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9 Jun 2003

Volume 82, Issue 23, pp. 4011-4195

Issue Cover Spotlight Figure

Appl. Phys. Lett. 82, 4160 (2003); http://dx.doi.org/10.1063/1.1580641 (3 pages)

Eva M. Höhberger, Tomas Krämer, Werner Wegscheider, and Robert H. Blick
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Molecular oxygen and moisture as traps in poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylene vinylene]: locations and detrapping by chain relaxation

Hao-En Tseng, Kang-Yung Peng, and Show-An Chen

Appl. Phys. Lett. 82, 4086 (2003); http://dx.doi.org/10.1063/1.1579557 (3 pages) | Cited 13 times

Online Publication Date: 2 June 2003

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We investigate locations of molecular oxygen and moisture (O2/H2O) serving as traps in poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylene vinylene] (MEH-PPV) by measurements of field-induced thermally stimulated current, photoexcitation thermally stimulated current (PE-TSC), and dynamic mechanical analysis. Two broad peaks of PE-TSC are found at 212 and 325 K in the samples with O2/H2O-rich MEH-PPV, which are in reasonable agreement with those of the side chain and main chain relaxation, respectively. These traps can be attributed to the presence of O2/H2O (most likely molecular oxygen) in the side chain region and the amorphous main chain region, and the detrapping process is induced by chain motions under elevated temperatures. © 2003 American Institute of Physics.
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72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
77.22.Ej Polarization and depolarization

Non-volatile memory cells based on ZnxCd1−xS ferroelectric Schottky diodes

P. van der Sluis

Appl. Phys. Lett. 82, 4089 (2003); http://dx.doi.org/10.1063/1.1581365 (3 pages) | Cited 18 times

Online Publication Date: 2 June 2003

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Ferroelectric Schottky diodes were fabricated with n-type Zn0.4Cd0.6S. These devices show promising nonvolatile memory properties and the integration into complementary metal-oxide-semiconductor (CMOS) circuits seems feasible. So far, we have demonstrated on-resistances down to 100 Ω, on/off ratios up to 107, switching voltages below 100 mV, operating temperatures up to 180 °C, and switching times below 50 ns. The devices can be deposited at low temperatures (200 °C) by conventional rf-sputtering and survive the 30-min anneal at 400 °C in forming gas, which is mandatory in CMOS processing. © 2003 American Institute of Physics.
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85.50.Gk Non-volatile ferroelectric memories
85.30.Kk Junction diodes
61.72.Cc Kinetics of defect formation and annealing

Analysis of the transport process providing spin injection through an Fe/AlGaAs Schottky barrier

A. T. Hanbicki, O. M. J. van ’t Erve, R. Magno, G. Kioseoglou, C. H. Li, B. T. Jonker, G. Itskos, R. Mallory, M. Yasar, and A. Petrou

Appl. Phys. Lett. 82, 4092 (2003); http://dx.doi.org/10.1063/1.1580631 (3 pages) | Cited 191 times

Online Publication Date: 2 June 2003

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Electron-spin polarizations of 32% are obtained in a GaAs quantum well via electrical injection through a reverse-biased Fe/AlGaAs Schottky contact. An analysis of the transport data using the Rowell criteria demonstrates that single-step tunneling is the dominant transport mechanism. The current–voltage data show a clear zero-bias anomaly and phonon signatures corresponding to the GaAs-like and AlAs-like LO phonon modes of the AlGaAs barrier, providing further evidence for tunneling. These results provide experimental confirmation of several theoretical analyses, indicating that tunneling enables significant spin injection from a metal into a semiconductor. © 2003 American Institute of Physics.
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72.25.Mk Spin transport through interfaces
72.25.Hg Electrical injection of spin polarized carriers
73.30.+y Surface double layers, Schottky barriers, and work functions
73.43.Jn Tunneling
73.40.Ns Metal-nonmetal contacts
68.35.Ja Surface and interface dynamics and vibrations
78.60.Fi Electroluminescence
73.63.Hs Quantum wells
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)

Realization of one-chip-multiple-wavelength laser diodes with II–VI/III–V compound semiconductors

J. S. Song, M. W. Cho, D. C. Oh, H. Makino, T. Hanada, T. Yao, B. P. Zhang, Y. Segawa, J. H. Chang, H. S. Song, I. S. Cho, H. W. Kim, and J. J. Jung

Appl. Phys. Lett. 82, 4095 (2003); http://dx.doi.org/10.1063/1.1578178 (3 pages) | Cited 2 times

Online Publication Date: 2 June 2003

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A laser diode which includes II–VI device structure directly grown on III–V device structure is proposed. This idea makes possible one-chip-multiple-wavelength operation in the visible wavelength region by the vertical integration of individual light emitters, which is demonstrated by a ZnCdSe/ZnSe/ZnMgBeSe quantum-well structure for a blue-green light emitter grown by molecular beam epitaxy directly on a metalorganic chemical vapor deposition grown InGaP/InGaAlP device wafer for a red light emitting device. The feasibility of the II–VI/III–V complex light emitter is demonstrated by optical-pumping experiments. Optically pumped lasing at 504 and 664 nm is achieved from II–VI and III–VI laser structures on one chip simultaneously at room temperature with a threshold power of 115 and 84 kW/cm2, respectively. The present results clearly show the feasibility of epitaxial integration of II–VI and III–V laser structures, which will stimulate the investigation of multifunctional optical devices. © 2003 American Institute of Physics.
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42.60.By Design of specific laser systems
78.67.De Quantum wells
78.66.Hf II-VI semiconductors
78.66.Fd III-V semiconductors
42.55.Px Semiconductor lasers; laser diodes
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
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Investigation on intergrain exchange coupling of nanocrystalline permanent magnets by Henkel plot

Hong-wei Zhang, Chuan-bing Rong, Xiao-bo Du, Jian Zhang, Shao-ying Zhang, and Bao-gen Shen

Appl. Phys. Lett. 82, 4098 (2003); http://dx.doi.org/10.1063/1.1576291 (3 pages) | Cited 40 times

Online Publication Date: 2 June 2003

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In a real magnet, the relation between isothermal remanence Jr(H) and dc demagnetization remanence Jd(H) is expressed as δm(H) = [Jd(H)−Jr(∞)+2Jr(H)]/J(∞). It is believed that nonzero δm is due to the interactions between particles in the magnet. Using Pr2Fe14B as a sample, the relation is examined by the micromagnetic finite element method. The positive value of δm is primarily caused by intergrain exchange coupling. The decrease of intergrain exchange coupling results in the drop of the maximum value of δm. However, the variation of anisotropy in grain boundaries produces no change in the maximum value of δm. A Henkel plot is suggested to be effective for checking intergrain exchange coupling in magnets. © 2003 American Institute of Physics.
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75.50.Tt Fine-particle systems; nanocrystalline materials
75.50.Ww Permanent magnets
75.30.Et Exchange and superexchange interactions
75.30.Gw Magnetic anisotropy
61.46.-w Structure of nanoscale materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
61.72.Mm Grain and twin boundaries

Effect of Li doping on the magnetotransport properties of La0.7Ca0.3−yLiyMnO3 system: Decrease of metal–insulator transition temperature

Sayani Bhattacharya, R. K. Mukherjee, B. K. Chaudhuri, and H. D. Yang

Appl. Phys. Lett. 82, 4101 (2003); http://dx.doi.org/10.1063/1.1580650 (3 pages) | Cited 18 times

Online Publication Date: 2 June 2003

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With increasing the Li doping level in La0.7Ca0.3−yLiyMnO3 (0 ⩽ y ⩽ 0.3), the system is driven from a higher-conductivity regime to a lower-conductivity regime, which is in sharp contrast with the behavior of Na or K doping. Compared to those of K or Na, the ionic radius of Li is much smaller than that of Ca. Therefore, substitution of Ca by Li results in a smaller average A-site radius, narrowing the bandwidth and hence enhancing the band gap and resistivity. The effect of random disorder of La3+ and A2+ also plays an important role leading to charge localization. © 2003 American Institute of Physics.
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72.60.+g Mixed conductivity and conductivity transitions
75.47.Lx Magnetic oxides
75.30.Mb Valence fluctuation, Kondo lattice, and heavy-fermion phenomena

Elastic properties of hot-isostatically-pressed magnesium diboride

V. F. Nesterenko and Y. Gu

Appl. Phys. Lett. 82, 4104 (2003); http://dx.doi.org/10.1063/1.1579566 (3 pages) | Cited 7 times

Online Publication Date: 2 June 2003

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Magnesium diboride was hot-isostatically pressed using three qualitatively different cycles: dense material cooled under pressure (DMCUP), “standard” cycle with pressure and temperature simultaneously reduced, and isothermal pressure release. Elastic properties of dense MgB2 were measured at normal conditions using resonant ultrasound spectroscopy method. The highest values of elastic moduli correspond to the sample processed using DMCUP cycle. The data for fully dense samples are in satisfactory agreement with theoretical predictions based on quantum mechanics calculations. The effect of lower density on elastic constants is consistent with a theoretical approach based on elasticity theory taking into account effect of porosity. © 2003 American Institute of Physics.
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81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.D- Elasticity
81.40.Vw Pressure treatment
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation

Spin valves with spin-engineered domain-biasing scheme

Z. Q. Lu and G. Pan

Appl. Phys. Lett. 82, 4107 (2003); http://dx.doi.org/10.1063/1.1581977 (3 pages) | Cited 1 time

Online Publication Date: 2 June 2003

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Synthetic spin-filter spin valves with spin-engineered biasing scheme sub/Ta/NiFe/IrMn/NiFe/NOL/Cu1/CoFe/Cu2/CoFe/Ru/CoFe/IrMn/Ta were developed. In the structure, the orthogonal magnetic configuration for biasing and pinning field was obtained by one-step magnetic annealing process by means of spin flop, which eliminated the need for two antiferromagnetic materials with distinctively different blocking temperatures and two-step magnetic annealing as in conventional exchange biasing scheme. The longitudinal domain biasing of spin valves was achieved by using interlayer coupling field through Cu1 spacer. By adjusting the thickness of the Cu1 layer, the interlayer coupling biasing field can provide domain stabilization and was sufficiently strong to constrain the magnetization in coherent rotation. This can prevent Barkhausen noises associated with magnetization reversal. We report here a proof of concept study of such a domain-biasing scheme, which has its important technological applications in nanoscale spin valve and magnetic tunneling junction read heads and other spintronic devices. © 2003 American Institute of Physics.
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72.25.Mk Spin transport through interfaces
72.25.Ba Spin polarized transport in metals
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
75.30.Et Exchange and superexchange interactions
75.40.-s Critical-point effects, specific heats, short-range order
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.70.Kw Domain structure (including magnetic bubbles and vortices)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.40.Gh Other heat and thermomechanical treatments
81.40.Rs Electrical and magnetic properties related to treatment conditions
75.60.Nt Magnetic annealing and temperature-hysteresis effects
75.47.Np Metals and alloys
85.75.-d Magnetoelectronics; spintronics: devices exploiting spin polarized transport or integrated magnetic fields
75.75.-c Magnetic properties of nanostructures

Vortex nucleation in submicrometer ferromagnetic disks

M. Rahm, M. Schneider, J. Biberger, R. Pulwey, J. Zweck, D. Weiss, and V. Umansky

Appl. Phys. Lett. 82, 4110 (2003); http://dx.doi.org/10.1063/1.1581363 (3 pages) | Cited 29 times

Online Publication Date: 2 June 2003

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We investigate both experimentally and by means of micromagnetic calculations magnetic states preceding vortex formation in permalloy nanodisks. In experiment, we used micro-Hall sensors fabricated from GaAs/AlGaAs heterojunction material to measure stray field hysteresis loops of individual disks. Micromagnetic calculations involving different micromagnetic codes allowed us to interpret the experimental results. Both calculations and experiments suggest that vortex formation can be reached via different precursor states. © 2003 American Institute of Physics.
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75.50.Bb Fe and its alloys
75.25.-j Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Tt Fine-particle systems; nanocrystalline materials
75.60.Jk Magnetization reversal mechanisms

High critical current density in iron-clad MgB2 tapes

H. Fang, S. Padmanabhan, Y. X. Zhou, and K. Salama

Appl. Phys. Lett. 82, 4113 (2003); http://dx.doi.org/10.1063/1.1582358 (3 pages) | Cited 51 times

Online Publication Date: 2 June 2003

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Iron-clad MgB2 superconducting tapes with a MgB2 core cross-section area of 1.07×10−3 cm2 were fabricated using the standard powder-in-tube method. The starting precursor was ultrafine Mg and B mixture powder prepared by high-energy ball milling. Very good grain connections as well as grain refinement were obtained in tapes annealed at 850 °C. Under a 1.5-T external magnetic field, Jc is 1.07×105 and 6.54×103 A/cm2 at 20 and 30 K, respectively. An extrapolation to zero field at 20 K gives a Jc of 3.0×105 A/cm2. © 2003 American Institute of Physics.
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74.70.Ad Metals; alloys and binary compounds (including A15, MgB2, etc.)
84.71.Mn Superconducting wires, fibers, and tapes
74.25.Sv Critical currents
81.40.Gh Other heat and thermomechanical treatments
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation

Cooperative versus superparamagnetic behavior of dense magnetic nanoparticles in Co80Fe20/Al2O3 multilayers

S. Sahoo, O. Petracic, W. Kleemann, S. Stappert, G. Dumpich, P. Nordblad, S. Cardoso, and P. P. Freitas

Appl. Phys. Lett. 82, 4116 (2003); http://dx.doi.org/10.1063/1.1581002 (3 pages) | Cited 32 times

Online Publication Date: 2 June 2003

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Spin glasslike cooperative freezing is evidenced at low temperatures in a magnetic nanoparticle system prepared as a discontinuous metal–insulator multilayer [Co80Fe20(0.9 nm)/Al2O3(3 nm)]10. The relaxational behavior clearly deviates from Arrhenius–Néel–Brown-type and rather hints at collective freezing into a spin glass phase below Tg ≃ 61 K. Holelike memory imprinting during a stop-and-wait magnetization procedure corroborates the collective nature of the frozen state. Consequences for future magnetic terabit storage devices are briefly discussed. © 2003 American Institute of Physics.
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75.50.Tt Fine-particle systems; nanocrystalline materials
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.50.Lk Spin glasses and other random magnets
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Bb Fe and its alloys

Current–voltage characteristics of Pb and Sn granular superconducting nanowires

Sébastien Michotte, Stefan Mátéfi-Tempfli, and Luc Piraux

Appl. Phys. Lett. 82, 4119 (2003); http://dx.doi.org/10.1063/1.1582356 (3 pages) | Cited 30 times

Online Publication Date: 2 June 2003

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Arrays of granular superconducting Pb and Sn nanowires (40–55 nm in diameter and 22 or 50 μm long) have been prepared by electrodeposition in nanoporous membranes. A simple technique has been developed to perform electrical transport measurement on a single nanowire. By sweeping the dc current inside the nanowire, we observed the formation of phase-slip-centers far below the critical temperature. In contrast, in voltage-driven experiments, an interesting S-shaped behavior has been observed in the nucleation region of these phase-slip-centers. © 2003 American Institute of Physics.
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74.70.Ad Metals; alloys and binary compounds (including A15, MgB2, etc.)
74.81.Bd Granular, melt-textured, amorphous, and composite superconductors
74.25.F- Transport properties
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Substrate effect on the crystal structure and ferroelectricity of low-temperature-deposited Pb(Zr, Ti)O3 thin films by metalorganic chemical vapor deposition

Kouji Tokita, Masanori Aratani, and Hiroshi Funakubo

Appl. Phys. Lett. 82, 4122 (2003); http://dx.doi.org/10.1063/1.1581975 (3 pages) | Cited 10 times

Online Publication Date: 2 June 2003

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Tetragonal Pb(Zr0.35Ti0.65)O3 thin films were deposited at deposition temperatures ranging from 395 °C to 510 °C on (111)Pt/Ti/SiO2/Si, (111)Ir/TiO2/SiO2/Si, and (100)Ru/SiO2/Si substrates by metalorganic chemical vapor deposition. When the deposition temperature was above 415 °C, the remanent polarization (Pr) and the coercive field (Ec) were almost the same for the Pb(Zr0.35Ti0.65)O3 thin films deposited on these substrates. This means that the electrical properties were not significantly affected by the type of substrate above 415 °C. However, at 395 °C, the film deposited on the (111)Pt/Ti/SiO2/Si substrate showed a larger Pr value than those on the (111)Ir/TiO2/SiO2/Si and (100)Ru/SiO2/Si substrates. The lower crystallinity of the films deposited on the (111)Ir/TiO2/SiO2/Si and (100)Ru/SiO2/Si substrates, due to the oxidation of the Ir and Ru surfaces before starting film deposition, thwarts the attainment of good ferroelectricity. © 2003 American Institute of Physics.
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77.55.-g Dielectric thin films
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
68.55.-a Thin film structure and morphology
77.80.-e Ferroelectricity and antiferroelectricity
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
61.66.Fn Inorganic compounds
77.22.Ej Polarization and depolarization

45° rotational epitaxy of SrTiO3 thin films on sulfide-buffered Si

Y.-Z. Yoo, P. Ahmet, Zheng-Wu Jin, K. Nakajima, T. Chikyow, M. Kawasaki, Y. Konishi, Y. Yonezawa, J. H. Song, and H. Koinuma

Appl. Phys. Lett. 82, 4125 (2003); http://dx.doi.org/10.1063/1.1581383 (3 pages) | Cited 7 times

Online Publication Date: 2 June 2003

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Sulfide was employed as a buffer layer for the growth of SrTiO3 (STO) thin films on Si. In order to utilize a relationship of a 45° rotational lattice match between Si and STO, ZnS, with almost the same lattice constant as Si, was used as the buffer. The buffer layer showed a partially disordered region at the ZnS/Si interface, owing to steady interdiffusion between ZnS and Si. STO film on ZnS buffered Si showed the rotational epitaxy with respect to Si and sharp STO/ZnS interface. Propagation of stacking faults from the ZnS/Si interface was observed, but those plane defects were terminated at the rotational STO/ZnS interface, resulting in high-quality STO films. The dielectric constant of the STO/ZnS film was 34. © 2003 American Institute of Physics.
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77.55.-g Dielectric thin films
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.Nn Stacking faults and other planar or extended defects
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.22.Ch Permittivity (dielectric function)
77.80.-e Ferroelectricity and antiferroelectricity

Different dynamic behaviors of Pb(Mg1/3Ta2/3)O3 and Ba(Mg1/3Ta2/3)O3 single crystals studied by micro-Brillouin scattering and dielectric spectroscopy

Jae-Hyeon Ko, Seiji Kojima, and S. G. Lushnikov

Appl. Phys. Lett. 82, 4128 (2003); http://dx.doi.org/10.1063/1.1582353 (3 pages) | Cited 22 times

Online Publication Date: 2 June 2003

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Acoustic and dielectric properties of Pb(Mg1/3Ta2/3)O3 (PMT) and Ba(Mg1/3Ta2/3)O3 (BMT) single crystals with B-site disorder were obtained in a wide temperature range by micro-Brillouin scattering and dielectric spectroscopy. The temperature dependences of both the dielectric constant and the Brillouin shift of the longitudinal acoustic (LA) mode of BMT showed that there is no structural phase transition below 860 K, consistent with thermal expansion measurements. A low dielectric constant ϵ∼20 of BMT reflected the low-level flux contamination. PMT crystals showed frequency-dependent dielectric maximum, significant softening of the Brillouin shift of LA mode deviating from the high-temperature linear behavior. The temperature dependence of the maximum relaxation time could be obtained by combining dielectric and acoustic data, which followed the Vogel–Fulcher law with a freezing temperature of 119±6 K. This temperature coincides with that estimated from the frequency dependence of the temperature of the dielectric maximum, which is the evidence of the real freezing of the relaxation-time spectrum of PMT at a finite temperature. © 2003 American Institute of Physics.
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77.80.-e Ferroelectricity and antiferroelectricity
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
78.35.+c Brillouin and Rayleigh scattering; other light scattering
77.22.Ch Permittivity (dielectric function)
65.40.De Thermal expansion; thermomechanical effects
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Electrical properties and transport in boron nitride nanotubes

M. Radosavljević, J. Appenzeller, V. Derycke, R. Martel, Ph. Avouris, A. Loiseau, J.-L. Cochon, and D. Pigache

Appl. Phys. Lett. 82, 4131 (2003); http://dx.doi.org/10.1063/1.1581370 (3 pages) | Cited 35 times

Online Publication Date: 2 June 2003

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We have fabricated electronic devices based on single-walled boron nitride nanotubes (BNNTs). Our measurements indicate that all BNNTs are semiconducting, and p-doped. Temperature dependence of two terminal transport experiments suggests that at low drain fields, transport is dominated by thermionic emission over 250–300 meV Schottky contact barriers. Gate-induced barrier modulation was observed in vertically scaled devices, resulting in field-effect transistor operation. © 2003 American Institute of Physics.
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85.35.Kt Nanotube devices
73.63.Fg Nanotubes
73.40.Ns Metal-nonmetal contacts

Large frequency dependence of lowered maximum dielectric constant temperature of LiTaO3 nanocrystals dispersed in mesoporous silicate

Shigemi Kohiki, Shinichiro Nogami, Shintaro Kawakami, Syozo Takada, Hirokazu Shimooka, Hiroyuki Deguchi, Masanori Mitome, and Masaoki Oku

Appl. Phys. Lett. 82, 4134 (2003); http://dx.doi.org/10.1063/1.1580991 (3 pages) | Cited 4 times

Online Publication Date: 2 June 2003

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A large frequency dependence of the maximum dielectric constant temperature was observed for LiTaO3 nanocrystals (the diameter ≈20 Å) dispersed in mesoporous silicate. At the applied field frequency of 100 kHz, the maximum temperatures in the real and imaginary parts were 365 and 345 °C, respectively. The maximum temperature in the real part is apparently lower than the paraelectric–ferroelectric transition temperature (645 °C) of bulk LiTaO3. The maximum temperature in the imaginary part rose from 285 to 420 °C with increasing frequency from 10 to 1000 kHz. Since the bulk LiTaO3 shows no relaxor behavior, such superparaelectric behavior is obviously a consequence of nanominiaturization of LiTaO3 crystal and insignificant cooperative interactions between the nanoparticles. © 2003 American Institute of Physics.
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77.84.Lf Composite materials
77.22.Ch Permittivity (dielectric function)

Low-temperature conductance measurements on single molecules

J. Reichert, H. B. Weber, M. Mayor, and H. v. Löhneysen

Appl. Phys. Lett. 82, 4137 (2003); http://dx.doi.org/10.1063/1.1574844 (3 pages) | Cited 63 times

Online Publication Date: 2 June 2003

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An experimental protocol which allows to perform conductance spectroscopy on organic molecules at low temperatures (T ≈ 30 K) has been developed. This extends the method of mechanically controlled break junctions which has recently demonstrated to be suitable to contact single molecules at room temperature. The conductance data obtained at low T with a conjugated sample molecule show a highly improved data quality with a higher stability, narrower linewidth, and substantially reduced noise. Thus, the comparability of experimental data with other measurements as well as with theoretical simulations is considerably improved. © 2003 American Institute of Physics.
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84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)
07.20.Mc Cryogenics; refrigerators, low-temperature detectors, and other low-temperature equipment
81.07.Nb Molecular nanostructures

Measurement of carbon nanotube–polymer interfacial strength

Asa H. Barber, Sidney R. Cohen, and H. Daniel Wagner

Appl. Phys. Lett. 82, 4140 (2003); http://dx.doi.org/10.1063/1.1579568 (3 pages) | Cited 134 times

Online Publication Date: 2 June 2003

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The force required to separate a carbon nanotube from a solid polymer matrix has been measured by performing reproducible nanopullout experiments using atomic force microscopy. The separation stress is found to be remarkably high, indicating that carbon nanotubes are effective at reinforcing a polymer. These results imply that the polymer matrix in close vicinity of the carbon nanotube is able to withstand stresses that would otherwise cause considerable yield in a bulk polymer specimen. © 2003 American Institute of Physics.
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68.35.Gy Mechanical properties; surface strains
62.25.-g Mechanical properties of nanoscale systems
68.37.Ps Atomic force microscopy (AFM)

Marangoni effect in nanosphere-enhanced laser nanopatterning of silicon

Y. Lu, S. Theppakuttai, and S. C. Chen

Appl. Phys. Lett. 82, 4143 (2003); http://dx.doi.org/10.1063/1.1581387 (3 pages) | Cited 26 times

Online Publication Date: 2 June 2003

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We report a Marangoni effect in nanosphere-enhanced laser direct nanopatterning of silicon surface. A monolayer of nanosphere array was formed on the silicon substrate by self-assembly. A 248-nm excimer laser was used to irradiate the sample surface. Due to optical field enhancement between the nanosphere and the substrate, the silicon surface was locally melted. The molten material was redistributed due to surface tension forces, resulting in the formation of a nanodent array. The morphology of the nanodents changed from bowl-type to “Sombrero” with increase of laser intensity as a result of a Marangoni effect that arises due to the competition between a thermocapillary force and a chemicapillary force acting on the molten material. © 2003 American Institute of Physics.
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81.16.Rf Micro- and nanoscale pattern formation
81.16.Dn Self-assembly
79.20.Ds Laser-beam impact phenomena
68.03.Cd Surface tension and related phenomena
61.82.Fk Semiconductors
68.35.Rh Phase transitions and critical phenomena
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)

Efficient field emission from single crystalline indium oxide pyramids

Hongbo Jia, Ye Zhang, Xihong Chen, Jing Shu, Xuhui Luo, Zhensheng Zhang, and Dapeng Yu

Appl. Phys. Lett. 82, 4146 (2003); http://dx.doi.org/10.1063/1.1582354 (3 pages) | Cited 65 times

Online Publication Date: 2 June 2003

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Well-aligned indium oxide pyramids were synthesized on a Ni-coated silicon (100) substrate by a chemical vapor deposition. Scanning electron microscopy and x-ray diffraction investigations show that these pyramids present a tetragonal morphology and single-crystalline cubic bixbyite structure. The size control of the pyramids was achieved by varying the growth temperature. Field-emission characteristics of the as-grown indium oxide pyramids were measured. The field-emission current density of the nanopyramids (average size: ∼180 nm) reached about 1 mA/cm2 at a threshold field of about 6.0 V/μm, which is comparable to that of carbon nanotubes, and can guarantee sufficient luminescence brightness in a flat panel display. © 2003 American Institute of Physics.
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79.70.+q Field emission, ionization, evaporation, and desorption
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
61.46.-w Structure of nanoscale materials
68.55.-a Thin film structure and morphology

Evidence for trans-polyacetylene in nanocrystalline diamond films from H–D isotropic substitution experiments

R. Pfeiffer, H. Kuzmany, N. Salk, and B. Günther

Appl. Phys. Lett. 82, 4149 (2003); http://dx.doi.org/10.1063/1.1582352 (2 pages) | Cited 33 times

Online Publication Date: 2 June 2003

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Raman spectra of nanocrystalline diamond (NCD) films show a peak around 1140 cm−1 that is usually considered to be a fingerprint of a NCD phase in the sample. From recent studies, it was suggested that this line is due to trans-polyacetylene in the films. We present Raman spectra of deuterated NCD films produced from a D2/CD4/Ar plasma. In these spectra, the 1140 cm−1 mode has disappeared and a peak at 860 cm−1 has emerged. The downshift of the peak at 1140 cm−1 is taken as a proof for its origin from trans-polyacetylene. © 2003 American Institute of Physics.
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78.66.Sq Composite materials
78.66.Qn Polymers; organic compounds
78.30.Jw Organic compounds, polymers
78.35.+c Brillouin and Rayleigh scattering; other light scattering

Growth of Si nanocrystals on alumina and integration in memory devices

T. Baron, A. Fernandes, J. F. Damlencourt, B. De Salvo, F. Martin, F. Mazen, and S. Haukka

Appl. Phys. Lett. 82, 4151 (2003); http://dx.doi.org/10.1063/1.1577409 (3 pages) | Cited 23 times

Online Publication Date: 2 June 2003

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We present a detailed study of the growth of Si quantum dots (Si QDs) by low pressure chemical vapor deposition on alumina dielectric deposited by atomic layer deposition. The Si QDs density is very high, 1012 cm−2, for a mean diameter between 5 and 10 nm. Al2O3/Si QD stacks have been integrated in memory devices as granular floating gate. The devices demonstrate good charge storage and data retention characteristics. © 2003 American Institute of Physics.
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81.07.Bc Nanocrystalline materials
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.07.Ta Quantum dots
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
84.30.Sk Pulse and digital circuits
68.65.Hb Quantum dots (patterned in quantum wells)
61.46.-w Structure of nanoscale materials

Growth and optical properties of GaN/AlN quantum wells

C. Adelmann, E. Sarigiannidou, D. Jalabert, Y. Hori, J.-L. Rouvière, B. Daudin, S. Fanget, C. Bru-Chevallier, T. Shibata, and M. Tanaka

Appl. Phys. Lett. 82, 4154 (2003); http://dx.doi.org/10.1063/1.1581386 (3 pages) | Cited 45 times

Online Publication Date: 2 June 2003

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We demonstrate the growth of GaN/AlN quantum-well structures by plasma-assisted molecular-beam epitaxy by taking advantage of the surfactant effect of Ga. The GaN/AlN quantum wells show photoluminescence emission with photon energies in the range between 4.2 and 2.3 eV for well widths between 0.7 and 2.6 nm, respectively. An internal electric field strength of 9.2±1.0 MV/cm is deduced from the dependence of the emission energy on the well width. © 2003 American Institute of Physics.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.07.St Quantum wells
78.67.De Quantum wells
78.55.Cr III-V semiconductors
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Development of gold-doped Hg0.79Cd0.21Te for very-long-wavelength infrared detectors

H. D. Shih, M. A. Kinch, F. Aqariden, P. K. Liao, H. F. Schaake, and V. Nathan

Appl. Phys. Lett. 82, 4157 (2003); http://dx.doi.org/10.1063/1.1581369 (3 pages) | Cited 4 times

Online Publication Date: 2 June 2003

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Gold-doped Hg1−xCdxTe samples of x = 0.2067 (in the very-long-wavelength infrared spectral band, with cutoff wavelengths ∼13.2 μm at 77 K) were prepared by tellurium-melt liquid-phase epitaxy. The samples were doped with indium to ∼ 2×1014 cm−3 and gold to ∼ 7×1015 cm−3, and were characterized by secondary ion mass spectroscopy, Hall measurements, and minority carrier lifetime measurements. State-of-the-art minority carrier lifetime of ∼0.82 μs was obtained. © 2003 American Institute of Physics.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
73.61.Ga II-VI semiconductors
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
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