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12 Apr 2010

Volume 96, Issue 15, Articles (15xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 96, 153701 (2010); http://dx.doi.org/10.1063/1.3385388 (3 pages)

Sinan Keten and Markus J. Buehler
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Electron-nuclear spin control in charged semiconductor quantum dots by electrical currents through micro-coils

Jungtaek Kim, J. Puls, Y. S. Chen, G. Bacher, and F. Henneberger

Appl. Phys. Lett. 96, 151908 (2010); http://dx.doi.org/10.1063/1.3373591 (3 pages) | Cited 2 times

Online Publication Date: 14 April 2010

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We have fabricated micrometer-sized single-turn coils on top of charged CdSe/ZnSe quantum dot heterostructures by lithographical techniques. Current injection creates magnetic fields in the some 10 mT range, strong enough to modulate the hyperfine interaction. The very low coil inductance allows for generation of fast field transients. We demonstrate local control of the resident electron spin as well as read-out of the nuclear spin state on the 10 ns time scale by electrical current pulses.
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73.21.La Quantum dots
81.07.Ta Quantum dots
81.16.Nd Micro- and nanolithography
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
71.70.Jp Nuclear states and interactions

Structural and antireflective characteristics of catalyst-free GaN nanostructures on GaN/sapphire template for solar cell applications

C. Y. Park, J. M. Lim, J. S. Yu, and Y. T. Lee

Appl. Phys. Lett. 96, 151909 (2010); http://dx.doi.org/10.1063/1.3386538 (3 pages) | Cited 3 times

Online Publication Date: 14 April 2010

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We report the structural and antireflective characteristics of catalyst-free GaN nanostructures on GaN/sapphire template for solar cell applications. The formation of GaN nanostructure depends on the growth temperature. At 530 °C, the nucleation of the initial seed due to the enhanced strain leads to the hexagonal closely packed nanorods. As the growth temperature decreases, the depression of atomic Ga transport changes the films into nanocolumns, and then the nanorods. The catalyst-free GaN nanorods have wurtzite structure and good single crystalline quality. The GaN nanorods exhibit a remarkably low reflectance over a wide-angle broadband spectrum, enhancing the antireflective property of GaN surface.
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68.55.ag Semiconductors
42.79.Wc Optical coatings
78.67.Qa Nanorods
78.30.Fs III-V and II-VI semiconductors
78.66.Fd III-V semiconductors
78.40.Fy Semiconductors

Dynamic smoothing of nanocomposite films

Y. T. Pei, A. A. Turkin, C. Q. Chen, K. P. Shaha, D. Vainshtein, and J. Th. M. De Hosson

Appl. Phys. Lett. 96, 151910 (2010); http://dx.doi.org/10.1063/1.3394019 (3 pages) | Cited 2 times

Online Publication Date: 14 April 2010

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In contrast to the commonly observed dynamic roughening in film growth we have observed dynamic smoothing in the growth of diamondlike-carbon nanocomposite (TiC/a-C) films up to 1.5 μm thickness. Analytical and numerical simulations, based on the Edwards–Wilkinson model and the Mullins model, visualize the effect of the diffusivity parameters and the noise strength on the interface evolution of dynamic smoothing. The prediction is in a good agreement with the measured roughness evolution. High-resolution transmission electron microscopy shows that the formation of an amorphous front layer 2 nm thick excludes possible influence of nanocrystallites on the dynamic growth behavior of the nanocomposite film.
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81.05.uj Diamond/nanocarbon composites
68.55.-a Thin film structure and morphology
81.16.-c Methods of micro- and nanofabrication and processing
68.37.Og High-resolution transmission electron microscopy (HRTEM)
68.35.Ct Interface structure and roughness
66.30.-h Diffusion in solids
61.46.-w Structure of nanoscale materials

Theoretical investigation of optical polarization properties in Al-rich AlGaN quantum wells with various substrate orientations

A. Atsushi Yamaguchi

Appl. Phys. Lett. 96, 151911 (2010); http://dx.doi.org/10.1063/1.3409121 (3 pages) | Cited 14 times

Online Publication Date: 15 April 2010

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The optical polarization properties of Al-rich AlGaN thin quantum wells on AlN substrates with various substrate orientations are numerically calculated using a 6×6 k⋅p Hamiltonian. The calculation results show that the predominant polarization direction abruptly switches from the in-plane direction to the c-axis direction at an Al composition of ∼ 0.76 in quantum wells on c-plane substrates. It is also shown that the polarization characteristics drastically change by small inclination of the substrates due to valence band mixing effects. It is found that the use of the vicinal substrates as well as semipolar and nonpolar substrates could be beneficial in improving optical device performance.
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78.67.De Quantum wells
71.20.Nr Semiconductor compounds
78.66.Fd III-V semiconductors

Optimization of silica–silver–gold layered nanoshell for large near-field enhancement

D. J. Wu and X. J. Liu

Appl. Phys. Lett. 96, 151912 (2010); http://dx.doi.org/10.1063/1.3398032 (3 pages) | Cited 7 times

Online Publication Date: 15 April 2010

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The near-field enhancement of silica–silver–gold (SSG) nanoshells has been investigated by using Mie theory. If the thickness of Au shell is smaller than 5 nm, the maximum of near-field for SSG increases first and then decreases with increasing Ag layer thickness. Thus, the near-field for SSG can be modified by Ag layer and can possess more excellent near-field enhancement. If the thickness of Au shell is larger than 10 nm, the maximum of near-field of SSG nanoshell decreases with increasing Ag layer thickness. We further discuss the influence of Au shell thickness on the near-field of SSG nanoshell.
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78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
78.30.-j Infrared and Raman spectra
78.40.-q Absorption and reflection spectra: visible and ultraviolet
61.46.-w Structure of nanoscale materials

Resonant photoluminescent charging of epitaxial graphene

S. D. Lounis, D. A. Siegel, R. Broesler, C. G. Hwang, E. E. Haller, and A. Lanzara

Appl. Phys. Lett. 96, 151913 (2010); http://dx.doi.org/10.1063/1.3396201 (3 pages) | Cited 2 times

Online Publication Date: 16 April 2010

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Photoluminescence spectroscopy (PL) and angle resolved photoemission spectroscopy have been used to study the interaction between epitaxially grown graphene and the silicon carbide (SiC) substrate. We report evidence of an anomalous temperature dependent shift in the Fermi energy with a maximum at 65 K. A similarly anomalous onset of the photoluminescence spectrum is also observed at this temperature. These results are explained by the formation of a Schottky barrier at the graphene/SiC interface, which is also responsible for large electron doping of epitaxially grown graphene films. Moreover, we identify a strong resonance between the sharp no-phonon peaks of the D1 photoluminescence spectrum in SiC and the electronic transition across the barrier, suggesting that epitaxial graphene might be also used to selectively detect photons of precise energies.
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78.66.Tr Fullerenes and related materials
73.30.+y Surface double layers, Schottky barriers, and work functions
78.55.Hx Other solid inorganic materials
73.22.Pr Electronic structure of graphene
68.55.-a Thin film structure and morphology
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Size dependence of transverse electric transport in single ZnO nanoneedles

Ya Yang, Junjie Qi, Wen Guo, Jing Zhao, Xueqiang Wang, and Yue Zhang

Appl. Phys. Lett. 96, 152101 (2010); http://dx.doi.org/10.1063/1.3386571 (3 pages) | Cited 1 time

Online Publication Date: 12 April 2010

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We report a size dependence of transverse electric transport in single ZnO nanoneedles with diameters ranging from 5 to 50 nm. Under the same voltages, the measured transverse current through the single ZnO nanoneedle was found to decrease dramatically with the decreasing diameters from 50 to 20 nm, and no current were detected when the diameters are smaller than 20 nm. A spherical electric transport model is proposed to explore the origin of the size dependence.
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73.63.Nm Quantum wires
72.80.Ey III-V and II-VI semiconductors
72.10.-d Theory of electronic transport; scattering mechanisms

High stability of amorphous hafnium-indium-zinc-oxide thin film transistor

Eugene Chong, Kyoung Chul Jo, and Sang Yeol Lee

Appl. Phys. Lett. 96, 152102 (2010); http://dx.doi.org/10.1063/1.3387819 (3 pages) | Cited 36 times

Online Publication Date: 12 April 2010

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Time dependence of the threshold voltage (Vth) shift in amorphous hafnium-indium-zinc oxide (a-HIZO) thin film transistor has been reported under on-current bias temperature stress measured at 60 °C. X-ray photoelectron spectroscopy results show the decrease in oxygen vacancies by Hf metal cations in a-HIZO systems after annealing process. High stability of a-HIZO systems has been observed due to low charge injection from the channel layer. Hf metal cations have been effectively incorporated into the IZO thin films as a suppressor against both the oxygen deficiencies and the carrier generation.
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85.30.Tv Field effect devices
81.05.Gc Amorphous semiconductors
73.61.Jc Amorphous semiconductors; glasses
79.60.Bm Clean metal, semiconductor, and insulator surfaces
61.72.Cc Kinetics of defect formation and annealing
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Anharmonic effects in ZnO optical phonons probed by Raman spectroscopy

Marius Millot, Ramon Tena-Zaera, Vicente Munoz-Sanjose, Jean-Marc Broto, and Jesus Gonzalez

Appl. Phys. Lett. 96, 152103 (2010); http://dx.doi.org/10.1063/1.3387843 (3 pages) | Cited 3 times

Online Publication Date: 12 April 2010

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We report Raman spectroscopy measurements on ZnO crystals grown by the vapor transport method and annealed. Vacuum annealing is found to yield single crystals with ultra low density of defects. We focus on the optical E2 phonon linewidth temperature dependence in the 10–500 K range. The linewidth decrease at low temperature is analyzed and discussed in the light of anharmonic up- and down-conversion processes, unveiling strongly different behaviors for the two E2 phonons.
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81.10.Bk Growth from vapor
78.55.Et II-VI semiconductors
61.72.Cc Kinetics of defect formation and annealing
63.20.Ry Anharmonic lattice modes
78.30.Fs III-V and II-VI semiconductors
81.05.Dz II-VI semiconductors

Quantum capacitance and density of states of graphene

S. Dröscher, P. Roulleau, F. Molitor, P. Studerus, C. Stampfer, K. Ensslin, and T. Ihn

Appl. Phys. Lett. 96, 152104 (2010); http://dx.doi.org/10.1063/1.3391670 (3 pages) | Cited 13 times

Online Publication Date: 12 April 2010

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We report on measurements of the quantum capacitance in graphene as a function of charge carrier density. A resonant LC-circuit giving high sensitivity to small capacitance changes is employed. The density of states, which is directly proportional to the quantum capacitance, is found to be significantly larger than zero at and around the charge neutrality point. This finding is interpreted to be a result of potential fluctuations with amplitudes of the order of 100 meV in good agreement with scanning single-electron transistor measurements on bulk graphene and transport studies on nanoribbons.
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71.20.Tx Fullerenes and related materials; intercalation compounds
73.61.Wp Fullerenes and related materials
73.50.Dn Low-field transport and mobility; piezoresistance
84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)
72.80.Vp Electronic transport in graphene

Effect of antisite defects on band structure and thermoelectric performance of ZrNiSn half-Heusler alloys

Pengfei Qiu, Jiong Yang, Xiangyang Huang, Xihong Chen, and Lidong Chen

Appl. Phys. Lett. 96, 152105 (2010); http://dx.doi.org/10.1063/1.3396981 (3 pages) | Cited 9 times

Online Publication Date: 14 April 2010

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Band structures for ZrNiSn with Zr/Sn antisite defects are calculated with ab initio methods. Antisite defects shrink the band gap and enhance the density of states slope near the Fermi level, which are favorable to electrical transport properties for intrinsic semiconductors. The degree of Zr/Sn antisite defects are controlled by annealing time experimentally, and measurements show low electrical resistivity and high Seebeck coefficient for unannealed ZrNiSn, which benefits from the modified electronic structure caused by antisite defects. The maximum ZT is 0.64 at 800 K for unannealed ZrNiSn, which is the highest value for ZrNiSn systems without exterior doping.
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71.20.Be Transition metals and alloys
61.72.J- Point defects and defect clusters
71.15.-m Methods of electronic structure calculations
72.15.Jf Thermoelectric and thermomagnetic effects
61.72.Cc Kinetics of defect formation and annealing
71.55.Ak Metals, semimetals, and alloys

Space-charge electric field in photorefractive multiple quantum wells

Xiangxue Zhang, Mohammad Samiullah, and Ping Yu

Appl. Phys. Lett. 96, 152106 (2010); http://dx.doi.org/10.1063/1.3367728 (3 pages) | Cited 1 time

Online Publication Date: 14 April 2010

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We have developed a graphical method to determine the space-charge electric field in photorefractive multiple quantum wells when the photocurrent is dominated by the drift current. The minima and maxima of the space-charge electric field due to space modulated light intensity are obtained from photocurrent measurements under uniform illumination. In addition, we find that the space-charge field depends nonlinearly on the applied electric field and the intensity of light, and changes sharply with the intensity up to a critical intensity beyond which it remains unchanged.
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77.22.Jp Dielectric breakdown and space-charge effects
73.63.Hs Quantum wells
72.40.+w Photoconduction and photovoltaic effects
78.67.De Quantum wells
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials

Atomic resolution in tunneling induced light emission from GaAs(110)

Maria Reinhardt, Guillaume Schull, Philipp Ebert, and Richard Berndt

Appl. Phys. Lett. 96, 152107 (2010); http://dx.doi.org/10.1063/1.3360203 (3 pages) | Cited 2 times

Online Publication Date: 14 April 2010

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A cryogenic scanning tunneling microscope is used to induce band edge luminescence from GaAs(110). The emission intensity varies within the unit mesh of the surface. This atomic resolution reflects variations of the efficiency of hole injection into states at the valence band maximum. Moreover, the hole injection efficiency is modulated by local potential fluctuations due to dopants.
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78.55.Cr III-V semiconductors
73.20.At Surface states, band structure, electron density of states
68.47.Fg Semiconductor surfaces
68.35.bg Semiconductors

Fermi level depinning at the germanium Schottky interface through sulfur passivation

Arun V. Thathachary, K. N. Bhat, Navakanta Bhat, and M. S. Hegde

Appl. Phys. Lett. 96, 152108 (2010); http://dx.doi.org/10.1063/1.3387760 (3 pages) | Cited 7 times

Online Publication Date: 15 April 2010

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We demonstrate the depinning of Fermi level on both p- and n-type germanium after sulfur passivation by aqueous (NH4)2S treatment. Schottky contacts realized using metals with a wide range of work functions produce nearly ideal behavior confirming that the Fermi level is depinned. Examination of the passivated surface using x-ray photoelectron spectroscopy reveals bonding between Ge and sulfur. It is shown that good Ohmic contacts to n-type Ge and a hole barrier height (ϕBp) of 0.6 eV to p-type Ge can be achieved after this passivation treatment, with Zr Schottky contacts. This is the highest ϕBp reported so far.
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73.20.At Surface states, band structure, electron density of states
73.30.+y Surface double layers, Schottky barriers, and work functions
81.65.Rv Passivation
79.60.Jv Interfaces; heterostructures; nanostructures
73.40.Ns Metal-nonmetal contacts

Determination of the sign of g factors for conduction electrons using time-resolved Kerr rotation

C. L. Yang, Junfeng Dai, W. K. Ge, and Xiaodong Cui

Appl. Phys. Lett. 96, 152109 (2010); http://dx.doi.org/10.1063/1.3402769 (3 pages) | Cited 2 times

Online Publication Date: 16 April 2010

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The knowledge of electron g factor is essential for spin manipulation in the field of spintronics and quantum computing. While there exist technical difficulties in determining the sign of g factor in semiconductors by the established magneto-optical spectroscopic methods. We develop a technique to precisely measure the sign and the amplitude of electron g factor in semiconductors using time resolved Kerr rotation.
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07.60.Rd Visible and ultraviolet spectrometers
78.67.De Quantum wells
78.20.Jq Electro-optical effects
78.47.D- Time resolved spectroscopy (>1 psec)
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
73.21.Fg Quantum wells
78.66.Fd III-V semiconductors
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Giant reversible magnetocaloric effect in metamagnetic HoCuSi compound

J. Chen, B. G. Shen, Q. Y. Dong, F. X. Hu, and J. R. Sun

Appl. Phys. Lett. 96, 152501 (2010); http://dx.doi.org/10.1063/1.3386536 (3 pages) | Cited 17 times

Online Publication Date: 12 April 2010

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The magnetic properties and magnetocaloric effect (MCE) of antiferromagnetic HoCuSi compound have been studied. It is found that HoCuSi undergoes a field-induced first order metamagnetic transition from antiferromagnetic (AFM) to ferromagnetic (FM) states below the Néel temperature (TN). A giant MCE without hysteresis loss is observed in HoCuSi around TN. The maximal magnetic entropy change (−ΔSM) and refrigerant capacity are 33.1 J/kgK and 385 J/kg, respectively, for a field change of 0–5 T. The excellent magnetocaloric properties can result from the field-induced AFM-FM transition below TN and the increase in magnetization change caused by the change in lattice volume at TN.
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75.30.Sg Magnetocaloric effect, magnetic cooling
75.50.Ee Antiferromagnetics
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
61.66.Dk Alloys

Gilbert damping in perpendicularly magnetized Pt/Co/Pt films investigated by all-optical pump-probe technique

S. Mizukami, E. P. Sajitha, D. Watanabe, F. Wu, T. Miyazaki, H. Naganuma, M. Oogane, and Y. Ando

Appl. Phys. Lett. 96, 152502 (2010); http://dx.doi.org/10.1063/1.3396983 (3 pages) | Cited 22 times

Online Publication Date: 13 April 2010

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To investigate the correlation between perpendicular magnetic anisotropy and intrinsic Gilbert damping, time-resolved magneto-optical Kerr effect was measured in Pt/Co(dCo)/Pt films. These films showed perpendicular magnetization at dCo = 1.0 nm and a perpendicular magnetic anisotropy energy Kueff that was inversely proportional to dCo. With an analysis based on the Landau–Lifshitz–Gilbert equation, the intrinsic Gilbert damping constant α was evaluated by parameter-fitting of frequency and lifetime expressions to experimental data of angular variations in spin precession frequency and life-times. The α values increased significantly with decreasing dCo but not inversely proportional to dCo.
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75.70.Ak Magnetic properties of monolayers and thin films
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
78.20.Ls Magneto-optical effects
75.30.Gw Magnetic anisotropy

Ferromagnetic and ordered MnSi(111) epitaxial layers

E. Magnano, F. Bondino, C. Cepek, F. Parmigiani, and M. C. Mozzati

Appl. Phys. Lett. 96, 152503 (2010); http://dx.doi.org/10.1063/1.3392373 (3 pages) | Cited 4 times

Online Publication Date: 14 April 2010

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We report a comprehensive study of ordered MnSi films grown on Si(111) which provides clear proofs that these MnSi films have the same magnetic and electronic properties of bulk MnSi compound, so closing a long-standing question. Furthermore, our measurements show the presence of a room-temperature ferromagnetic transition consistent with the ferromagnetic ground state predicted for Mn atoms with reduced coordination near surfaces and interfaces of silicon by recent calculations of Hortamani et al. [Phys. Rev. B 78, 104402 (2008)] . The possibility of growing layers on semiconductors which are ferromagnetic at room temperature (RT) is of paramount importance for nonvolatile memories and spintronic devices based on the injection of spin-polarized current from a ferromagnetic metal into a semiconductor. In this perspective MnSi films grown on Si substrates represent an interesting case study.
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81.05.Hd Other semiconductors
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.55.A- Nucleation and growth
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.70.Ak Magnetic properties of monolayers and thin films
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)

Current driven discontinuous insulator-metal transition and low-field colossal magnetoresistance in Sm0.6Sr0.4MnO3

A. Rebello and R. Mahendiran

Appl. Phys. Lett. 96, 152504 (2010); http://dx.doi.org/10.1063/1.3386535 (3 pages) | Cited 4 times

Online Publication Date: 15 April 2010

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We show that with increasing magnitude of current (I), insulator-metal (I-M) transition in Sm0.6Sr0.4MnO3 becomes discontinuous and shifts down in temperature, which is accompanied by an abrupt decrease in temperature of the sample while cooling. The I-M transition exhibits a hysteresis while warming. A magnetic field of μ0H = 0.5 T results in −99% magnetoresistance for I = 11 mA compared to −32% for I = 1 mA. Our results underscore the importance of inhomogeneous Joule heating that leads to coexistence of the high temperature paramagnetic phase with the low temperature ferromagnetic phase over a wide temperature range.
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75.47.Gk Colossal magnetoresistance
75.47.Lx Magnetic oxides
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
72.60.+g Mixed conductivity and conductivity transitions
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Perpendicular magnetic anisotropy in Co/Pt multilayers studied from a view point of anisotropy of magnetic Compton profiles

M. Ota, M. Itou, Y. Sakurai, A. Koizumi, and H. Sakurai

Appl. Phys. Lett. 96, 152505 (2010); http://dx.doi.org/10.1063/1.3374881 (3 pages) | Cited 3 times

Online Publication Date: 15 April 2010

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Magnetic Compton profiles (MCPs) of Co/Pt multilayers have been measured from a view point of perpendicular magnetic anisotropy (PMA). The PMA and the MCPs are discussed in the present Co/Pt results together with the previous Co/Pd results. The anisotropies of the MCPs have been decomposed into each magnetic quantum number |m| = 0, 1, and 2. The decomposition analysis has suggested that the |m| = 1 state contributes to the PMA when the multilayer films change in-plane magnetic anisotropy to the PMA, and that the |m| = 2 state contributes to the PMA when the multilayer films have large PMA energy.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.30.Gw Magnetic anisotropy
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
78.70.-g Interactions of particles and radiation with matter

Direct imaging of current induced magnetic vortex gyration in an asymmetric potential well

Andre Bisig, Jan Rhensius, Matthias Kammerer, Michael Curcic, Hermann Stoll, Gisela Schütz, Bartel Van Waeyenberge, Kang Wei Chou, Tolek Tyliszczak, Laura J. Heyderman, Stephen Krzyk, Arndt von Bieren, and Mathias Kläui

Appl. Phys. Lett. 96, 152506 (2010); http://dx.doi.org/10.1063/1.3373590 (3 pages) | Cited 4 times

Online Publication Date: 16 April 2010

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Employing time-resolved x-ray microscopy, we investigate the dynamics of a pinned magnetic vortex domain wall in a magnetic nanowire. The gyrotropic motion of the vortex core is imaged in response to an exciting ac current. The elliptical vortex core trajectory at resonance reveals asymmetries in the local potential well that are correlated with the pinning geometry. Using the analytical model of a two-dimensional harmonic oscillator, we determine the resonance frequency of the vortex core gyration and, from the eccentricity of the vortex core trajectory at resonance, we can deduce the stiffness of the local potential well.
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75.60.Ch Domain walls and domain structure
75.75.Fk Domain structures in nanoparticles
75.78.Fg Dynamics of domain structures
75.25.-j Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.)
75.50.Tt Fine-particle systems; nanocrystalline materials
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Multiferroic properties and surface potential behaviors in cobalt-doped BiFeO3 film

Q. Zhang, C. H. Kim, Y. H. Jang, H. J. Hwang, and J. H. Cho

Appl. Phys. Lett. 96, 152901 (2010); http://dx.doi.org/10.1063/1.3391667 (3 pages) | Cited 11 times

Online Publication Date: 12 April 2010

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The spatial coexistence of magnetic and ferroelectric domains in multiferroic BiFe0.96Co0.04O3 film is confirmed by multimode scanning probe microscopy. The applied bias dependence of the surface potential in BiFe0.96Co0.04O3 indicates that surface potential is determined by the interplay of polarization and surface charges. It is also shown that multiferroic BiFe0.96Co0.04O3 can more easily trap surface charges than the well-known ferroelectric PbZr0.53Ti0.47O3. The time evolution of surface potential exhibits an exponential decay, which is closely related to the observed spread of surface charges. The study on BiFe0.96Co0.04O3 unveils the origin and evolution behavior of the surface potential in BiFeO3-based multiferroic films.
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77.55.Nv Multiferroic/magnetoelectric films
77.80.Dj Domain structure; hysteresis
75.60.Ch Domain walls and domain structure
75.50.Dd Nonmetallic ferromagnetic materials
61.72.up Other materials

Significant enhancement of magnetoelectric output in multiferroic heterostructural films modulated by electric polarization cycles

Yujie Wu, Jian-guo Wan, Jun-ming Liu, and Guanghou Wang

Appl. Phys. Lett. 96, 152902 (2010); http://dx.doi.org/10.1063/1.3394008 (3 pages) | Cited 5 times

Online Publication Date: 12 April 2010

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The Pb(Zr,Ti)O3/CoFe2O4/Pb(Zr,Ti)O3 heterostructural film was prepared and the variation in its magnetoelectric output with the cycling electric polarization was investigated. The giant magnetoelectric output, which was about one order enhancement in magnitude compared with the original film, was observed after the film was subjected to the cycling electric polarization with the strength of 45 MV/m and cycling number of ∼ 2.2×108. We consider that both oxygen vacancy migration in the heterostructure and the polarized electric charges in the CoFe2O4 layer play important roles in such significant magnetoelectric enhancement.
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75.85.+t Magnetoelectric effects, multiferroics
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
77.80.-e Ferroelectricity and antiferroelectricity
77.84.-s Dielectric, piezoelectric, ferroelectric, and antiferroelectric materials
77.55.Nv Multiferroic/magnetoelectric films
75.50.Dd Nonmetallic ferromagnetic materials

Properties of a nanodielectric cryogenic resin

Georgios Polizos, Enis Tuncer, Isidor Sauers, and Karren L. More

Appl. Phys. Lett. 96, 152903 (2010); http://dx.doi.org/10.1063/1.3394011 (3 pages) | Cited 5 times

Online Publication Date: 12 April 2010

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Physical properties of a nanodielectric composed of in situ synthesized titanium dioxide (TiO2) nanoparticles ( ≤ 5 nm in diameter) and a cryogenic resin are reported. The dielectric losses were reduced by a factor of 2 in the nanocomposite, indicating that the presence of small TiO2 nanoparticles restricted the mobility of the polymer chains. Dielectric breakdown data of the nanodielectric was distributed over a narrower range than that of the unfilled resin. The nanodielectric had 1.56 times higher 1% breakdown probability than the resin, yielding 0.64 times thinner insulation thickness for the same voltage level, which is beneficial in high voltage engineering.
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77.22.Gm Dielectric loss and relaxation
77.22.Jp Dielectric breakdown and space-charge effects
81.05.Qk Reinforced polymers and polymer-based composites
81.16.-c Methods of micro- and nanofabrication and processing
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
77.84.Lf Composite materials

Right-angle piezoelectric cantilever with improved energy harvesting efficiency

Jia Wen Xu (徐佳文), Wei Wei Shao (邵维维), Fan Rang Kong (孔凡让), and Zhi Hua Feng (冯志华)

Appl. Phys. Lett. 96, 152904 (2010); http://dx.doi.org/10.1063/1.3374880 (3 pages) | Cited 8 times

Online Publication Date: 12 April 2010

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Show Abstract
This paper reports a piezoelectric device based on a cantilever with an extended auxiliary part that forms a right angle with the basic part. Theoretical analyses and experiments support that, by using such a device, uniform strain distribution in piezoelectric element surfaces can be obtained, and thus the piezoelectric materials can be used more efficiently. A piezoelectric element on a right-angle cantilever can generate a useful power twice that of a traditional cantilever under the same strain limitation.
Show PACS
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
84.60.-h Direct energy conversion and storage
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