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28 Nov 2005

Volume 87, Issue 22, Articles (22xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 87, 221108 (2005); http://dx.doi.org/10.1063/1.2137458 (3 pages)

V. Barna, S. Ferjani, A. De Luca, R. Caputo, N. Scaramuzza, C. Versace, and G. Strangi
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Amorphization/templated recrystallization method for changing the orientation of single-crystal silicon: An alternative approach to hybrid orientation substrates

K. L. Saenger, J. P. de Souza, K. E. Fogel, J. A. Ott, A. Reznicek, C. Y. Sung, D. K. Sadana, and H. Yin

Appl. Phys. Lett. 87, 221911 (2005); http://dx.doi.org/10.1063/1.2138795 (3 pages) | Cited 19 times

Online Publication Date: 23 November 2005

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We demonstrate that the crystal orientation of single-crystal silicon layers may be changed in selected areas from one orientation to another by an amorphization/templated recrystallization (ATR) process, and then introduce ATR as an alternative approach for fabricating planar hybrid orientation substrates with surface regions of (100)- and (110)-oriented Si. The ATR technique, applied to a starting substrate comprising a thin (50–200 nm) overlayer of (100) or (110) Si on a (110) or (100) Si handle wafer, consists of two process steps: (i) Si+ or Ge+ ion implantation to create an amorphous silicon (a-Si) layer extending from the top of the overlayer to a depth below the overlayer/handle wafer interface, and (ii) a thermal anneal to produce the handle-wafer-templated epitaxial recrystallization of the a-Si layer. Regions exposed to the ATR process assume the orientation of the handle wafer while regions not exposed to the ATR process retain their original orientation. The practicality of this approach is demonstrated with the fabrication of a planar hybrid orientation substrate comprising (100) and (110) Si regions separated by SiO2-filled trenches.
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81.05.Cy Elemental semiconductors
81.05.Gc Amorphous semiconductors
81.10.Jt Growth from solid phases (including multiphase diffusion and recrystallization)
61.50.-f Structure of bulk crystals
61.43.Dq Amorphous semiconductors, metals, and alloys
81.40.Gh Other heat and thermomechanical treatments
61.72.uf Ge and Si
61.80.Jh Ion radiation effects
61.72.Cc Kinetics of defect formation and annealing
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Trapping-detrapping defects in single crystal diamond films grown by chemical vapor deposition

A. Balducci, Marco Marinelli, E. Milani, M. E. Morgada, G. Prestopino, M. Scoccia, A. Tucciarone, and G. Verona-Rinati

Appl. Phys. Lett. 87, 222101 (2005); http://dx.doi.org/10.1063/1.2135384 (3 pages) | Cited 5 times

Online Publication Date: 21 November 2005

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High-quality single-crystal diamond films were homoepitaxially grown by chemical vapor deposition onto low cost high-pressure high-temperature diamond substrates. The transport properties of the obtained samples were studied by photoresponse characterization. Fast ultraviolet (5 ns) laser pulses at 215 nm were used as a probe. The time evolution of the photoinduced current was observed to closely reproduce the laser pulse shape, thus indicating a time response lower than the adopted laser pulse duration. Very stable and reproducible response was measured, so that neither priming nor memory effects are observed. However, a minor slow component shows up in the charge-integrated sample response, whose temperature dependence was investigated in a −25–+50 °C range. A systematic speed up of this slow component of the sample signal is observed, indicating the presence of shallow centers producing trapping-detrapping effects. The experimental results are discussed in the framework of a trapping-detrapping model affecting the charge transport mechanism and an activation energy of Ea = 0.4 eV was derived for the shallow trapping centers.
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71.55.Cn Elemental semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
73.50.Pz Photoconduction and photovoltaic effects
73.61.Cw Elemental semiconductors

β-Ga2O3 nanowires: Synthesis, characterization, and p-channel field-effect transistor

Pai-Chun Chang, Zhiyong Fan, Wei-Yu Tseng, A. Rajagopal, and Jia G. Lu

Appl. Phys. Lett. 87, 222102 (2005); http://dx.doi.org/10.1063/1.2135867 (3 pages) | Cited 19 times

Online Publication Date: 21 November 2005

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Quasione-dimensional Ga2O3 nanowires are synthesized via catalytic chemical vapor deposition method. Their morphology and crystal structure are characterized by electron microscopy and x-ray diffraction techniques, and their optical property is studied by photoluminescence measurement. To develop their future application in nanoelectronic devices, the as-grown Ga2O3 nanowires are doped with zinc to increase its carrier concentration and subsequently fabricated into field-effect transistors. Electron transport measurements show that the doped nanowires exhibit p-type semiconducting behavior with a significant enhancement of conductivity.
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81.07.Bc Nanocrystalline materials
85.30.Tv Field effect devices
68.65.La Quantum wires (patterned in quantum wells)
73.21.Hb Quantum wires
73.63.Nm Quantum wires
78.67.Lt Quantum wires
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.16.Hc Catalytic methods
82.30.Vy Homogeneous catalysis in solution, polymers and zeolites
68.37.Lp Transmission electron microscopy (TEM)
78.55.Hx Other solid inorganic materials
61.72.up Other materials

Steady-state and transient electron transport within bulk wurtzite indium nitride: An updated semiclassical three-valley Monte Carlo simulation analysis

Stephen K. O’Leary, Brian E. Foutz, Michael S. Shur, and Lester F. Eastman

Appl. Phys. Lett. 87, 222103 (2005); http://dx.doi.org/10.1063/1.2135876 (3 pages) | Cited 35 times

Online Publication Date: 21 November 2005

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Recent experimentation, performed on bulk wurtzite InN, suggests that the energy gap, the effective mass of the electrons in the lowest-energy valley, and the nonparabolicity coefficient of the lowest-energy valley are not as originally believed for this material. Using a semiclassical three-valley Monte Carlo simulation approach, we analyze the steady-state and transient electron transport that occurs within bulk wurtzite InN using a revised set of material parameters, this revised set of parameters taking into account this recently observed phenomenology. We find that the peak electron drift velocity is considerably greater than that found previously. The impact that this revised set of parameters has upon the transient electron transport is also found to be significant.
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72.20.Fr Low-field transport and mobility; piezoresistance
71.20.Nr Semiconductor compounds
61.66.Fn Inorganic compounds
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor

Phonon localization in periodic uniaxially nanostructured silicon

Sylvain G. Cloutier, Rodney S. Guico, and Jimmy M. Xu

Appl. Phys. Lett. 87, 222104 (2005); http://dx.doi.org/10.1063/1.2135881 (3 pages) | Cited 11 times

Online Publication Date: 21 November 2005

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Phonon spectroscopy of low-dimensional silicon nanostructures may help identify and understand their unique physical properties for potentially enabling new applications. High-resolution Raman spectroscopy reveals that fabrication of such nanostructures can lead to the creation of nanosize crystallites at the silicon interface due to the introduction of defect centers which is most likely responsible for local crystal-symmetry breaking and phonon localization. By examining these nanocrystallites created in periodic crystalline silicon nanodot arrays formed in silicon-on-insulator and their dispersive and power-dependent phonon spectra, we found clear evidence of spatial phonon localization, which in turn suggests a breaking of the fundamental phonon-selection rule limiting radiative recombination in silicon’s indirect band structure.
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63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
78.30.Hv Other nonmetallic inorganics
61.72.-y Defects and impurities in crystals; microstructure
61.50.Ah Theory of crystal structure, crystal symmetry; calculations and modeling

Average energy dissipated by mega-electron-volt hydrogen and helium ions per electron-hole pair generation in 4H-SiC

Alessandro Lo Giudice, Franco Fizzotti, Claudio Manfredotti, Ettore Vittone, and Filippo Nava

Appl. Phys. Lett. 87, 222105 (2005); http://dx.doi.org/10.1063/1.2135507 (3 pages) | Cited 6 times

Online Publication Date: 21 November 2005

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The pulse height response for He and H ions with energies between 1 and 6 MeV incident upon n-type 4H-SiC epitaxial Schottky diodes has been investigated. The average amount of energy, ε, given up by the incident radiation to form electron-hole pair in this material was obtained by comparison with the average energy loss per pair in silicon detectors and it was found to be (7.78±0.05) eV at room temperature. This value is smaller than that foreseen by Klein’s semiempirical linear relationship between ε and the semiconductor band gap.
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85.30.Kk Junction diodes
85.30.Hi Surface barrier, boundary, and point contact devices

Hydrogen sensing at room temperature with Pt-coated ZnO thin films and nanorods

L. C. Tien, P. W. Sadik, D. P. Norton, L. F. Voss, S. J. Pearton, H. T. Wang, B. S. Kang, F. Ren, J. Jun, and J. Lin

Appl. Phys. Lett. 87, 222106 (2005); http://dx.doi.org/10.1063/1.2136070 (3 pages) | Cited 96 times

Online Publication Date: 21 November 2005

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A comparison is made of the sensitivities for detecting hydrogen with Pt-coated single ZnO nanorods and thin films of various thicknesses (20–350 nm). The Pt-coated single nanorods show a current response of approximately a factor of 3 larger at room temperature upon exposure to 500 ppm H2 in N2 than the thin films of ZnO. The power consumption with both types of sensors can be very small (in the nW range) when using discontinuous coatings of Pt. Once the Pt coating becomes continuous, the current required to operate the sensors increases to the μW range. The optimum ZnO thin film thickness under our conditions was between 40–170 nm, with the hydrogen sensitivity falling off outside this range. The nanorod sensors show a slower recovery in air after hydrogen exposure than the thin films, but exhibit a faster response to hydrogen, consistent with the notion that the former adsorb relatively more hydrogen on their surface. Both ZnO thin and nanorods cannot detect oxygen.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
68.55.-a Thin film structure and morphology
81.65.-b Surface treatments

Modulation in optical second harmonic generation signal from channel of pentacene field effect transistors during device operation

Takaaki Manaka, Eunju Lim, Ryosuke Tamura, and Mitsumasa Iwamoto

Appl. Phys. Lett. 87, 222107 (2005); http://dx.doi.org/10.1063/1.2136075 (3 pages) | Cited 20 times

Online Publication Date: 21 November 2005

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The channel formation process of the pentacene field effect transistor (FET) was shown by the optical second harmonic generation (SHG) ascribed to the electric field induced SHG. The SHG signal probed successfully and nondestructively the off and on states. The enhancement of the SHG signal at the off state was observed with applying the source-drain voltage in the absence of the gate voltage, whereas it remarkably decayed with applying the gate voltage, indicating the channel formation. At the channel formation, holes injected from the source electrode changed the potential profile in pentacene film at the off state and the SHG signal was suppressed.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
85.30.Tv Field effect devices

Epitaxial, ferromagnetic Cu2−xMnxO films on (001) Si by near-room-temperature electrodeposition

Y. L. Liu, S. Harrington, K. A. Yates, M. Wei, M. G. Blamire, J. L. MacManus-Driscoll, and Y. C. Liu

Appl. Phys. Lett. 87, 222108 (2005); http://dx.doi.org/10.1063/1.2136349 (3 pages) | Cited 6 times

Online Publication Date: 21 November 2005

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∼ 1 micron thick Cu2−xMnxO films were grown both on Au-coated and uncoated (001) Si from sulphate solutions at 60 °C, several hundred degrees lower than normally used for growth of dilute magnetic semiconductors. The Mn concentration in the films was controlled very sensitively by controlling both the ratio of Mn:Cu in solution and the deposition potential. An optimum Mn concentration of 0.3% in the films produced saturation magnetization values of 0.6 μB/Mn at room temperature. The Cu2−xMnxO films were semiconducting with resistivitity value lower than the undoped film. Photoluminscence measurements showed that Mn substitutes on the Cu lattice sites.
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75.50.Pp Magnetic semiconductors
75.50.Dd Nonmetallic ferromagnetic materials
81.15.Pq Electrodeposition, electroplating
75.70.Ak Magnetic properties of monolayers and thin films
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
78.55.Hx Other solid inorganic materials
78.66.Li Other semiconductors

Blends of semiconductor polymer and small molecular crystals for improved-performance thin-film transistors

D. M. Russell, C. J. Newsome, S. P. Li, T. Kugler, M. Ishida, and T. Shimoda

Appl. Phys. Lett. 87, 222109 (2005); http://dx.doi.org/10.1063/1.2136356 (3 pages) | Cited 13 times

Online Publication Date: 21 November 2005

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Incorporating dihexyl-quarterthiophene (DH4T) into the active layer of a poly(3-hexylthiophene) thin-film transistor can enhance the mobility by a factor of 10. The DH4T concentration dependence shows the improvement in mobility is due to the formation of crystals within the blend film, which occur at a critical concentration of 29% DH4T. Application of percolation theory reveals that transport in blend devices is limited by the mobility of the poly(3-hexylthiophene) (P3HT) and by the crystal packing. With improved polymer performance, the mobility in blend films is expected to approach 1 cm2/V s.
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85.30.Tv Field effect devices

Double injection as a technique to study charge carrier transport and recombination in bulk-heterojunction solar cells

G. Juška, K. Arlauskas, G. Sliaužys, A. Pivrikas, A. J. Mozer, N. S. Sariciftci, M. Scharber, and R. Österbacka

Appl. Phys. Lett. 87, 222110 (2005); http://dx.doi.org/10.1063/1.2137454 (3 pages) | Cited 16 times

Online Publication Date: 22 November 2005

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Ambipolar charge carrier mobility and recombination in bulk-heterojunction solar cells based on the mixture of regioregular poly(3-hexylthiophene) and 1-(3-methoxycarbonyl)propyl-1-phenyl-[6,6]-methanofullerene (PCBM) has been studied using injection current transients. The experimental results demonstrate double injection with bimolecular recombination limiting the injection current. We found that charge carrier bimolecular recombination is significantly reduced compared to Langevin recombination. We have measured the temperature and electric field dependence of the reduced bimolecular recombination coefficient and the results suggest that the electron and hole pathways are different and the recombination is controlled by the probability of the carriers to meet at the polymer/PCBM interface.
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84.60.Jt Photoelectric conversion
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
85.65.+h Molecular electronic devices

Nanoscale stress analysis of strained-Si metal-oxide-semiconductor field-effect transistors by quantitative electron diffraction contrast imaging

J. Li, D. Anjum, R. Hull, G. Xia, and J. L. Hoyt

Appl. Phys. Lett. 87, 222111 (2005); http://dx.doi.org/10.1063/1.2135388 (3 pages) | Cited 6 times

Online Publication Date: 22 November 2005

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A technique that uses quantitative electron diffraction contrast imaging (EDCI) to measure stress with a spatial resolution on the order of 10 nm and sensitivity on the order of tens of MPa is applied to strained-Si metal-oxide-semiconductor field-effect transistors. This is accomplished by utilizing transmission electron microscopy and focused ion beam micromachining in conjunction with finite element modeling and electron diffraction contrast simulations. Our techniques enable quantitative interpretation of EDCI intensity, as a function of the magnitude of the local stress field. Analysis shows that the stress distribution in the strained-Si channel is very sensitive to the stress state of the surrounding materials, especially TiSi2, which can modify the stress distribution in the channel by well over 100 MPa.
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85.30.Tv Field effect devices
85.30.De Semiconductor-device characterization, design, and modeling

Deep levels in n-type AlGaN grown by hydride vapor-phase epitaxy on sapphire characterized by deep-level transient spectroscopy

J. Osaka, Y. Ohno, S. Kishimoto, K. Maezawa, and T. Mizutani

Appl. Phys. Lett. 87, 222112 (2005); http://dx.doi.org/10.1063/1.2137901 (3 pages) | Cited 7 times

Online Publication Date: 22 November 2005

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Deep levels in unintentionally doped n-type Al0.09Ga0.91N and Al0.17Ga0.83N films grown on sapphire by hydride vapor-phase epitaxy were characterized using capacitance deep-level transient spectroscopy and were compared to the reported electron traps in GaN grown by various techniques. It was shown that at least three dominant deep levels exist in each sample. The Al mole fraction dependence of their activation energy suggested that each of these three levels has the same origin as the three dominant well known point-defect-related deep levels in GaN, respectively. It is thought that deep levels in GaN change their electric characteristics in low Al content AlGaN.
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71.55.Eq III-V semiconductors
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Formation of p-n homojunctions in n-ZnO bulk single crystals by diffusion from a Zn3P2 source

Soohwan Jang, Jau-Jiun Chen, B. S. Kang, F. Ren, D. P. Norton, S. J. Pearton, J. Lopata, and W. S. Hobson

Appl. Phys. Lett. 87, 222113 (2005); http://dx.doi.org/10.1063/1.2137988 (3 pages) | Cited 15 times

Online Publication Date: 22 November 2005

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p-n junctions have been formed in lightly n-type (1017 cm−3) bulk, single-crystal ZnO substrates by diffusion of P from a Cd3P2, arsenic and red phosphorous dopant source in a closed-ampoule system. The P incorporation depth was found to be ∼ 200 nm after diffusion at 550 °C for 30 min, as determined by secondary ion mass spectrometry profiling. The resulting structures show rectification, with on-off current ratios of ∼ 70 at +3/−5 V. The forward current ideality factor was ≥ 2, consistent with multiple current transport mechanisms present in the junction, such as defect-assisted tunneling and conventional carrier recombination in the space-charge region via midgap deep levels. The forward turn-on voltage, VF was ∼ 4 V at 300 K with a specific on-state resistance (RON) of ∼ 21 mΩ cm2. The activation energy of the forward current at low forward biases was ∼ 1.4 eV. This is also consistent with carrier recombination in the space charge region via a midgap deep level.
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66.30.J- Diffusion of impurities
71.55.Gs II-VI semiconductors
73.61.Ga II-VI semiconductors
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
61.72.uj III-V and II-VI semiconductors
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
73.40.Ei Rectification
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Ferroelectric switch for spin injection

M. Ye. Zhuravlev, S. S. Jaswal, E. Y. Tsymbal, and R. F. Sabirianov

Appl. Phys. Lett. 87, 222114 (2005); http://dx.doi.org/10.1063/1.2138365 (3 pages) | Cited 46 times

Online Publication Date: 23 November 2005

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A method for the switching of the spin polarization of the electric current injected into a semiconductor is proposed, based on injecting spins from a diluted magnetic semiconductor through a ferroelectric tunnel barrier. We show that the reversal of the electric polarization of the ferroelectric results in a sizable change in the spin polarization of the injected current, thereby providing a two-state electrical control of this spintronic device. We also predict a possibility of switching of tunneling magnetoresistance in magnetic tunnel junctions with a ferroelectric barrier and coexistence of tunneling magnetoresistance and giant electroresistance effects in these multiferroic tunnel junctions.
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77.80.Fm Switching phenomena
72.25.Dc Spin polarized transport in semiconductors
75.47.Pq Other materials

Efficient blue electroluminescent device using tetra(β-naphthyl)silane as a hole-blocking material

Gui Yu, Xinjun Xu, Yunqi Liu, Zuoquan Jiang, Shiwei Yin, Zhigang Shuai, Daoben Zhu, Xiaobang Duan, and Ping Lu

Appl. Phys. Lett. 87, 222115 (2005); http://dx.doi.org/10.1063/1.2138812 (3 pages) | Cited 13 times

Online Publication Date: 23 November 2005

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We report an efficient blue light-emitting diode (LED) using N, N′-bis(1-naphthyl)-N, N′-diphenylbenzidine as an emitting layer and tetra(β-naphthyl)silane (TNS) as a hole-blocking layer (HBL). We find that the hole-blocking performance, thermal stability, and film-forming ability of TNS are improved over those of the prototypical hole-blocking material 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP). The device that used TNS as the HBL exhibits a narrower light emission and higher current efficiency (2.5 cd/A) as compared with the device containing BCP as the HBL. TNS should be promising as an excellent hole-blocking layer in LEDs.
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85.60.Jb Light-emitting devices
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Rectifying properties of the YBa2Cu3O7−δ/SrTiO3:Nb heterojunction

J. R. Sun, C. M. Xiong, Y. Z. Zhang, and B. G. Shen

Appl. Phys. Lett. 87, 222501 (2005); http://dx.doi.org/10.1063/1.2136407 (3 pages) | Cited 11 times

Online Publication Date: 21 November 2005

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A heterojunction has been fabricated by growing a YBa2Cu3O7−δ (YBCO) film of the thickness of 1000 Å on a 0.5 wt %Nb-doped SrTiO3 (STON) crystal, and its resistive behavior was experimentally studied. The strong asymmetry of the current-voltage (I–V) relation with respect to bias polarity indicates an excellent rectifying property of the junction in the whole temperature range studied. The superconducting transition of YBCO causes a visible reduction of diffusion potential, measured by the forward voltage corresponding to the current rush in the I–V curves, though the general rectifying behavior remains unchanged. This is possibly a result of the variation of the Fermi level of YBCO relative to that of STON, and suggests an alternative technique detecting the effects of superconducting transition in YBCO.
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74.78.-w Superconducting films and low-dimensional structures
74.72.-h Cuprate superconductors
73.40.Ei Rectification
74.10.+v Occurrence, potential candidates
74.25.Jb Electronic structure (photoemission, etc.)
74.25.F- Transport properties

Synthesis of high-purity samples of CrO2 by a simple route

A. Bajpai and A. K. Nigam

Appl. Phys. Lett. 87, 222502 (2005); http://dx.doi.org/10.1063/1.2136411 (3 pages) | Cited 18 times

Online Publication Date: 21 November 2005

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Practical applications of the spintronic material CrO2 have been limited, primarily because of the difficulty in its synthesis, as it is not known to form in ambient pressures in a pure form. Here we show that CrO2 can be prepared by a simple route that bypasses the need to either apply any external pressure or measure and control it during synthesis. These samples not only exhibit saturation magnetization (MS) values close to the theoretical predicted one, but also exhibit a substantially enhanced grain size, at least an order of magnitude larger as compared to that reported prior to this work. In addition, the method provides some easy steps to tune the grain size and grain boundary density, thus enabling an investigation of this technologically important material in hitherto unexplored microstructural regimes.
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81.05.Bx Metals, semimetals, and alloys
75.50.Cc Other ferromagnetic metals and alloys
61.72.Mm Grain and twin boundaries
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Influence of dual-Ru intermediate layers on magnetic properties and recording performance of CoCrPt–SiO2 perpendicular recording media

J. Z. Shi, S. N. Piramanayagam, C. S. Mah, H. B. Zhao, J. M. Zhao, Y. S. Kay, and C. K. Pock

Appl. Phys. Lett. 87, 222503 (2005); http://dx.doi.org/10.1063/1.2137447 (3 pages) | Cited 33 times

Online Publication Date: 22 November 2005

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CoCrPt–SiO2 perpendicular recording media containing dual-Ru intermediate layers have been studied. The bottom Ru layer deposited under a higher mobility condition, i.e., low Ar gas pressure and bias on substrate, helps to achieve a good crystalline texture, and the top Ru layer under a lower mobility condition, i.e., high Ar gas pressure, promotes the formation of a columnar microstructure. Three kinds of grain boundaries have been observed. The nucleation field and the coercivity as a function of the thickness and dc bias of the bottom Ru layer have been investigated. Medium noise reduction has been observed for dual-Ru intermediate layer media (dual-Ru media) in comparison with that of single intermediate layer media (single-Ru media). This is mainly attributed to the optimization of the physical grain segregation.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Ss Magnetic recording materials
61.72.Mm Grain and twin boundaries
64.75.-g Phase equilibria

Fe–Ga/Pb(Mg1/3Nb2/3)O3–PbTiO3 magnetoelectric laminate composites

Shuxiang Dong, Junyi Zhai, Naigang Wang, Feiming Bai, JieFang Li, D. Viehland, and T. A. Lograsso

Appl. Phys. Lett. 87, 222504 (2005); http://dx.doi.org/10.1063/1.2137455 (3 pages) | Cited 26 times

Online Publication Date: 22 November 2005

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We have found large magnetoelectric (ME) effects in long-type laminate composites of Fe–20%Ga magnetostrictive alloys and piezoelectric Pb(Mg1/3Nb2/3)O3–PbTiO3 single crystals. At lower frequencies, the ME voltage coefficient of a laminate with longitudinally magnetized and longitudinally polarized (i.e., L-L mode) layers was 1.41 V/Oe (or 1.01 V/cm Oe). Near the natural resonant frequency ( ∼ 91 kHz) of the laminate, the ME voltage coefficients were found to be dramatically increased to 50.7 V/Oe (36.2 V/cm Oe) for the L-L mode. In addition, the laminate can detect a minute magnetic field as low as ∼ 2×10−12 T at resonance frequency, and ∼ 1×10−10 T at lower frequencies.
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75.80.+q Magnetomechanical effects, magnetostriction
75.50.Bb Fe and its alloys
77.65.-j Piezoelectricity and electromechanical effects
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates

Nanoscale hysteresis loop of individual Co dots by field-dependent magnetic force microscopy

M. V. Rastei, R. Meckenstock, and J. P. Bucher

Appl. Phys. Lett. 87, 222505 (2005); http://dx.doi.org/10.1063/1.2138349 (3 pages) | Cited 6 times

Online Publication Date: 22 November 2005

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We present an approach in which field-dependent magnetic force microscopy (MFM) is used in order to determine the magnetic properties of individual magnetic nanodots. In this work, the integral value of the cantilever phase shift obtained in vibrating MFM experiment is used as a measure of the field dependent magnetization of single objects. The method accounts for details that are resolved at the 10 nm scale, including fine structures during magnetization reversal. Measurements have been done on a model system of embedded dots since the flatness of the free surface reduces strongly the topographic contaminations. It is shown that the method can easily be applied to investigate both out-of-plane and in-plane magnetized dots.
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75.50.Tt Fine-particle systems; nanocrystalline materials
75.50.Cc Other ferromagnetic metals and alloys
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.60.Jk Magnetization reversal mechanisms

High-frequency magnetic microstrip local bandpass filters

Bijoy K. Kuanr, D. L. Marvin, T. M. Christensen, R. E. Camley, and Z. Celinski

Appl. Phys. Lett. 87, 222506 (2005); http://dx.doi.org/10.1063/1.2138364 (3 pages) | Cited 30 times

Online Publication Date: 22 November 2005

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This paper presents results for a compact, local bandpass filter. We fabricated the filter using two different ferromagnetic materials, Fe and NiFe, in a microstrip geometry. The different values of saturation magnetization of the two ferromagnets give rise to different gyromagnetic resonance frequencies and provide a local bandpass region between them. The results show that the center frequency of the filter can be tuned over a wide range by adjusting the magnitude of the bias magnetic field. The filter’s bandwidth is almost constant (3.5±0.5 GHz) over the entire tuning frequency range (6–26 GHz). Theoretical calculations are in good agreement with the experimental results.
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84.40.Az Waveguides, transmission lines, striplines
85.70.-w Magnetic devices

Frequency and field dependence of magnetoelectric interactions in layered ferromagnetic transition metal-piezoelectric lead zirconate titanate

V. M. Laletin, N. Paddubnaya, G. Srinivasan, C. P. De Vreugd, M. I. Bichurin, V. M. Petrov, and D. A. Filippov

Appl. Phys. Lett. 87, 222507 (2005); http://dx.doi.org/10.1063/1.2137450 (3 pages) | Cited 32 times

Online Publication Date: 23 November 2005

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The strength of magnetoelectric (ME) coupling at 10 Hz–3 MHz has been measured in trilayers of Fe, Co, or Ni and lead zirconate titanate (PZT). The strongest ME coupling is measured for trilayers with Ni and the weakest in Co. Data on ME voltage coefficient αE versus bias magnetic field H for Fe–PZT–Fe show unique features including zero crossing and sign reversal. Measurements of frequency dependence of αE reveal a giant ME coupling due to the electromechanical resonance at 200–300 kHz for radial modes and at ∼ 2.7 MHz for thickness modes. Theoretical estimates of field and frequency dependence of αE are in very good agreement with the data.
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75.80.+q Magnetomechanical effects, magnetostriction
75.50.Bb Fe and its alloys
75.50.Cc Other ferromagnetic metals and alloys
77.65.-j Piezoelectricity and electromechanical effects
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)

Giant tunneling magnetoresistance in fully epitaxial body-centered-cubic Co/MgO/Fe magnetic tunnel junctions

Shinji Yuasa, Toshikazu Katayama, Taro Nagahama, Akio Fukushima, Hitoshi Kubota, Yoshishige Suzuki, and Koji Ando

Appl. Phys. Lett. 87, 222508 (2005); http://dx.doi.org/10.1063/1.2138355 (3 pages) | Cited 41 times

Online Publication Date: 23 November 2005

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Fully epitaxial bcc Fe1−xCox(001)/MgO(001)/Fe(001) magnetic tunnel junctions (x = 0, 0.5, 1) were fabricated with molecular-beam epitaxy and microfabrication techniques. While the bcc Fe(001) and Fe0.5Co0.5(001) electrodes had similar magnetoresistance (MR) ratios of about 180% at room temperature, the bcc Co(001) electrode exhibited a higher MR ratio up to 271% at room temperature (353% at 20 K). The fact that the MR ratio for a bcc Co electrode is much higher than that for a bcc Fe electrode is consistent with first-principle calculations, indicating the importance of electrode band structure in the k‖ = 0 direction.
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75.50.Bb Fe and its alloys
75.47.De Giant magnetoresistance
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
71.15.-m Methods of electronic structure calculations
71.20.Ps Other inorganic compounds

Bidomain state in exchange biased FeF2/Ni

O. Petracic, Zhi-Pan Li, Igor V. Roshchin, M. Viret, R. Morales, X. Batlle, and Ivan K. Schuller

Appl. Phys. Lett. 87, 222509 (2005); http://dx.doi.org/10.1063/1.2138357 (3 pages) | Cited 24 times

Online Publication Date: 23 November 2005

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Independently exchange biased subsystems can coexist in ferromagnet/antiferromagnet bilayers after various field-cooling protocols. We find well separated double hysteresis loops in FeF2/Ni bilayers for intermediate cooling fields, while for small or large cooling fields a negatively or positively shifted single loop, respectively, are encountered. The antiferromagnet breaks into a bidomain state with opposite signs but equal magnitude of bias acting on the ferromagnet. This idea is supported by micromagnetic simulations. Experiments are presented, where thermally activated motion of these antiferromagnetic domain boundaries can be achieved.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.60.Ch Domain walls and domain structure
75.70.Kw Domain structure (including magnetic bubbles and vortices)
75.50.Dd Nonmetallic ferromagnetic materials
75.50.Ee Antiferromagnetics
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Et Exchange and superexchange interactions
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