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24 Dec 2001

Volume 79, Issue 26, pp. 4271-4458

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Large flexoelectric polarization in ceramic lead magnesium niobate

Wenhui Ma and L. Eric Cross

Appl. Phys. Lett. 79, 4420 (2001); http://dx.doi.org/10.1063/1.1426690 (3 pages) | Cited 40 times

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Flexoelectric coefficient μ12 is greatly enhanced in the relaxor ferroelectric lead magnesium niobate ceramic. Phenomenological analysis suggests the high dielectric permittivity is inadequate to explain the great enhancement. Temperature dependent measurement reveals a close relation between the flexoelectric polarization and the preexisting polar microregions in this relaxor ferroelectrics. It is proposed that the strain gradient might change the Gibbs free energy of the relaxor system and easily reorient the already existing polar microregions, leading to the greatly enhanced flexoelectric effect. © 2001 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.65.Ly Strain-induced piezoelectric fields
77.22.Ej Polarization and depolarization
77.22.Ch Permittivity (dielectric function)
77.22.Gm Dielectric loss and relaxation
77.80.-e Ferroelectricity and antiferroelectricity
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Giant photoresistivity and optically controlled switching in self-assembled nanowires

N. Kouklin, L. Menon, A. Z. Wong, D. W. Thompson, J. A. Woollam, P. F. Williams, and S. Bandyopadhyay

Appl. Phys. Lett. 79, 4423 (2001); http://dx.doi.org/10.1063/1.1427156 (3 pages) | Cited 47 times

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We report the observation of giant photoresistivity in electrochemically self-assembled CdS and ZnSe nanowires electrodeposited in a porous alumina film. The resistance of these nanowires increases by one to two orders of magnitude when exposed to infrared radiation, possibly because of real-space transfer of electrons from the nanowires into the surrounding alumina by photon absorption. This phenomenon has potential applications in “normally on” infrared photodetectors and optically controlled switches. © 2001 American Institute of Physics.
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73.63.Nm Quantum wires
85.60.Gz Photodetectors (including infrared and CCD detectors)
73.50.Pz Photoconduction and photovoltaic effects
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
73.63.Bd Nanocrystalline materials
81.15.Pq Electrodeposition, electroplating

Investigation of In segregation in InAs/AlAs quantum-well structures

M. Schowalter, A. Rosenauer, D. Gerthsen, M. Arzberger, M. Bichler, and G. Abstreiter

Appl. Phys. Lett. 79, 4426 (2001); http://dx.doi.org/10.1063/1.1427148 (3 pages) | Cited 13 times

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In this letter, we report the investigation of In segregation in InAs/AlAs heterostructures. InAs layers with different thicknesses were grown by molecular beam epitaxy on GaAs (001) substrates. The layers were investigated by transmission electron microscopy. Profiles of the chemical composition of the InAs layers in the [001] direction were deduced from high-resolution lattice fringe images using the composition evaluation by lattice fringe analysis method. The segregation efficiency was derived by fitting the measured In concentration profiles with the segregation model of Muraki et al. [K. Muraki et al., Appl. Phys. Lett. 61, 557 (1992)]. We obtain efficiency of R = 0.77±0.03 for the segregation of In in AlAs/InAs at a temperature of 530 °C. © 2001 American Institute of Physics.
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68.65.Fg Quantum wells
68.35.Dv Composition, segregation; defects and impurities
81.07.St Quantum wells
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Magnetic anisotropy in prismatic nickel nanowires

L. Sun, P. C. Searson, and C. L. Chien

Appl. Phys. Lett. 79, 4429 (2001); http://dx.doi.org/10.1063/1.1428113 (3 pages) | Cited 34 times

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Nickel nanowire arrays with a diamond-shaped cross section and the same orientation have been fabricated in nanoporous single mica crystal membranes by electrodeposition. All wires are 5 μm long with an effective diameter of 120 nm. The sample can be considered as a collection of laterally and vertically aligned identical micromagnetic prisms. We report on the magnetic anisotropy due to the quasi-one-dimensional wire shape and diamond cross section. © 2001 American Institute of Physics.
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75.50.Tt Fine-particle systems; nanocrystalline materials
75.30.Gw Magnetic anisotropy
81.07.Bc Nanocrystalline materials
75.60.Jk Magnetization reversal mechanisms
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Plasmon energy shift in porous silicon measured by x-ray photoelectron spectroscopy

N. Mannella, G. Gabetta, and F. Parmigiani

Appl. Phys. Lett. 79, 4432 (2001); http://dx.doi.org/10.1063/1.1425956 (3 pages) | Cited 2 times

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In order to provide experimental support for quantum confinement models describing electronic effects in porous silicon (p-Si), the Si 2s and Si 2p plasmon losses have been studied by x-ray photoelectron spectroscopy. The p-Si plasmon energy was found at a value 0.8÷1.6 eV higher than that of bulk Si (17.4 eV), as measured on the cleaned Si substrate as a reference. The magnitude of these shifts suggests possible quantum confinement effects ascribed to the p-Si nanostructures. © 2001 American Institute of Physics.
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73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons
73.22.Lp Collective excitations
79.60.Bm Clean metal, semiconductor, and insulator surfaces

Optical properties of self-assembled InAs quantum islands grown on InP(001) vicinal substrates

B. Salem, J. Olivares, G. Guillot, G. Bremond, J. Brault, C. Monat, M. Gendry, G. Hollinger, F. Hassen, and H. Maaref

Appl. Phys. Lett. 79, 4435 (2001); http://dx.doi.org/10.1063/1.1427742 (3 pages) | Cited 23 times

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We have investigated the effect of misorientated InP(001) substrates on the optical properties of InAs quantum islands (QIs) grown by molecular-beam epitaxy in the Stranski–Krastanow regime. Detailed temperature-dependent photoluminescence (PL), excitation density PL, and polarization of photoluminescence (PPL) are studied. PPL shows a high degree of linear polarization (near 40%) for the nominally oriented substrate n and for the substrate with 2° off miscut angle toward the [110] direction (2° F), while it is near 15% for the substrate with 2° off miscut angle towards [010] direction (2° B), indicating the growth of InAs quantum wires on nominal and 2° F substrates and of InAs quantum dots on 2° B substrate. These island shapes are confirmed by morphological investigations performed by atomic force microscopy. The integrated PL intensity remains very strong at room temperature, as much as 36% of that at 8 K, indicating a strong spatial localization of the carriers in the InAs QIs grown on InP(001). © 2001 American Institute of Physics.
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78.55.Cr III-V semiconductors
78.67.Hc Quantum dots
78.67.Lt Quantum wires
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
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Simulation of charge injection enhancements in organic light-emitting diodes

B. Masenelli, D. Berner, M. N. Bussac, F. Nüesch, and L. Zuppiroli

Appl. Phys. Lett. 79, 4438 (2001); http://dx.doi.org/10.1063/1.1426683 (3 pages) | Cited 15 times

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We have investigated by numerical simulation of real devices the reasons for electron injection enhancement due to lithium fluoride (LiF) and for hole injection enhancement due to copper phtalocyanine (CuPc) in organic light-emitting diodes (OLEDs). The reference data introduced in the code were obtained from Kelvin probe and charge transport measurements. In the case of LiF, the reduction of the injection barrier is mainly due to a static dipolar charge distribution across the ionic layer, while in CuPc the space charge which lowers the barrier results from a large hole accumulation at the CuPc/hole-transmitting layer interface, during injection. © 2001 American Institute of Physics.
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85.60.Jb Light-emitting devices
73.61.Ph Polymers; organic compounds
73.20.-r Electron states at surfaces and interfaces
73.30.+y Surface double layers, Schottky barriers, and work functions

Multiple-tunneling noise in superconducting tunnel junctions from partial current integration

L. J. Hiller, M. L. van den Berg, and S. E. Labov

Appl. Phys. Lett. 79, 4441 (2001); http://dx.doi.org/10.1063/1.1428618 (3 pages) | Cited 6 times

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Superconducting tunnel junctions can be used as high-resolution particle or photon energy spectrometers. A photon absorbed in a superconductor breaks Cooper pairs into quasiparticles. These quasiparticles tunnel through the junction barrier and are detected as a pulse of excess current. Many junction designs allow the quasiparticles to tunnel more than once, an exponentially mixed Poisson process. However, multiple tunneling increases the fluctuation in the measured charge. We calculate the significance of these fluctuations algebraically as a function of time during the current pulse. We also calculate the finite integration window that minimizes the contribution of this noise. In addition, we calculate the effects of a low-pass amplifier and a Gaussian-shaping amplifier on the tunneling noise. With certain filtering time constants, the tunneling noise can be reduced while still providing some gain. © 2001 American Institute of Physics.
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74.50.+r Tunneling phenomena; Josephson effects
74.20.Fg BCS theory and its development
74.40.-n Fluctuation phenomena

Magnetotunneling spectroscopy of resonant anticrossing in terahertz intersubband emitters

Benjamin S. Williams, Hans Callebaut, Qing Hu, and John L. Reno

Appl. Phys. Lett. 79, 4444 (2001); http://dx.doi.org/10.1063/1.1426694 (3 pages) | Cited 8 times

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Intersubband transport and electroluminescence has been investigated in a double-quantum-well structure based on an intrawell (vertical) THz radiative transition. Magnetotunneling spectroscopy was used to determine subband energies, including the minimum energy separation (∼1.7 meV) between two anticrossed levels. The presence of this anticrossing indicates that in this structure, electron removal from the lower radiative state should be modeled by coherent resonant tunneling rather than incoherent sequential tunneling. © 2001 American Institute of Physics.
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73.63.Hs Quantum wells
73.21.Fg Quantum wells
78.67.De Quantum wells
73.23.-b Electronic transport in mesoscopic systems
78.60.Fi Electroluminescence
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
42.55.Px Semiconductor lasers; laser diodes

Amplification of the signal in triode structures of ion detectors based on 6H-SIC epitaxial films

A. A. Lebedev, N. B. Strokan, A. M. Ivanov, D. V. Davydov, N. S. Savkina, E. V. Bogdanova, A. N. Kuznetsov, and R. Yakimova

Appl. Phys. Lett. 79, 4447 (2001); http://dx.doi.org/10.1063/1.1428765 (3 pages) | Cited 5 times

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The possibility of about 50 times the inneramplification of signals in SiC-based detectors of short-range ions is shown. The detector has an n–p–n+-like structure, where the p-type base was grown epitaxially on a 6H n+-SiC substrate. To complete the structure a Schottky barrier was made on top. Detector parameters were investigated in a “floating base” regime. Alpha particles from 244Cm were used and the augmentation of signal (E) with increasing applied voltage (U) was investigated. A superlinear increase of E was observed with a significant (tens of times) amplification of the introduced by the alpha particle nonequilibrium charge. It was also found that the nonuniformity of the diffusion-drift carrier transport parameters in the films does not exceed 10%. © 2001 American Institute of Physics.
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29.40.Wk Solid-state detectors
73.61.Le Other inorganic semiconductors
85.30.Pq Bipolar transistors
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Triple-layer passivation for longevity of polymer light-emitting diodes

Seung Ho Kwon, Sang Yoon Paik, Oh Jun Kwon, and Jae Soo Yoo

Appl. Phys. Lett. 79, 4450 (2001); http://dx.doi.org/10.1063/1.1428770 (3 pages) | Cited 18 times

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A poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylene vinylene](MEH-PPV) light-emitting diode was coated with passivation layers in order to improve the longevity of conjugated polymer-based diodes. High-density polyethylene (HDPE), which is an insulator, was used as the passivation material in combination with a metal layer to minimize oxygen and water diffusion into the polymer light-emitting diodes. The simplicity of the HDPE(1 μm)/Al–Li(120 nm)/HDPE(1 μm) structure, which was successively thermal coated on the diode, was demonstrated. The longevity of this simple structure was dramatically enhanced after exposure to atmospheric oxygen and moisture. © 2001 American Institute of Physics.
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85.60.Jb Light-emitting devices
81.65.Rv Passivation
78.66.Qn Polymers; organic compounds
78.60.Fi Electroluminescence

Design of lightweight multilayer partitions based on sonic crystals

Antonio Uris, Constanza Rubio, Hermelando Estelles, Juan V. Sanchez-Perez, Rosa Martinez-Sala, and Jaime Llinares

Appl. Phys. Lett. 79, 4453 (2001); http://dx.doi.org/10.1063/1.1425464 (2 pages) | Cited 3 times

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The sound transmission coefficient of different multilayer partitions commonly encountered in buildings has been measured as a function of frequency. Most of the samples studied showed an increase in the sound transmission coefficient over a specific frequency, called the critical frequency, depending on the layer material. However, for partitions built with the same materials, but built with a periodic arrangement of layers, this behavior has not been observed. This kind of periodic multilayer partition can be considered as a sonic crystal, because the stopband corresponding to a one-dimensional sonic crystal with a constant lattice equal to the modulation of the partition is in the same range as the critical frequency of the panel. © 2001 American Institute of Physics.
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43.50.Jh Noise in buildings and general machinery noise
43.55.Rg Sound transmission through walls and through ducts: theory and measurement
43.55.Ev Sound absorption properties of materials: theory and measurement of sound absorption coefficients; acoustic impedance and admittance
43.50.Fe Noise masking systems

Simulation of higher harmonics generation in tapping-mode atomic force microscopy

O. Sahin and A. Atalar

Appl. Phys. Lett. 79, 4455 (2001); http://dx.doi.org/10.1063/1.1429296 (3 pages) | Cited 20 times

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In tapping-mode atomic force microscopy, nonlinear tip–sample interactions give rise to higher harmonics of the cantilever vibration. We present an electrical circuit to model the atomic force microscope cantilever with its first three flexural eigenmodes. An electrical circuit simulator is used to simulate the tapping-mode operation. Amplitude and phase responses of the third flexural eigenmode are obtained for different sample properties. It is found that amplitude and phase of higher harmonics depend highly on sample properties. © 2001 American Institute of Physics.
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07.79.Lh Atomic force microscopes
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Erratum: “Piezoelectric properties and poling effect of Pb(Zr,Ti)O3 thick films prepared for microactuators by aerosol deposition” [Appl. Phys. Lett. 77, 1710 (2000)]

J. Akedo and M. Lebedev

Appl. Phys. Lett. 79, 4458 (2001); http://dx.doi.org/10.1063/1.1427149 (1 page)

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Abstract Unavailable
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99.10.Cd Errata
77.65.-j Piezoelectricity and electromechanical effects
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.55.-g Dielectric thin films
68.60.Bs Mechanical and acoustical properties
07.10.Cm Micromechanical devices and systems
68.55.-a Thin film structure and morphology
77.22.Ej Polarization and depolarization
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