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27 Sep 1999

Volume 75, Issue 13, pp. 1821-1987

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Electroluminescence of polymer/J-aggregate composites

Eugene I. Mal’tsev, Dmitry A. Lypenko, Boris I. Shapiro, Maria A. Brusentseva, George H. W. Milburn, Jeffrey Wright, Andre Hendriksen, Vladimir I. Berendyaev, Boris V. Kotov, and Anatoly V. Vannikov

Appl. Phys. Lett. 75, 1896 (1999); http://dx.doi.org/10.1063/1.124864 (3 pages) | Cited 32 times

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Efficient electroluminescence was revealed in single-layer light-emitting diodes based on electron-hole conducting polymers containing the nanocrystalline phase of cyanine dyes (J-aggregates). These species exhibit a very narrow emission band with a maximum in the red to infrared spectrum range. The J-aggregates play an active role in the charge carrier transport of the composites. © 1999 American Institute of Physics.
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78.60.Fi Electroluminescence
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Persistent photoconductivity in Ga1−xInxNyAs1−y

J. Z. Li, J. Y. Lin, H. X. Jiang, J. F. Geisz, and Sarah R. Kurtz

Appl. Phys. Lett. 75, 1899 (1999); http://dx.doi.org/10.1063/1.124865 (3 pages) | Cited 23 times

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Electrical properties of unintentionally doped p-type Ga0.95In0.05N0.013As0.987 quaternary alloys grown by metal–organic vapor-phase epitaxy have been investigated by Hall-effect and photoconductivity measurements. Persistent photoconductivity (PPC) has been observed in this material at temperatures T<320 K. The PPC buildup and decay kinetics have been systematically measured at different temperatures and photoexcitation energies and formulated in the context of lattice-relaxed deep levels (or AX-like centers). The parameters which characterize the AX centers in GaInNAs, namely, the thermal and optical ionization energies, hole capture barrier, and the Stokes shift, have been determined. Our results indicate that AX-like deep levels strongly influence the electronic properties of the GaInNAs quaternary system. © 1999 American Institute of Physics.
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73.50.Pz Photoconduction and photovoltaic effects
71.55.Eq III-V semiconductors
73.61.Ey III-V semiconductors
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)

Metal/fluorinated-dielectric interactions in microelectronic interconnections: Rapid diffusion of fluorine through aluminum

S. E. Kim and Ch. Steinbrüchel

Appl. Phys. Lett. 75, 1902 (1999); http://dx.doi.org/10.1063/1.124866 (3 pages) | Cited 6 times

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Rather surprising behavior has been observed when aluminum (Al) is in contact with fluorine-doped silicon dioxide (FSG). With Al deposited onto FSG, x-ray photoelectron spectroscopy shows that there is only a very minor reaction at the interface, producing a small amount of AlF3. No fluorine is observed in the bulk of the Al film, but fluorine diffuses readily through the Al even at room temperature and reacts at the free metal surface. On the other hand, with FSG deposited onto Al, the native aluminum oxide provides quite good protection against fluorine diffusion. By contrast, when pure Cu is in contact with FSG, there is almost no interaction or fluorine diffusion. Various approaches to reducing fluorine diffusion into a metal are also discussed, including using a diffusion barrier (TiN, Ta, TaN) or a suitable plasma treatment of the FSG before metal deposition. © 1999 American Institute of Physics.
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85.40.Ls Metallization, contacts, interconnects; device isolation
66.30.Ny Chemical interdiffusion; diffusion barriers
68.35.Fx Diffusion; interface formation
73.40.Ns Metal-nonmetal contacts
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
61.72.Cc Kinetics of defect formation and annealing

Photoluminescence study of the initial stages of island formation for Ge pyramids/domes and hut clusters on Si(001)

O. G. Schmidt, C. Lange, and K. Eberl

Appl. Phys. Lett. 75, 1905 (1999); http://dx.doi.org/10.1063/1.124867 (3 pages) | Cited 73 times

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Stranski–Krastanov growth of Ge on Si(001) can result in various different types of islands such as domes, pyramids, and hut clusters. A systematic study of the impact of the different island phases on photoluminescence (PL) spectra is presented and reveals simultaneous PL from the wetting layer and islands in the pyramids/domes phase and only island related PL in the phase of hut clusters. A rather abrupt transformation from pyramids/domes to hut clusters is reported by changing the growth temperature from 600 to 580 °C. The wetting layer and island related energy transitions as a function of Ge coverage are presented for growth temperatures ranging from 360 to 700 °C. At Ts = 360 °C no island formation is present. The influence of Oswald ripening and material interdiffusion on the PL properties is discussed. © 1999 American Institute of Physics.
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68.55.-a Thin film structure and morphology
78.55.Ap Elemental semiconductors
78.66.Db Elemental semiconductors and insulators
81.05.Cy Elemental semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
66.30.Ny Chemical interdiffusion; diffusion barriers
68.35.Fx Diffusion; interface formation

High-Q wet-etched GaAs microdisks containing InAs quantum boxes

B. Gayral, J. M. Gérard, A. Lemaître, C. Dupuis, L. Manin, and J. L. Pelouard

Appl. Phys. Lett. 75, 1908 (1999); http://dx.doi.org/10.1063/1.124894 (3 pages) | Cited 109 times

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A two-steps wet-etching fabrication process producing high-quality GaAs microdisks is presented. We report an optical characterization of these microdisks, using the photoluminescence of InAs quantum boxes as an internal light source. Thanks to an improved smoothness of the microdisk sidewall, cavity Q’s as high as 12 000 are observed, which opens very challenging novel application prospects for semiconductor microdisks. © 1999 American Institute of Physics.
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42.82.Cr Fabrication techniques; lithography, pattern transfer
42.55.Sa Microcavity and microdisk lasers
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
81.65.Cf Surface cleaning, etching, patterning

Interpretation of electrical and galvanomagnetic properties of diamond monocrystals

K. Somogyi

Appl. Phys. Lett. 75, 1911 (1999); http://dx.doi.org/10.1063/1.124868 (3 pages) | Cited 2 times

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An exponential type description of the temperature dependence of hole mobility and the experimentally observed mobility maxima reveal that activation energies obtained from the temperature dependence of the resistivity and that of the hole concentration differ from each other in a range from 0.03 to 0.08 eV for diamond monocrystals. This difference is too high to be simply neglected. On the other hand, the existence of a mobility maximum and of a steep high temperature slope on the temperature dependence of mobility is explained here solely by the dominance of the ionized impurity scattering. © 1999 American Institute of Physics.
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72.80.Cw Elemental semiconductors
72.20.Fr Low-field transport and mobility; piezoresistance
72.20.My Galvanomagnetic and other magnetotransport effects
72.20.Dp General theory, scattering mechanisms

Band-gap control of GaInP using Sb as a surfactant

J. K. Shurtleff, R. T. Lee, C. M. Fetzer, and G. B. Stringfellow

Appl. Phys. Lett. 75, 1914 (1999); http://dx.doi.org/10.1063/1.124869 (3 pages) | Cited 36 times

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The use of surfactants to control specific aspects of the vapor-phase epitaxial growth process is beginning to be studied for both the elemental and III/V semiconductors. To date, most reported surfactant effects for semiconductors relate to the morphology of the growing films. However, semiconductor alloys with CuPt ordering exhibit much more dramatic effects. The change in the CuPt order parameter induced by the surfactant translates into a marked change in the band-gap energy. Previous work concentrated on the effects of the donor tellurium. Te is less than ideal as a surfactant, since the change in band-gap energy is coupled to a large change in the conductivity. This letter presents the results of a study of the effects of an isoelectronic surfactant on the ordering process in GaInP. Sb has been found to act as a surfactant during organometallic vapor-phase epitaxial growth. At an estimated Sb concentration in the solid of 1×10−4, order is eliminated, as indicated by the band-gap energy. Surface photoabsorption (SPA) data indicate that the effect is due to a change in the surface reconstruction. Adding Sb leads to attenuation of the peak at 400 nm in the SPA spectrum associated with [math10] P dimers. The addition of Sb during the growth cycle has been used to produce a heterostructure with a 135 meV band-gap difference between two layers with the same solid composition. © 1999 American Institute of Physics.
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71.20.Nr Semiconductor compounds
68.55.-a Thin film structure and morphology
81.05.Ea III-V semiconductors
68.35.Md Surface thermodynamics, surface energies
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.35.Rh Phase transitions and critical phenomena
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
78.40.Fy Semiconductors
81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Electrical isolation of a silicon δ-doped layer in GaAs by ion irradiation

I. Danilov, J. P. de Souza, H. Boudinov, A. V. Murel, V. M. Daniltsev, and V. I. Shashkin

Appl. Phys. Lett. 75, 1917 (1999); http://dx.doi.org/10.1063/1.124870 (3 pages) | Cited 2 times

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The electrical isolation of a n-type δ-doped layer embedded into undoped GaAs was studied using proton or helium ion bombardment. The threshold dose for isolation Dth of the δ-doped layer was found to be ≈ 2 times higher than that predicted for thick doped layers of similar carrier concentration. The thermal stability of the isolation, i.e., the persistence of sheet resistance Rs at values >109Ω/□ after subsequent thermal annealing, is limited to temperatures below 400 °C. This temperature limit for the thermal stability Tsm is markedly lower than those observed in wider doped layers in which Tsm is ≅ 650 °C. A previously isolated δ-doped layer presents p-type conductivity after annealing at temperatures >600 °C . © 1999 American Institute of Physics.
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61.72.uj III-V and II-VI semiconductors
73.61.Ey III-V semiconductors
61.80.Jh Ion radiation effects
61.82.Fk Semiconductors
61.72.Cc Kinetics of defect formation and annealing
68.60.Dv Thermal stability; thermal effects

Fabrication of ohmic contacts to buried diamond layers using Pt layer in the diamond chemical-vapor-deposition process

Chunlei Wang and Toshimichi Ito

Appl. Phys. Lett. 75, 1920 (1999); http://dx.doi.org/10.1063/1.124871 (3 pages) | Cited 1 time

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Electrical contacts to a buried chemical-vapor-deposited (CVD) diamond layer can be accomplished using a process in which Pt columns automatically grow from the buried layer to the diamond surface by diamond overgrown on a thin Pt film. Hall effect measurements were employed in a temperature region from room temperature to 450 °C to investigate and compare transport properties of a buried B-doped homoepitaxial diamond film with such Pt column electrodes before and after the overgrowth of the upper layer. A useful ohmic contact to the B-doped CVD diamond interlayer was formed by this type of buried electrodes. © 1999 American Institute of Physics.
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73.40.Ns Metal-nonmetal contacts
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
73.61.Cw Elemental semiconductors
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
81.05.ub Fullerenes and related materials

Implantation-induced amorphization of InP characterized with perturbed angular correlation

E. Bezakova, A. P. Byrne, C. J. Glover, M. C. Ridgway, and R. Vianden

Appl. Phys. Lett. 75, 1923 (1999); http://dx.doi.org/10.1063/1.124872 (3 pages) | Cited 7 times

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The perturbed angular correlation (PAC) technique has been used to characterize the implantation-induced crystalline-to-amorphous transformation in InP. Radioactive 111In probes were first introduced in InP substrates which were then irradiated with Ge ions over an ion-dose range extending 2 orders of magnitude beyond that required for amorphization. Crystalline, disordered and amorphous probe environments were subsequently identified with PAC. The dose dependence of the relative fractions of the individual probe environments were determined, a direct amorphization process consistent with the overlap model was quantified and evidence for a second amorphization process via the overlap of disordered regions was observed. Given the ability to differentiate disordered and amorphous probe environments, a greater effective resolution was achieved with the PAC technique compared with other common analytical methodologies. © 1999 American Institute of Physics.
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61.72.uj III-V and II-VI semiconductors
61.80.Jh Ion radiation effects
61.82.Fk Semiconductors
76.80.+y Mössbauer effect; other γ-ray spectroscopy
61.43.Dq Amorphous semiconductors, metals, and alloys

Long-wavelength lasing from multiply stacked InAs/InGaAs quantum dots on GaAs substrates

A. E. Zhukov, A. R. Kovsh, N. A. Maleev, S. S. Mikhrin, V. M. Ustinov, A. F. Tsatsul’nikov, M. V. Maximov, B. V. Volovik, D. A. Bedarev, Yu. M. Shernyakov, P. S. Kop’ev, Zh. I. Alferov, N. N. Ledentsov, and D. Bimberg

Appl. Phys. Lett. 75, 1926 (1999); http://dx.doi.org/10.1063/1.124873 (3 pages) | Cited 62 times

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An InAs quantum dot (QD) array covered by a thin InGaAs layer was used as the active region of diode lasers grown by molecular beam epitaxy on GaAs substrates. The wavelength of the ground-state transition in such heterostructures is in the 1.3 μm range. In the laser based on the single layer of QDs, lasing proceeds via the excited states due to insufficient gain of the ground level. Stacking of three QD planes prevents gain saturation and results in a low threshold (85 A/cm2 in broad-area 1.9-mm-long stripe) long-wavelength (1.25 μm) lasing at room temperature via the QD ground state with relatively high differential efficiency (>50%). © 1999 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Photoluminescence linewidths of piezoelectric quantum wells

E. A. Khoo, J. P. R. David, J. Woodhead, R. Grey, and G. J. Rees

Appl. Phys. Lett. 75, 1929 (1999); http://dx.doi.org/10.1063/1.124874 (3 pages) | Cited 5 times

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The photoluminescence linewidths of strained InxGa1−xAs/GaAs quantum wells grown on (111)B GaAs substrates are shown to differ radically from those grown on (001) substrates. In (111)B structures, the linewidth in wide wells is broadened significantly compared with (001) structures. This broadening cannot be explained by well width or alloy fluctuations alone, and suggests the presence of another mechanism which we believe is due to the piezoelectric field and its sensitivity to screening under illumination. © 1999 American Institute of Physics.
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78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
77.65.Ly Strain-induced piezoelectric fields
78.20.Jq Electro-optical effects

Linear electro-optic effect due to the built-in electric field in InGaN/GaN quantum wells

Hongtao Jiang and Jasprit Singh

Appl. Phys. Lett. 75, 1932 (1999); http://dx.doi.org/10.1063/1.124875 (3 pages) | Cited 11 times

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A strong piezoelectric effect and large lattice mismatch allow one to incorporate high built-in electric fields in InGaN/GaN quantum wells. This letter examines the implications of these fields on the absorption spectra and refractive index changes induced by an external perpendicular electric field. We find that InGaN/GaN quantum wells show linear electro-optic effect due to quantum confined Stark effect. Our results suggest application of InGaN/GaN quantum wells in Mach–Zehnder type modulators and in electroabsorption modulators in the blue light region. © 1999 American Institute of Physics.
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78.20.Jq Electro-optical effects
78.66.Fd III-V semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
77.65.Ly Strain-induced piezoelectric fields
78.30.Fs III-V and II-VI semiconductors
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
42.79.Hp Optical processors, correlators, and modulators

Confinement induced decrease of the exciton-longitudinal optical phonon coupling in GaN quantum dots

Peter Ramvall, Satoru Tanaka, Shintaro Nomura, Philippe Riblet, and Yoshinobu Aoyagi

Appl. Phys. Lett. 75, 1935 (1999); http://dx.doi.org/10.1063/1.124876 (3 pages) | Cited 7 times

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We report on an investigation of the coupling between excitons and longitudinal optical phonons as a function of GaN quantum dot size. Photoluminescence measurements of the quantum dots from cryogenic temperatures up to above room temperature are presented. The experiments were performed on ensembles of AlN capped GaN quantum dots grown on an Al0.15Ga0.85N surface by means of metalorganic vapor phase epitaxy. The results are analyzed on the basis of a Bose–Einstein-type expression describing the exciton to longitudinal optical phonon coupling of the dots as a function of the lattice temperature. A reduction of the exciton to LO-phonon coupling with decreasing quantum dot size was found. © 1999 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
63.20.kk Phonon interactions with other quasiparticles
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
71.35.-y Excitons and related phenomena

Evidence from scanning tunneling microscopy in support of a structural model for the InSb(001)-c(8×2) surface

A. A. Davis, R. G. Jones, G. Falkenberg, L. Seehofer, R. L. Johnson, and C. F. McConville

Appl. Phys. Lett. 75, 1938 (1999); http://dx.doi.org/10.1063/1.124877 (3 pages) | Cited 8 times

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In this letter we present evidence from scanning tunneling microscopy studies in support of a recently proposed structural model for the indium-terminated c(8×2) surface of InSb(001). This structural model, by Norris and co-workers, is based on a surface x-ray diffraction study [Surf. Sci. 409, 27 (1998)], and represents a significant departure from previously suggested models for the c(8×2) reconstruction on any (001) surface of the common III–V semiconductor materials. Although filled state images of the InSb(001)-c(8×2) surface have previously been published, empty states image of sufficient quality to extract any meaningful information have not previously been reported. The observations are in excellent agreement with the recently proposed model for this surface reconstruction. © 1999 American Institute of Physics.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy
73.20.At Surface states, band structure, electron density of states
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Use of magnetocrystalline anisotropy in spin-dependent tunneling

R. A. Lukaszew, Y. Sheng, C. Uher, and R. Clarke

Appl. Phys. Lett. 75, 1941 (1999); http://dx.doi.org/10.1063/1.124878 (3 pages) | Cited 13 times

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Epitaxial growth techniques are used to impose in-plane magnetocrystalline anisotropy on a spin-polarized tunneling configuration. A Cu(100) buffer layer grown on a Si(100) substrate stabilizes epitaxial face-centered-cubic cobalt as one of the ferromagnetic electrodes. The negative magnetocrystalline constant of this metastable phase favors easy axes along Co 〈110〉 and, due to the single crystal nature of this layer, the coercivity is more than an order of magnitude larger than in the polycrystalline layers which form the second electrode. Our approach provides a way to access the high degree of spin polarization characteristic of the 3d transition metals. © 1999 American Institute of Physics.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.45.+j Macroscopic quantum phenomena in magnetic systems
75.30.Gw Magnetic anisotropy
75.50.Cc Other ferromagnetic metals and alloys
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
78.20.Ls Magneto-optical effects
72.15.Gd Galvanomagnetic and other magnetotransport effects
73.61.At Metal and metallic alloys

Spin-polarized scanning tunneling microscopy on ferromagnets

Wulf Wulfhekel and Jürgen Kirschner

Appl. Phys. Lett. 75, 1944 (1999); http://dx.doi.org/10.1063/1.124879 (3 pages) | Cited 62 times

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A straightforward approach to spin-polarized scanning tunneling microscopy based on the magnetotunnel effect between a ferromagnetic tip and a ferromagnetic sample is demonstrated. By periodically changing the magnetization of the tip in combination with a lock-in technique, topographic and spin-dependent parts of the tunnel current are separated and the topography and the magnetic structure of the sample are recorded simultaneously. Results are given for polycrystalline Ni and single crystalline Co(0001) surfaces, revealing a high spin contrast, low data acquisition times, and a resolution down to 10 nm. Potentials and limitations of this technique are discussed. © 1999 American Institute of Physics.
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75.25.-j Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.)
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy
68.35.B- Structure of clean surfaces (and surface reconstruction)
75.60.Ch Domain walls and domain structure
75.50.Cc Other ferromagnetic metals and alloys

Magnetic imaging of perovskite thin films by ferromagnetic resonance microscopy—La0.7Sr0.3MnO3

S. E. Lofland, S. M. Bhagat, Q. Q. Shu, M. C. Robson, and R. Ramesh

Appl. Phys. Lett. 75, 1947 (1999); http://dx.doi.org/10.1063/1.124880 (2 pages) | Cited 13 times

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We present ferromagnetic resonance scans of epitaxial thin films of La0.7Sr0.3MnO3. In most films, the resonance field indicates the presence of large stresses, the line is wide and both the field and width vary significantly with position. However, in the perpendicular geometry (field normal to the film plane) the best films show narrow lines (<20 Oe) which are relatively independent of position, indicative of magnetic homogeneity. The experiments show that this technique can be used as a contactless, nondestructive diagnostic tool for assessing the magnetic quality of colossal magnetoresistance thin films. © 1999 American Institute of Physics.
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76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance
75.47.Gk Colossal magnetoresistance
75.70.Ak Magnetic properties of monolayers and thin films
75.50.Dd Nonmetallic ferromagnetic materials
75.80.+q Magnetomechanical effects, magnetostriction

Atomic order, electron structure, and critical parameters of epitaxial YBaCuO films

V. D. Okunev, Z. A. Samoilenko, A. Abal’oshev, P. Gierłowski, A. Klimov, and S. J. Lewandowski

Appl. Phys. Lett. 75, 1949 (1999); http://dx.doi.org/10.1063/1.124881 (3 pages) | Cited 15 times

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X-ray structural and optical methods were applied to make a detailed investigation of atomic and electronic structure of superconducting YBa2Cu3O7−δ films obtained by pulsed laser deposition. Optical transmission spectrum was found to depend not only on intraband (ℏω<1.2 eV) and interband (ℏω>1.95 eV) transitions, but also on contributions from charge transfer transitions O 2p⇒Cu 3d in the dielectric phase due to local order in a system of crystallographic (11l) planes. Superconducting properties of the films are determined by orientational structural transition (00l)+(11l)⇒(00l) and by Anderson type transition from a charge transfer O 2p⇒Cu 3d insulator to a strongly degenerate semiconductor with metallic conductivity. We show the effects of ordering on transition temperature Tc and demonstrate that at the concentration of (00l) clusters below the percolation threshold (20%) the behavior of Tc has catastrophic character. © 1999 American Institute of Physics.
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74.78.-w Superconducting films and low-dimensional structures
74.72.-h Cuprate superconductors
74.25.Jb Electronic structure (photoemission, etc.)
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition
68.55.-a Thin film structure and morphology
74.25.Gz Optical properties
71.30.+h Metal-insulator transitions and other electronic transitions

High oxygen pressure generation of flux-pinning centers in melt-textured YBa2Cu3O7

T. Puig, J. Plain, F. Sandiumenge, X. Obradors, J. Rabier, and J. A. Alonso

Appl. Phys. Lett. 75, 1952 (1999); http://dx.doi.org/10.1063/1.124882 (3 pages) | Cited 19 times

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A strong enhancement of the critical current density, Jcab(H,T), has been generated in melt-textured YBa2Cu3O7/Y2BaCuO5 composites by means of high oxygen pressure (≈100 bar, ∼400 °C). Enhancement factors as high as 180% have been found at low temperatures leading high sample performances at 77 K (Jcab ≈ 1.2×105 A/cm2 at null field). Transmission electron microscopy studies show a high concentration of dendritic-like stacking faults generated as a consequence of the strong nonequilibrium conditions of the transformation from YBa2Cu3O7 to YBa2Cu4O8. The high concentration of 1/6〈031〉 partial dislocations within the (001) planes are proposed as point-defect pinning centers enhancing Jcab(H,T) for the H∥c configuration. © 1999 American Institute of Physics.
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74.72.-h Cuprate superconductors
74.81.Bd Granular, melt-textured, amorphous, and composite superconductors
74.25.Sv Critical currents
74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
81.40.Gh Other heat and thermomechanical treatments
61.72.Nn Stacking faults and other planar or extended defects
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)

High temperature c-axis resistivity of Bi2Sr2CaCu2O8+x single crystals and dependence on oxygen stoichiometry

G. Yang, J. S. Abell, and C. E. Gough

Appl. Phys. Lett. 75, 1955 (1999); http://dx.doi.org/10.1063/1.124883 (3 pages) | Cited 12 times

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The c-axis resistivity of Bi2Sr2CaCu2O8+x crystals has been measured as a function of thermal cycling in the range between 70 and 856 K in flowing oxygen and nitrogen. Hysteresis in the temperature-dependent c-axis resistivity provides evidence of thermally activated oxygen diffusion in and out of the crystal varying as D(T) = 6×107 exp(−Δ1/kT) and D(T) = 55 exp(−Δ2/kT), where Δ1 = 2.2 eV and Δ2 = 1.2 eV, respectively. Oxygen diffusion into the crystals becomes significant above T0 ∼ 595 K and out of the crystal above T1 ∼ 750 K. The implications for the stoichiometric control, superconductivity, and intrinsic high temperature dependence of the resistivity of Bi2Sr2CaCu2O8+x crystals are considered. © 1999 American Institute of Physics.
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72.20.Fr Low-field transport and mobility; piezoresistance
72.80.Sk Insulators
74.72.-h Cuprate superconductors
61.66.Bi Elemental solids
61.66.Dk Alloys
66.30.H- Self-diffusion and ionic conduction in nonmetals
61.72.Cc Kinetics of defect formation and annealing
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The ferroelectricity of perovskite-type oxides with alkylamine interlayer

Zhaohui Zhong, Weiping Ding, Yi Chen, Xiaoyuan Chen, Yongyuan Zhu, and Naiben Min

Appl. Phys. Lett. 75, 1958 (1999); http://dx.doi.org/10.1063/1.124884 (3 pages) | Cited 6 times

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The ferroelectricity of layer perovskite-type oxides intermittent with alkylamine, synthesized by hydrothermal method, has been reported. Ferroelectric hysteresis loops were observed in these newly synthesized powder crystals, which were pressed into wafers with platinum electrodes deposited by a pulsed laser. Element analysis shows 69% cations between two layers were exchanged into alkyl ammonium. X-ray powder diffraction pattern, infrared spectra, Raman spectra, and electron microscopy were used to characterize the samples. The results show that perovskite layer contributes to the ferroelectric property. So-synthesized samples may make up a new group of materials with potential use especially in the field of fatigue-free ferroelectricity. © 1999 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.Dj Domain structure; hysteresis
78.30.-j Infrared and Raman spectra
77.80.Fm Switching phenomena
81.10.Dn Growth from solutions

Structure determination of a planar defect in SrBi2Ta2O9

Y. Yan, M. M. Al-Jassim, Z. Xu, X. Lu, D. Viehland, M. Payne, and S. J. Pennycook

Appl. Phys. Lett. 75, 1961 (1999); http://dx.doi.org/10.1063/1.124885 (3 pages) | Cited 9 times

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The atomic structure of a planar defect with a (001) habit plane in single crystal layered perovskite SrBi2Ta2O9 is determined by high-resolution Z-contrast imaging. We found that the defect forms a structure, with two Sr–Ta–O perovskite blocks connected by a metallic Sr2 plane, rather than a Bi2O2 layer as in the perfect crystal. This defect is expected to be an efficient hole trap and may have important implications for the electronic properties and the ferroelectric response of the SrBi2Ta2O9 material. © 1999 American Institute of Physics.
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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
71.55.Ht Other nonmetals
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Lp Transmission electron microscopy (TEM)

The dependence of electron emission on ferroelectric properties of Pb(ZrxTi1−x)O3

Yong Tae Kim, Ki Hyun Yoon, Tae Heui Kim, and Kyung Bong Park

Appl. Phys. Lett. 75, 1964 (1999); http://dx.doi.org/10.1063/1.124886 (3 pages) | Cited 7 times

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The characteristics of pulse electric field induced electron emission from the Pb(ZrxTi1−x)O3 ceramics have been investigated with a particular emphasis on the relationship to the ferroelectric properties. The emission charge of the negative pulse field to the rear electrode was smaller and more stable than that of the positive field. The emission threshold field and the emission charge were indeed affected by the coercive field and polarization change. However, the emission properties were minimally affected by the dielectric constant. The emission charge increased exponentially with the pulse field and polarization change. The electron emission can be regarded as a field emission by polarization change. © 1999 American Institute of Physics.
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79.70.+q Field emission, ionization, evaporation, and desorption
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.22.Ej Polarization and depolarization
77.80.Dj Domain structure; hysteresis
77.80.Fm Switching phenomena

High dielectric constant Hf–Sn–Ti–O thin films

L. F. Schneemeyer, R. B. van Dover, and R. M. Fleming

Appl. Phys. Lett. 75, 1967 (1999); http://dx.doi.org/10.1063/1.124887 (3 pages) | Cited 33 times

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High dielectric constant Hf–Sn–Ti–O thin-film materials were identified using a compositional-spread approach. Thin films of composition Hf0.2Sn0.05Ti0.75O2 prepared at 250 °C have excellent dielectric properties: 40–70-nm-thick films with a dielectric constant of 40–60 were obtained, depending on the processing conditions, yielding a specific capacitance of 9–17 fF/μm2. Breakdown fields were measured to be about 3–4 MV/cm, yielding a figure of merit ϵϵ0Ebr ∼ 19 μC/cm2. Leakage currents, measured at 1 MV/cm, were in the range 10−7−10−6 A/cm2. © 1999 American Institute of Physics.
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77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.55.-g Dielectric thin films
77.22.Ch Permittivity (dielectric function)
77.22.Jp Dielectric breakdown and space-charge effects
81.15.Cd Deposition by sputtering
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