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14 Apr 2003

Volume 82, Issue 15, pp. 2371-2540

Issue Cover Spotlight Figure

Appl. Phys. Lett. 82, 2491 (2003); http://dx.doi.org/10.1063/1.1566791 (3 pages)

Jun Li, Qi Ye, Alan Cassell, Hou Tee Ng, Ramsey Stevens, Jie Han, and M. Meyyappan
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Coherent optical phonon oscillations in cubic ZnSe

Yong-Sik Lim, Seok-Chan Yoon, Ki-Ju Yee, Yeong-Hwan Ahn, E. Oh, and Jai-Hyung Lee

Appl. Phys. Lett. 82, 2446 (2003); http://dx.doi.org/10.1063/1.1567827 (3 pages) | Cited 6 times

Online Publication Date: 7 April 2003

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We report the observation of coherent optical phonon oscillations in cubic bulk ZnSe(001). With a photon energy far below the band gap, the generation mechanism of the coherent longitudinal optical phonon mode is revealed to be the impulsive stimulated Raman scattering. Dephasing of the coherent longitudinal optical phonon modes by electron-phonon interaction and anharmonic processes is studied by investigating excitation intensity and temperature dependence of the dephasing rates. © 2003 American Institute of Physics.
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63.20.Ry Anharmonic lattice modes
63.20.K- Phonon interactions
78.30.Fs III-V and II-VI semiconductors

Ferromagnetic resonant tunneling diodes as spin polarimeters

Francesco Giazotto, Fabio Taddei, Rosario Fazio, and Fabio Beltram

Appl. Phys. Lett. 82, 2449 (2003); http://dx.doi.org/10.1063/1.1567812 (3 pages) | Cited 10 times

Online Publication Date: 7 April 2003

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A method for measuring the degree of spin polarization of magnetic materials based on spin-dependent resonant tunneling is proposed. The device we consider is a ballistic double-barrier resonant structure consisting of a ferromagnetic layer embedded between two insulating barriers. A simple procedure, based on a detailed analysis of the differential conductance, allows one to accurately determine the polarization of the ferromagnet. The spin-filtering character of such a system is furthermore addressed. We show that a 100% spin selectivity can be achieved under appropriate conditions. This approach is believed to be well suited for the investigation of diluted magnetic semiconductor heterostructures. © 2003 American Institute of Physics.
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85.75.Mm Spin polarized resonant tunnel junctions
72.25.Mk Spin transport through interfaces
85.30.Kk Junction diodes
85.30.Mn Junction breakdown and tunneling devices (including resonance tunneling devices)

Relaxed silicon–germanium-on-insulator substrates by oxygen implantation into pseudomorphic silicon germanium/silicon heterostructure

Zhenghua An, Yanjun Wu, Miao Zhang, Zengfeng Di, Chenglu Lin, Ricky K. Y. Fu, Peng Chen, Paul K. Chu, W. Y. Cheung, and S. P. Wong

Appl. Phys. Lett. 82, 2452 (2003); http://dx.doi.org/10.1063/1.1567807 (3 pages) | Cited 5 times

Online Publication Date: 7 April 2003

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We have developed a modified separation-by-implantation-of-oxygen (SIMOX) process for fabricating relaxed silicon–germanium-on-insulator (SGOI) substrates without using thick graded SiGe buffer structures. Oxygen ions are implanted into a pseudomorphically grown 115 nm Si0.86Ge0.14 layer, with the implant peak located slightly below the heterostructure interface. Following two annealing processes ( ∼ 800+1350 °C) instead of conventional one-step annealing ( ∼ 1350 °C) in traditional SIMOX, a buried silicon dioxide layer is created near the original SiGe/Si interface, resulting in a fully relaxed SGOI structure. Our results show that an annealing step at a moderate temperature ( ∼ 800 °C) leads to less Ge loss. © 2003 American Institute of Physics.
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85.40.Ry Impurity doping, diffusion and ion implantation technology
61.72.uf Ge and Si
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
61.72.Cc Kinetics of defect formation and annealing

Hot-phonon bottleneck in the photoinjected plasma in GaN

A. R. Vasconcellos, R. Luzzi, C. G. Rodrigues, and V. N. Freire

Appl. Phys. Lett. 82, 2455 (2003); http://dx.doi.org/10.1063/1.1566467 (3 pages) | Cited 9 times

Online Publication Date: 7 April 2003

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The evolution on the picosecond scale of the macroscopic (nonequilibrium thermodynamic) state of a highly excited photoinjected plasma in bulk GaN is analyzed. We present the equations of evolution for the quasitemperature (level of excitation) of the hot carriers and of the optical phonons. A hot-phonon temperature overshoot is evidenced, as well as a preferential production of phonons in excess of equilibrium in a reduced off-center region of the Brillouin zone. A comparative analysis of the influence of the length of the exciting laser pulse is also performed. © 2003 American Institute of Physics.
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72.30.+q High-frequency effects; plasma effects
72.80.Ey III-V and II-VI semiconductors
63.20.-e Phonons in crystal lattices
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Spin engineering of CoPd alloy films via the inverse piezoelectric effect

Jeong-Won Lee, Sung-Chul Shin, and Sang-Koog Kim

Appl. Phys. Lett. 82, 2458 (2003); http://dx.doi.org/10.1063/1.1566795 (3 pages) | Cited 19 times

Online Publication Date: 7 April 2003

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The spin engineering of CoxPd1−x alloy films on Pb(Zr0.52Ti0.48)O3 substrates was studied by measuring the polar Kerr rotation hysteresis loops and their electric field dependencies. The electric field dependence of polar Kerr rotation strongly depends on the composition of the CoPd alloys. This is especially so in the case of Co0.25Pd0.75 alloy film where the hysteresis loop of magnetic remanence with respect to voltage applied is nearly squared, i.e., the direction of magnetization maintains its initial state even when the voltage applied is turned off. This spin engineering in a ferromagnetic/piezoelectric hybrid system is possible mainly due to a combination of the magnetostrictive effect and the inverse piezoelectric effect. The results are applicable to future nonvolatile memory devices. © 2003 American Institute of Physics.
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75.70.Ak Magnetic properties of monolayers and thin films
75.50.Cc Other ferromagnetic metals and alloys
77.65.-j Piezoelectricity and electromechanical effects
75.80.+q Magnetomechanical effects, magnetostriction
78.20.Ls Magneto-optical effects
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.47.Np Metals and alloys
85.75.-d Magnetoelectronics; spintronics: devices exploiting spin polarized transport or integrated magnetic fields

L10 ordering of off-stoichiometric FePt (001) thin films at reduced temperature

T. Seki, T. Shima, K. Takanashi, Y. Takahashi, E. Matsubara, and K. Hono

Appl. Phys. Lett. 82, 2461 (2003); http://dx.doi.org/10.1063/1.1567053 (3 pages) | Cited 48 times

Online Publication Date: 7 April 2003

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We have investigated the effect of extensive compositional change on the structure and magnetic properties of FePt sputtered films deposited at a substrate temperature of 300 °C. The Fe concentration in the FePt films was varied from 19 to 68 at. %. In the x-ray diffraction patterns, (001) and (003) superlattice peaks were observed at a Pt-rich composition range, indicating the formation of a L10 ordered structure. A L10 ordered Fe38Pt62 film exhibited perpendicular magnetization with a large uniaxial magnetic anisotropy of Ku = 1.8×107 erg/cm3. © 2003 American Institute of Physics.
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75.70.Ak Magnetic properties of monolayers and thin films
68.55.-a Thin film structure and morphology
75.50.Bb Fe and its alloys
75.50.Ss Magnetic recording materials
81.15.Cd Deposition by sputtering
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Gw Magnetic anisotropy

Parametrically driven first-order Suhl instability and nonlinearities in bismuth-substituted yttrium iron garnet films

A. Y. Elezzabi and S. E. Irvine

Appl. Phys. Lett. 82, 2464 (2003); http://dx.doi.org/10.1063/1.1567047 (3 pages) | Cited 2 times

Online Publication Date: 7 April 2003

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We have demonstrated the enhancement of spin-wave nonlinearities in a bismuth-substituted yttrium iron garnet (Bi-YIG) film by parametrically exciting the first-order Suhl instability at the difference frequency of two simultaneous driving frequencies. The results show that parametric excitation of spin waves can cause this instability to grow at low threshold powers, which, in turn, channels power to other nonlinear spin-wave modes. Multiple interactions between spin waves lead to the enhancement of nonlinear processes. © 2003 American Institute of Physics.
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75.30.Ds Spin waves
75.50.Gg Ferrimagnetics
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
75.70.Ak Magnetic properties of monolayers and thin films
78.66.Nk Insulators
78.20.Ls Magneto-optical effects

Effects of interlayer electrode thickness in Nb/(MoSi2/Nb)N stacked Josephson junctions

Yonuk Chong, P. D. Dresselhaus, S. P. Benz, and J. E. Bonevich

Appl. Phys. Lett. 82, 2467 (2003); http://dx.doi.org/10.1063/1.1566797 (3 pages) | Cited 25 times

Online Publication Date: 7 April 2003

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Dense, vertically stacked Josephson junction arrays are being developed for voltage metrology applications. We present measurements of the uniformity and reproducibility of Nb/(MoSi2/Nb)N vertically stacked junctions that clarify the superconducting properties of the middle Nb superconducting electrode. Middle electrode thicknesses down to 20 nm have shown minimal suppression of the superconducting order parameter as measured through the critical current density. Even with a middle electrode thickness of 5 nm, excellent junction uniformity has been observed as demonstrated by the measurement of large Shapiro steps when the arrays are biased with microwaves. We also discuss the role of the superconducting coherence length in these arrays of high-density junctions.
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74.50.+r Tunneling phenomena; Josephson effects
74.81.Fa Josephson junction arrays and wire networks
74.25.Sv Critical currents
74.45.+c Proximity effects; Andreev reflection; SN and SNS junctions
74.25.Ha Magnetic properties including vortex structures and related phenomena

Switching field phase diagram of Co nanoring magnets

Y. G. Yoo, M. Kläui, C. A. F. Vaz, L. J. Heyderman, and J. A. C. Bland

Appl. Phys. Lett. 82, 2470 (2003); http://dx.doi.org/10.1063/1.1568167 (3 pages) | Cited 74 times

Online Publication Date: 7 April 2003

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We have studied the magnetic switching behavior of arrays of Co ring elements as a function of film thickness (2 ⩽ t ⩽ 32 nm), ring width (0.15 ⩽ w ⩽ 0.7 μm), and external diameter (0.5 ⩽ D ⩽ 2.0 μm), using magneto-optical Kerr effect magnetometry. For thick rings, two stable magnetic states are observed, a high remanence state (called the “onion” state) and a low remanence state (called the vortex state). The switching field for the transition from the onion to the vortex state increases with increasing thickness t and external diameter D, and with decreasing width w. In particular, for thin rings, the switching occurs between the two oppositely magnetized onion states, i.e., no vortex states develop during the reversal process. The transition between these two regimes depends on the diameter and width of the rings, and phase diagrams for the dependence of the switching behavior on the geometric parameters are presented. The switching behavior is discussed in terms of the competition between the exchange and magnetostatic energy terms. © 2003 American Institute of Physics.
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75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.50.Tt Fine-particle systems; nanocrystalline materials
75.70.Ak Magnetic properties of monolayers and thin films
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
81.07.Bc Nanocrystalline materials
75.50.Cc Other ferromagnetic metals and alloys
75.30.Ds Spin waves
75.30.Et Exchange and superexchange interactions
75.60.Jk Magnetization reversal mechanisms
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
78.20.Ls Magneto-optical effects
78.66.Bz Metals and metallic alloys

Tilted media in a perpendicular recording system for high areal density recording

Y. Y. Zou, J. P. Wang, C. H. Hee, and T. C. Chong

Appl. Phys. Lett. 82, 2473 (2003); http://dx.doi.org/10.1063/1.1565503 (3 pages) | Cited 34 times

Online Publication Date: 7 April 2003

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To overcome the high sensitivity of the signal-to-noise ratio (SNR) to the switching field distribution in the perpendicular media, we proposed to use tilted media in the perpendicular recording system in this letter. It was found that a much better tolerance of the easy-axis distribution could be achieved when tilted media were used instead of perpendicular media in a perpendicular recording system. We then analyzed the range of the switching field at the freezing points, and found that high Ku magnetic material is feasible in tilted media. The results indicated that the areal density could be more than 62% higher than that of perpendicular media when 45° easy-axis tilted media with Ku = 7.0×106 erg/cm3 were used. Finally, simulation of the switching dynamics revealed that a much faster magnetization switching could be achieved in 45°-tilted media than in perpendicular media. © 2003 American Institute of Physics.
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75.50.Ss Magnetic recording materials
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
75.30.Gw Magnetic anisotropy
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
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Characterization of porosity and dielectric constant of fluorocarbon porous films synthesized by using plasma-enhanced chemical vapor deposition and solvent process

Kazuo Takahashi, Takashi Mitamura, Kouichi Ono, Yuichi Setsuhara, Atsushi Itoh, and Kunihide Tachibana

Appl. Phys. Lett. 82, 2476 (2003); http://dx.doi.org/10.1063/1.1567050 (3 pages) | Cited 11 times

Online Publication Date: 7 April 2003

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Fluorocarbon films obtained in plasma-enhanced chemical vapor deposition with a C4F8 compound were composed of a carbon cross-linked network and unlinked species encapsulated in the network [J. Appl. Phys. 89, 893 (2001)]. The unlinked species were effectively removed from the films. Then, the network probably containing the pore of the species was extracted on wafers when the films were dipped into tetrahydrofran (THF) solvent. The fact implied that fluorocarbon porous films with a low-dielectric constant might be formed by using dry and wet processes. In the present study, x-ray analyses showed that the THF-treated films actually became porous in the dipping process. The dielectric constant of the THF-treated films was consistently low (<1.9) and reduced by 10% from that of as-deposited films. The fluorocarbon network as a porous medium may be applied to interlayer dielectrics for ultralarge-scale integrated circuits. © 2003 American Institute of Physics.
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77.55.-g Dielectric thin films
77.84.Jd Polymers; organic compounds
77.22.Ch Permittivity (dielectric function)

Polarization enhancement and coercive field reduction in W- and Mo-doped Bi3.35La0.75Ti3O12 thin films

Xusheng Wang and Hiroshi Ishiwara

Appl. Phys. Lett. 82, 2479 (2003); http://dx.doi.org/10.1063/1.1566087 (3 pages) | Cited 65 times

Online Publication Date: 7 April 2003

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Bi3.35La0.75(Ti1−xWx)3O12 (BLTW) and Bi3.35La0.75(Ti1−xMox)3O12 (BLTM) (x = 0.3%, 0.5%, 1%, and 2%) films were fabricated on Pt/Ti/SiO2/Si〈100〉 structures by a sol-gel method at 750 °C. The B-site substitution with high-valent cations, W6+ or Mo6+, in Bi3.35La0.75Ti3O12 (BLT) enhanced the remanent polarization and reduced the coercive field of the films. The remanent polarization (2Pr) values of the BLTW05 (x = 0.5%) and BLTM05 (x = 0.5%) films were 26 and 27 μC/cm2, respectively, which were higher than that of BLT (20 μC/cm2). The coercive field (2Ec) values of the BLTW05 and BLTM05 films were 125 and 126 kV/cm, respectively, which were much lower than that of BLT (190 kV/cm) and close to that of SrBi2Ta2O9 (∼110 kV/cm). These films also showed fatigue-free response up to 2×109 switching cycles and lower leakage current densities than 4×10−7 A/cm2 up to 200 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
77.80.Fm Switching phenomena
77.22.Ej Polarization and depolarization
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)

Extended Arrhenius law of time-to-breakdown of ultrathin gate oxides

Mingzhen Xu, Changhua Tan, and MingFu Li

Appl. Phys. Lett. 82, 2482 (2003); http://dx.doi.org/10.1063/1.1566460 (3 pages) | Cited 5 times

Online Publication Date: 7 April 2003

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A stress-induced double-donor conductivity model is proposed to investigate the temperature dependence of time-to-breakdown in ultrathin gate oxides. The permittivity-to-breakdown is defined as the product of conductivity and time-to-breakdown. The breakdown of oxides occurs when the permittivity-to-breakdown reaches a critical value. This model shows that the overall temperature dependence of time-to-breakdown can be described in terms of the extended Arrhenius law. In this case, there exist three temperature regions with different activation energies, where Arrhenius behavior still holds in each region. © 2003 American Institute of Physics.
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77.22.Jp Dielectric breakdown and space-charge effects
77.22.Ch Permittivity (dielectric function)
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
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One-step formation of aligned carbon nanotube field emitters at 400 °C

Y. Shiratori, H. Hiraoka, Y. Takeuchi, S. Itoh, and M. Yamamoto

Appl. Phys. Lett. 82, 2485 (2003); http://dx.doi.org/10.1063/1.1566803 (3 pages) | Cited 30 times

Online Publication Date: 7 April 2003

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Fabrication of field emitters by the radio-frequency plasma-enhanced chemical vapor deposition of vertically aligned carbon nanotubes (CNT) on soda-lime glass is reported. CNT was produced at 400 °C by the control of the collision energy of carbonic cations to a substrate through a dc bias voltage. The CNTs produced in this work were of a cup-stacked type and had catalyst particles on the top. The CNT emitters formed by our method were integrated into triode-type microcathodes and showed field-emission properties suitable for display applications. © 2003 American Institute of Physics.
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81.07.De Nanotubes
85.45.Db Field emitters and arrays, cold electron emitters
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
85.35.Kt Nanotube devices
85.45.Fd Field emission displays (FEDs)
79.70.+q Field emission, ionization, evaporation, and desorption
52.77.Dq Plasma-based ion implantation and deposition

Sub-Poissonian shot noise in molecular wires

S. Dallakyan and S. Mazumdar

Appl. Phys. Lett. 82, 2488 (2003); http://dx.doi.org/10.1063/1.1567805 (3 pages) | Cited 7 times

Online Publication Date: 7 April 2003

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We investigate the transport behavior of polyene molecules sandwiched between two metallic contacts using the nonequilibrium Green’s function formalism. We calculate both current and noise power as a function of applied voltage and show that they decrease with increasing size of the polyene molecules. We find that even with symmetric connection to metallic contacts, current-versus-voltage curves can be asymmetric for asymmetrically substituted polyenes. Most importantly, we demonstrate a crossover from Poissonian to sub-Poissonian behavior in the shot noise as a function of applied voltage. The algorithm for noise power calculation can be used for designing molecules with low noise. © 2003 American Institute of Physics.
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85.65.+h Molecular electronic devices
73.50.Td Noise processes and phenomena
73.61.Ph Polymers; organic compounds

Bottom-up approach for carbon nanotube interconnects

Jun Li, Qi Ye, Alan Cassell, Hou Tee Ng, Ramsey Stevens, Jie Han, and M. Meyyappan

Appl. Phys. Lett. 82, 2491 (2003); http://dx.doi.org/10.1063/1.1566791 (3 pages) | Cited 175 times

Online Publication Date: 7 April 2003

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We report a bottom-up approach to integrate multiwalled carbon nanotubes (MWNTs) into multilevel interconnects in silicon integrated-circuit manufacturing. MWNTs are grown vertically from patterned catalyst spots using plasma-enhanced chemical vapor deposition. We demonstrate the capability to grow aligned structures ranging from a single tube to forest-like arrays at desired locations. SiO2 is deposited to encapsulate each nanotube and the substrate, followed by a mechanical polishing process for planarization. MWNTs retain their integrity and demonstrate electrical properties consistent with their original structure. © 2003 American Institute of Physics.
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85.40.Ls Metallization, contacts, interconnects; device isolation
81.07.De Nanotubes
85.35.Kt Nanotube devices
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
52.77.Dq Plasma-based ion implantation and deposition
81.16.Hc Catalytic methods
81.65.Ps Polishing, grinding, surface finishing
85.40.Sz Deposition technology

Enhanced cathodoluminescent properties of ZnO encapsulated ZnS:Ag phosphors using an electrochemical deposition coating

Han-Ho Choi, M. Ollinger, and R. K. Singh

Appl. Phys. Lett. 82, 2494 (2003); http://dx.doi.org/10.1063/1.1567040 (3 pages) | Cited 10 times

Online Publication Date: 7 April 2003

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An electrochemical deposition coating method was developed to encapsulate the surface of micron-sized ZnS:Ag particulates with nanosized ZnO particles. The particle size of the as-synthesized ZnO particles was estimated to be below 10 nm from x-ray powder diffraction and transmission electron microscopy. The thickness of coating layer was measured to be from a few nm to about 100 nm using transmission electron microscopy. X-ray photoelectron spectroscopy analysis demonstrated the presence of ZnO particle layers on the surface of ZnS:Ag particulates. With the use of this ZnO coating layer, the cathodoluminescent lifetime of ZnS:Ag phosphors was dramatically improved. © 2003 American Institute of Physics.
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78.60.Hk Cathodoluminescence, ionoluminescence
78.66.Hf II-VI semiconductors
81.15.Pq Electrodeposition, electroplating
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
81.07.Bc Nanocrystalline materials
68.55.-a Thin film structure and morphology
85.45.Fd Field emission displays (FEDs)
61.46.-w Structure of nanoscale materials
79.60.Jv Interfaces; heterostructures; nanostructures
68.37.Lp Transmission electron microscopy (TEM)

Early self-assembled stages in epitaxial SrRuO3 on LaAlO3

E. Vasco, R. Dittmann, S. Karthäuser, and R. Waser

Appl. Phys. Lett. 82, 2497 (2003); http://dx.doi.org/10.1063/1.1566798 (3 pages) | Cited 26 times

Online Publication Date: 7 April 2003

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The stress-induced self-assembled growth of SrRuO3 on LaAlO3 was studied by atomic force microscopy and x-ray diffraction. SrRuO3 epitaxially grown on LaAlO3 by pulsed laser deposition shows two types of out-of-plane arrangements and four in-plane matches. The lattice mismatch (stress) produced by these arrangements was estimated and correlated with the SrRuO3 growth dynamics. After 1 nm, the SrRuO3 film surface exhibits a ripple structure, which serves as a template for the development of a nanopattern of flat islands. These islands coalesce anisotropically resulting in a regular array of “infinite” wires. The wire coalescence for the 12–20 nm thick film nullifies the surface symmetry, while SrRuO3 keeps growing in three dimensions. © 2003 American Institute of Physics.
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68.55.A- Nucleation and growth
81.15.Fg Pulsed laser ablation deposition
81.16.Mk Laser-assisted deposition
81.16.Dn Self-assembly

Polarization dynamics in a ferroelectric relaxor excited by short pulses

I. Boscolo and S. Cialdi

Appl. Phys. Lett. 82, 2500 (2003); http://dx.doi.org/10.1063/1.1565706 (3 pages)

Online Publication Date: 7 April 2003

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Polarization dynamics in a relaxor ferroelectric is investigated by exciting samples, set at different temperatures, with short high voltage (≈1 kV) rectangular pulses (≈200 ns) and then by measuring the charge carried to the sample, i.e., the polarization. Further important information is extracted from the trailing edge of the charge signals, which detect the relaxation of the polarization. Polarization dynamics of zero-field-cooled samples show a logarithmic increase during the voltage pulse plateau and a logarithmic decay after the pulse. The slopes depend on the field amplitude and temperature. The model of reorientable noninteracting polar clusters adequately describes the experimental behaviors. © 2003 American Institute of Physics.
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77.80.-e Ferroelectricity and antiferroelectricity
77.22.Ej Polarization and depolarization

Simulating collective magnetic dynamics in nanodisk arrays

A. J. Bennett and J. M. Xu

Appl. Phys. Lett. 82, 2503 (2003); http://dx.doi.org/10.1063/1.1566792 (3 pages) | Cited 16 times

Online Publication Date: 7 April 2003

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We study the magnetostatic interactions in planar arrays of single domain, magnetic disk nanostructures. We derive equations for the time evolution of magnetization and energy, and use these results to simulate the relaxation of these systems with a Monte-Carlo model. Our model confirms that relaxation of a one-dimensional array into one of its ground states occurs by propagating the inversion site along the line. A two-dimensional honeycomb array enters a metastable state of frustrated spiral domains due to the availability of low-energy configurational states. This model has potential application in the design of magnetic nanostructure systems for data storage and data processing applications. © 2003 American Institute of Physics.
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75.75.-c Magnetic properties of nanostructures
75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)
75.40.Mg Numerical simulation studies

Simple and efficient method for carbon nanotube attachment to scanning probes and other substrates

A. Hall, W. G. Matthews, R. Superfine, M. R. Falvo, and S. Washburn

Appl. Phys. Lett. 82, 2506 (2003); http://dx.doi.org/10.1063/1.1567049 (3 pages) | Cited 16 times

Online Publication Date: 7 April 2003

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We present a fast, high yield, low cost method for the production of scanning probes with aligned carbon nanotubes protruding from the ends. The procedure is described and images of undercut films are used to demonstrate the improved probe quality for topography measurements. A magnetophoretic model of the attachment and alignment processes is discussed. © 2003 American Institute of Physics.
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85.35.Kt Nanotube devices
07.79.Lh Atomic force microscopes
68.37.Ps Atomic force microscopy (AFM)

Optical absorption of intersubband transitions in In0.3Ga0.7As/GaAs multiple quantum dots

B. Pattada, Jiayu Chen, Qiaoying Zhou, M. O. Manasreh, M. L. Hussein, W. Ma, and G. J. Salamo

Appl. Phys. Lett. 82, 2509 (2003); http://dx.doi.org/10.1063/1.1567813 (3 pages) | Cited 7 times

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Fourier-transform infrared spectroscopy technique was employed to investigate the optical absorption coefficient of intersubband transitions in Si-doped In0.3Ga0.7As/GaAs multiple quantum dot structures. Waveguides with 45° polished facets were fabricated from molecular beam epitaxy grown wafers with different quantum dot size. The measured maximum optical absorption coefficient was found to be in the order of 1.10×104 cm−3. The peak position energy of the intersubband transition was observed to shift toward lower energy when the quantum dot size is increased as expected. The photoluminescence spectra were also measured for different samples with different quantum dot size. The internal quantum efficiency was estimated to be in the order of 58% for a sample with 40 periods of 6 nm dot size. © 2003 American Institute of Physics.
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78.67.Hc Quantum dots
78.55.Cr III-V semiconductors
73.21.La Quantum dots
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.30.Fs III-V and II-VI semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Tensile yielding of multiwall carbon nanotubes

Chenyu Wei, Kyeongjae Cho, and Deepak Srivastava

Appl. Phys. Lett. 82, 2512 (2003); http://dx.doi.org/10.1063/1.1567041 (3 pages) | Cited 23 times

Online Publication Date: 7 April 2003

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The tensile yielding of multiwall carbon nanotubes (MWCNTs) has been studied using molecular-dynamics simulations and a transition state theory based model. We find a strong dependence of the yielding on the strain rate. A critical strain rate has been predicted above/below which yielding strain of a MWCNT is larger/smaller than that of the corresponding single-wall carbon nanotubes (CNTs). At an experimentally feasible strain rate of 1%/h and T = 300 K, the yield strain of a MWCNT is estimated to be about 3%–4% higher than that of an equivalent single-wall CNT. This is in good agreement with recent experimental observations. © 2003 American Institute of Physics.
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62.25.-g Mechanical properties of nanoscale systems
02.70.Ns Molecular dynamics and particle methods

Field emission from aligned carbon nanofibers grown in situ by hot filament chemical vapor deposition

Chia-Fu Chen, Chien-Liang Lin, and Chi-Ming Wang

Appl. Phys. Lett. 82, 2515 (2003); http://dx.doi.org/10.1063/1.1568163 (3 pages) | Cited 8 times

Online Publication Date: 7 April 2003

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Aligned high-aspect-ratio carbon nanofibers were grown in situ using modified hot filament chemical vapor deposition. The field-emission properties were then studied. An Fe–Cr wire filament acted as a catalytic source and a heat source. Carbon nanofibers were deposited on a Si substrate with CO2 as a carrier gas through ethanol. The experimental results indicate that the flow in the horizontal direction to the substrate produces carbon nanofibers with diameters of less than 10 nm. The field-emission current of 2 V/μm was 0.54 mA/cm2; the turn-on field of the sample was 1.1 V/μm. © 2003 American Institute of Physics.
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79.70.+q Field emission, ionization, evaporation, and desorption
81.05.U- Carbon/carbon-based materials
81.07.De Nanotubes
61.46.-w Structure of nanoscale materials
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
73.22.-f Electronic structure of nanoscale materials and related systems

Self-assembled molecular chains formed by selective adsorption of lead–phthalocyanine on InSb(100)-(4×2)/c(8×2)

N. Papageorgiou, Y. Ferro, J. M. Layet, L. Giovanelli, A. J. Mayne, G. Dujardin, H. Oughaddou, and G. Le Lay

Appl. Phys. Lett. 82, 2518 (2003); http://dx.doi.org/10.1063/1.1566802 (3 pages) | Cited 15 times

Online Publication Date: 7 April 2003

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We study the structure of ultra thin lead–phthalocyanine (PbPc) overlayers deposited on the indium terminated InSb(100)-(4×2)/c(8×2) reconstructed surface by low-energy electron diffraction and scanning tunneling microscopy. The diffraction pattern for the PbPc monolayer grown on this surface corresponds to a 4×3 structure. We show that this structure is induced by a selective adsorption of the PbPc molecules on the indium stripes of the InSb(100) substrate. The adsorption is dominated by the interaction between the central lead atom of the molecule and the topmost indium atoms of the surface. © 2003 American Institute of Physics.
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68.43.Fg Adsorbate structure (binding sites, geometry)
68.47.Fg Semiconductor surfaces
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