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23 Jul 2012

Volume 101, Issue 4, Articles (04xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 101, 043101 (2012); http://dx.doi.org/10.1063/1.4737152 (4 pages)

Toshiaki Tanigaki, Yoshikatsu Inada, Shinji Aizawa, Takahiro Suzuki, Hyun Soon Park, Tsuyoshi Matsuda, Akira Taniyama, Daisuke Shindo, and Akira Tonomura
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Enhanced magnetic and dielectric properties of Eu and Co co-doped BiFeO3 nanoparticles

Kaushik Chakrabarti, Kajari Das, Babusona Sarkar, Sirshendu Ghosh, S. K. De, Godhuli Sinha, and J. Lahtinen

Appl. Phys. Lett. 101, 042401 (2012); http://dx.doi.org/10.1063/1.4738992 (5 pages) | Cited 8 times

Online Publication Date: 23 July 2012

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Bi1−xEuxFe1−yCoyO3 (x = 0, 0.01; y = 0, 0.01) nanoparticles, having an average size of 13 nm, were prepared by a simple sol gel route. Strong electronegativity of Eu3+ and smaller oxidation-reduction potential of Co3+/Co2+ (0.55 eV) than Fe3+/Fe2+ (1.3 eV) increase the concentration of Fe3+ ions with doping. Distinct magnetic hysteresis and complete saturation of magnetisation indicate the presence of ferromagnetic phase. The successful co-doping of Eu and Co into BiFeO3 (BFO) lattice dramatically enhances the saturation magnetization (Ms) and coercivity (Hc) by about 20 times than that of pure BiFeO3. A large value of dielectric constant of about 650, low loss (<0.001), and small leakage current density (1.79 × 10−8 A/cm2) are observed for the co-doped sample.
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75.75.Cd Fabrication of magnetic nanostructures
75.50.Tt Fine-particle systems; nanocrystalline materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
77.22.Ch Permittivity (dielectric function)
77.22.Gm Dielectric loss and relaxation
81.16.-c Methods of micro- and nanofabrication and processing

Magnetoelastic resonance sensor for remote strain measurements

Thomas Huber, Bernhard Bergmair, Christoph Vogler, Florian Bruckner, Gino Hrkac, and Dieter Suess

Appl. Phys. Lett. 101, 042402 (2012); http://dx.doi.org/10.1063/1.4735340 (3 pages)

Online Publication Date: 23 July 2012

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A low cost passive wireless strain sensor is proposed. The basis of the sensor is formed by two softmagnetic magnetostrictive ribbons. The first magnetostrictive ribbon transforms mechanical stress into a stress dependent magnetic field. The second ribbon senses this field by magnetoacoustic oscillations. The resonance frequency directly depends on the applied mechanical stress. For the proposed sensor, a gauge factor Gf, which is defined as the relative change of the resonance frequency divided by the strain ɛ, of Gf = 380 is obtained. This is significantly higher than the gauge factor of standard metal foil strain gages.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
07.10.Pz Instruments for strain, force, and torque
75.80.+q Magnetomechanical effects, magnetostriction
85.70.Ec Magnetostrictive, magnetoacoustic, and magnetostatic devices

Interface induced inverse spin Hall effect in bismuth/permalloy bilayer

Dazhi Hou, Z. Qiu, K. Harii, Y. Kajiwara, K. Uchida, Y. Fujikawa, H. Nakayama, T. Yoshino, T. An, K. Ando, Xiaofeng Jin, and E. Saitoh

Appl. Phys. Lett. 101, 042403 (2012); http://dx.doi.org/10.1063/1.4738786 (4 pages) | Cited 1 time

Online Publication Date: 24 July 2012

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Inverse spin Hall effect has been investigated in bismuth(Bi)/permalloy(Py) bilayer films by using the spin pumping at room temperature. From the ferromagnetic-resonance-spectrum linewidth data, Bi is proved to be a good spin sink in our structure. We measured inverse spin Hall voltage and conductance of the Bi/Py bilayer and found that the inverse spin Hall current, Ic, decreases with increasing the Bi thickness, which is in contrast to the former understanding in similar bilayer systems, e.g., Pt/Py. We constructed a model to explain the thickness dependence of Ic quantitatively, in which spin transport modulation near Bi/Py interface is considered.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance
72.20.My Galvanomagnetic and other magnetotransport effects
72.25.Mk Spin transport through interfaces
75.50.Bb Fe and its alloys
75.70.Ak Magnetic properties of monolayers and thin films

Huge Goos-Hänchen effect for spin waves: A promising tool for study magnetic properties at interfaces

Yu. S. Dadoenkova, N. N. Dadoenkova, I. L. Lyubchanskii, M. L. Sokolovskyy, J. W. Kłos, J. Romero-Vivas, and M. Krawczyk

Appl. Phys. Lett. 101, 042404 (2012); http://dx.doi.org/10.1063/1.4738987 (5 pages)

Online Publication Date: 24 July 2012

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A possibility to observe huge lateral shift (Goos-Hänchen effect) of exchange spin wave reflected from the interface of two ferromagnetic materials is theoretically investigated. The strong dependence of this effect on the exchange coupling between two magnetic media as well as on the magnetic field is obtained. We show that nonzero interlayer exchange is necessary to observe the lateral shift of reflected spin-wave, and this shift can reach values up to a few hundreds of wavelengths. The observed effect can be a useful tool in investigation of the magnetic coupling between two magnetic materials also through nonmagnetic spacer.
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75.30.Ds Spin waves
75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)

Interfacial current-induced torques in Pt/Co/GdOx

Satoru Emori, David C. Bono, and Geoffrey S. D. Beach

Appl. Phys. Lett. 101, 042405 (2012); http://dx.doi.org/10.1063/1.4737899 (4 pages) | Cited 1 time

Online Publication Date: 24 July 2012

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Current-driven domain wall (DW) motion is investigated in Pt/Co/GdOx nanostrips with perpendicular magnetic anisotropy. Measurements of the propagation field and the energy barrier for thermally activated DW motion reveal a large current-induced torque equivalent to an out-of-plane magnetic field of ∼60 Oe per 1011 A/m2. This same field-to-current scaling is shown to hold in both the slow thermally activated and fast near-flow regimes of DW motion. The current-induced torque decreases with 4 Å of Pt decorating the Co/GdOx interface and vanishes entirely with Pt replacing GdOx, suggesting that the Co/GdOx interface contributes directly to highly efficient current-driven DW motion.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.75.Fk Domain structures in nanoparticles
75.30.Gw Magnetic anisotropy
75.60.Ch Domain walls and domain structure

Evidence of oxygen-vacancy-induced ferromagnetic order in single crystal Mn-doped SrTiO3

Srimanta Middey, Carlo Meneghini, and Sugata Ray

Appl. Phys. Lett. 101, 042406 (2012); http://dx.doi.org/10.1063/1.4738785 (4 pages) | Cited 1 time

Online Publication Date: 25 July 2012

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The appearance of ferromagnetic order in the presence of oxygen vacancies has been investigated in dilute Mn-doped SrTiO3 single crystals. The sample without vacancy is paraelectric and paramagnetic down to low temperature. However, incorporation of vacancy makes the system metallic and clear ferromagnetic hysteresis loop is observed at low temperature. X-ray diffraction, x-ray absorption near edge spectroscopy measurement do not reveal any signature of secondary magnetic phase. Diffuse reflectivity measurement negates the bound magnetic polaron model for ferromagnetism in the reduced system and thus spontaneous magnetism suggests the possibility of a carrier-mediated Ruderman-Kittel-Kasuya-Yosida mechanism.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
78.70.Dm X-ray absorption spectra
61.72.jd Vacancies
71.70.Gm Exchange interactions
75.50.Dd Nonmetallic ferromagnetic materials

Biaxial strain effect of spin dependent tunneling in MgO magnetic tunnel junctions

Ajeesh M. Sahadevan, Ravi K. Tiwari, Gopinadhan Kalon, Charanjit S. Bhatia, Mark Saeys, and Hyunsoo Yang

Appl. Phys. Lett. 101, 042407 (2012); http://dx.doi.org/10.1063/1.4738787 (5 pages) | Cited 1 time

Online Publication Date: 25 July 2012

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We study the effect of strain on magnetic tunnel junctions induced by a diamond like carbon (DLC) film. The junction resistance as well as the tunnel magnetoresistance (TMR) reduces with the DLC film. Non-equilibrium Green’s function quantum transport calculations show that the application of biaxial strain increases the conductance for both the parallel and anti-parallel configurations. However, the conductance for the minority channel and for the anti-parallel configuration is significantly more sensitive to strain, which drastically increases transmission through a MgO tunnel barrier, therefore, the TMR ratio decreases with biaxial strain.
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73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
75.70.Ak Magnetic properties of monolayers and thin films
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)

Spectroscopic defect imaging in magnetic nanostructure arrays

Han-Jong Chia, Feng Guo, L. M. Belova, and R. D. McMichael

Appl. Phys. Lett. 101, 042408 (2012); http://dx.doi.org/10.1063/1.4738789 (4 pages) | Cited 1 time

Online Publication Date: 25 July 2012

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We introduce a method for imaging defective structures in an array of magnetic nanodevices using ferromagnetic resonance force microscopy with contrast between normal and defective devices provided through differences in resonance condition. In a demonstration of this technique, two dimensional scans of an array resolve not only intentional differences in resonant field between 200 nm circular dots and an intentional oval “defect,” but also smaller differences between the nominally identical circular dots in the array.
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85.70.-w Magnetic devices
07.79.Pk Magnetic force microscopes

Nanomagnetism of cobalt ferrite-based spin filters probed by spin-polarized tunneling

Sylvia Matzen, Jean-Baptiste Moussy, Richard Mattana, Karim Bouzehouane, Cyrile Deranlot, and Frédéric Petroff

Appl. Phys. Lett. 101, 042409 (2012); http://dx.doi.org/10.1063/1.4738790 (4 pages) | Cited 1 time

Online Publication Date: 25 July 2012

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The magnetism of ferrite ultrathin films has been probed at nanoscale by spin-polarized tunneling transport in CoFe2O4-based room-temperature spin filters. By significantly reducing the Pt/CoFe2O4/Al2O3/Co junctions’ size (cross sections ∼5 nm) in comparison with usual microjunctions, transport through a ferrite single magnetic domain has been achieved. Our tunnel magnetoresistance measurements at the nanoscale have revealed very well defined resistance states and the generation of the highest spin filtering efficiency (−8%) at room temperature. A uniaxial magnetic anisotropy has been evidenced in CoFe2O4, showing that these magnetotransport measurements offer a unique probe of a single magnetic domain in ferrite ultrathin films.
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85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
FREE

Spin waves turning a corner

K. Vogt, H. Schultheiss, S. Jain, J. E. Pearson, A. Hoffmann, S. D. Bader, and B. Hillebrands

Appl. Phys. Lett. 101, 042410 (2012); http://dx.doi.org/10.1063/1.4738887 (3 pages) | Cited 4 times

Online Publication Date: 25 July 2012

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We studied the propagation of spin waves in a Ni81Fe19 micro-waveguide comprising a smooth, S-shaped bend using Brillouin light scattering microscopy. A direct current flowing through a gold wire underneath the Ni81Fe19 provides a local magnetic field, which maintains a transverse magnetization around the bend of the waveguide. It is demonstrated that spin-wave propagation inside the bend can be realized in contrast to the case of an externally applied magnetic field, which generates strong inhomogeneities in the internal effective field distribution, preventing any spin-wave propagation across the bend.
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75.30.Ds Spin waves
75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)

Influence of rare earth moment ordering on magnetic entropy change in Nd0.5Sr0.5CoO3

Pawan Kumar and R. Mahendiran

Appl. Phys. Lett. 101, 042411 (2012); http://dx.doi.org/10.1063/1.4738889 (5 pages) | Cited 2 times

Online Publication Date: 25 July 2012

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Field-cooled magnetization of Nd0.5Sr0.5CoO3 shows an anomalous maximum at T* = 76 K ≪ TC = 228 K, where TC is the ferromagnetic Curie temperature of the Co-sublattice. While T* shows a systematic shift with increasing magnetic field(H), the maximum does not disappear even at H = 7 T. We suggest that Nd(4f) moment is polarized by the molecular field of Co sublattice and order antiparallel to the Co(3d) spin lattice below T*, which causes magnetic entropy to decrease (increase) with increasing H for T > T* (T below T*). Critical exponents associated with the ferromagnetic phase transition were analyzed and found to be close to the mean-field model values.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.50.Dd Nonmetallic ferromagnetic materials

Wireless and passive temperature indicator utilizing the large hysteresis of magnetic shape memory alloys

Bernhard Bergmair, Jian Liu, Thomas Huber, Oliver Gutfleisch, and Dieter Suess

Appl. Phys. Lett. 101, 042412 (2012); http://dx.doi.org/10.1063/1.4739836 (4 pages)

Online Publication Date: 26 July 2012

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An ultra-low cost, wireless magnetoelastic temperature indicator is presented. It comprises a magnetostrictive amorphous ribbon, a Ni-Mn-Sn-Co magnetic shape memory alloy with a highly tunable transformation temperature, and a bias magnet. It allows to remotely detect irreversible changes due to transgressions of upper or lower temperature thresholds. Therefore, the proposed temperature indicator is particularly suitable for monitoring the temperature-controlled supply chain of, e.g., deep frozen and chilled food or pharmaceuticals.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.80.+q Magnetomechanical effects, magnetostriction
75.50.Kj Amorphous and quasicrystalline magnetic materials

Remarkable current-enhanced photoconductivity in oxygen-deficient La7/8Sr1/8MnO3−δ thin film

L. Hu, Z. G. Sheng, Y. N. Huang, W. H. Song, and Y. P. Sun

Appl. Phys. Lett. 101, 042413 (2012); http://dx.doi.org/10.1063/1.4739842 (4 pages) | Cited 1 time

Online Publication Date: 26 July 2012

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Effects of light and electrical current on the electrical transport properties of oxygen-deficient La7/8Sr1/8MnO3−δ thin films have been investigated. The light illumination causes a resistance drop to show photoconductivity effect. Moreover, the photoconductivity can be remarkably enhanced by increasing the electrical current, that is, it exhibits current-enhanced photoconductivity (CEPC) effect. The CEPC ratio achieves 80% at 300 K with light intensity of 56.7 mW cm−2 and electrical current of 20 μA. The phenomena are explained by a photoinduced localized insulator-metal transition and stabilization of conducting paths by the electrical current. These results may be important for practical applications in photoelectric devices.
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73.50.Pz Photoconduction and photovoltaic effects
73.61.Ng Insulators
71.30.+h Metal-insulator transitions and other electronic transitions
72.40.+w Photoconduction and photovoltaic effects

Half metallic character of NiMoO3 driven by the electron correlation and spin-orbit coupling

J. Wang and Z. J. Wu

Appl. Phys. Lett. 101, 042414 (2012); http://dx.doi.org/10.1063/1.4739847 (4 pages)

Online Publication Date: 26 July 2012

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The semiconducting behavior of NiCrO3 is driven by the strong electron correlation of transition metal 3d electrons. By substituting Cr with more itinerant 4d transition metal Mo, NiMoO3 is designed and studied by the first principles. It is isostructural and isovalent to NiCrO3. Compensated half metal is obtained when considering electron correlation alone. Inclusion both spin-orbit coupling and electron correlation induce a large orbital moment on Ni (−0.23 μB) due to the Coulomb enhanced spin-orbit coupling. This makes NiMoO3 a half metallic ferrimagnet with nonintegral magnetic moment. The orbital moment of Mo is negligible. Pressure destroys the half metallic character.
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71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
75.30.Cr Saturation moments and magnetic susceptibilities
75.50.Gg Ferrimagnetics
71.15.Dx Computational methodology (Brillouin zone sampling, iterative diagonalization, pseudopotential construction)
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons
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Pressure effects on the superconducting thin film Ba1−xKxFe2As2

Eunsung Park, Nam Hoon Lee, Won Nam Kang, and Tuson Park

Appl. Phys. Lett. 101, 042601 (2012); http://dx.doi.org/10.1063/1.4738783 (4 pages)

Online Publication Date: 23 July 2012

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We report electrical resistivity measurements on a high-quality Ba1−xKxFe2As2 thin film (x = 0.4) under pressure. The superconducting transition temperature (=39.95 K) of the optimally doped thin film shows a dome shape with pressure, reaching a maximal value 40.8 K at 11.8 kbar. The unusually high superconducting transition temperature and its anomalous pressure dependence are ascribed to a lattice mismatch between the LaAlO3 substrate and the thin film. The local temperature exponent of the resistivity (n = dlnΔρ/dlnT) shows a funnel shape around the optimal pressure, suggesting that fluctuations associated with the anomalous normal state are responsible for high-temperature superconductivity.
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74.25.F- Transport properties
74.70.Xa Pnictides and chalcogenides
74.62.-c Transition temperature variations, phase diagrams
74.78.-w Superconducting films and low-dimensional structures

Noise properties of high-Tc superconducting flux transformers fabricated using chemical-mechanical polishing

M. Chukharkin, A. Kalabukhov, J. F. Schneiderman, F. Öisjöen, O. Snigirev, Z. Lai, and D. Winkler

Appl. Phys. Lett. 101, 042602 (2012); http://dx.doi.org/10.1063/1.4738782 (5 pages) | Cited 1 time

Online Publication Date: 24 July 2012

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Reproducible high-temperature superconducting multilayer flux transformers were fabricated using chemical mechanical polishing. The measured magnetic field noise of the flip-chip magnetometer based on one such flux transformer with a 9 × 9 mm2 pickup loop coupled to a bicrystal dc SQUID was 15 fT/Hz1/2 above 2 kHz. We present an investigation of excess 1/f noise observed at low frequencies and its relationship with the microstructure of the interlayer connections within the flux transformer. The developed high-Tc SQUID magnetometers may be advantageous in ultra-low field magnetic resonance imaging and, with improved low frequency noise, magnetoencephalography applications.
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74.40.De Noise and chaos
07.55.Ge Magnetometers for magnetic field measurements
81.65.Ps Polishing, grinding, surface finishing
85.25.Dq Superconducting quantum interference devices (SQUIDs)

Electric-field-induced superconductivity at 9.4 K in a layered transition metal disulphide MoS2

Kouji Taniguchi, Akiyo Matsumoto, Hidekazu Shimotani, and Hidenori Takagi

Appl. Phys. Lett. 101, 042603 (2012); http://dx.doi.org/10.1063/1.4740268 (3 pages) | Cited 5 times

Online Publication Date: 27 July 2012

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Electro-static carrier doping was attempted in a layered transition metal disulphide MoS2 by constructing an electric double-layer transistor with an ionic liquid. With the application of gate voltage VG higher than 3 V, a metallic behavior was observed in the MoS2 channel. We found an onset of electric field-induced superconductivity in the field induced metallic phase. A maximum TC ∼ 9.4 K was observed, which could be higher than those in chemically doped bulk materials.
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74.20.Pq Electronic structure calculations
74.70.-b Superconducting materials other than cuprates

Frequency division multiplexing readout and simultaneous manipulation of an array of flux qubits

M. Jerger, S. Poletto, P. Macha, U. Hübner, E. Il’ichev, and A. V. Ustinov

Appl. Phys. Lett. 101, 042604 (2012); http://dx.doi.org/10.1063/1.4739454 (4 pages) | Cited 1 time

Online Publication Date: 27 July 2012

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An important desired ingredient of superconducting quantum circuits is a readout scheme whose complexity does not increase with the number of qubits involved in the measurement. Here, we present a readout scheme employing a single microwave line, which enables simultaneous readout of multiple qubits. Consequently, scaling up superconducting qubit circuits is no longer limited by the readout apparatus. Parallel readout of 6 flux qubits using a frequency division multiplexing technique is demonstrated, as well as simultaneous manipulation and time resolved measurement of 3 qubits. We discuss how this technique can be scaled up to read out hundreds of qubits on a chip.
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03.67.Lx Quantum computation architectures and implementations
85.25.Am Superconducting device characterization, design, and modeling
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Direct physical evidence of mechanisms of leakage and equivalent oxide thickness reduction in metal-insulator-metal capacitors based on RuOx/TiOx/SrxTiyOz/TiN stacks

M. A. Pawlak, J. Swerts, M. Popovici, B. Kaczer, M.-S. Kim, W.-C. Wang, K. Tomida, B. Govoreanu, J. Delmotte, V. V. Afanas’ev, M. Schaekers, W. Vandervorst, and J. A. Kittl

Appl. Phys. Lett. 101, 042901 (2012); http://dx.doi.org/10.1063/1.4737871 (3 pages) | Cited 2 times

Online Publication Date: 23 July 2012

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We present direct physical evidence supporting the mechanisms we proposed to explain low leakage (Jg) and low equivalent oxide thickness (EOT) in RuOx/TiOx/Sr-rich SrxTiyOz(STO)/TiN metal-insulator-metal capacitors which achieve Jg = 10−7 A/cm2 (1 V) at 0.45 nm EOT: (1) healing of STO traps by O incorporation from RuOx during STO crystallization anneal for low leakage and (2) TiOx/Sr-rich STO intermixing during STO crystallization anneal resulting in a higher Ti-content, higher k-value STO layer for low EOT. Proof of oxygen incorporation into the STO layer from the RuOx electrode as well as of TiOx/STO intermixing were obtained by secondary ion mass spectrometry performed on samples fabricated using O18 for Ru oxidation. We also show excellent match between measured leakage vs. voltage and simulations of trap-assisted leakage with asymmetric trap profiles due to STO trap healing next to RuOx, further supporting our model.
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84.32.Tt Capacitors

Strongly coupled phase transition in ferroelectric/correlated electron oxide heterostructures

Lu Jiang, Woo Seok Choi, Hyoungjeen Jeen, Takeshi Egami, and Ho Nyung Lee

Appl. Phys. Lett. 101, 042902 (2012); http://dx.doi.org/10.1063/1.4738784 (4 pages)

Online Publication Date: 24 July 2012

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We fabricated ultrathin ferroelectric/correlated electron oxide heterostructures composed of the ferroelectric Pb(Zr0.2Ti0.8)O3 and the correlated electron oxide (CEO) La0.8Sr0.2MnO3 on SrTiO3 substrates by pulsed laser epitaxy. The hole accumulation in the ultrathin CEO layer was substantially modified by heterostructuring with the ferroelectric layer, resulting in an insulator-metal transition. In particular, our thickness dependent study showed that drastic changes in transport and magnetic properties were strongly coupled to the modulation of charge carriers by ferroelectric field effect, which was confined to the vicinity of the interface. Thus, our results provide crucial evidence that strong ferroelectric field effect control can be achieved in ultrathin (10 nm) heterostructures, yielding at least a 100 000-fold change in resistivity.
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71.30.+h Metal-insulator transitions and other electronic transitions
72.60.+g Mixed conductivity and conductivity transitions
73.40.Ns Metal-nonmetal contacts
77.80.bn Strain and interface effects
68.35.Ct Interface structure and roughness

Valence band offset at the amorphous hydrogenated boron nitride-silicon (100) interface

S. W. King, M. French, J. Bielefeld, M. Jaehnig, M. Kuhn, G. Xu, and B. French

Appl. Phys. Lett. 101, 042903 (2012); http://dx.doi.org/10.1063/1.4739474 (4 pages) | Cited 1 time

Online Publication Date: 24 July 2012

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In order to understand the fundamental behavior of various boron nitride heterostructure devices, we have utilized x-ray photoelectron spectroscopy to determine the valence band offset (VBO) present at interfaces formed by plasma enhanced chemical vapor deposition of hexagonal amorphous hydrogenated boron nitride (a-BN:H) on Si (100) substrates. For an a-BN:H/Si interface with some interfacial SiNx and SiBx bonding, we determined the valence band offset to be 1.9 ± 0.15 eV. The conduction band offset was likewise determined to be 2.2 ± 0.2 eV with a type I alignment.
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71.23.Cq Amorphous semiconductors, metallic glasses, glasses
79.60.Bm Clean metal, semiconductor, and insulator surfaces
81.05.Ea III-V semiconductors
81.05.Gc Amorphous semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
61.43.Dq Amorphous semiconductors, metals, and alloys

Local surface potential distribution and its relaxation in ferroelectric poly(vinylidenefluoride-co-trifluoroethylene) thin films

Hyunwoo Choi, Jongin Hong, and Kwangsoo No

Appl. Phys. Lett. 101, 042904 (2012); http://dx.doi.org/10.1063/1.4734870 (3 pages)

Online Publication Date: 25 July 2012

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Local surface potential distributions and their relaxation behavior in ferroelectric poly(vinylidene fluoride-co-trifluoroethylene) thin films were investigated using Kelvin-probe force microscopy. All surface potentials were negative regardless of the sign of the applied voltage because of the intrinsic negative charges that originated from the self-aligned region of dipoles at the ferroelectric/electrode interface. Importantly, the intrinsic charges would have a remarkable influence on the reliability of written data.
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77.22.Gm Dielectric loss and relaxation
77.80.Fm Switching phenomena
77.84.Jd Polymers; organic compounds
68.55.am Polymers and organics
77.80.Jk Relaxor ferroelectrics
61.41.+e Polymers, elastomers, and plastics

Bipolar piezoelectric fatigue of Bi(Zn0.5Ti0.5)O3-(Bi0.5K0.5)TiO3-(Bi0.5Na0.5)TiO3 Pb-free ceramics

Eric A. Patterson and David P. Cann

Appl. Phys. Lett. 101, 042905 (2012); http://dx.doi.org/10.1063/1.4738770 (4 pages)

Online Publication Date: 26 July 2012

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The piezoelectric fatigue behavior of Pb-free ceramics based on solid solutions of Bi(Zn0.5Ti0.5)O3-(Bi0.5K0.5)TiO3-(Bi0.5Na0.5)TiO3 was characterized at 50 kV/cm after 106 bipolar cycles. Ferroelectric compositions containing 2.5% Bi(Zn0.5Ti0.5)O3 exhibited only minor losses in maximum strain (∼10%). In compositions with 5% Bi(Zn0.5Ti0.5)O3 that exhibit large electric field-induced strains, the electromechanical strain actually increased 4%, exhibiting essentially fatigue free behavior. This finding demonstrates that these materials have excellent potential for demanding high cycle applications such as microelectromechanical systems actuators.
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77.65.Ly Strain-induced piezoelectric fields
77.80.-e Ferroelectricity and antiferroelectricity
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.me Fatigue

Effects of Ca-substitution on structural, dielectric, and ferroelectric properties of Ba5SmTi3Nb7O30 tungsten bronze ceramics

Kun Li, Xiao Li Zhu, Xiao Qiang Liu, and Xiang Ming Chen

Appl. Phys. Lett. 101, 042906 (2012); http://dx.doi.org/10.1063/1.4739841 (4 pages) | Cited 1 time

Online Publication Date: 26 July 2012

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Effects of Ca-substitution on the crystal structure and dielectric properties were investigated for Ba5SmTi3Nb7O30 tungsten bronze ceramics. The tetragonal tungsten bronze structure in space group P4bm was determined in Ba4CaSmTi3Nb7O30 ceramics, which was the same for Ba5SmTi3Nb7O30. The c-axis off center displacement in both B1 and B2-sites for Ba5SmTi3Nb7O30 was slightly larger than that in BaCaSmTi3Nb7O30, while the distortion of Ti/Nb(2)O6 octahedra in Ba4CaSmTi3Nb7O30 was obviously suppressed compared with that in Ba5SmTi3Nb7O30. Though there were also two dielectric anomalies observed in Ba4CaSmTi3Nb7O30, the relaxor ferroelectric nature was changed to the normal ferroelectric one, and both the endothermal peak in differential scanning calorimetry curve and the significant thermal hysteresis of the phase transition confirmed the first order ferroelectric transition. These results indicated that the ferroelectric nature of Ba4CaSmTi3Nb7O30 was more close to that in Ba4Sm2Ti4Nb6O30, and it could be concluded that the ferroelectric nature in filled tungsten bronze ceramics was primarily dominated by the A-site occupation rather than B-site occupation.
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61.66.Fn Inorganic compounds
77.22.Ch Permittivity (dielectric function)
77.22.Gm Dielectric loss and relaxation
77.80.Dj Domain structure; hysteresis
77.80.Jk Relaxor ferroelectrics
77.84.Ek Niobates and tantalates

Atomic-resolution chemical imaging of oxygen local bonding environments by electron energy loss spectroscopy

Julia A. Mundy, Qingyun Mao, Charles M. Brooks, Darrell G. Schlom, and David A. Muller

Appl. Phys. Lett. 101, 042907 (2012); http://dx.doi.org/10.1063/1.4737208 (5 pages) | Cited 4 times

Online Publication Date: 26 July 2012

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Electron energy loss spectroscopy on an aberration-corrected scanning transmission electron microscope was used to map the elemental composition and bonding in a thin film of the multiferroic LuFe2O4 with atomic resolution. A two-dimensional analysis of the fine structure of the O-K edge yielded distinct signals for the two inequivalent oxygen sites in the crystal. Comparison to an ab-initio simulation showed that these two components can be interpreted in terms of the differing hybridization of the O p orbitals to the Lu and Fe d orbitals, thus producing an atomic-resolution map of the local oxygen bonding environment.
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68.55.aj Insulators
77.55.Nv Multiferroic/magnetoelectric films
77.80.-e Ferroelectricity and antiferroelectricity
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
79.20.Uv Electron energy loss spectroscopy
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