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11 Sep 2000

Volume 77, Issue 11, pp. 1569-1731

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On the use of total reflection x-ray topography for the observation of misfit dislocation strain at the surface of a Si/Ge–Si heterostructure

Patrick J. McNally, G. Dilliway, J. M. Bonar, A. Willoughby, T. Tuomi, R. Rantamäki, A. N. Danilewsky, and D. Lowney

Appl. Phys. Lett. 77, 1644 (2000); http://dx.doi.org/10.1063/1.1308269 (3 pages) | Cited 5 times

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Synchrotron x-ray topography was used in total reflection topography (TRT) mode to observe strain-induced surface bumps due to the presence of underlying misfit dislocations in strained-layer SiGe on Si epitaxial heterostructures. In these experiments, the x rays approached the sample surfaces at grazing incident angles below the critical angles for total external reflection for a number of reflections, and hence, surface strain features nominally less than a few tens of angstrøms from the sample surface have been observed. These are similar to the surface bumpiness observed by atomic force microscopy, albeit on a much larger lateral length scale. The fact that TRT mode images were taken was confirmed by the observation of conventional backreflection topographic images of misfit dislocations in all samples when the grazing incidence angle became greater than the critical angle. © 2000 American Institute of Physics.
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68.60.Bs Mechanical and acoustical properties
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
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Low-resistance Ti/Au ohmic contacts to Al-doped ZnO layers

Han-Ki Kim, Sang-Heon Han, Tae-Yeon Seong, and Won-Kook Choi

Appl. Phys. Lett. 77, 1647 (2000); http://dx.doi.org/10.1063/1.1308527 (3 pages) | Cited 65 times

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We report on low-resistance ohmic contacts to the moderately doped n-type ZnO:Al(nd = 2×1017 cm−3) obtained using Ti (30 nm)/Au (50 nm) metallization schemes. Annealed Ti/Au contacts exhibit linear current–voltage characteristics, showing that high-quality ohmic contacts are formed. The Ti/Au scheme produces a specific contact resistance of 2×10−4 Ω cm2 when annealed at 300 °C for 1 min in a N2 atmosphere. © 2000 American Institute of Physics.
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73.40.Ns Metal-nonmetal contacts
85.40.Ls Metallization, contacts, interconnects; device isolation

Nitrogen dependence of the GaAsN interband critical points E1 and E1+Δ1 determined by spectroscopic ellipsometry

G. Leibiger, V. Gottschalch, B. Rheinländer, J. Šik, and M. Schubert

Appl. Phys. Lett. 77, 1650 (2000); http://dx.doi.org/10.1063/1.1309021 (3 pages) | Cited 27 times

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The effects of the nitrogen concentrations on the E1 and E1+Δ1 transitions of tensile-strained GaAs1−yNy (0.1% ⩽ y ⩽ 3.7%) grown pseudomorphically to GaAs by metalorganic vapor-phase epitaxy are studied by spectroscopic ellipsometry. Adachi’s critical-point composite model is employed for ellipsometry data analysis. Contrary to the well-known redshift of the band-gap energy E0, we observe linearly blueshifted E1 and E1+Δ1 transition energies with increasing nitrogen composition y. For nitrogen compositions of 0 ⩽ y ⩽ 1.65%, the observed blueshift of the E1 energy is well explained by the sum of the effects of biaxial (001) strain and alloying. © 2000 American Institute of Physics.
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71.20.Nr Semiconductor compounds
07.60.Fs Polarimeters and ellipsometers
78.66.Fd III-V semiconductors

Si/SiGe electron resonant tunneling diodes

D. J. Paul, P. See, I. V. Zozoulenko, K.-F. Berggren, B. Kabius, B. Holländer, and S. Mantl

Appl. Phys. Lett. 77, 1653 (2000); http://dx.doi.org/10.1063/1.1309020 (3 pages) | Cited 22 times

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Resonant tunneling diodes have been fabricated using strained-Si wells and strained Si0.4Ge0.6 barriers on a relaxed Si0.8Ge0.2 n-type substrate, which demonstrate negative differential resistance at 298 K. Peak current densities of 5 kA/cm2 with peak-to-valley current ratios of 1.1 have been achieved. Theoretical modeling of the structure demonstrates that the major current peak results from the tunneling of light-mass electrons from the relaxed substrate and not from the heavy-mass electrons in the emitter accumulation layer. © 2000 American Institute of Physics.
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85.30.Mn Junction breakdown and tunneling devices (including resonance tunneling devices)
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
85.30.De Semiconductor-device characterization, design, and modeling
73.50.Fq High-field and nonlinear effects

SiGe heterojunction vertical p-type metal–oxide–semiconductor field-effect transistors with Si cap

Xiangdong Chen, Qiqing Ouyang, David M. Onsongo, Sankaran Kartik Jayanarayanan, Al Tasch, and Sanjay Banerjee

Appl. Phys. Lett. 77, 1656 (2000); http://dx.doi.org/10.1063/1.1309018 (3 pages) | Cited 2 times

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SiGe source heterojunction p-type metal–oxide–semiconductor field-effect transistors (p-MOSFETs) have been used before to suppress the short channel effect for sub-100 nm devices. While the leakage is reduced, the drive current is also reduced due to the heterojunction. In this letter, we discuss a SiGe source heterojunction vertical p-MOSFET with a few nanometers thick Si cap. With this device structure, the absence of the heterojunction-induced potential barrier right below the oxide interface improves the drive current substantially while the drain induced barrier lowering (DIBL) effect and floating body effect are still suppressed. The electrical characterization of the device shows it exhibits higher drive current and less DIBL compared with a Si control device. © 2000 American Institute of Physics.
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85.30.Tv Field effect devices
81.05.Hd Other semiconductors

Control of the residual doping of InAs/(GaIn)Sb infrared superlattices

L. Bürkle, F. Fuchs, J. Schmitz, and W. Pletschen

Appl. Phys. Lett. 77, 1659 (2000); http://dx.doi.org/10.1063/1.1310167 (3 pages) | Cited 21 times

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Magnetotransport and photoluminescence (PL) measurements on InAs/(GaIn)Sb superlattices (SLs) grown by molecular-beam epitaxy on GaSb substrates at different substrate temperatures are reported. With increasing growth temperature, a transition of the SLs from residual n type to residual p-type doping was observed. For n-type samples, a decrease in the electron concentration leads to a strong increase in the PL intensity. In contrast, the PL intensity of p-type samples is only weakly dependent on the hole concentration. This correlation can be used to control the residual doping of the SLs. © 2000 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
61.72.uj III-V and II-VI semiconductors
73.61.Ey III-V semiconductors
78.66.Fd III-V semiconductors
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.55.Cr III-V semiconductors
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
85.60.Gz Photodetectors (including infrared and CCD detectors)

Band discontinuities at epitaxial SrTiO3/Si(001) heterojunctions

S. A. Chambers, Y. Liang, Z. Yu, R. Droopad, J. Ramdani, and K. Eisenbeiser

Appl. Phys. Lett. 77, 1662 (2000); http://dx.doi.org/10.1063/1.1310209 (3 pages) | Cited 93 times

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We have used photoemission methods to directly measure the valence and conduction band offsets at SrTiO3/Si(001) interfaces, as prepared by molecular-beam epitaxy. Within experimental error, the measured values are the same for growth on n- and p-Si, with the entire band discontinuity occurring at the valence band edge. In addition, band bending is much larger at the p-Si heterojunction than at the n-type heterojunction. Previously published threshold voltage behavior for these interfaces can now be understood in light of the present results. © 2000 American Institute of Physics.
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73.20.At Surface states, band structure, electron density of states
79.60.Jv Interfaces; heterostructures; nanostructures
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Controlled oxide removal for the preparation of damage-free InAs(110) surfaces

T. D. Veal and C. F. McConville

Appl. Phys. Lett. 77, 1665 (2000); http://dx.doi.org/10.1063/1.1310211 (3 pages) | Cited 8 times

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Controlled oxide removal from InAs(110) surfaces using atomic hydrogen (H∗) has been achieved by monitoring the contaminant vibrational modes with high resolution electron energy loss spectroscopy (HREELS). The contributing oxide vibrational modes of the partially H∗ cleaned surface have been identified. Following hydrocarbon desorption during preliminary annealing at 360 °C, exposure to atomic hydrogen at 400 °C initially removes the arsenic oxides and indium suboxides; complete indium oxide removal requires significantly higher hydrogen doses. After a total molecular hydrogen dose of 120 kL, a clean, ordered surface, exhibiting a sharp (1×1) pattern, was confirmed by low energy electron diffraction and x-ray photoelectron spectroscopy. Energy dependent HREELS studies of the near-surface electronic structure indicate that no residual electronic damage or dopant passivation results from the cleaning process. © 2000 American Institute of Physics.
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81.65.Cf Surface cleaning, etching, patterning
81.05.Ea III-V semiconductors
68.35.B- Structure of clean surfaces (and surface reconstruction)
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
68.35.Ja Surface and interface dynamics and vibrations
79.20.Kz Other electron-impact emission phenomena
79.60.Bm Clean metal, semiconductor, and insulator surfaces
73.20.At Surface states, band structure, electron density of states

Light-induced conductance resonance in ultrasmall Si nanoparticles

Joel Therrien, Gennadiy Belomoin, and Munir Nayfeh

Appl. Phys. Lett. 77, 1668 (2000); http://dx.doi.org/10.1063/1.1308524 (3 pages) | Cited 12 times

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Ultrasmall, uniform-size (∼1 nm) Si nanoparticles, dispersed from p-type boron-doped silicon, are reconstituted on a Si substrate. Electronic transport processes are studied by current–voltage spectroscopy at room temperature, using scanning tunneling microscopy, in a two-terminal configuration, under both dark conditions and light illumination. Unlike the dark conditions, we observe, under light irradiation, for negative tip biasing, a regular structure at ∼1.0 eV period. The series is discussed in terms of light-induced hole states that otherwise are highly infrequent in ultrasmall Si particles, under standard low doping. © 2000 American Institute of Physics.
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72.40.+w Photoconduction and photovoltaic effects
72.80.Cw Elemental semiconductors
73.22.-f Electronic structure of nanoscale materials and related systems
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
71.20.Mq Elemental semiconductors

Capacitance–voltage characteristics of InAs/GaAs quantum dots embedded in a pn structure

R. Wetzler, A. Wacker, E. Schöll, C. M. A. Kapteyn, R. Heitz, and D. Bimberg

Appl. Phys. Lett. 77, 1671 (2000); http://dx.doi.org/10.1063/1.1290137 (3 pages) | Cited 27 times

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We study the electronic states of self-organized InAs quantum dots embedded in a pn junction by means of capacitance–voltage (C–V) characteristics. A model based on the self-consistent solution of the Poisson equation and the drift-diffusion equations is proposed for calculating the capacitance. This model allows us to determine the energy levels of the quantum dot states and their inhomogeneous broadening from a comparison with experimental C–V data. Good quantitative agreement between predictions of the model and the low-frequency C–V characteristics is obtained. © 2000 American Institute of Physics.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
73.61.Ey III-V semiconductors
02.30.Jr Partial differential equations
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Thickness-dependent transport properties of Nd2/3Sr1/3MnO3 thin films

A. Barman and G. Koren

Appl. Phys. Lett. 77, 1674 (2000); http://dx.doi.org/10.1063/1.1309028 (3 pages) | Cited 11 times

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A systematic study is reported on the thickness dependence of the electrical resistivity in thin films of the giant magnetoresistance manganite Nd2/3Sr1/3MnO3. We observed a first-order phase transition versus thickness in these films, which is seen as a jump of about 30 K in the metal-to-insulator transition temperature (Tp) at film thickness of 50–60 nm. This phenomenon is attributed to a sudden release of strain in the film as its thickness increases. We also observed at low temperatures, 5–30 K, another transition from localized-to-metallic behavior versus film thickness, which is also related to the strain relief in the films. © 2000 American Institute of Physics.
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75.47.De Giant magnetoresistance
73.61.Ng Insulators
71.30.+h Metal-insulator transitions and other electronic transitions
75.70.Ak Magnetic properties of monolayers and thin films

Flux trapping in a superconducting thin film as revealed by simulations and scanning superconducting quantum interference device microscope observations

Keiichi Tanaka, Toshimitsu Morooka, Akikazu Odawara, Kazuo Chinone, Yasunori Mawatari, and Masao Koyanagi

Appl. Phys. Lett. 77, 1677 (2000); http://dx.doi.org/10.1063/1.1310177 (3 pages) | Cited 2 times

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Penetration of magnetic fluxes into a superconducting thin film that contained holes was studied for fast and slow cooling rates (0.18 and 0.009 K/s, respectively) under an ambient magnetic field of about 3 μT. By using a scanning superconducting quantum interference device microscope, we observed trapped magnetic fluxes both inside and outside of holes prepared in a superconducting film. The trapped fluxes outside the holes appeared in a regular arrangement when the superconducting film was cooled at the slow rate. Observed arrangements of the trapped fluxes were compared with a simulation that was based on a theoretical model that considered the surface barrier and the interaction among fluxes. The simulation explained well the observed arrangements of magnetic fluxes. © 2000 American Institute of Physics.
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74.78.-w Superconducting films and low-dimensional structures
74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
74.25.Ha Magnetic properties including vortex structures and related phenomena

Dynamic nuclear polarization by spin injection

Mark Johnson

Appl. Phys. Lett. 77, 1680 (2000); http://dx.doi.org/10.1063/1.1310173 (3 pages) | Cited 8 times

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A theory is presented to describe quantitatively how nuclear spin polarization can be induced in a metal by a dc electric bias current driven through the sample. The bias current is spin polarized by passing through a thin ferromagnetic film in interfacial contact with the sample, with the polarization axis determined by the magnetization orientation of the ferromagnetic layer. The nuclear spins are polarized due to spin angular momentum transfer from the electrons to the nuclei mediated by the contact hyperfine interaction. Upon reversing the polarity of the bias current, the sign of the nuclear polarization is reversed. Unlike other methods of dynamic nuclear polarization, spin-injected dynamic nuclear polarization is a zero frequency technique that in principle does not require an applied magnetic field.
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76.70.Fz Double nuclear magnetic resonance (DNMR), dynamical nuclear polarization
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Magnetoresistance effect in the fluctuating-valence BaSmFe2O5+w system

J. Nakamura, J. Lindén, M. Karppinen, and H. Yamauchi

Appl. Phys. Lett. 77, 1683 (2000); http://dx.doi.org/10.1063/1.1310170 (3 pages) | Cited 10 times

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The occurrence of negative magnetoresistance (MR) in semiconductive BaSmFe2O5+w double-perovskite samples is demonstrated. A peak in the MR value was observed at the Verwey–type transition temperature. The transition signifies the charge separation of the Fe2.5+ fluctuating mixed valence state into high-spin Fe2+ and Fe3+. The samples were ferrimagnetic with a Curie temperature of ∼ 710 K. Upon oxidizing/reducing the samples the size of the MR peak and the temperature at which the peak occurred varied. The largest MR value observed was 1.4% at 7 T. © 2000 American Institute of Physics.
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72.20.My Galvanomagnetic and other magnetotransport effects
75.50.Pp Magnetic semiconductors
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.50.Gg Ferrimagnetics
71.28.+d Narrow-band systems; intermediate-valence solids

Dependence of critical current on field angle in off-c-axis grown Bi2Sr2CaCu2O8 film

J. H. Durrell, G. Gibson, Z. H. Barber, J. E. Evetts, R. Rössler, J. D. Pedarnig, and D. Bäuerle

Appl. Phys. Lett. 77, 1686 (2000); http://dx.doi.org/10.1063/1.1310174 (3 pages) | Cited 6 times

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Critical current measurements for varying angles of applied field have been performed on Bi2Sr2CaCu2O8 thin films grown on 10° vicinal (001) substrates. Measurements were performed on current tracks orientated both parallel (L) and transverse (T) to the vicinal steps. No Josephson vortex channeling effect was observed, in contrast to results previously obtained on both oxygenated and deoxygenated YBa2Cu3O7−δ films grown on vicinal substrates. In addition, no force-free peak was observed when the applied field was parallel to the current. This provides experimental evidence that there is a difference between the pancake coupling mechanism in YBa2Cu3O7−δ at small field angles where Josephson vortices are present and that in Bi2Sr2CaCu2O8. © 2000 American Institute of Physics.
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74.72.-h Cuprate superconductors
74.78.-w Superconducting films and low-dimensional structures
74.25.Sv Critical currents
74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
74.50.+r Tunneling phenomena; Josephson effects

Determination of first and second magnetic anisotropy constants of magnetic recording media

Yasushi Endo, Osamu Kitakami, Satoshi Okamoto, and Yutaka Shimada

Appl. Phys. Lett. 77, 1689 (2000); http://dx.doi.org/10.1063/1.1310166 (3 pages) | Cited 16 times

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We propose a simple method to evaluate the first and second magnetic anisotropy constants of high-density magnetic recording media with their easy axis in the film plane. By measuring the magnetization curve along the film normal, uniaxial anisotropy constants K1 and K2 can be determined simultaneously. The present method has been applied to (11⋅0) oriented CoCrPtTa hard disk media. The measured anisotropy constants are presented along with their temperature dependence. We also point out serious shortcomings of the currently used evaluation methods, such as the rotational hysteresis method and the singular point detection technique, which usually overestimate the magnetic anisotropy constant. © 2000 American Institute of Physics.
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75.30.Gw Magnetic anisotropy
75.50.Ss Magnetic recording materials
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Edge-pinned states in patterned submicron NiFeCo structures

Jing Shi and S. Tehrani

Appl. Phys. Lett. 77, 1692 (2000); http://dx.doi.org/10.1063/1.1290599 (3 pages) | Cited 23 times

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Magnetization reversal in patterned submicron NiFeCo structures has been studied. Application of a transverse field lowers the easy axis switching threshold of the center of the structures but the edge magnetization remains pinned along the initial direction until a higher reversal field is applied. Complete switching between the two stable magnetization states occurs only after depinning and reversal of the edge magnetization. The edge depinning field is found to be very insensitive to the transverse field strength. Micromagnetic simulations are used to characterize the magnetization reversal process. © 2000 American Institute of Physics.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Bb Fe and its alloys
75.40.Mg Numerical simulation studies
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Dielectric properties in heteroepitaxial Ba0.6Sr0.4TiO3 thin films: Effect of internal stresses and dislocation-type defects

C. L. Canedy, Hao Li, S. P. Alpay, L. Salamanca-Riba, A. L. Roytburd, and R. Ramesh

Appl. Phys. Lett. 77, 1695 (2000); http://dx.doi.org/10.1063/1.1308531 (3 pages) | Cited 146 times

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A series of heteroepitaxial Ba0.6Sr0.4TiO3 were grown on 0.29(LaAlO3):0.35(Sr2TaAlO6) substrates using pulsed-laser deposition. X-ray characterization revealed compressive in-plane stresses in the thinnest films, which were relaxed in a continuous fashion with increasing thickness. A theoretical treatment of the misfit strain was in good agreement with the measured out-of-plane lattice parameter. The low-frequency dielectric constant was measured to be significantly less than the bulk value and found to decrease rapidly for films less than 100 nm. A thermodynamic model was developed to understand the reduction in dielectric constant. By observing the microstructure using plan-view and cross-section transmission electron microscopy, we identified local strain associated with a threading dislocation density on the order of 1011 cm−2 as a possible mechanism for dielectric degradation in these films. © 2000 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
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
77.22.Ch Permittivity (dielectric function)
77.80.-e Ferroelectricity and antiferroelectricity
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
68.60.Bs Mechanical and acoustical properties

Large strain electrostrictive actuation in barium titanate

E. Burcsu, G. Ravichandran, and K. Bhattacharya

Appl. Phys. Lett. 77, 1698 (2000); http://dx.doi.org/10.1063/1.1308533 (3 pages) | Cited 59 times

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Large strain electrostriction in single-crystal ferroelectric materials is investigated. The mode of electrostriction is based on a combined electromechanical loading used to induce cyclic, 90° domain switching. Experiments have been performed on crystals of barium titanate with constant compressive stress and oscillating electric-field input. Induced strains of more than 0.8% have been measured. Strains as large as 5% are predicted for other materials of the same class. The results demonstrate a possible avenue for obtaining large actuation strains in electromechanical devices. © 2000 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.Fm Switching phenomena
77.80.Dj Domain structure; hysteresis
77.65.Bn Piezoelectric and electrostrictive constants
85.50.-n Dielectric, ferroelectric, and piezoelectric devices

Piezoelectric response of epitaxial Pb(Zr0.2Ti0.8)O3 films measured by scanning tunneling microscopy

O. Kuffer, I. Maggio-Aprile, J.-M. Triscone, Ø. Fischer, and Ch. Renner

Appl. Phys. Lett. 77, 1701 (2000); http://dx.doi.org/10.1063/1.1309017 (3 pages) | Cited 20 times

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We report on scanning tunneling microscopy measurements of the piezoelectric response in ferroelectric heterostructures grown by off-axis rf magnetron sputtering. The samples are composed of a single-crystalline ferroelectric film of Pb(Zr0.2Ti0.8)O3 deposited on a conducting substrate and covered with an ultrathin metallic film of gold. The high quality of the c-axis oriented ferroelectric layer is evidenced by sharp polarization hysteresis loops. By applying a voltage to the bilayer and recording the inverse piezoelectric effect with the scanning tunneling microscope, we demonstrate the ability to measure the phase response as well as the ferroelectric switching. We obtained strain-field plots with a butterfly loop shape, and a quantitative measurement of the longitudinal piezoelectric coefficient (d33). © 2000 American Institute of Physics.
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77.55.-g Dielectric thin films
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
77.65.Bn Piezoelectric and electrostrictive constants
68.55.-a Thin film structure and morphology
77.80.Fm Switching phenomena
77.80.Dj Domain structure; hysteresis
77.22.Ej Polarization and depolarization

Ultrathin zirconium silicate film with good thermal stability for alternative gate dielectric application

Wen-Jie Qi, Renee Nieh, Easwar Dharmarajan, Byoung Hun Lee, Yongjoo Jeon, Laegu Kang, Katsunori Onishi, and Jack C. Lee

Appl. Phys. Lett. 77, 1704 (2000); http://dx.doi.org/10.1063/1.1308535 (3 pages) | Cited 54 times

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Zirconium silicate (ZrSixOy) films have been sputtered by comagnetron-reactive sputtering. The composition of ZrSixOy has been controlled by adjusting the sputtering powers of Si and Zr targets to achieve various effective dielectric constants. The sputtered silicate layers showed low equivalent oxide thickness of 14.5 Å with a low leakage of 3.3×10−3 A/cm2 at −1.5 V relative to flat band voltage. The silicate films also exhibited good high-temperature stability and smooth interfacial properties on silicon substrate. © 2000 American Institute of Physics.
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81.15.Cd Deposition by sputtering
68.60.Dv Thermal stability; thermal effects
77.22.Ch Permittivity (dielectric function)
77.55.-g Dielectric thin films
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)

Anomalies in the temperature dependence of the microwave dielectric properties of Ba6−xSm8+2x/3Ti18O54

Anatolii G. Belous, Oleg V. Ovchar, Matjaz Valant, and Danilo Suvorov

Appl. Phys. Lett. 77, 1707 (2000); http://dx.doi.org/10.1063/1.1309024 (3 pages) | Cited 7 times

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Measurements of the microwave dielectric properties of Ba6−xSm8+2x/3Ti18O54 solid solutions revealed the existence of a broad maximum in the temperature dependence of the permittivity as well as the dielectric loss. Submillimeter-wave frequency measurements confirmed the intrinsic origin of the observed anomaly, which could possibly be ascribed to phase transition with unknown nature in the Ba6−xSm8+2x/3Ti18O54 solid solution. The temperature of the anomaly, which is in the range of 90–120 °C, depends on composition of Ba6−xSm8+2x/3Ti18O54 and decreases with an increase in x. © 2000 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.22.Ch Permittivity (dielectric function)
77.22.Gm Dielectric loss and relaxation
84.40.-x Radiowave and microwave (including millimeter wave) technology
64.70.K- Solid-solid transitions

Piezoelectric properties and poling effect of Pb(Zr, Ti)O3 thick films prepared for microactuators by aerosol deposition

J. Akedo and M. Lebedev

Appl. Phys. Lett. 77, 1710 (2000); http://dx.doi.org/10.1063/1.1309029 (3 pages) | Cited 61 times

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Crack-free [Pb(Zr0.52, Ti0.48)O3] (PZT) films with more than 10 μm thickness as the piezoelectric material, were formed on stainless-steel (SUS304) and Pt/Ti/SiO2/Si substrates by aerosol deposition and then annealed at 600 °C in air. The deposition rate was 20 μm/min in an area of 5×5 mm2. To estimate the piezoelectric and mechanical properties of PZT films, a unimorph structured PZT and a free-standing cantilever were fabricated. The Young’s modulus (Y11) of the PZT film was 80 GPa. Poling at 40 kV/cm, 250 °C for 20 min increased the properties by a factor of 4.0–5.5, resulting in the piezoelectric coefficient (−d31) varying from 80 to 180 pm/V. © 2000 American Institute of Physics.
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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

Effect of electron irradiation on poly(vinylidene fluoride-trifluoroethylene) copolymers

Yiwen Tang, Xing-Zhong Zhao, Helen L. W. Chan, and C. L. Choy

Appl. Phys. Lett. 77, 1713 (2000); http://dx.doi.org/10.1063/1.1290266 (3 pages) | Cited 16 times

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Electrical field-induced strain response of electron-irradiated poly(vinylidene fluoride-trifluoroethylene) copolymer has been studied by a Mach–Zehnder type heterodyne interferometer in the frequency range of 3–9 kHz. The electrostrictive constant is calculated from the strain results, which is of the same order of magnitude as those obtained at 1 Hz by a bimorph-based strain sensor but at much lower electrical field. Changes in the dielectric property, phase transition behavior and crystal structure of the same copolymer have also been studied. The reversible solid–state transition between the polar and nonpolar phase in the crystalline regions of the copolymer driven by the external electric field is suggested to be responsible for the significant high electrostrictive strain of the electron-irradiated copolymer. © 2000 American Institute of Physics.
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61.82.Pv Polymers, organic compounds
61.80.Fe Electron and positron radiation effects
77.84.Jd Polymers; organic compounds
77.65.Bn Piezoelectric and electrostrictive constants
61.41.+e Polymers, elastomers, and plastics
64.70.K- Solid-solid transitions
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Microchannel plate for high-efficiency field emission display

Whikun Yi, Sunghwan Jin, Taewon Jeong, Jeonghee Lee, SeGi Yu, Yongsoo Choi, and J. M. Kim

Appl. Phys. Lett. 77, 1716 (2000); http://dx.doi.org/10.1063/1.1309025 (3 pages) | Cited 13 times

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The efficiency of a field emission display was improved significantly with a newly developed microchannel plate. The key features of this unit and its fabrication are summarized as follows: (a) bulk alumina is used as a substrate material, (b) channel location is defined by a programed-hole puncher, and (c) thin film deposition is conducted by electroless plating followed by a sol–gel process. With the microchannel plate between the cathode and the anode of a field emission display, the brightness of luminescent light increases three- to fourfold by electron multiplication through an array of pores in the device. In addition, the fabricated microchannel plate prevents spreading of electrons emitted from the cathode tips, thus improving both display resolution and picture quality. © 2000 American Institute of Physics.
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85.45.Fd Field emission displays (FEDs)
42.79.Ls Scanners, image intensifiers, and image converters
85.60.Ha Photomultipliers; phototubes and photocathodes
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