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3 Mar 2003

Volume 82, Issue 9, pp. 1323-1488

Issue Cover Spotlight Figure

Appl. Phys. Lett. 82, 1437 (2003); http://dx.doi.org/10.1063/1.1556958 (3 pages)

T. K. Yamada, M. M. J. Bischoff, T. Mizoguchi, and H. van Kempen
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Fabrication of Zn/ZnS nanocable heterostructures by thermal reduction/sulfidation

Quan Li and Chunrui Wang

Appl. Phys. Lett. 82, 1398 (2003); http://dx.doi.org/10.1063/1.1558957 (3 pages) | Cited 39 times

Online Publication Date: 25 February 2003

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Single-crystalline Zn/ZnS coaxial nanocables were fabricated through thermal reduction of ZnS using graphite powder at elevated temperatures. Energy dispersive x-ray analysis of the as-fabricated samples indicated that the nanowires were composed of Zn and S only. Transmission-electron-microscopic study of the nanowires revealed that they had core/sheath contrast, suggesting a Zn core/ZnS sheath heterostructure. Epitaxial relationship was observed between the Zn and the ZnS. The possible formation mechanisms of such nanocables are discussed. © 2003 American Institute of Physics.
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68.65.La Quantum wires (patterned in quantum wells)
61.46.-w Structure of nanoscale materials
81.16.Be Chemical synthesis methods
73.40.Ns Metal-nonmetal contacts

Growth and optical properties of single-crystal tubular ZnO whiskers

J. Q. Hu and Y. Bando

Appl. Phys. Lett. 82, 1401 (2003); http://dx.doi.org/10.1063/1.1558899 (3 pages) | Cited 136 times

Online Publication Date: 25 February 2003

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The growth of single-crystal tubular ZnO whiskers was achieved via a process of first reduction and following oxidation of ZnS powders. The products were characterized using x-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, and photoluminescence spectroscopy. The whiskers are tubular single crystals with the [001] growth crystallographic direction, and most have outer diameters of ∼ 400 nm, lengths of up to 15 μm, and wall thickness range of 100–150 nm. Room-temperature photoluminescence spectrum of the whiskers reveals a strong and sharp UV emission band at 381 nm and a weak and broad green emission band at 583 nm. Possible growth mechanism of the ZnO whiskers was briefly discussed. © 2003 American Institute of Physics.
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68.70.+w Whiskers and dendrites (growth, structure, and nonelectronic properties)
78.55.Et II-VI semiconductors
61.46.-w Structure of nanoscale materials
78.67.Ch Nanotubes
81.07.De Nanotubes

In situ growth of blue-emitting thin films of cerium-doped barium chloride hydrate at low temperatures

Jianhua Hao, Zhidong Lou, and Michael Cocivera

Appl. Phys. Lett. 82, 1404 (2003); http://dx.doi.org/10.1063/1.1558891 (3 pages) | Cited 3 times

Online Publication Date: 25 February 2003

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Blue emission was observed from thin films of barium chloride hydrate doped with cerium. The films were deposited by spray pyrolysis of aqueous solutions with substrate temperatures between 250 and 450 °C. The cathodoluminescence (CL) spectrum consists of two peaks at 443 and 485 nm due to 4f-5d transitions of cerium ion. The dependence of the emission band on deposition temperature and Ce/Ba ratio is discussed. The CL luminance and luminous efficiency at 5 kV were 120 cd/m2 and 0.48 lm/W, respectively, for the films deposited at temperatures as low as 250 °C. The results indicate barium chloride hydrate doped with cerium is a blue phosphor that exhibits relatively efficient luminescence after processing at low temperatures. © 2003 American Institute of Physics.
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78.60.Hk Cathodoluminescence, ionoluminescence
81.15.Rs Spray coating techniques
78.66.Nk Insulators

Measuring electronic structure of wurtzite InN using electron energy loss spectroscopy

K. A. Mkhoyan, J. Silcox, E. S. Alldredge, N. W. Ashcroft, H. Lu, W. J. Schaff, and L. F. Eastman

Appl. Phys. Lett. 82, 1407 (2003); http://dx.doi.org/10.1063/1.1559660 (3 pages) | Cited 14 times

Online Publication Date: 25 February 2003

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The electronic structure of wurtzite InN has been investigated by electron energy loss spectroscopy (EELS). Spectra of the nitrogen K edge and the indium M4,5 edge have been measured and were compared with calculated partial, N 2p and In 5p conduction band density of states in InN. Excellent agreement on the relative positions of the characteristic peaks were obtained. From low-loss EELS the bulk plasmon energy at 15.5 eV, location of the In 4d deep valence states at about 16.3 eV below the conduction band maximum and strong interband transitions with 6.2 eV excitation energy are also found. © 2003 American Institute of Physics.
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71.20.Nr Semiconductor compounds
79.20.Uv Electron energy loss spectroscopy
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons

Illumination-induced recovery of Cu(In,Ga)Se2 solar cells after high-energy electron irradiation

A. Jasenek, U. Rau, K. Weinert, H. W. Schock, and J. H. Werner

Appl. Phys. Lett. 82, 1410 (2003); http://dx.doi.org/10.1063/1.1559648 (3 pages) | Cited 4 times

Online Publication Date: 25 February 2003

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Cu(In,Ga)Se2/CdS/ZnO solar cells irradiated with a 1 MeV electron fluence of 1018 cm−2 degrade to about 80% of their initial conversion efficiency. Illumination with white light at an intensity of 100 mW cm−2 for 3 h at room temperature restores more than 90% of the preirradiation efficiency. The healing process is more efficient if the device is kept under open-circuit conditions during illumination than for short-circuit conditions. Injecting minority carriers by voltage bias in the dark, instead of illumination, does not cause enduring device recovery. This behavior of Cu(In,Ga)Se2 is in contrast to illumination-induced defect healing processes reported for other semiconductor materials, like GaAs, InP, or GaP. © 2003 American Institute of Physics.
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84.60.Jt Photoelectric conversion
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.61.Le Other inorganic semiconductors
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Studies of field-induced nonequilibrium electron transport in an InxGa1−xN (x ≅ 0.6) epilayer grown on GaN

W. Liang, K. T. Tsen, D. K. Ferry, K. H. Kim, J. Y. Lin, and H. X. Jiang

Appl. Phys. Lett. 82, 1413 (2003); http://dx.doi.org/10.1063/1.1556576 (3 pages) | Cited 7 times

Online Publication Date: 25 February 2003

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Field-induced electron transport in an InxGa1−xN (x ≅ 0.6) sample grown on GaN has been studied by subpicosecond Raman spectroscopy. Nonequilibrium electron distribution and electron drift velocity due to the presence of piezoelectric and spontaneous fields in the InxGa1−xN layer have been directly measured. The experimental results are compared with ensemble Monte Carlo calculations and reasonable agreements are obtained. © 2003 American Institute of Physics.
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73.61.Ey III-V semiconductors
78.66.Fd III-V semiconductors
77.65.Ly Strain-induced piezoelectric fields
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
78.30.Fs III-V and II-VI semiconductors

Stimulated emission and ultrafast carrier relaxation in InGaN multiple quantum wells

Ümit Özgür, Henry O. Everitt, Stacia Keller, and Steven P. DenBaars

Appl. Phys. Lett. 82, 1416 (2003); http://dx.doi.org/10.1063/1.1557770 (3 pages) | Cited 10 times

Online Publication Date: 25 February 2003

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Stimulated emission (SE) was measured from two InGaN multiple quantum well (MQW) laser structures with different QW In compositions x. SE threshold energy densities (Ith) increased with increasing x-dependent QW depth. Time-resolved differential transmission measurements mapped the carrier relaxation mechanisms and explained the dependence of Ith on x. Carriers are captured from the barriers to the QWs in <1 ps, while carrier recombination rates increased with increasing x. For excitation above Ith, an additional, fast relaxation mechanism appears due to the loss of carriers in the barriers through a cascaded refilling of the QW state undergoing SE. The increased material inhomogeneity with increasing x provides additional relaxation channels outside the cascaded refilling process, removing carriers from the SE process and increasing Ith. © 2003 American Institute of Physics.
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78.67.De Quantum wells
42.55.Px Semiconductor lasers; laser diodes
78.45.+h Stimulated emission
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
78.66.Fd III-V semiconductors
81.07.St Quantum wells
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
73.21.Cd Superlattices
73.21.Fg Quantum wells
78.47.-p Spectroscopy of solid state dynamics
61.66.Bi Elemental solids
61.66.Dk Alloys

Nonvolatile electrical bistability of organic/metal-nanocluster/organic system

Liping Ma, Seungmoon Pyo, Jianyong Ouyang, Qianfei Xu, and Yang Yang

Appl. Phys. Lett. 82, 1419 (2003); http://dx.doi.org/10.1063/1.1556555 (3 pages) | Cited 167 times

Online Publication Date: 25 February 2003

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Two-terminal electrical bistable devices have been fabricated using a sandwich structure of organic/metal/organic as the active medium, sandwiched between two external electrodes. The nonvolatile electrical bistability of these devices can be controlled using a positive and a negative electrical bias alternatively. A forward bias may switch the device to a high-conductance state, while a reverse bias is required to restore it to a low-conductance state. In this letter, a model to explain this electrical bistability is proposed. It is found that the bistability is very sensitive to the nanostructure of the middle metal layer. For obtaining the devices with well-controlled bistability, the middle metal layer is incorporated with metal nanoclusters separated by thin oxide layers. These nanoclusters behave as the charge storage elements, which enable the nonvolatile electrical bistability when biased to a sufficiently high voltage. This mechanism is supported by the experimental data obtained from UV–visible absorption spectra, atomic force microscopy, and impedance spectroscopy. © 2003 American Institute of Physics.
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73.40.Ns Metal-nonmetal contacts
68.37.Ps Atomic force microscopy (AFM)
78.40.Kc Metals, semimetals, and alloys
78.66.Bz Metals and metallic alloys

Band offsets at CdCr2Se4–(AlGa)As and CdCr2Se4–ZnSe interfaces

H. B. Zhao, Y. H. Ren, B. Sun, G. Lüpke, A. T. Hanbicki, and B. T. Jonker

Appl. Phys. Lett. 82, 1422 (2003); http://dx.doi.org/10.1063/1.1558956 (3 pages) | Cited 3 times

Online Publication Date: 25 February 2003

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The band discontinuities of CdCr2Se4–(AlGa)As and CdCr2Se4–ZnSe heterojunctions are measured to high resolution by internal photoemission using a widely tunable optical parametric amplifier system. The conduction band offsets ΔEc = 660 and 530 meV at the CdCr2Se4–GaAs and CdCr2Se4–ZnSe interfaces are determined from the threshold energies of the photocurrent spectrum at room temperature. © 2003 American Institute of Physics.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
79.60.Jv Interfaces; heterostructures; nanostructures

Hole density dependence of effective mass, mobility and transport time in strained Ge channel modulation-doped heterostructures

T. Irisawa, M. Myronov, O. A. Mironov, E. H. C. Parker, K. Nakagawa, M. Murata, S. Koh, and Y. Shiraki

Appl. Phys. Lett. 82, 1425 (2003); http://dx.doi.org/10.1063/1.1558895 (3 pages) | Cited 17 times

Online Publication Date: 25 February 2003

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We performed systematic low-temperature (T = 350 mK–15 K) magnetotransport measurements on the two-dimensional hole gas with various sheet carrier densities Ps = (0.57–2.1)×1012 cm−2 formed in the strained Ge channel modulation-doped (MOD) SiGe heterostructures grown on Si substrates. It was found that the effective hole mass deduced by temperature dependent Shubnikov–de Hass oscillations increased monotonically from (0.087±0.05)m0 to (0.19±0.01)m0 with the increase of Ps, showing large band nonparabolicity in strained Ge. In contrast to this result, the increase of the mobility with increasing Ps (up to 29 000 cm2/V s) was observed, suggesting that Coulomb scattering played a dominant role in the transport of the Ge channel at low temperatures. In addition, the Dingle ratio of the transport time to the quantum lifetime was found to increase with increasing Ps, which was attributed to the increase of remote impurity scattering with the increase of the doping concentration in MOD SiGe layers. © 2003 American Institute of Physics.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
72.20.My Galvanomagnetic and other magnetotransport effects

Electrical characteristics of proton-irradiated Sc2O3 passivated AlGaN/GaN high electron mobility transistors

B. Luo, Jihyun Kim, F. Ren, J. K. Gillespie, R. C. Fitch, J. Sewell, R. Dettmer, G. D. Via, A. Crespo, T. J. Jenkins, B. P. Gila, A. H. Onstine, K. K. Allums, C. R. Abernathy, S. J. Pearton, et al.

Appl. Phys. Lett. 82, 1428 (2003); http://dx.doi.org/10.1063/1.1559631 (3 pages) | Cited 17 times

Online Publication Date: 25 February 2003

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Sc2O3-passivated AlGaN/GaN high electron mobility transistors (HEMTs) were irradiated with 40 MeV protons to a fluence corresponding to approximately 10 years in low-earth orbit (5×109 cm−2). Devices with an AlGaN cap layer showed less degradation in dc characteristics than comparable GaN-cap devices, consistent with differences in average band energy. The changes in device performance could be attributed completely to bulk trapping effects, demonstrating that the effectiveness of the Sc2O3 layers in passivating surface states in the drain-source region was undiminished by the proton irradiation. Sc2O3-passivated AlGaN/HEMTs appear to be attractive candidates for space and terrestrial applications where resistance to high fluxes of ionizing radiation is a criteria. © 2003 American Institute of Physics.
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85.30.Tv Field effect devices
73.61.Ey III-V semiconductors
81.65.Rv Passivation
61.80.Jh Ion radiation effects
61.82.Ms Insulators
61.82.Fk Semiconductors

Unified closed-form model of thermionic-field and field emissions through a triangular potential barrier

Shreepad Karmalkar and D. Mahaveer Sathaiya

Appl. Phys. Lett. 82, 1431 (2003); http://dx.doi.org/10.1063/1.1557773 (3 pages) | Cited 6 times

Online Publication Date: 25 February 2003

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We report a simple closed-form model of the total emission through a triangular potential barrier due to thermionic field emission (TFE) and field emission (FE). Such a model has not been derived previously, since the energy distribution function of emitted electrons is not analytically integrable. We overcame this difficulty using a geometrical approximation of the integration operation. Our model so derived reveals the energy location and spread of the emission, which allow estimation of the emission through any fraction of the barrier. It also yields a characteristic field parameter in terms of the barrier height, temperature, and effective mass, which can be used to identify the TFE, FE, and TE regimes of device operation. © 2003 American Institute of Physics.
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79.40.+z Thermionic emission
79.70.+q Field emission, ionization, evaporation, and desorption
02.60.Jh Numerical differentiation and integration
73.40.Cg Contact resistance, contact potential
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Strain-induced magnetic stripe domains in La0.7Sr0.3MnO3 thin films

Joonghoe Dho, Y. N. Kim, Y. S. Hwang, J. C. Kim, and N. H. Hur

Appl. Phys. Lett. 82, 1434 (2003); http://dx.doi.org/10.1063/1.1556967 (3 pages) | Cited 67 times

Online Publication Date: 25 February 2003

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We have investigated magnetic microstructures of magnetoresistive La0.7Sr0.3MnO3 (LSMO) thin films. Magnetic images are strongly dependent on structural strain induced by the substrates. The LSMO film on SrTiO3 dominated by tensile stress effect displays a feather-like pattern, whereas LSMO films on LaAlO3 and NdGaO3 substrates under compressive stress show stripe domains. In particular, the magnetic image of the film on NdGaO3 reveals distinctive straight stripe domain patterns on the order of about 120 nm, suggesting the presence of a sizable out-of-plane magnetization. The ordering of the stripe domains is also sensitive to the field direction. © 2003 American Institute of Physics.
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75.70.Kw Domain structure (including magnetic bubbles and vortices)
75.70.Ak Magnetic properties of monolayers and thin films
68.37.Rt Magnetic force microscopy (MFM)
68.60.Bs Mechanical and acoustical properties
75.47.Gk Colossal magnetoresistance
75.47.Lx Magnetic oxides
75.30.Gw Magnetic anisotropy

Use of voltage pulses to detect spin-polarized tunneling

T. K. Yamada, M. M. J. Bischoff, T. Mizoguchi, and H. van Kempen

Appl. Phys. Lett. 82, 1437 (2003); http://dx.doi.org/10.1063/1.1556958 (3 pages) | Cited 16 times

Online Publication Date: 25 February 2003

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The present letter describes a method to make a spin-polarized scanning tunneling microscopy tip by applying voltage pulses between a W tip and a magnetic sample. This spin-polarized tip has the similar characteristics as an Fe-coated W tip, which was confirmed by observations of antiferromagnetically coupled ferromagnetic Mn(001) layers (>3 ML) grown on an Fe(001) whisker at 370 K. Furthermore, we demonstrate that these voltage pulses can vary the tip magnetization direction. © 2003 American Institute of Physics.
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07.79.Cz Scanning tunneling microscopes
75.50.Cc Other ferromagnetic metals and alloys
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.35.B- Structure of clean surfaces (and surface reconstruction)

Giant magnetothermopower associated with large magnetoresistance in Ag2−δTe

Young Sun, M. B. Salamon, M. Lee, and T. F. Rosenbaum

Appl. Phys. Lett. 82, 1440 (2003); http://dx.doi.org/10.1063/1.1558896 (3 pages) | Cited 7 times

Online Publication Date: 25 February 2003

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We have probed the temperature and magnetic-field dependence of the thermopower and resistance of a p-type silver chalcogenide, Ag2−δTe. The application of a magnetic field causes not only a large magnetoresistance but also a giant magnetothermopower effect. The maximum change of thermopower is as high as 470 μV/K in a 7 T magnetic field. Both the magnetoresistance and the magnetothermopower show a pronounced peak and nearly linear behavior near the sign change of the thermopower. Bandcrossing and quantum confinement due to disorder appear to play key roles in the heightened response to field. © 2003 American Institute of Physics.
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72.20.Pa Thermoelectric and thermomagnetic effects
72.20.My Galvanomagnetic and other magnetotransport effects
72.80.Jc Other crystalline inorganic semiconductors

Magnetic coupling in Co/Cr2O3/CrO2 “trilayer” films

Ruihua Cheng, A. N. Caruso, L. Yuan, S.-H. Liou, and P. A. Dowben

Appl. Phys. Lett. 82, 1443 (2003); http://dx.doi.org/10.1063/1.1558212 (3 pages) | Cited 6 times

Online Publication Date: 25 February 2003

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The ferromagnetic coupling between Co and CrO2, through an insulator (Cr2O3) was characterized by in situ magneto-optic Kerr effect. By evaporating 20–60 Å Co thin films on top of epitaxial CrO2 films, a Co/Cr2O3/CrO2 trilayer system can be readily fabricated; this is possible because the native surface layer of CrO2 is Cr2O3. In situ x-ray photoemission studies show that the Co is oxidized at the interface between Co and Cr2O3, so that the system more resembles Co/CoO/Cr2O3/CrO2. The Co thickness and temperature dependence of the magnetic hysteresis loops indicate that magnetic coupling strength increases with increasing Co thickness and decreases with increasing temperature. The magnetic coupling through the insulator barrier may be related to defect states in the insulating barrier layer. © 2003 American Institute of Physics.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.50.Cc Other ferromagnetic metals and alloys
75.50.Dd Nonmetallic ferromagnetic materials
78.20.Ls Magneto-optical effects
78.66.Bz Metals and metallic alloys
78.66.Nk Insulators
79.60.Jv Interfaces; heterostructures; nanostructures
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
73.20.Hb Impurity and defect levels; energy states of adsorbed species

Enhanced effect of magnetic anisotropy on free clusters

Yuannan Xie and John A. Blackman

Appl. Phys. Lett. 82, 1446 (2003); http://dx.doi.org/10.1063/1.1558211 (3 pages) | Cited 4 times

Online Publication Date: 25 February 2003

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We propose a simple model to estimate the effective moments of free clusters in a magnetic field. Compared with supported clusters, the effect of magnetic anisotropy is significantly enhanced, in good agreement with experimental results. The controversy of relations between the effective moment and cluster temperature presented in experiments is explained within our model. We can evaluate the magnetic anisotropy energies of free clusters from Stern–Gerlach experimental results. © 2003 American Institute of Physics.
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75.30.Gw Magnetic anisotropy
36.40.Cg Electronic and magnetic properties of clusters
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Cr Saturation moments and magnetic susceptibilities
75.50.Tt Fine-particle systems; nanocrystalline materials
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Fatigue-free La-modified PbTiO3 thin films prepared by pulsed-laser deposition on Pt/Ti/SiO2/Si substrates

Zhenggao Dong, Mingrong Shen, and Wenwu Cao

Appl. Phys. Lett. 82, 1449 (2003); http://dx.doi.org/10.1063/1.1556559 (3 pages) | Cited 10 times

Online Publication Date: 25 February 2003

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Fatigue-free 14 mol % La-modified PbTiO3 (PLT) thin films were grown on Pt/Ti/SiO2/Si substrates using pulsed-laser deposition and crystallized by furnace annealing at 600 °C. The 220-nm-thick PLT film capacitors with a Pt top electrode showed excellent ferroelectric properties. The remanent polarization (2Pr) and the coercive field (2Ec) were about 20 μC/cm2 and 70 kV/cm, respectively, and the PLT capacitors did not show any noticeable fatigue up to 3×109 read/write switching cycles at a frequency of 1 MHz and switching voltage of 5 V. By comparing the microstructures, electric, and dielectric properties with those of pure PbTiO3 thin films, the suppression of oxygen vacancies and/or charged defects, and the coral-like microstructures developed in PLT films were attributed to its fatigue-free feature. © 2003 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.55.-g Dielectric thin films
77.80.Fm Switching phenomena
77.22.Ej Polarization and depolarization
81.15.Fg Pulsed laser ablation deposition
81.40.Gh Other heat and thermomechanical treatments
68.55.-a Thin film structure and morphology
77.80.Dj Domain structure; hysteresis
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)

Layered Cu-based electrode for high-dielectric constant oxide thin film-based devices

W. Fan, S. Saha, J. A. Carlisle, O. Auciello, R. P. H. Chang, and R. Ramesh

Appl. Phys. Lett. 82, 1452 (2003); http://dx.doi.org/10.1063/1.1556959 (3 pages) | Cited 17 times

Online Publication Date: 25 February 2003

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Ti–Al/Cu/Ta multilayered electrodes were fabricated on SiO2/Si substrates by ion beam sputtering deposition, to overcome the problems of Cu diffusion and oxidation encountered during the high dielectric constant (κ) materials integration. The Cu and Ta layers remained intact through the annealing in oxygen environment up to 600 °C. The thin oxide layer, formed on the Ti–Al surface, effectively prevented the oxygen penetration toward underneath layers. Complex oxide (BaxSr1−x)TiO3 (BST) thin films were grown on the layered Ti–Al/Cu/Ta electrodes using rf magnetron sputtering. The deposited BST films exhibited relatively high permittivity (150), low dielectric loss (0.007) at zero bias, and low leakage current <2×10−8 A/cm2 at 100 kV/cm. © 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
84.32.Tt Capacitors
77.22.Gm Dielectric loss and relaxation
77.22.Ch Permittivity (dielectric function)
81.05.Bx Metals, semimetals, and alloys
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
81.40.Gh Other heat and thermomechanical treatments
81.40.Rs Electrical and magnetic properties related to treatment conditions
81.65.Mq Oxidation
81.15.Cd Deposition by sputtering

Electro-optic characteristics of (001)-oriented Ba0.6Sr0.4TiO3 thin films

Dal-Young Kim, Seung Eon Moon, Eun-Kyung Kim, Su-Jae Lee, Jong-Jin Choi, and Hyoun-Ee Kim

Appl. Phys. Lett. 82, 1455 (2003); http://dx.doi.org/10.1063/1.1556962 (3 pages) | Cited 22 times

Online Publication Date: 25 February 2003

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Ba0.6Sr0.4TiO3 thin films were grown on MgO(001) substrates using pulsed-laser deposition. The films were highly oriented along the (001) direction, and showed a high electro-optic response to an external electric field. The quadratic electro-optic coefficient Rc was 1.0×10−14 m2/V2, and the birefringence variation was as large as 0.09. Various electro-optic applications as well as the microwave applications of barium strontium titanate thin films are expected. © 2003 American Institute of Physics.
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78.20.Jq Electro-optical effects
78.66.Nk Insulators
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)
77.55.-g Dielectric thin films
81.15.Fg Pulsed laser ablation deposition
78.20.Fm Birefringence
42.70.-a Optical materials
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Linear and nonlinear optical properties of single-walled carbon nanotubes within an ordered array of nanosized silica spheres

H. Han, S. Vijayalakshmi, A. Lan, Z. Iqbal, H. Grebel, E. Lalanne, and A. M. Johnson

Appl. Phys. Lett. 82, 1458 (2003); http://dx.doi.org/10.1063/1.1557322 (3 pages) | Cited 15 times

Online Publication Date: 25 February 2003

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The linear and nonlinear optical properties of well-separated, single-walled carbon nanotubes were measured. The tubes were grown into the voids of an ordered array of silica spheres. Transmission of light through these tubes increased with the incident laser intensity. The nonlinear decay time of a λ = 800-nm probe was measured at 320 fs when the sample was pumped with 400-nm light. Current–voltage characteristics changed upon illumination with a laser beam. Raman scattering decreased as electrical biasing increased. © 2003 American Institute of Physics.
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78.67.Ch Nanotubes
42.65.Pc Optical bistability, multistability, and switching, including local field effects
78.30.Na Fullerenes and related materials
73.63.Fg Nanotubes

Insight into the premelting and melting processes of metal nanoparticles through capacitance measurements

G. B. Parravicini, A. Stella, P. Tognini, P. G. Merli, A. Migliori, P. Cheyssac, and R. Kofman

Appl. Phys. Lett. 82, 1461 (2003); http://dx.doi.org/10.1063/1.1556968 (3 pages) | Cited 8 times

Online Publication Date: 25 February 2003

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We demonstrate that capacitance measurements on metallic nanosystems (specifically Ga nanoparticles embedded in dielectric matrix) yield information to clarify the complex phenomenon of melting, where different mechanisms may interplay. The technique is proved to be extremely powerful to study the role of surfaces and interfaces on a twofold basis: very short (of the order of a few angstroms) penetration depth of the probing electric field and a strict relationship of capacity with entropy. We show that initial disorder starts to take place ≈65 °C before full melting, with evidence of two regimes in the premelting and melting region. © 2003 American Institute of Physics.
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64.70.D- Solid-liquid transitions
61.46.-w Structure of nanoscale materials
64.70.Nd Structural transitions in nanoscale materials
65.80.-g Thermal properties of small particles, nanocrystals, nanotubes, and other related systems
81.07.Bc Nanocrystalline materials
73.63.Bd Nanocrystalline materials
65.40.G- Other thermodynamical quantities
72.80.Tm Composite materials

Self-limiting size control of hemispherical grains of microcrystalline Si self-assembled on an amorphous Si film surface

Housei Akazawa

Appl. Phys. Lett. 82, 1464 (2003); http://dx.doi.org/10.1063/1.1558214 (3 pages) | Cited 2 times

Online Publication Date: 25 February 2003

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When a hydrogen-free amorphous silicon film deposited by rf plasma sputtering is annealed at temperatures above 540 °C, hemispherical grains of microcrystalline Si nucleate on its surface. The film surface is maintained macroscopically flat without any protrusions around the grains, indicating that only Si atoms at the outermost surface aggregate into grains. The size distribution of the grains was very narrow; the deviation from the mean was less than 8%. Even when the annealing temperature was varied between 600 and 850 °C, the mean base radii and the mean heights of the grains stayed within the ranges of 45 to 48.5 and 35 to 42 nm, respectively. Also, 3 h of annealing produced a saturation of the self-assembling process. This observation suggests that the grain size can be controlled in a self-limiting manner in terms of the temperature and period of annealing. © 2003 American Institute of Physics.
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68.47.Fg Semiconductor surfaces
68.35.Dv Composition, segregation; defects and impurities
61.72.Cc Kinetics of defect formation and annealing
61.43.Dq Amorphous semiconductors, metals, and alloys
68.55.A- Nucleation and growth

Chirality-dependent curvature effect in smallest single-walled carbon nanotubes

Irene L. Li, G. D. Li, H. J. Liu, C. T. Chan, and Z. K. Tang

Appl. Phys. Lett. 82, 1467 (2003); http://dx.doi.org/10.1063/1.1558892 (3 pages) | Cited 18 times

Online Publication Date: 25 February 2003

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Polarized Raman spectra are measured for 0.4 nm single-walled carbon nanotubes embedded in the zeolite matrix. The polarization dependence of the Raman intensity of the radial breathing mode showed that the carbon nanotubes inside the channels of the zeolite are perfectly aligned. The observed radial breathing mode frequencies deviated from those predicted by the elastic model. The strong curvature effect leads to two features: (i) the radial breathing mode frequencies show obvious softening and (ii) the degree of the softening depends on the tube chirality, which agrees well with the theoretic calculations. © 2003 American Institute of Physics.
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61.46.-w Structure of nanoscale materials
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
78.67.Ch Nanotubes
81.07.De Nanotubes
63.70.+h Statistical mechanics of lattice vibrations and displacive phase transitions
78.30.Na Fullerenes and related materials
78.20.Ek Optical activity

Electrochemical route for the fabrication of alkanethiolate-capped gold nanoparticles

P. Zhang, P. S. Kim, and T. K. Sham

Appl. Phys. Lett. 82, 1470 (2003); http://dx.doi.org/10.1063/1.1558901 (3 pages) | Cited 5 times

Online Publication Date: 25 February 2003

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Nearly monodispersed gold nanoparticles (NPs) of a few nanometers were fabricated and immobilized simultaneously on silicon surface by the galvanostatic reduction of HAuCl4 in the presence of dodecanethiol. X-ray absorption spectra at both sulfur K edge and gold L3 edge confirm the existence of the alkanethiolate-protected Au NPs and reveal their structural and bonding characteristics. Alkanethiolate-capped Au NPs were also successfully fabricated, with the same technique, on porous silicon, a functional substrate with high surface area. The hybrid thiol-capping/electrodeposition method reported here offers an attractive approach to the fabrication of highly stable gold NPs on various functional substrates with a simple, fast, and easily controlled experimental procedure. © 2003 American Institute of Physics.
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61.46.-w Structure of nanoscale materials
82.45.Aa Electrochemical synthesis
82.45.Yz Nanostructured materials in electrochemistry
82.45.Qr Electrodeposition and electrodissolution
81.16.Be Chemical synthesis methods
81.15.Pq Electrodeposition, electroplating
78.70.Dm X-ray absorption spectra
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