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2 Sep 2002

Volume 81, Issue 10, pp. 1753-1925

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Effectively left-handed (negative index) composite material

D. R. Fredkin and A. Ron

Appl. Phys. Lett. 81, 1753 (2002); http://dx.doi.org/10.1063/1.1505119 (3 pages) | Cited 75 times

Online Publication Date: 26 August 2002

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We show that a layered material, with alternating layers having negative permittivity (ε<0) and negative permeability (μ<0), responds to electromagnetic fields in many ways like a homogeneous left-handed material with ε<0 and μ<0. In particular, such a layered structure supports electromagnetic waves with group velocity antiparallel to the phase velocity. However, phase-sensitive measurements of the scattering matrix would distinguish the material from a homogeneous left-handed material. The appearance of a mode with positive index of refraction (right-handed mode) at frequencies for which ε and μ are negative is a surprising feature. © 2002 American Institute of Physics.
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41.20.Jb Electromagnetic wave propagation; radiowave propagation

Scaling quantum-dot light-emitting diodes to submicrometer sizes

A. Fiore, J. X. Chen, and M. Ilegems

Appl. Phys. Lett. 81, 1756 (2002); http://dx.doi.org/10.1063/1.1504880 (3 pages) | Cited 20 times

Online Publication Date: 26 August 2002

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We introduce a device structure and a fabrication technique that allow the realization of efficient light-emitting diodes (LEDs) with dimensions of the active area in the ≈ 100 nm range. Using optical lithography, selective oxidation, and an active region consisting of InAs quantum dots (QDs), we fabricated LEDs with light–current–voltage characteristics which scale well with nominal device area down to 600 nm diam at room temperature. The scaling behavior provides evidence for strong carrier confinement in the QDs and shows the potential for the realization of high-efficiency single-photon LEDs operating at room temperature. © 2002 American Institute of Physics.
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85.60.Jb Light-emitting devices
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
81.16.Nd Micro- and nanolithography
81.07.Ta Quantum dots
85.40.Hp Lithography, masks and pattern transfer
81.65.Mq Oxidation

Luminescence quenching in thermally-treated barium magnesium aluminate phosphor

Kee-Sun Sohn, Sang Sub Kim, and Hee Dong Park

Appl. Phys. Lett. 81, 1759 (2002); http://dx.doi.org/10.1063/1.1504866 (3 pages) | Cited 52 times

Online Publication Date: 26 August 2002

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BaMgAl10O17:Eu2+ (BAM) phosphors used for plasma display panels (PDP) are compelled to be exposed to an oxidizing environment at about 500 °C, which is currently unavoidable in the actual manufacturing process of PDP. We investigated the mechanism of the luminance degradation of BAM caused by the annealing at 500 °C, using photoluminescence (PL), decay measurement, and synchrotron light source x-ray absorption and diffraction measurements. The annealing treatment altered the valence state of Eu ions, whereas no new Eu compounds were detected. By estimating the exact fraction of divalent Eu ions and by comparing it with the luminance data, we found that more than 30% degradation of luminance was induced at the expense of only a few percent of divalent Eu. This finding led us to suggest that the origin of the dramatic decrease in PL intensity is not due to the valence state change but due to the local structure change surrounding the Eu2+ ions. © 2002 American Institute of Physics.
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78.55.Hx Other solid inorganic materials
81.40.Tv Optical and dielectric properties related to treatment conditions
78.47.-p Spectroscopy of solid state dynamics
81.40.Gh Other heat and thermomechanical treatments
78.70.Dm X-ray absorption spectra
61.66.Fn Inorganic compounds

Two-dimensional optics with surface plasmon polaritons

H. Ditlbacher, J. R. Krenn, G. Schider, A. Leitner, and F. R. Aussenegg

Appl. Phys. Lett. 81, 1762 (2002); http://dx.doi.org/10.1063/1.1506018 (3 pages) | Cited 209 times

Online Publication Date: 26 August 2002

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We report the experimental realization of highly efficient optical elements built up from metal nanostructures to manipulate surface plasmon polaritons propagating along a silver/polymer interface. Mirrors, beamsplitters, and interferometers produced by electron-beam lithography are investigated. The plasmon fields are imaged by detecting the fluorescence of molecules dispersed in the polymer. © 2002 American Institute of Physics.
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78.68.+m Optical properties of surfaces
42.70.Jk Polymers and organics
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
81.07.Bc Nanocrystalline materials
42.79.Bh Lenses, prisms and mirrors
42.79.Fm Reflectors, beam splitters, and deflectors
07.60.Ly Interferometers
42.82.Cr Fabrication techniques; lithography, pattern transfer
81.16.Nd Micro- and nanolithography
78.55.Kz Solid organic materials

In situ measurement of laser power at the focus of a high numerical aperture objective using a microbolometer

N. B. Viana, O. N. Mesquita, and A. Mazolli

Appl. Phys. Lett. 81, 1765 (2002); http://dx.doi.org/10.1063/1.1506014 (3 pages) | Cited 5 times

Online Publication Date: 26 August 2002

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We built a simple mercury-based microbolometer to measure “in situ” laser power at the focus of high numerical aperture objectives used in optical microscopy and optical tweezers. With an optical microscope equipped with a high numerical aperture objective, we visualize a mercury droplet immersed in water that is heated by an infrared laser, whose power we want to determine. For a given laser power the mercury droplet reaches the boiling temperature of the water and then jumps, making a precise determination of this point very easy. We solve the heat equation for this system and, using known material parameters and the size of the mercury droplet, we determine the local power of the infrared laser. © 2002 American Institute of Physics.
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07.60.Pb Conventional optical microscopes
42.79.Bh Lenses, prisms and mirrors
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
85.60.Gz Photodetectors (including infrared and CCD detectors)
84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)
07.10.Cm Micromechanical devices and systems
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation

Electric charge measurement on a single microparticle using thermodynamic analysis of electrostatic forces

Ken-ichiro Wada, Keiji Sasaki, and Hiroshi Masuhara

Appl. Phys. Lett. 81, 1768 (2002); http://dx.doi.org/10.1063/1.1503398 (3 pages) | Cited 5 times

Online Publication Date: 26 August 2002

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A method is proposed for analyzing the electric charge at the shear plane of a single microparticle. A particle dispersed in solution is three-dimensionally trapped with a focused laser beam, and an electrostatic field is applied with microelectrodes. The thermal motion of the particle is sequentially measured with a quadrant photodiode, such that the potential energy exerted on the particle can be estimated by thermodynamic analysis. A potential profile of an electrostatic force is obtained as the energy difference between two potential curves observed with and without the electrostatic field. The strength of the force exerted on a 4.5 μm polystyrene latex particle in 5×10−4 M NaCl solution was determined to be 1.6×10−13 N, which corresponded to the net charge of 5.8×10−17 C. © 2002 American Institute of Physics.
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41.20.Cv Electrostatics; Poisson and Laplace equations, boundary-value problems
82.70.Dd Colloids
05.40.Jc Brownian motion

Experimental demonstration of oxide-mode influence in a dual-purpose oxide-confined vertical-cavity surface-emitting laser/resonant detector

V. Bardinal, L. Averseng, C. Bringer, T. Camps, J. Polesel-Maris, P. Dubreuil, C. Fontaine, E. Bedel-Pereira, C. Vergnenegre, and A. Muñoz-Yagüe

Appl. Phys. Lett. 81, 1771 (2002); http://dx.doi.org/10.1063/1.1506013 (2 pages) | Cited 5 times

Online Publication Date: 26 August 2002

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We report on design, fabrication, and characterization of a vertical-cavity surface-emitting laser (VCSEL) used as a resonant-cavity-enhanced detector for dual-purpose application. The geometry of this oxide-confined VCSEL takes advantage of the properties of the buried oxide layer to allow both single-mode laser emission and detection on a large surface. Here, we demonstrate the presence and the influence of oxide modes in the optical sensitivity spectrum of the device through spatially localized detection measurements. The wavelength of these modes has been correlated to the dip on the reflectivity spectrum measured at the same area of the device surface. © 2002 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
85.60.Gz Photodetectors (including infrared and CCD detectors)
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In vacuo electron-spin-resonance study on amorphous fluorinated carbon films for understanding of surface chemical reactions in plasma etching

Kenji Ishikawa, Shoji Kobayashi, Mitsuru Okigawa, Makoto Sekine, Satoshi Yamasaki, Tetsuji Yasuda, and Jun-ichi Isoya

Appl. Phys. Lett. 81, 1773 (2002); http://dx.doi.org/10.1063/1.1505121 (3 pages) | Cited 6 times

Online Publication Date: 26 August 2002

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An in vacuo electron-spin-resonance (ESR) technique was applied to study amorphous fluorinated carbon (a-C:F) films and their chemical reactivity with oxygen molecules. It was found that the carbon dangling bond (C-DB) density of an a-C:F film deposited at room temperature is as high as 2×1021 cm−3 and stable in vacuum. ESR spectra showed that there is a strong hyperfine interaction between the dangling bonds and the surrounding fluorine atoms. Experimental results indicate that an a-C:F film has a characteristic property that is suitable for SiO2 etching. Because a-C:F is highly reactive with oxygen, it can easily react with oxygen in underlying SiO2 to increase Si dangling bonds in SiO2. © 2002 American Institute of Physics.
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76.30.Mi Color centers and other defects
81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
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Light-induced change of charge transfer band in nanocrystalline Y2O3:Eu3+

Hongwei Song, Baojiu Chen, Hongshang Peng, and Jisen Zhang

Appl. Phys. Lett. 81, 1776 (2002); http://dx.doi.org/10.1063/1.1501441 (3 pages) | Cited 45 times

Online Publication Date: 26 August 2002

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In this letter, we report the observation of ultraviolet light-induced change of excited charge-transfer band in nanocrystalline Y2O3:Eu3+, which is attributed to the rearrangements of local environments surrounding the Eu3+ ions in the near surface of nanoparticles. © 2002 American Institute of Physics.
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78.55.Hx Other solid inorganic materials
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
61.82.Rx Nanocrystalline materials
71.70.Jp Nuclear states and interactions

Measurement of thermal-mechanical noise in microelectromechanical systems

T. H. Stievater, W. S. Rabinovich, H. S. Newman, R. Mahon, P. G. Goetz, J. L. Ebel, and D. J. McGee

Appl. Phys. Lett. 81, 1779 (2002); http://dx.doi.org/10.1063/1.1505122 (3 pages) | Cited 11 times

Online Publication Date: 26 August 2002

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We report absolute measurements of thermal-mechanical noise in microelectromechanical systems. The devices are studied with an optical microcavity technique that has a resolution on the order of tens of femtometers per root hertz. The measured noise spectrum agrees with the calculated noise level to within 25%, a discrepancy most likely due to uncertainty in the effective dynamic mass of the vibrating bridge. These measurements demonstrate that thermal-mechanical noise can be the dominant noise source in actuated microelectromechanical devices. © 2002 American Institute of Physics.
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07.10.Cm Micromechanical devices and systems
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices

Reduced electromigration of Cu wires by surface coating

C.-K. Hu, L. Gignac, R. Rosenberg, E. Liniger, J. Rubino, C. Sambucetti, A. Domenicucci, X. Chen, and A. K. Stamper

Appl. Phys. Lett. 81, 1782 (2002); http://dx.doi.org/10.1063/1.1504491 (3 pages) | Cited 67 times

Online Publication Date: 26 August 2002

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Electromigration in on-chip Cu interconnections with a selective electroless metal coating, CoWP, CoSnP, or Pd, on the top surface of Cu damascene lines has been investigated. The 10–20 nm thick metal cap significantly improves electromigration lifetime by providing protection against interface diffusion of Cu which has been the leading contributor to metal line failure by electromigration. © 2002 American Institute of Physics.
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85.40.Ls Metallization, contacts, interconnects; device isolation

Spinodal decomposition range of InxGa1−xNyAs1−y alloys

R. Asomoza, V. A. Elyukhin, and R. Peña-Sierra

Appl. Phys. Lett. 81, 1785 (2002); http://dx.doi.org/10.1063/1.1504870 (3 pages) | Cited 16 times

Online Publication Date: 26 August 2002

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Spinodal decomposition range of InxGa1−xNyAs1−y quaternary alloys as the result of the strain and coherency strain energies, transformations of the bonds, and a lattice mismatch between the GaAs substrate and an alloy is described. The alloys are considered in the strictly regular approximation. The strain energy is presented in the valence-force field model. The spinodal decomposition temperatures of InxGa1−xNyAs1−y alloys are demonstrated up to 1000 °C. It is shown that nitrogen dramatically increases the temperature of the coherent spinodal. © 2002 American Institute of Physics.
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64.75.-g Phase equilibria
81.30.Mh Solid-phase precipitation
81.05.Ea III-V semiconductors
61.50.Lt Crystal binding; cohesive energy

Photoemission study of Zr- and Hf-silicates for use as high-κ oxides: Role of second nearest neighbors and interface charge

R. L. Opila, G. D. Wilk, M. A. Alam, R. B. van Dover, and B. W. Busch

Appl. Phys. Lett. 81, 1788 (2002); http://dx.doi.org/10.1063/1.1505120 (3 pages) | Cited 61 times

Online Publication Date: 26 August 2002

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We show a systematic trend of x-ray photoelectron binding energy shifts for Zr- and Hf-silicates, which are related to the composition of the films. The binding energy for the core photoelectrons can shift by up to 2 eV, depending on the relative electronegativities of the second nearest-neighbor elements. Understanding these shifts helps determine the underlying local electronic and chemical nature of the silicate network. Furthermore, we explain how charge at the dielectric-semiconductor interface can lead to shifts in the measured Si 2p peak binding energy by as much as 1 eV. The direction and magnitude of the binding energy shift can be used to determine the sign and density of the charge at the interface. © 2002 American Institute of Physics.
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79.60.Jv Interfaces; heterostructures; nanostructures
79.60.Bm Clean metal, semiconductor, and insulator surfaces

Combined optical and spatial modulation THz-spectroscopy for the analysis of thin-layered systems

M. Brucherseifer, P. Haring Bolivar, and H. Kurz

Appl. Phys. Lett. 81, 1791 (2002); http://dx.doi.org/10.1063/1.1505118 (3 pages) | Cited 5 times

Online Publication Date: 26 August 2002

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We present a combined optical and spatial modulation technique to enhance drastically the resolution threshold of time-domain THz spectroscopy. By this approach, relative changes of THz transmission can be resolved down to unprecedented values of −90 dB, enabling the broadband analysis of extremely thin layered systems. The system capabilities are demonstrated by characterizing dielectric films, specifically a 1.2 μm thick polymer and a 100 nm thick SiO2 film. © 2002 American Institute of Physics.
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78.70.Gq Microwave and radio-frequency interactions
78.47.-p Spectroscopy of solid state dynamics
77.55.-g Dielectric thin films
78.66.Qn Polymers; organic compounds
78.66.Nk Insulators

Determination of the next-nearest neighbor order in β phase in Cu-Al-Ni shape memory alloys

J. I. Pérez-Landazábal, V. Recarte, R. B. Pérez-Sáez, M. L. Nó, J. Campo, and J. San Juan

Appl. Phys. Lett. 81, 1794 (2002); http://dx.doi.org/10.1063/1.1504883 (3 pages) | Cited 20 times

Online Publication Date: 26 August 2002

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The metastable β phase undergoes two order–disorder transitions during quenching from high temperature in Cu-based shape memory alloys. First, it undergoes a B2 ordering at nearest neighbors and then a second one at next-nearest neighbors that has not been clearly established. Neutron powder diffraction measurements have been performed at room temperature in a fully ordered alloy (Cu-27.4 Al-3.6 Ni at. %). Rietveld analysis allows to conclude that a L21 order at next-nearest neighbors is present in the ordered phase. The site occupancy of the different positions has been determined. © 2002 American Institute of Physics.
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81.30.Hd Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder
64.70.K- Solid-solid transitions
81.30.Kf Martensitic transformations
81.40.Lm Deformation, plasticity, and creep

X-ray and Raman analyses of GaN produced by ultrahigh-rate magnetron sputter epitaxy

Minseo Park, J.-P. Maria, J. J. Cuomo, Y. C. Chang, J. F. Muth, R. M. Kolbas, R. J. Nemanich, E. Carlson, and J. Bumgarner

Appl. Phys. Lett. 81, 1797 (2002); http://dx.doi.org/10.1063/1.1506781 (3 pages) | Cited 12 times

Online Publication Date: 26 August 2002

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Thick films of GaN were studied by x-ray diffraction and Raman spectroscopy. The GaN thick films were deposited on (0001) sapphire using ultrahigh-rate magnetron sputter epitaxy with typical growth rates as high as 10–60 μm/min. The width of the x-ray rocking curve from the (0002) reflection for the sample produced by this technique is ∼300 arcsec, which is unprecedented for GaN produced by a sputtering-type process. Our recent sample shows an x-ray rocking curve width of 240 arcsec. Only allowed modes were observed in the polarized Raman spectra. The background free carrier concentration is lower than 3×1016 cm−3. The phonon lifetime of the Raman E2(2) mode of the sputtered GaN was comparable to that of bulk single crystal GaN grown by sublimation. The quality of the film was uniform across the wafer. The film was thermally stable upon annealing in N2 ambient. The x-ray and Raman analyses revealed that the sputtered GaN films are of high crystalline quality. © 2002 American Institute of Physics.
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81.15.Cd Deposition by sputtering
78.66.Fd III-V semiconductors
78.30.Fs III-V and II-VI semiconductors
81.05.Ea III-V semiconductors
61.72.Cc Kinetics of defect formation and annealing
68.55.-a Thin film structure and morphology

Low-stress indium–tin–oxide thin films rf magnetron sputtered on polyester substrates

P. F. Carcia, R. S. McLean, M. H. Reilly, Z. G. Li, L. J. Pillione, and R. F. Messier

Appl. Phys. Lett. 81, 1800 (2002); http://dx.doi.org/10.1063/1.1504874 (3 pages) | Cited 18 times

Online Publication Date: 26 August 2002

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Using rf magnetron sputtering, we have grown low resistivity ( ∼ 3×10−4 Ω cm), high transparency (>80%) indium–tin–oxide thin films with near zero stress on polyester substrates, near room temperature. We concluded from analysis of sputtered ions and atoms that bombardment by energetic (>70 eV) negative oxygen ions caused high stress (∼1 GPa) in films grown at lower (6 mTorr) pressure. Sputtering at 12 mTorr dissipated energetic bombardment and reduced film stress to about zero, independent of oxygen partial pressure (pO2). However, increasing pO2 did affect film microstructure, that is, crystallinity, roughness, and grain size. © 2002 American Institute of Physics.
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81.15.Cd Deposition by sputtering
68.55.A- Nucleation and growth
61.72.-y Defects and impurities in crystals; microstructure

Near-infrared intersubband absorption in GaN/AlN quantum wells grown by molecular beam epitaxy

Norio Iizuka, Kei Kaneko, and Nobuo Suzuki

Appl. Phys. Lett. 81, 1803 (2002); http://dx.doi.org/10.1063/1.1505116 (3 pages) | Cited 88 times

Online Publication Date: 26 August 2002

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GaN/AlN multiple-quantum-well structures were grown by molecular beam epitaxy. Abrupt interfaces and good periodicity were confirmed. Absorption measurements indicated that intersubband absorptions occurred at wavelengths of 1.3–2.2 μm. Spectral fits by Lorentzians suggested that the well thicknesses fluctuated by two monolayers. The linewidths of the individual fits were as narrow as 80–120 meV. The characteristics of the absorption saturation were investigated at a wavelength of 1.46 μm. A relaxation time of 400 fs and saturation energy density of 0.5 pJ/μm2 were obtained. These results are promising for realizing ultrafast optical switches with energy consumption of the picojoule order. © 2002 American Institute of Physics.
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78.67.De Quantum wells
78.30.Fs III-V and II-VI semiconductors
42.50.Md Optical transient phenomena: quantum beats, photon echo, free-induction decay, dephasings and revivals, optical nutation, and self-induced transparency
78.47.-p Spectroscopy of solid state dynamics

Femtosecond three-pulse photon echo and population grating studies of the optical properties of CdTe/ZnSe quantum dots

Lap Van Dao, Martin Lowe, Peter Hannaford, Hisao Makino, Toshiaki Takai, and Takafumi Yao

Appl. Phys. Lett. 81, 1806 (2002); http://dx.doi.org/10.1063/1.1505111 (3 pages) | Cited 12 times

Online Publication Date: 26 August 2002

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Femtosecond three-pulse two-color photon echo and population grating (PG) techniques have been used to characterize CdTe quantum dots (QDs) grown on ZnSe by molecular beam epitaxy. The time evolution of the PG signal exhibits a fast decay (2.5–3 ps), which is attributed to migration and tunneling of photoexcited carriers to neighboring QDs, followed by a slow decay (∼20 ps for small dots and >100 ps for large dots), which is ascribed to the lifetime of excitons in the quantum dots. The three-pulse photon echo intensity versus population time can be used to deduce values for the homogeneous broadening (Γh = 0.8–1.2 meV) and the exciton binding energy (∼13 meV). A weak dependence of these quantities on the detection wavelength is associated with a difference in dot sizes, which alters the coupling between the exciton and the acoustic phonons. © 2002 American Institute of Physics.
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78.67.Hc Quantum dots
78.66.Hf II-VI semiconductors
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
78.47.-p Spectroscopy of solid state dynamics
81.07.Ta Quantum dots
81.05.Dz II-VI semiconductors
42.50.Md Optical transient phenomena: quantum beats, photon echo, free-induction decay, dephasings and revivals, optical nutation, and self-induced transparency
71.35.Cc Intrinsic properties of excitons; optical absorption spectra
63.20.kk Phonon interactions with other quasiparticles
73.21.La Quantum dots
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Growth and optical studies of two-dimensional electron gas of Al-rich AlGaN/GaN heterostructures

K. B. Nam, J. Li, M. L. Nakarmi, J. Y. Lin, and H. X. Jiang

Appl. Phys. Lett. 81, 1809 (2002); http://dx.doi.org/10.1063/1.1504881 (3 pages) | Cited 7 times

Online Publication Date: 26 August 2002

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Al0.5Ga0.5N/GaN heterostructures were grown by metalorganic chemical vapor deposition on sapphire substrates. Time-resolved photoluminescence (PL) emission spectroscopy was employed to study the optical properties of these samples. A very strong and broad emission band was observed under high excitation intensity (Io = 104 W/cm2) and its spectral peak position varies from 3.382 and 3.444 eV (at 10 K) depending on the top AlGaN layer thickness (d). This emission line is related to the recombination between the two-dimensional electron gas (2DEG) and photoexcited holes in Al0.5Ga0.5N/GaN heterostructures. In a sharp contrast to the AlGaAs/GaAs heterostructure system in which the PL emission line associated with the 2DEG is observable only at low temperatures (T<20 K), the 2DEG emission line in Al0.5Ga0.5N/GaN heterostructures is observable at temperature as high as 220 K. This is due to the strong piezoelectric polarization and deep triangular potential resulting from the large band offset in high Al content AlGaN/GaN heterostructures. For AlxGa1−xN/GaN (x = 0.5) heterostructures with d = 110 Å, five emission lines were resolved at 10 K at emission energies 70, 97, 126, 157, and 216 meV below the GaN bound exciton peak under a low excitation intensity (10 W/cm2), due to the recombination between the 2DEG electrons in different subbands and photoexcited holes. © 2002 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
78.47.-p Spectroscopy of solid state dynamics
71.35.Cc Intrinsic properties of excitons; optical absorption spectra
81.05.Ea III-V semiconductors

Characteristics of deep levels in As-implanted GaN films

L. Lee, W. C. Lee, H. M. Chung, M. C. Lee, W. H. Chen, W. K. Chen, and H. Y. Lee

Appl. Phys. Lett. 81, 1812 (2002); http://dx.doi.org/10.1063/1.1499739 (3 pages) | Cited 5 times

Online Publication Date: 26 August 2002

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Hall, current–voltage and deep level transient spectroscopy measurements were used to characterize the electric properties of n-type GaN films implanted with As atoms. After 800 °C thermal annealing for 60 min, one additional deep level located at EC−0.766 eV was found in the films. We presume this induced trap is an arsenic-related point defect, most likely antisite in nature. © 2002 American Institute of Physics.
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71.55.Eq III-V semiconductors
73.61.Ey III-V semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
72.20.My Galvanomagnetic and other magnetotransport effects
72.80.Ey III-V and II-VI semiconductors
61.72.Cc Kinetics of defect formation and annealing

Spin-injection device based on EuS magnetic tunnel barriers

A. T. Filip, P. LeClair, C. J. P. Smits, J. T. Kohlhepp, H. J. M. Swagten, B. Koopmans, and W. J. M. de Jonge

Appl. Phys. Lett. 81, 1815 (2002); http://dx.doi.org/10.1063/1.1503406 (3 pages) | Cited 27 times

Online Publication Date: 26 August 2002

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We propose a spin-valve device consisting of a nonmagnetic semiconductor quantum well, sandwiched between ferromagnetic semiconductor layers that act as barriers. The total conductance through such a trilayer depends on the relative magnetization of the two ferromagnetic-barrier layers which act as “spin filters.” With respect to practical realization, EuS/PbS heterostructures may be a suitable candidate. The magnetoresistance should exceed 100% for a wide range of the thicknesses of both the quantum well and the ferromagnetic barriers. From a fundamental physics point of view, the device may not only give insight into the spin lifetimes of the nonmagnetic layer, but the strong spin accumulation taking place in the quantum well may lead to novel optical and nuclear magnetic resonance properties. © 2002 American Institute of Physics.
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75.47.De Giant magnetoresistance
72.25.Dc Spin polarized transport in semiconductors
85.75.-d Magnetoelectronics; spintronics: devices exploiting spin polarized transport or integrated magnetic fields
75.50.Pp Magnetic semiconductors
72.25.Mk Spin transport through interfaces
75.50.Dd Nonmetallic ferromagnetic materials
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.45.+j Macroscopic quantum phenomena in magnetic systems
73.63.Hs Quantum wells

Interface structures generated by negative-bias temperature instability in Si/SiO2 and Si/SiOxNy interfaces

Jiro Ushio, Takuya Maruizumi, and Keiko Kushida-Abdelghafar

Appl. Phys. Lett. 81, 1818 (2002); http://dx.doi.org/10.1063/1.1504872 (3 pages) | Cited 38 times

Online Publication Date: 26 August 2002

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We used a density functional method to investigate the mechanism of negative-bias temperature instability (NBTI) and resultant structural changes of Si/SiO2 and Si/SiOxNy interfaces. The reaction energies for the water- and hydrogen-originated instabilities of several interface defects show that water-originated reactions of oxygen and nitrogen vacancies occur most easily. The larger instability of the Si/SiOxNy interface, compared with the Si/SiO2 interface, can be understood in terms of the difference in reaction energies. According to the calculated nitrogen 1s core-level shifts of the nitrogen atoms at the Si/SiOxNy interface, it is possible to identify a NBTI-generated structure at the Si/SiOxNy interface by x-ray photoelectron spectroscopy. © 2002 American Institute of Physics.
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68.35.Ct Interface structure and roughness
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
73.20.At Surface states, band structure, electron density of states

Electronic properties of vacancy–oxygen complex in Ge crystals

V. P. Markevich, I. D. Hawkins, A. R. Peaker, V. V. Litvinov, L. I. Murin, L. Dobaczewski, and J. L. Lindström

Appl. Phys. Lett. 81, 1821 (2002); http://dx.doi.org/10.1063/1.1504871 (3 pages) | Cited 29 times

Online Publication Date: 26 August 2002

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It is argued that the vacancy–oxygen (VO) complex (A center) in Ge has three charge states: double negative, single negative, and neutral. Corresponding energy levels are located at Ec−0.21 eV (VO−−/−) and Ev+0.27 eV (VO−/0). An absorption line at 716 cm−1 has been assigned to the asymmetrical stretching vibration mode of the doubly negatively charged VO complex. © 2002 American Institute of Physics.
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71.55.Cn Elemental semiconductors
61.72.Yx Interaction between different crystal defects; gettering effect
61.72.J- Point defects and defect clusters
63.20.-e Phonons in crystal lattices
78.30.Am Elemental semiconductors and insulators

Study of interface states and oxide quality to avoid contrast reversal in scanning capacitance microscopy

Didier Goghero, Vito Raineri, and Filippo Giannazzo

Appl. Phys. Lett. 81, 1824 (2002); http://dx.doi.org/10.1063/1.1499228 (3 pages) | Cited 18 times

Online Publication Date: 26 August 2002

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We demonstrate that the contrast reversal effect in scanning capacitance microscopy (SCM) is related to the Si/SiO2 interface microroughness. The surface roughness has been associated with the concentration of states at the Si/SiO2 interface and a monotonic behavior of the SCM imaging is preferentially observed for a smooth surface and consequently a low state concentration. Changes in the oxide quality have also been found to strongly influence the measurements. A criterion based on the hysteresis measurements from forward and reverse dC/dV–V curves is discussed to better evaluate the oxide quality and to obtain reproducible SCM data. © 2002 American Institute of Physics.
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68.37.-d Microscopy of surfaces, interfaces, and thin films
68.35.Ct Interface structure and roughness
73.20.At Surface states, band structure, electron density of states
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