguide titanium nitride resonators fabricated on silicon wafers. Three different methods were investigated: fluorine- and chlorine-based reactive ion etches and an argon-ion mill. At high microwave probe powers, the reactive etched resonators showed low internal loss, whereas the ion-milled samples showed dramatically higher loss. At single-photon powers, we found that the fluorine-etched resonators exhibited substantially lower loss than the chlorine-etched ones. We interpret the results by use of numerically calculated filling factors and find that the silicon surface exhibits a higher loss when chlorine-etched than when fluorine-etched. We also find from microscopy that re-deposition of silicon onto the photoresist and side walls is the probable cause for the high loss observed for the ion-milled resonators.
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85.25.Qc Superconducting surface acoustic wave devices and other superconducting devices
84.40.Az Waveguides, transmission lines, striplines
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Trench-filled cellular parylene electret for piezoelectric transducer

Yue Feng, Kei Hagiwara, Yoshinori Iguchi, and Yuji Suzuki

Appl. Phys. Lett. 100, 262901 (2012); http://dx.doi.org/10.1063/1.4730952 (4 pages)

Online Publication Date: 25 June 2012

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Cellular ferroelectrets with charged voids are promising for piezoelectric transducers, but the long-term stability or reproducibility due to the conventional “stochastic” fabrication and the corona charging methods is of concern. We microfabricated a high-density cellular piezoelectret with high-aspect-ratio polymer structures based on the trench-filled parylene technology. Vertical walls of the parylene structures are charged using soft x-ray to realize uniform artificial dipoles, of which moments could vary along with parylene structural deformation driven by the inertia of a seismic mass. Charge and voltage sensitivities of 9600 pC/N and 960 V/N with respect to the in-plane resonant oscillation have been achieved at 149 Hz, respectively.
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85.50.-n Dielectric, ferroelectric, and piezoelectric devices
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
07.10.Cm Micromechanical devices and systems

Dielectric elastomer transducers with enhanced force output and work density

Hristiyan Stoyanov, Paul Brochu, Xiaofan Niu, Enrico Della Gaspera, and Qibing Pei

Appl. Phys. Lett. 100, 262902 (2012); http://dx.doi.org/10.1063/1.4730953 (3 pages) | Cited 2 times

Online Publication Date: 25 June 2012

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We demonstrate that the force output and work density of polydimethylsiloxane (PDMS) based dielectric elastomer transducers can be significantly enhanced by the addition of high permittivity titanium dioxide nanoparticles. The nanocomposites are capable of maintaining the actuation strain performance of the pure PDMS at relatively low electric fields while increasing the force output and work density due to mechanical reinforcement. A model relating the Maxwell stress to the measured force from the actuator was used to determine the dielectric permittivity at high electric fields thus providing results that can be directly correlated to device performance. This approach toward higher work density materials should enable smaller, lighter, and less intrusive actuator systems ideal for biomedical and robotic devices in particular.
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07.07.Mp Transducers
85.50.-n Dielectric, ferroelectric, and piezoelectric devices

Three-state resistive switching in CoFe2O4/Pb(Zr0.52Ti0.48)O3/ZnO heterostructure

Ziwei Li, Mingxiu Zhou, Wangfeng Ding, Hang Zhou, Bo Chen, Jian-Guo Wan, Jun-Ming Liu, and Guanghou Wang

Appl. Phys. Lett. 100, 262903 (2012); http://dx.doi.org/10.1063/1.4730965 (5 pages) | Cited 1 time

Online Publication Date: 25 June 2012

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The heterostructural film combining multiferroic CoFe2O4/Pb(Zr0.52Ti0.48)O3 bilayer with semiconductor ZnO layer was prepared. Three-state resistive switching was demonstrated by time-dependent current measurements under different stimuli combination of voltage pulse and magnetic bias. The asymmetry diodelike current-voltage, capacitance-voltage, and polarization-voltage loops, which seriously depend on magnetic bias, were observed. We revealed that three-state resistive switching was dominated by the changes in the charge carriers in the heterostructure, which were modulated by the magnetoelectric coupling between ferromagnetic and ferroelectric layers and interface polarization coupling between ferroelectric and semiconductor layers. This work provides promising candidates for developing advanced switchable devices with multifunctional memory.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
77.22.Ej Polarization and depolarization
77.80.Fm Switching phenomena
77.55.Nv Multiferroic/magnetoelectric films

Reduced leakage currents and possible charge carriers tuning in Mg-doped Ga0.6Fe1.4O3 thin films

C. Lefevre, R. H. Shin, J. H. Lee, S. H. Oh, F. Roulland, A. Thomasson, E. Autissier, C. Meny, W. Jo, and N. Viart

Appl. Phys. Lett. 100, 262904 (2012); http://dx.doi.org/10.1063/1.4729872 (4 pages)

Online Publication Date: 26 June 2012

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Ga0.6Fe1.4O3 is predicted to be magnetoelectric with non zero magnetization at room temperature. However, in thin films, electric properties are overshadowed by strong leakage currents. In this Letter, we show that Mg doping in Ga0.6Fe1.4O3 thin films grown by pulsed laser deposition allows decreasing the leakage current density by four orders of magnitude and might simultaneously allow tuning the carriers’ nature. These results suggest the possibility to develop a new class of material exhibiting room temperature magnetization, tunable transport properties, and magnetoelectric properties.
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77.55.Nv Multiferroic/magnetoelectric films
73.61.Le Other inorganic semiconductors
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.15.Fg Pulsed laser ablation deposition
68.55.ag Semiconductors
75.85.+t Magnetoelectric effects, multiferroics

Detection of a piezoelectric effect in thin films of thermally grown SiO2 via lock-in ellipsometry

Guy Lazovski, Ellen Wachtel, and Igor Lubomirsky

Appl. Phys. Lett. 100, 262905 (2012); http://dx.doi.org/10.1063/1.4731287 (3 pages)

Online Publication Date: 26 June 2012

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We report the observation of structural piezoelectricity in partially ordered thin films of thermally grown silicon dioxide (SiO2). The piezoelectric coefficient was determined to be 0.14-0.26 pm/V, and the piezoelectricity was found to originate in a layer with thickness at least 3.5 nm. This value is consistent with literature descriptions of SiO2 residual ordering based on structural measurements and modeling. Our observation demonstrates that the residual ordering in thermally grown silicon SiO2 is non-centrosymmetric and provides a rare example of diffusion controlled uniaxial growth producing macroscopic piezoelectricity.
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77.55.H- Piezoelectric and electrostrictive films
77.65.-j Piezoelectricity and electromechanical effects
07.60.Fs Polarimeters and ellipsometers

Non-volatile ferroelectric gating of magnetotransport anisotropy in (Ga,Mn)(As,P)

E. Mikheev, I. Stolichnov, Z. Huang, A. W. Rushforth, J. A. Haigh, R. P. Campion, K. W. Edmonds, B. L. Gallagher, and N. Setter

Appl. Phys. Lett. 100, 262906 (2012); http://dx.doi.org/10.1063/1.4731245 (4 pages) | Cited 2 times

Online Publication Date: 27 June 2012

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We demonstrate charge-mediated and non-volatile control of anisotropic magnetoresistance (AMR) in a dilute magnetic semiconductor (Ga,Mn)(As,P) with an integrated polymer ferroelectric gate. The persistent electric field associated with switchable polarization in the ferroelectric layer is shown to be capable of strongly modulating the AMR magnitude. Furthermore, ferroelectric gate switching has a profound impact on the nature of AMR, changing the symmetry of the effect and enhancing/suppressing the crystalline component of AMR. Thus, in addition to a rather weak modulation of the ferromagnetic Curie temperature (4-5 K) reported previously, the ferroelectric gate can induce a strong deterministic switching of the magnetotransport anisotropy.
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72.20.My Galvanomagnetic and other magnetotransport effects
75.30.Gw Magnetic anisotropy
75.50.Pp Magnetic semiconductors
77.80.Fm Switching phenomena
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)

Magnetoelectric relaxation in rhombohedral LiNbO3-CoFe2O4

Yemei Han, Yueying Liu, Peter Zavalij, Lourdes Salamanca-Riba, Elizabeth Cantando, Richard Bergstrom, Jr., Lingxia Li, and Manfred Wuttig

Appl. Phys. Lett. 100, 262907 (2012); http://dx.doi.org/10.1063/1.4729933 (4 pages)

Online Publication Date: 27 June 2012

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We demonstrate a magnetoelectric nanocomposite, LiNbO3-CoFe2O4 (LNO-CFO), consisting of rhombohedral R3c LNO and R3m CFO phases. It is characterized by a maximum inverse magnetoelectric coefficient of 6.5 Oe cm·V−1 measured in a 106 V/m electric field, and a magnetic field dependent Vogel–Fulcher-like relaxation characterized by a relaxation time τ = τ0exp(−ΔH/k(Tm−TvfH)), τ0 = 29.66 s, ΔH = 1.06 eV, TvfH represents the magnetic field-dependent Vogel-Fulcher temperature. The activation energy equals the activation energy of oxygen vacancy diffusion in niobate-based crystals. The room temperature electric field-induced magnetization change relaxes as τ = 18.05 s.
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75.85.+t Magnetoelectric effects, multiferroics
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
61.72.jd Vacancies

High-stability oxygen sensor based on amorphous zinc tin oxide thin film transistor

Yu-Chun Chen, Ting-Chang Chang, Hung-Wei Li, Wan-Fang Chung, Chang-Pei Wu, Shih-Ching Chen, Jin Lu, Yi-Hsien Chen, and Ya-Hsiang Tai

Appl. Phys. Lett. 100, 262908 (2012); http://dx.doi.org/10.1063/1.4731773 (3 pages)

Online Publication Date: 27 June 2012

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This research presents a sol-gel derived zinc tin oxide thin film transistor (TFT) as a high-stability oxygen sensor. Due to its high sensitivity, oxygen has been traditionally regarded as having a negative influence on the electrical characteristics of zinc-based TFTs; however, TFTs can also act as an oxygen sensor. After illumination with visible light in oxygen-rich ambient, a significant increase in drain current of nearly 104 times occurs with fixed gate and drain voltages. It is expected that an optimized method of illumination can help to reset the electrical characteristics or distinguish the on/off state of this reliable oxygen sensor.
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85.30.Tv Field effect devices
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing

Stress dependence of thermally driven pyroelectric charge release during FER-FEO phase transformations in [011] cut relaxor ferroelectric crystals

Wen D. Dong, Peter Finkel, Ahmed Amin, and Christopher S. Lynch

Appl. Phys. Lett. 100, 262909 (2012); http://dx.doi.org/10.1063/1.4731791 (4 pages) | Cited 3 times

Online Publication Date: 29 June 2012

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The stress dependence of thermally driven polarization change is reported for a ferroelectric rhombohedral to ferroelectric orthorhombic phase transformation in [011] cut and poled Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT). A jump in polarization and strain is associated with a phase transformation of the ferroelectric material. The phase transformation temperature can be tuned, over a broad temperature range, through the application of bias stress. This phenomenon has applications in the field of energy harvesting and thermal sensing.
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77.70.+a Pyroelectric and electrocaloric effects
77.80.Jk Relaxor ferroelectrics
77.80.bn Strain and interface effects
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Site-controlled formation of InAs/GaAs quantum-dot-in-nanowires for single photon emitters

J. Tatebayashi, Y. Ota, S. Ishida, M. Nishioka, S. Iwamoto, and Y. Arakawa

Appl. Phys. Lett. 100, 263101 (2012); http://dx.doi.org/10.1063/1.4731208 (4 pages) | Cited 3 times

Online Publication Date: 25 June 2012

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We report the demonstration of site-controlled InAs/GaAs quantum dots (QDs) embedded in GaAs nanowires (NWs) by selective metalorganic chemical vapor deposition. InAs/GaAs quantum-dot-in-nanowires (QD-in-NWs) with various InAs thicknesses are realized on patterned GaAs(111)B substrates in the form of InAs/GaAs heterostructures and identified by structural analyses using scanning transmission electron microscopy and photoluminescence characterization. Sharp excitonic emission peaks at 10 K from single QD-in-NWs with the narrowest exciton linewidth of 87 μeV are observed. Light emission from the single QD-in-NW shows photon antibunching, along with biexciton-exciton cascaded emission process, which evidences single photon emission from high-quality QD-in-NWs.
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68.65.Hb Quantum dots (patterned in quantum wells)
81.07.Ta Quantum dots
68.65.La Quantum wires (patterned in quantum wells)
81.07.Vb Quantum wires
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
78.55.Cr III-V semiconductors

Three-dimensional photoluminescence mapping and emission anisotropy of single gold nanorods

Frank Wackenhut, Antonio Virgilio Failla, Tina Züchner, Mathias Steiner, and Alfred J. Meixner

Appl. Phys. Lett. 100, 263102 (2012); http://dx.doi.org/10.1063/1.4729152 (4 pages) | Cited 5 times

Online Publication Date: 25 June 2012

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We use raster-scanning confocal microscopy in combination with radially and azimuthally polarized laser excitation for mapping the three-dimensional (3D) orientation of individual spatially isolated gold nanorods (GNRs). The simultaneous acquisition of both the elastic scattering patterns and the one-photon luminescence patterns of the same GNR allows for determining both the particle position and the orientation with high precision. By analyzing experimental patterns and comparing them to theoretical results obtained by computer simulations, we establish a complete 3D photoluminescence map of single GNRs. Both elastic scattering and luminescence patterns of the same particle are found to display modifications of the refractive index of the dielectric environment. The polarization dependence of GNRs photoluminescence suggests a plasmon-mediated process.
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78.67.Qa Nanorods
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.55.Hx Other solid inorganic materials

Kinetics of axial composition evolution in multi-component alloy nanowires

H. Ye, Z. Y. Yu, S. Kodambaka, and V. B. Shenoy

Appl. Phys. Lett. 100, 263103 (2012); http://dx.doi.org/10.1063/1.4731628 (4 pages) | Cited 1 time

Online Publication Date: 25 June 2012

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The axial composition profiles in two-component alloy semiconductor nanowires are theoretically studied based on a comprehensive transient growth model which accounts for both surface diffusion and direct impingement of atoms to catalyst. The composition variation derives from the different growth rates contributed by each component. Our simulations reveal that the component with larger (smaller) diffusivity will segregate near the bottom (top) of the nanowire. In the presence (absence) of direct deposition on nanowire sidewalls, the steady state alloy composition is determined by the ratio of effective diffusion lengths (impingement rates to the catalyst).
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81.16.-c Methods of micro- and nanofabrication and processing
68.35.Dv Composition, segregation; defects and impurities
68.35.Fx Diffusion; interface formation
66.30.Pa Diffusion in nanoscale solids
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)
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Spontaneous formation of double helical structure due to interfacial adhesion

Xiang-Ying Ji, Meng-Qiang Zhao, Fei Wei, and Xi-Qiao Feng

Appl. Phys. Lett. 100, 263104 (2012); http://dx.doi.org/10.1063/1.4731199 (5 pages) | Cited 2 times

Online Publication Date: 26 June 2012

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Many quasi-one-dimensional micro/nanomaterials assume double or multi-stranded helical conformations, but the reasons are still unclear. On the basis of continuum mechanics analysis, we demonstrate that interfacial adhesion is a significant physical mechanism responsible for the formation of some double helices, especially at micro and nano scales and for soft materials. With the formation of a double helical structure by two nanowires, surface energy decreases while elastic strain energy increases. Their competition dictates the global morphology of adhered micro/nanowires or tubes. The theoretical model agrees well with relevant experiments.
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68.35.Np Adhesion
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.D- Elasticity
61.46.Np Structure of nanotubes (hollow nanowires)
62.23.Hj Nanowires
65.40.gp Surface energy

Gas field ion source current stability for trimer and single atom terminated W(111) tips

Radovan Urban, Jason L. Pitters, and Robert A. Wolkow

Appl. Phys. Lett. 100, 263105 (2012); http://dx.doi.org/10.1063/1.4726112 (4 pages) | Cited 1 time

Online Publication Date: 26 June 2012

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Tungsten W(111) oriented trimer-terminated tips as well as single atom tips, fabricated by a gas and field assisted etching and evaporation process, were investigated with a view to scanning ion microscopy and ion beam writing applications. In particular, ion current stability was studied for helium and neon imaging gases. Large ion current fluctuations from individual atomic sites were observed when a trimer-terminated tip was used for the creation of neon ion beam. However, neon ion current was stable when a single atom tip was employed. No such current oscillations were observed for either a trimer or a single atom tip when imaged with helium.
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81.65.Cf Surface cleaning, etching, patterning
68.43.Mn Adsorption kinetics
61.80.Jh Ion radiation effects
07.77.Ka Charged-particle beam sources and detectors
07.79.-v Scanning probe microscopes and components

Effect of oxygen deficiency on SrTiO3(001) surface reconstructions

Ryota Shimizu, Katsuya Iwaya, Takeo Ohsawa, Susumu Shiraki, Tetsuya Hasegawa, Tomihiro Hashizume, and Taro Hitosugi

Appl. Phys. Lett. 100, 263106 (2012); http://dx.doi.org/10.1063/1.4730409 (4 pages) | Cited 1 time

Online Publication Date: 26 June 2012

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The contribution of oxygen deficiencies to SrTiO3(001) surface reconstructions is studied using low-energy electron diffraction and scanning tunneling microscopy. We have prepared a SrTiO3 sample with spatially graded oxygen deficiencies, in which R33.7°-(math×math), (2×1), and R26.6°-(math×math) surface reconstructions are observed while increasing the amount of oxygen deficiencies. This indicates that oxygen nonstoichiometry has an influence on the formation of various surface reconstructions as one of the important factors. This concept is also applicable to other transition metal oxides to prepare atomically ordered surfaces in a reproducible manner.
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68.35.bt Other materials
61.66.Bi Elemental solids
61.66.Dk Alloys
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)

Synchrotron x-ray nano-tomography characterization of the sintering of multilayered systems

Zilin Yan, Olivier Guillon, Steve Wang, Christophe L. Martin, Chul-Seung Lee, and Didier Bouvard

Appl. Phys. Lett. 100, 263107 (2012); http://dx.doi.org/10.1063/1.4730625 (4 pages)

Online Publication Date: 26 June 2012

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Synchrotron x-ray nano-tomography was used to characterize the microstructures of multi-layer ceramic capacitors before and after sintering. 3D microstructures of the same sample were reconstructed and quantitatively analyzed. The discontinuities observed in inner electrodes were found to originate from initial heterogeneities of nickel powders in the electrodes. They are supposed to grow due to the constraint of adjacent dielectric layers. Dielectric layers show anisotropic shrinkage with a decrease in density as function of layer position in the multilayer.
Show PACS
84.32.Tt Capacitors
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