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1 Feb 2010

Volume 96, Issue 5, Articles (05xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 96, 053107 (2010); http://dx.doi.org/10.1063/1.3280078 (3 pages)

Desalegne Teweldebrhan, Vivek Goyal, Muhammad Rahman, and Alexander A. Balandin
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High-efficiency, large-bandwidth silicon-on-insulator grating coupler based on a fully-etched photonic crystal structure

Liu Liu (刘柳), Minhao Pu (蒲敏皓), Kresten Yvind, and Jørn M. Hvam

Appl. Phys. Lett. 96, 051126 (2010); http://dx.doi.org/10.1063/1.3304791 (3 pages) | Cited 15 times

Online Publication Date: 5 February 2010

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A grating coupler for interfacing between single-mode fibers and photonic circuits on silicon-on-insulator is demonstrated. It consists of columns of fully etched photonic crystal holes, which are made in the same lithography and etching processes used for making the silicon-on-insulator wire waveguide. The holes have a diameter of around 143 nm, and are defined with electron-beam lithography. A peak coupling efficiency of 42% at 1550 nm and 1 dB bandwidth of 37 nm, as well as a low back reflection, are achieved. The performance of the proposed fully etched grating coupler is comparable to that based on the conventional shallowly etched grating, which needs additional fabrication steps.
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42.82.Et Waveguides, couplers, and arrays
42.81.Qb Fiber waveguides, couplers, and arrays
42.82.Cr Fabrication techniques; lithography, pattern transfer
42.79.Dj Gratings
42.70.Qs Photonic bandgap materials
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Multiple diagnostics in a high-pressure hydrogen microwave plasma torch

J. Torres, J. J. A. M. van der Mullen, A. Gamero, and A. Sola

Appl. Phys. Lett. 96, 051501 (2010); http://dx.doi.org/10.1063/1.3306731 (3 pages)

Online Publication Date: 3 February 2010

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We present an experimental study of a hydrogen plasma produced by a microwave axial injection torch, launching the plasma in a helium-filled chamber. Three different diagnostic methods have been used to obtain the electron density and temperature as follows: The Stark intersection method of Balmer spectral lines (already tested in argon and helium plasmas); the modified Boltzmann-plot showing that the plasma is far from the local thermodynamic equilibrium but ruled by the excitation-saturation balance; and a study by the disturbed bilateral relations theory. All of these diagnostic techniques show a good agreement.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.75.Hn Plasma torches

High density conics in a magnetically expanding helicon plasma

C. Charles

Appl. Phys. Lett. 96, 051502 (2010); http://dx.doi.org/10.1063/1.3309668 (3 pages) | Cited 7 times

Online Publication Date: 3 February 2010

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A two-dimensional mapping of ion density and plasma potential in a diverging magnetized low pressure (0.4 mTorr) carbon dioxide helicon plasma containing a double layer reveals the presence of high density conics ( ∼ 7×109 cm−3) along the most diverging magnetic field lines exiting the helicon source and connecting with the grounded expansion chamber. The density in the conic is about 30% greater than the density at the double layer and this results from local ionization associated with the presence of a high energy tail in the electron energy probability function. The plasma potential along the conic is constant at about 30 V.
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52.25.Xz Magnetized plasmas
52.80.-s Electric discharges
02.50.Cw Probability theory
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Anisotropic relaxation and crystallographic tilt in BiFeO3 on miscut SrTiO3 (001)

Rebecca J. Sichel, Alexei Grigoriev, Dal-Hyun Do, Seung-Hyub Baek, Ho-Won Jang, Chad M. Folkman, Chang-Beom Eom, Zhonghou Cai, and Paul G. Evans

Appl. Phys. Lett. 96, 051901 (2010); http://dx.doi.org/10.1063/1.3299256 (3 pages) | Cited 2 times

Online Publication Date: 1 February 2010

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Epitaxial BiFeO3 thin films on miscut (001) SrTiO3 substrates relax via mechanisms leading to an average rotation of the crystallographic axes of the BiFeO3 layer with respect to the substrate. The angle of the rotation reaches a maximum in the plane defined by the surface normal of the film and the direction of the surface miscut. X-ray microdiffraction images show that each BiFeO3 mosaic block is rotated by a slightly different angle and contains multiple polarization domains. These effects lead to a complicated overall symmetry in BiFeO3 thin films. This relaxation mechanism can be extended to other complex oxides.
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68.55.-a Thin film structure and morphology
68.55.A- Nucleation and growth
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Acoustic band gaps in phononic crystal strip waveguides

Feng-Chia Hsu, Chiung-I Lee, Jin-Chen Hsu, Tsun-Che Huang, Chin-Hung Wang, and Pin Chang

Appl. Phys. Lett. 96, 051902 (2010); http://dx.doi.org/10.1063/1.3298643 (3 pages) | Cited 5 times

Online Publication Date: 1 February 2010

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We study the elastic wave propagation in phononic-crystal strip waveguides cut from a silicon phononic-crystal plate with square-lattice vacuum holes through analyzing the band structure and transmission spectra. We show the influence of different cutting ways is crucial to the band-gap formation, and four types of native strip modes are deserved to be fully taken into account. The results show that though there is no band gap existing in the phononic-crystal plates with a low filling fraction, band gaps are created in their corresponding cut strip waveguide because the derivative traction-free boundaries strongly modulate the shear-horizontal bands.
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63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
43.20.Mv Waveguides, wave propagation in tubes and ducts

Mass density of individual cobalt nanowires

L. Philippe, B. Cousin, Zhao Wang, D. F. Zhang, and J. Michler

Appl. Phys. Lett. 96, 051903 (2010); http://dx.doi.org/10.1063/1.3299013 (3 pages) | Cited 1 time

Online Publication Date: 1 February 2010

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The mass density of nanowires is determined using in situ resonance frequency experiments combined with quasistatic nanotensile tests. Our results reveal an average mass density of 7.36 g/cm3, which is below the theoretical density of bulk cobalt. The results are discussed in terms of the measurement accuracy and the microstructure of the nanowires.
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61.46.Km Structure of nanowires and nanorods (long, free or loosely attached, quantum wires and quantum rods, but not gate-isolated embedded quantum wires)
81.07.Gf Nanowires
61.72.-y Defects and impurities in crystals; microstructure
81.70.Bt Mechanical testing, impact tests, static and dynamic loads

Monolayer rigid arrays of cavity-controllable metallic mesoparticles: Electrochemical preparation and light transmission resonances

Zhuo Chen, Han Dong, Jian Pan, Peng Zhan, Chaojun Tang, and Zhen-Lin Wang

Appl. Phys. Lett. 96, 051904 (2010); http://dx.doi.org/10.1063/1.3300640 (3 pages) | Cited 4 times

Online Publication Date: 2 February 2010

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We report an efficient and robust electrochemical deposition method to fabricate large-scale two-dimensional rigid arrays of metal colloids with a precise control of the particle morphology by monitoring metal growth that is confined within a templated organic porous mold. Light transmission resonances through the metallic periodic microstructures are observed and the resonance wavelengths are found to depend on the morphology of the scattering elements. Further numerical simulations confirm these transmission resonances and reveal that they are attributed to the excitations of localized or propagating surface plasmon modes supported by the specific structures. The present method of tailoring metallic microstructures could find applications in plasmonics.
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81.15.Pq Electrodeposition, electroplating
82.45.Mp Thin layers, films, monolayers, membranes
68.55.A- Nucleation and growth
78.66.Bz Metals and metallic alloys
73.22.Lp Collective excitations
82.45.Qr Electrodeposition and electrodissolution

Tadpole shaped Ge0.96Mn0.04 magnetic semiconductors grown on Si

Yong Wang, Faxian Xiu, Jin Zou, Kang L. Wang, and Ajey P. Jacob

Appl. Phys. Lett. 96, 051905 (2010); http://dx.doi.org/10.1063/1.3297880 (3 pages) | Cited 7 times

Online Publication Date: 3 February 2010

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Magnetic and structural properties of a Ge0.96Mn0.04 thin film grown on Si has been investigated by transmission electron microscopy and superconducting quantum interference device. Tadpole shaped coherent GeMn clusters induced by spinodal decomposition were revealed in the film. Although these coherent clusters are dominant, Mn5Ge3 precipitates can be still detectable, contributing to a complex ferromagnetism. The Ge buffer layer, by relieving the misfit strain between Si and Ge, can significantly reduce the density of lattice defects in the subsequent GeMn layer. Our findings unveil a particular morphology of GeMn clusters, which would contribute to better understand the GeMn system.
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75.70.-i Magnetic properties of thin films, surfaces, and interfaces
85.75.-d Magnetoelectronics; spintronics: devices exploiting spin polarized transport or integrated magnetic fields
72.25.-b Spin polarized transport
75.50.Dd Nonmetallic ferromagnetic materials
75.50.Pp Magnetic semiconductors

Effect of boron on interstitial-related luminescence centers in silicon

S. Charnvanichborikarn, B. J. Villis, B. C. Johnson, J. Wong-Leung, J. C. McCallum, J. S. Williams, and C. Jagadish

Appl. Phys. Lett. 96, 051906 (2010); http://dx.doi.org/10.1063/1.3300836 (3 pages) | Cited 2 times

Online Publication Date: 3 February 2010

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Photoluminescence measurements have been used to investigate the optically active defect centers formed by silicon implantation and a subsequent anneal at 275, 400, or 525 °C. The presence of boron in p-type silicon is found to produce deleterious effects on the luminescence of the interstitial-related W- and X-centers as well as a lower energy broad luminescence band. This effect has not been previously reported but it is consistent with the suppression of interstitial-related {311} extended defect formation in the presence of high boron concentrations at higher annealing temperatures. The results presented in this letter provide insight into the role of boron in the initial stages of interstitial cluster formation.
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78.55.Ap Elemental semiconductors
81.05.Cy Elemental semiconductors
61.72.uf Ge and Si
61.72.jj Interstitials
61.72.Cc Kinetics of defect formation and annealing

Effect of V/III flux ratio on luminescence properties and defect formation of Er-doped GaN

Shaoqiang Chen, Akira Uedono, Shoji Ishibashi, Shigeo Tomita, Hiroshi Kudo, and Katsuhiro Akimoto

Appl. Phys. Lett. 96, 051907 (2010); http://dx.doi.org/10.1063/1.3306736 (3 pages)

Online Publication Date: 4 February 2010

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Erbium-doped GaN samples grown with different V/III ratios through gas source molecular beam epitaxy were prepared to investigate the influence of the V/III ratio on the defect formation and the optical activity of the Er-related luminescence center. Obvious V/III ratio dependence was observed in photoluminescence measurement. Positron annihilation spectroscopy measurements suggested that VGa-VN vacancy-complexes formed in these samples and that the VN/VGa ratio depended on the V/III ratio. The generation of Er-VN defect complexes, which act as high optical active luminescence centers, is suggested as the cause of improved optical properties of Er-doped GaN grown with a lower V/III ratio.
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78.66.Fd III-V semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.jd Vacancies
78.55.Cr III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.ag Semiconductors

Structural and electrical properties of ZnO nanorods and Ti buffer layers

C.-H. Kwak, B.-H. Kim, C.-I. Park, S.-Y. Seo, S.-H. Kim, and S.-W. Han

Appl. Phys. Lett. 96, 051908 (2010); http://dx.doi.org/10.1063/1.3308498 (3 pages) | Cited 3 times

Online Publication Date: 4 February 2010

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Vertically-well-aligned ZnO nanorods were synthesized on Ti buffer layers by a metal-organic chemical-vapor deposition process. Structural analyses demonstrated that the ZnO nanorods were well-aligned in the c-axis and ab-plane. Transmission electron microscopy (TEM) showed that the Ti buffer layer was amorphous and interdiffused into the ZnO nanorods. Energy-dispersive spectroscopy (EDS) analysis revealed the Ti buffer layers to be slightly oxide. Extended x-ray absorption fine structure confirmed the TEM and EDS results. The I-V characteristic measurements showed a 20-fold increase in current density with the Ti buffer layer, suggesting excellent electrical contact between the Ti buffer layer and ZnO nanorods.
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73.63.Bd Nanocrystalline materials
78.70.Dm X-ray absorption spectra
81.05.Dz II-VI semiconductors
61.46.Km Structure of nanowires and nanorods (long, free or loosely attached, quantum wires and quantum rods, but not gate-isolated embedded quantum wires)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase

The absorption spectrum of hydrogenated silicon carbide nanocrystals from ab initio calculations

Márton Vörös, Péter Deák, Thomas Frauenheim, and Adam Gali

Appl. Phys. Lett. 96, 051909 (2010); http://dx.doi.org/10.1063/1.3308495 (3 pages) | Cited 9 times

Online Publication Date: 5 February 2010

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The electronic structure and absorption spectrum of hydrogenated silicon carbide nanocrystals (SiC NCs) have been determined by first principles calculations. We show that the reconstructed surface can significantly change not just the onset of absorption but the shape of the spectrum at higher energies. We compare our results with two recent experiments on ultrasmall SiC NCs.
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78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
73.22.-f Electronic structure of nanoscale materials and related systems
71.15.-m Methods of electronic structure calculations

Calibrating the single-wall carbon nanotube resonance Raman intensity by high resolution transmission electron microscopy for a spectroscopy-based diameter distribution determination

P. B. C. Pesce, P. T. Araujo, P. Nikolaev, S. K. Doorn, K. Hata, R. Saito, M. S. Dresselhaus, and A. Jorio

Appl. Phys. Lett. 96, 051910 (2010); http://dx.doi.org/10.1063/1.3297904 (3 pages) | Cited 5 times

Online Publication Date: 5 February 2010

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We study a single-wall carbon nanotube (SWNT) sample grown by water-assisted chemical vapor deposition with both resonance Raman scattering (RRS) and high resolution transmission electron microscopy. High resolution transmission electron microscopy measurements of 395 SWNTs determined the diameter distribution of the sample, allowing us to calibrate an RRS radial breathing mode (RBM) map obtained with 51 laser excitation energies from 1.26 to 1.73 eV. Thus, we determined the diameter dependence of the RRS RBM cross-section, which in turn allows the determination of the diameter distribution of any SWNT sample by measuring the RBM Raman signal.
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81.07.De Nanotubes
61.48.De Structure of carbon nanotubes, boron nanotubes, and other related systems
78.30.Na Fullerenes and related materials
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

In situ synchrotron x-ray studies of strain and composition evolution during metal-organic chemical vapor deposition of InGaN

M.-I. Richard, M. J. Highland, T. T. Fister, A. Munkholm, J. Mei, S. K. Streiffer, Carol Thompson, P. H. Fuoss, and G. B. Stephenson

Appl. Phys. Lett. 96, 051911 (2010); http://dx.doi.org/10.1063/1.3293441 (3 pages) | Cited 8 times

Online Publication Date: 5 February 2010

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Composition and strain inhomogeneities strongly affect the optoelectronic properties of InGaN but their origin has been unclear. Here we report real-time x-ray reciprocal space mapping that reveals the development of strain and composition distributions during metal-organic chemical vapor deposition of InxGa1−xN on GaN. Strong, correlated inhomogeneities of the strain state and In fraction x arise during growth in a manner consistent with models for instabilities driven by strain relaxation.
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81.05.Ea III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances

Surface changes on AlH3 during the hydrogen desorption

Shunsuke Kato, Michael Bielmann, Kazutaka Ikeda, Shin-ichi Orimo, Andreas Borgschulte, and Andreas Züttel

Appl. Phys. Lett. 96, 051912 (2010); http://dx.doi.org/10.1063/1.3269598 (3 pages) | Cited 14 times

Online Publication Date: 5 February 2010

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Surface change of α-AlH3 during the hydrogen desorption was investigated by means of in situ x-ray photoelectron spectroscopy combined with thermal desorption spectroscopy. The surface of AlH3 covered by an oxide layer significantly changes upon hydrogen desorption and the hydrogen desorption rate increases remarkably. In this study, the role of the surface oxide layer on AlH3 in view of the hydrogen desorption kinetics was investigated. AlH3 only decomposes into Al and H2 at the free surface and not in the bulk. Therefore, a closed surface oxide layer prevents the thermodynamically unstable AlH3 from decomposition.
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68.43.Vx Thermal desorption
68.35.bt Other materials
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
79.60.Dp Adsorbed layers and thin films

Herringbone buckling patterns of anisotropic thin films on elastomeric substrates

J. Song

Appl. Phys. Lett. 96, 051913 (2010); http://dx.doi.org/10.1063/1.3309696 (3 pages) | Cited 1 time

Online Publication Date: 5 February 2010

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Highly ordered herringbone buckling patterns have been observed in stiff thin films on elastomeric substrates under an equibiaxial compression. Existing mechanics models assume the thin film to be isotropic, which does not agree with recent experiments of single crystal thin films (e.g., silicon) on elastomeric substrates, where the film has cubic symmetry with anisotropic material properties. A theoretical model for herringbone buckling patterns of anisotropic thin films on elastomeric substrates is developed in this paper. The prediction of the buckling directions agrees well with experiments. The approximation of the use of isotropic material properties is also analyzed.
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62.20.mq Buckling
61.41.+e Polymers, elastomers, and plastics
68.60.Bs Mechanical and acoustical properties
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Sorption properties of NO2 gas and its strong influence on hole concentration of H-terminated diamond surfaces

Michal Kubovic, Makoto Kasu, and Hiroyuki Kageshima

Appl. Phys. Lett. 96, 052101 (2010); http://dx.doi.org/10.1063/1.3291616 (3 pages) | Cited 6 times

Online Publication Date: 1 February 2010

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The hole concentration of hydrogen-terminated diamond surfaces was studied during exposure to different concentrations of NO2 gas. The hole concentration increased during adsorption of NO2 molecules on the diamond surface, and decreased when the exposure stopped and NO2 molecules desorbed from the surface. The increase in hole concentration can be directly linked to the NO2 concentration. The low NO2 concentration in air ( ∼ 20 ppb) is responsible the hole concentration normally measured in air, and with increasing NO2 concentration the maximum hole concentration increases even more. The time evolution of hole concentration was analyzed using the Elovich sorption model. Further analysis based on the Ritchie model indicated that an adsorbed NO2 molecule occupies two different surface sites. Temperature-dependent measurements indicate low activation energy between 0.1 and 0.2 eV.
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68.43.Mn Adsorption kinetics
68.43.Nr Desorption kinetics

Schottky barrier height and conduction mechanisms in ferroelectric bismuth titanate

Fen Liu, Ying Ma, Feng Yang, and Yichun Zhou

Appl. Phys. Lett. 96, 052102 (2010); http://dx.doi.org/10.1063/1.3298645 (3 pages) | Cited 1 time

Online Publication Date: 1 February 2010

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Band structure of ferroelectric bismuth titanate is calculated by first-principles computations under the framework of density functional theory. Using the metal induced gap state model, the Schottky barrier height on Pt electrode is estimated to be as high as 1.26 eV, which indicates that the Schottky effect may not be the dominant conduction mechanism in bismuth titanate. By further comparisons with the experimental data, we conclude that the leakage current behavior of bismuth titanate films is dominated by bulk limited conduction mechanisms and can be reduced by better processing conditions or doping.
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77.84.Cg PZT ceramics and other titanates
77.80.-e Ferroelectricity and antiferroelectricity
73.30.+y Surface double layers, Schottky barriers, and work functions
73.61.Ng Insulators
73.20.At Surface states, band structure, electron density of states
77.55.fp Other ferroelectric films

Electron energy band alignment at the (100)Si/MgO interface

V. V. Afanas’ev, A. Stesmans, K. Cherkaoui, and P. K. Hurley

Appl. Phys. Lett. 96, 052103 (2010); http://dx.doi.org/10.1063/1.3294328 (3 pages) | Cited 1 time

Online Publication Date: 1 February 2010

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The electron energy band diagram at the (100)Si/MgO interface is characterized using internal photoemission of electrons and holes from Si into the oxide. For the as-deposited amorphous MgO the interface barriers correspond to a band gap width of 6.1 eV, i.e., much lower than the conventionally assumed bulk crystal value (7.83 eV). The annealing-induced crystallization of MgO mostly affects the energy of the valence band while the conduction band bottom retains its energy position at 3.37±0.05 eV above the top of the silicon valence band.
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73.20.At Surface states, band structure, electron density of states
64.70.K- Solid-solid transitions
79.60.Jv Interfaces; heterostructures; nanostructures
81.40.Gh Other heat and thermomechanical treatments

Electron spin filtering by thin GaNAs/GaAs multiquantum wells

Y. Puttisong, X. J. Wang, I. A. Buyanova, H. Carrére, F. Zhao, A. Balocchi, X. Marie, C. W. Tu, and W. M. Chen

Appl. Phys. Lett. 96, 052104 (2010); http://dx.doi.org/10.1063/1.3299015 (3 pages) | Cited 6 times

Online Publication Date: 1 February 2010

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Effectiveness of the recently discovered defect-engineered spin-filtering effect is closely examined in GaNAs/GaAs multiquantum wells (QWs) as a function of QW width. In spite of narrow well widths of 3–9 nm, rather efficient spin filtering is achieved at room temperature. It leads to electron spin polarization larger than 18% and an increase in photoluminescence intensity by 65% in the 9 nm wide QWs. A weaker spin filtering effect is observed in the narrower QWs, mainly due to a reduced sheet concentration of spin-filtering defects (e.g., Gai interstitial defects).
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72.25.Fe Optical creation of spin polarized carriers
73.21.Fg Quantum wells
73.63.Hs Quantum wells
78.55.Cr III-V semiconductors

Supergrains produced by lateral growth using Joule-heating induced crystallization without artificial control

Won-Eui Hong, Jangkyun Chung, Donghyun Kim, Seungho Park, and Jae-Sang Ro

Appl. Phys. Lett. 96, 052105 (2010); http://dx.doi.org/10.1063/1.3253704 (3 pages) | Cited 3 times

Online Publication Date: 2 February 2010

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In Joule-heating induced crystallization, phase transformation can occur through solid-to-solid or liquid-to-solid phases, according to the input conditions of the pulsed power. It was observed that during a Joule-heating period of several tens of microseconds, randomly nucleated liquid seeds followed by rapid solidification in an amorphous matrix play an important role, especially for liquid-to-solid transformation. Meanwhile, under high-power input processing conditions, supergrains of greater than 5 μm in size were produced by lateral growth from the initial seeds without artificial control.
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81.30.Fb Solidification
64.70.D- Solid-liquid transitions
64.70.dg Crystallization of specific substances

Band bending effect induced by gate voltage on the charge loss behavior of charge trap flash memory devices

M. Chang, H. Hwang, and S. Jeon

Appl. Phys. Lett. 96, 052106 (2010); http://dx.doi.org/10.1063/1.3295697 (3 pages) | Cited 1 time

Online Publication Date: 2 February 2010

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We found that the polarity of the gate voltage (Vg) during the retention characteristics for a SiO2/Si3N4/Al2O3 (ONA) stack can affect the charge loss direction, due to band bending. Positive Vg could induce electron de-trapping through Al2O3, while a negative Vg could induce the same through SiO2. Consequently, the charge loss rates exhibited a hairpin curve with Vg. We clearly observed that increases of the SiO2 thickness of the ONA stack induced negative shifts of hairpin curve. This result suggests that the dominant charge loss path could be changed from SiO2 to Al2O3 by increasing the SiO2 thickness without Vg.
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84.30.Sk Pulse and digital circuits

Band offsets of Al2O3/InxGa1−xAs (x = 0.53 and 0.75) and the effects of postdeposition annealing

N. V. Nguyen, M. Xu, O. A. Kirillov, P. D. Ye, C. Wang, K. Cheung, and J. S. Suehle

Appl. Phys. Lett. 96, 052107 (2010); http://dx.doi.org/10.1063/1.3306732 (3 pages) | Cited 13 times

Online Publication Date: 2 February 2010

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Band offsets at the interfaces of InxGa1−xAs/Al2O3/Al where x = 0.53 and 0.75 were determined by internal photoemission and spectroscopic ellipsometry. The photoemission energy threshold at the InxGa1−xAs/Al2O3 interface was found to be insensitive to the indium composition but shifted to a lower energy after a postdeposition annealing at high temperatures. Subthreshold electron photoemission was also observed for the annealed sample and was attributed to interfacial layer formation during the annealing process.
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73.20.At Surface states, band structure, electron density of states
81.05.Ea III-V semiconductors
79.60.Bm Clean metal, semiconductor, and insulator surfaces
61.72.Cc Kinetics of defect formation and annealing
68.35.Fx Diffusion; interface formation

Observation of sub-100 femtosecond electron cooling time in InN

Yi-En Su, Yu-Chieh Wen, Hong-Mao Lee, Shangjr Gwo, and Chi-Kuang Sun

Appl. Phys. Lett. 96, 052108 (2010); http://dx.doi.org/10.1063/1.3302467 (3 pages) | Cited 2 times

Online Publication Date: 2 February 2010

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We report that the electron cooling time in indium nitride can be as fast as sub-100 femtosecond at low electron concentration (<5×1017/cm3), which is much faster than previous reports. Through investigating the dependence of the measured carrier cooling time on electron density, our study proved the dominant role of the screened Fröhlich interaction in the reduction in carrier cooling rate at an electron density higher than 1.8×1018/cm3.
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72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.20.Fr Low-field transport and mobility; piezoresistance
72.10.Di Scattering by phonons, magnons, and other nonlocalized excitations
71.38.Fp Large or Fröhlich polarons
81.05.Ea III-V semiconductors

Hydrogen and inert species in solid phase epitaxy

R. R. Lieten, S. Degroote, F. Clemente, M. Leys, and G. Borghs

Appl. Phys. Lett. 96, 052109 (2010); http://dx.doi.org/10.1063/1.3293453 (3 pages) | Cited 2 times

Online Publication Date: 2 February 2010

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The incorporation of hydrogen during deposition of amorphous germanium can influence solid phase epitaxy in many ways. We show that Ge–H bonds are not important during the crystallization process. However, atomic hydrogen is important during deposition to obtain a highly disordered layer. We have found that highly disordered layers can also be obtained when using a beam of inert gas species during ultrahigh vacuum deposition. These inert species effectively increase the disorder of the layer by limiting the surface mobility of adsorbed germanium atoms. In this way subsequent solid phase epitaxy can be improved significantly.
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81.15.Np Solid phase epitaxy; growth from solid phases
68.55.ag Semiconductors
61.43.Dq Amorphous semiconductors, metals, and alloys
81.05.Cy Elemental semiconductors
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