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4 Jan 2010

Volume 96, Issue 1, Articles (01xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 96, 013107 (2010); http://dx.doi.org/10.1063/1.3280900 (3 pages)

L. Fernández, M. Corso, F. Schiller, M. Ilyn, M. Holder, and J. E. Ortega
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Dependence of magnetic susceptibility on stress in textured polycrystalline Fe81.6Ga18.4 and Fe79.1Ga20.9 Galfenol alloys

A. Mahadevan, P. G. Evans, and M. J. Dapino

Appl. Phys. Lett. 96, 012502 (2010); http://dx.doi.org/10.1063/1.3280374 (3 pages) | Cited 5 times

Online Publication Date: 5 January 2010

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Magnetization and magnetostriction measurements in constant tension and compression as a function of applied magnetic field are reported for 〈100〉 oriented, textured polycrystalline Fe81.6Ga18.4 and Fe79.1Ga20.9 Galfenol alloys. The susceptibility change with stress, or sensitivity, is maximum at zero field for both alloys. The greatest sensitivity is observed for the 18.4 at. % Ga alloy between −10 and +20 MPa, where domain wall motion dominates. The sensitivity is greater for the 20.9 at. % Ga alloy than for the 18.4 at. % Ga alloy below −15 MPa (domain rotation region). The difference in behavior is attributed to a difference in the anisotropy coefficient.
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75.30.Cr Saturation moments and magnetic susceptibilities
75.30.Gw Magnetic anisotropy
75.60.Ch Domain walls and domain structure
75.80.+q Magnetomechanical effects, magnetostriction
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity

Precise probing spin wave mode frequencies in the vortex state of circular magnetic dots

A. A. Awad, K. Y. Guslienko, J. F. Sierra, G. N. Kakazei, V. Metlushko, and F. G. Aliev

Appl. Phys. Lett. 96, 012503 (2010); http://dx.doi.org/10.1063/1.3268453 (3 pages) | Cited 3 times

Online Publication Date: 5 January 2010

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We report on detailed broadband ferromagnetic resonance measurements of azimuthal and radial spin wave excitations in circular Permalloy dots in the vortex ground state. Dots with aspect ratio (β = height over radius) varied from 0.03 to 0.1 were explored. The frequency splitting of two lowest azimuthal modes was observed. The experimentally observed dependence of the frequency splitting on β was reasonably well described by dynamic splitting model accounting the spin waves and vortex gyrotropic mode interaction.
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75.30.Ds Spin waves
75.50.Tt Fine-particle systems; nanocrystalline materials
76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance
75.50.Bb Fe and its alloys
75.78.-n Magnetization dynamics
75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)

Induced magnetism of carbon atoms at the graphene/Ni(111) interface

M. Weser, Y. Rehder, K. Horn, M. Sicot, M. Fonin, A. B. Preobrajenski, E. N. Voloshina, E. Goering, and Yu. S. Dedkov

Appl. Phys. Lett. 96, 012504 (2010); http://dx.doi.org/10.1063/1.3280047 (3 pages) | Cited 27 times

Online Publication Date: 5 January 2010

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We report an element-specific investigation of electronic and magnetic properties of the graphene/Ni(111) system. Using x-ray magnetic circular dichroism, the occurrence of an induced magnetism of the carbon atoms in the graphene layer is observed. We attribute this magnetic moment to the strong hybridization between C π and Ni 3d valence band states. The net magnetic moment of carbon in the graphene layer is estimated to be in the range of 0.05–0.1 μB per atom.
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73.20.At Surface states, band structure, electron density of states
68.35.Ct Interface structure and roughness
78.20.Ls Magneto-optical effects
75.30.Cr Saturation moments and magnetic susceptibilities
78.70.Dm X-ray absorption spectra

Adjust the resonance frequency of (Co90Nb10/Ta)n multilayers from 1.4 to 6.5 GHz by controlling the thickness of Ta interlayers

Guozhi Chai (柴国志), Yuancai Yang (阳远才), Jingyi Zhu (朱静怡), Min Lin (林敏), Wenbo Sui (隋文波), Dangwei Guo (郭党委), Xiling Li (李喜玲), and Desheng Xue (薛德胜)

Appl. Phys. Lett. 96, 012505 (2010); http://dx.doi.org/10.1063/1.3290252 (3 pages) | Cited 13 times

Online Publication Date: 7 January 2010

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In this work, the static and high frequency magnetic properties of (Co90Nb10/Ta)n multilayers have been investigated. The results show that the in-plane uniaxial magnetic anisotropy fields can be adjusted from 12 to 520 Oe only by decreasing the thickness of Ta interlayers from 8.0 to 1.8 nm. As a consequence, the resonance frequencies of the multilayers continuously increased from 1.4 to 6.5 GHz. It was found that the changes in the in-plane uniaxial anisotropy field are ascribed to the interlayer interactions among the magnetic layers by investigating the δM(H) curves.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.30.Gw Magnetic anisotropy
75.40.Cx Static properties (order parameter, static susceptibility, heat capacities, critical exponents, etc.)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Manipulation of magnetism by electrical field in a real recording system

Tiejun Zhou, S. H. Leong, Z. M. Yuan, S. B. Hu, C. L. Ong, and B. Liu

Appl. Phys. Lett. 96, 012506 (2010); http://dx.doi.org/10.1063/1.3276553 (3 pages) | Cited 6 times

Online Publication Date: 8 January 2010

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We report an electrically controlled magnetism in a real recording system with CoCrPt–TiO2 nanocomposite thin films as recording medium. We show that in a spin-stand test, with a small voltage of 3 V applied across the head-media gap during recording, a 13% reduction of saturation current was observed and the read back waveforms showed sharper transitions. These account for the 3 dB improvement in read back signal-noise-ratio of the written magnetic information. The improved recording performance is mainly attributed to the reduction of anisotropy of the recording medium in the presence of electrical field. Simulations were carried out to understand the magnetization reversal process under applied electric and magnetic fields.
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75.85.+t Magnetoelectric effects, multiferroics
75.50.Tt Fine-particle systems; nanocrystalline materials
75.50.Ss Magnetic recording materials
75.30.Gw Magnetic anisotropy
75.70.-i Magnetic properties of thin films, surfaces, and interfaces
75.60.Jk Magnetization reversal mechanisms

Microstructure and superconductivity of Ir-doped BaFe2As2 superconductor

X. L. Wang, H. Y. Shi, X. W. Yan, Y. C. Yuan, Z.-Y. Lu, X. Q. Wang, and T.-S. Zhao

Appl. Phys. Lett. 96, 012507 (2010); http://dx.doi.org/10.1063/1.3290983 (3 pages) | Cited 7 times

Online Publication Date: 8 January 2010

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Polycrystalline samples with nominal composition of Ba(Fe1−xIrx)2As2 (x = 0.10, 0.15, and 0.20) were investigated by means of x-ray diffraction (XRD), scanning electron microscopy (SEM), electrical resistivity, and magnetization measurements. XRD and SEM results showed that almost single phase samples were obtained. Bulk superconductivity with TC ∼ 28 K was observed in the x = 0.10 sample. TC ∼ 28 K is the highest superconducting critical temperature among the reported data for electron-doped AFe2As2-type (A = Ca, Sr, and Ba) superconductors. The upper critical field Hc2(0) reaches as high as 65 T for the x = 0.10 sample. The underlying physics is discussed in connection with Co-doping case.
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74.25.fc Electric and thermal conductivity
74.70.Xa Pnictides and chalcogenides
74.25.Op Mixed states, critical fields, and surface sheaths
74.10.+v Occurrence, potential candidates
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
74.25.Ha Magnetic properties including vortex structures and related phenomena

Ferromagnetic ordering of silicon vacancies in N-doped silicon carbide

Mingwen Zhao, Fengchun Pan, and Liangmo Mei

Appl. Phys. Lett. 96, 012508 (2010); http://dx.doi.org/10.1063/1.3291562 (3 pages) | Cited 9 times

Online Publication Date: 8 January 2010

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We perform first-principles calculations to investigate the roles of silicon vacancy (VSi) and nitrogen impurity in the magnetic properties of silicon carbide (3C-SiC). High-spin configurations are predicted for the negatively-charged (VSi) defects. The coupling is ferromagnetic between the (VSi) defects at −2e charge state, whereas the (VSi) defects at -e charge state prefer to interact antiferromagnetically. Substituting C with N atoms can manipulate the charge states of (VSi) defects and the magnetic interactions between them. Our work offers a possible route toward high Curie temperature (Tc) ferromagnetism in metal-free 3C-SiC materials.
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75.30.Et Exchange and superexchange interactions
61.72.jd Vacancies
61.72.S- Impurities in crystals
75.50.Pp Magnetic semiconductors
75.50.Ee Antiferromagnetics
75.50.Dd Nonmetallic ferromagnetic materials
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Twinning rotation and ferroelectric behavior of epitaxial BiFeO3 (001) thin film

Huajun Liu, Ping Yang, Kui Yao, and John Wang

Appl. Phys. Lett. 96, 012901 (2010); http://dx.doi.org/10.1063/1.3276543 (3 pages) | Cited 9 times

Online Publication Date: 4 January 2010

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A twinning rotation structure is revealed by reciprocal space mappings obtained from synchrotron X-ray diffraction for the epitaxial BiFeO3 thin film that was grown on (001) SrTiO3 substrate. The lattice strain is not fully relaxed at a film thickness of 720 nm. The structure is indexed as a monoclinic with lattice parameters a = 5.610(1) Å, b = 5.529(1) Å, c = 4.031(1) Å, and β = 89.34(1)°. The twinning rotation leads to an enhanced remanent polarization (2Pr = 164 μC/cm2, 2Ec = 510 kV/cm) and greatly reduced leakage current density of 1.2×10−6 A/cm2 at 100 kV/cm.
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77.55.fp Other ferroelectric films
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
61.72.Mm Grain and twin boundaries
77.22.Ej Polarization and depolarization
68.55.-a Thin film structure and morphology
75.70.Ak Magnetic properties of monolayers and thin films

The role of La surface chemistry in the passivation of Ge

A. Dimoulas, D. Tsoutsou, Y. Panayiotatos, A. Sotiropoulos, G. Mavrou, S. F. Galata, and E. Golias

Appl. Phys. Lett. 96, 012902 (2010); http://dx.doi.org/10.1063/1.3284655 (3 pages) | Cited 23 times

Online Publication Date: 4 January 2010

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The oxidation of a Ge surface by molecular oxygen in the presence of ultrathin La, Al, and Hf layers was examined by in situ x-ray photoelectron spectroscopy. Upon exposure to O2, clean bare Ge and Hf-covered or Al-covered Ge surfaces show no Ge–O bond formation. On the contrary, a La-covered Ge surface strongly reacts with O2 forming a stable germanate LaGeOx compound. This has a beneficial side effect for the interface because the formation of volatile GeO is suppressed, resulting in the good passivating properties of LaGeOx. The photoemission results are correlated with the oxygen density differences in the corresponding oxides.
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81.65.Rv Passivation
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
81.65.Mq Oxidation
81.05.Cy Elemental semiconductors
79.60.Bm Clean metal, semiconductor, and insulator surfaces

Temperature induced change in the hysteretic behavior of the capacitance-voltage characteristics of Pt–ZnO–Pb(Zr0.2Ti0.8)O3–Pt heterostructures

L. Pintilie, C. Dragoi, R. Radu, A. Costinoaia, V. Stancu, and I. Pintilie

Appl. Phys. Lett. 96, 012903 (2010); http://dx.doi.org/10.1063/1.3284659 (3 pages) | Cited 5 times

Online Publication Date: 4 January 2010

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Pt–ZnO–Pb(Zr0.2Ti0.8)O3–Pt (PZT-ZnO) heterostructures were fabricated by using a sol-gel process. Capacitance-voltage measurements performed on a wide temperature range (20–450 K) have revealed the presence of a hysteresis that undergo a change of direction from clockwise at temperatures below 350 K to counter-clockwise at higher temperatures. In the first case, the hysteresis is produced by charge injection, similar to the case of classical metal-oxide-semiconductor capacitors. In the last case, the hysteresis is the fingerprint of polarization reversal, as reported for metal-ferroelectric-semiconductor (MFS) structures based on n-Si. The memory window at 450 K is about 6 V. This result suggests that PZT-ZnO MFS heterostructures can be used for memory devices working at elevated temperatures, in which the ZnO plays the role of the semiconductor.
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77.80.Dj Domain structure; hysteresis
77.55.fg Pb(Zr,Ti)O3-based films
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
77.22.Ej Polarization and depolarization
85.50.Gk Non-volatile ferroelectric memories
81.10.Dn Growth from solutions
81.10.Fq Growth from melts; zone melting and refining
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)

Structure and electrical properties of Bi3.15Nd0.85Ti3O12 nanofibers synthesized by electrospinning and sol-gel method

M. Liao, X. L. Zhong, J. B. Wang, S. H. Xie, and Y. C. Zhou

Appl. Phys. Lett. 96, 012904 (2010); http://dx.doi.org/10.1063/1.3276688 (3 pages) | Cited 6 times

Online Publication Date: 5 January 2010

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Bi3.15Nd0.85Ti3O12 (BNT) nanofibers with radii in the range of 30–200 nm have been prepared by the electrospinning and sol-gel method, and the structure and morphology of the nanofibers were characterize by x-ray diffraction, scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy. The phase transition and piezoelectric characteristics of the BNT nanofibers were performed by thermal analysis and scanning probe microscopy, respectively. The BNT nanofiber exhibits an effective piezoelectric coefficient of 89 pm/V and a Curie temperature of 500 °C, which are higher than that of the BNT bulk.
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78.30.Hv Other nonmetallic inorganics
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
81.16.Ta Atom manipulation
77.65.Bn Piezoelectric and electrostrictive constants
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)

Systematic variations in structural and electronic properties of BiFeO3 by A-site substitution

Zhen Zhang, Ping Wu, Lang Chen, and Junling Wang

Appl. Phys. Lett. 96, 012905 (2010); http://dx.doi.org/10.1063/1.3279137 (3 pages) | Cited 11 times

Online Publication Date: 5 January 2010

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Systematic variations in the structural and electronic properties of BiFeO3 with A-site substitutions were studied using first-principles density functional theory calculations. It is found that the ferroelectric distortion of BiFeO3 with group IIIA element (Sc3+, Y3+, and La3+) substitutions is significantly affected by the hybridization between substitute d states and oxygen 2p states, while that with group VB element (Sb3+) substitution is stabilized by the s2 lone pair electrons. For both groups, the substitute with smaller ionic size and larger electronegativity causes more significant off-center displacement and narrower band gap.
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71.20.Ps Other inorganic compounds
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
75.85.+t Magnetoelectric effects, multiferroics
77.80.-e Ferroelectricity and antiferroelectricity

Border traps in Al2O3/In0.53Ga0.47As (100) gate stacks and their passivation by hydrogen anneals

Eun Ji Kim, Lingquan Wang, Peter M. Asbeck, Krishna C. Saraswat, and Paul C. McIntyre

Appl. Phys. Lett. 96, 012906 (2010); http://dx.doi.org/10.1063/1.3281027 (3 pages) | Cited 50 times

Online Publication Date: 6 January 2010

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Charge-trapping defects in Pt/Al2O3/In0.53Ga0.47As metal-oxide-semiconductor capacitors and their passivation by hydrogen are investigated in samples with abrupt oxide/III-V interfaces. Tunneling of electrons into defect states (border traps) in the atomic layer deposited Al2O3 near the oxide/semiconductor interface is found to control the frequency dispersion of the capacitance in accumulation. Hydrogen anneals effectively passivate border traps in the oxide, in addition to some of the midgap states that control carrier generation in the channel. This is evident in the reduced frequency dispersion in accumulation, reduced capacitance-voltage stretch-out through depletion, and suppression of the inversion carrier response in capacitance-voltage measurements.
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84.32.Tt Capacitors
85.30.Tv Field effect devices
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)

A complete set of material properties of single domain 0.26Pb(In1/2Nb1/2)O3–0.46Pb(Mg1/3Nb2/3)O3–0.28PbTiO3 single crystals

Xiaozhou Liu, Shujun Zhang, Jun Luo, Thomas R. Shrout, and Wenwu Cao

Appl. Phys. Lett. 96, 012907 (2010); http://dx.doi.org/10.1063/1.3275803 (3 pages) | Cited 19 times

Online Publication Date: 6 January 2010

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Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 (PIN-PMN-PT) single crystals have been developed recently, which can increase the operating temperature by at least 20 °C compared to PMN-PT crystals. We have measured a complete set of material properties of single domain PIN-PMN-PT crystal, which is urgently needed in theoretical studies and electromechanical device designs using this crystal. Because the rotated values of d33∗ = 1122 pC/N and k33∗ = 89% along [001]c calculated using the single domain data obtained here are in good agreement with the [001]c poled multidomain PIN-PMN-PT crystals, one may conclude that the physical origin of the ultrahigh piezoelectric properties mainly come from orientation effect.
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77.84.Cg PZT ceramics and other titanates
77.22.Ej Polarization and depolarization
77.65.-j Piezoelectricity and electromechanical effects

Nanoscale domain growth dynamics of ferroelectric poly(vinylidene fluoride-co-trifluoroethylene) thin films

Yunseok Kim, Wooyoung Kim, Hyunwoo Choi, Seungbum Hong, Hyungsoo Ko, Heechul Lee, and Kwangsoo No

Appl. Phys. Lett. 96, 012908 (2010); http://dx.doi.org/10.1063/1.3290247 (3 pages) | Cited 10 times

Online Publication Date: 7 January 2010

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Nanoscale domain growth dynamics of ferroelectric poly(vinylidene fluoride-co-trifluoroethylene) thin films were investigated by piezoresponse force microscopy. A 90 nm thick ferroelectric polymer thin films were fabricated on Au substrate by spin-coating method. The domain size of nanoscale dot pattern was linearly proportional to logarithmic value of the pulse width. However there was a significant asymmetry in nucleation and lateral domain growth depending on the voltage polarity, which implies the existence of the preferred polarization states. The obtained activation field indicates the nucleation-limited domain switching behaviors of ferroelectric polymer thin films.
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68.55.am Polymers and organics
81.16.Rf Micro- and nanoscale pattern formation
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
77.84.Jd Polymers; organic compounds
77.22.Ej Polarization and depolarization

Oxygen concentration and its effect on the leakage current in BiFeO3 thin films

H. Yang, Y. Q. Wang, H. Wang, and Q. X. Jia

Appl. Phys. Lett. 96, 012909 (2010); http://dx.doi.org/10.1063/1.3291044 (3 pages) | Cited 21 times

Online Publication Date: 8 January 2010

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Epitaxial c-axis oriented BiFeO3 (BFO) films were fabricated on (001) oriented SrTiO3 substrates by pulsed laser deposition. Nuclear resonance backscattering spectrometry was used to directly measure the oxygen concentration of as-deposited and annealed BFO films. Compared to the ideal stoichiometry of BFO, the as-deposited BFO film shows more than 10% oxygen deficiency. However, postannealing the as-deposited BFO films reduces the oxygen deficiency almost half. The reduced oxygen vacancies in annealed BFO films are believed to be responsible for the different leakage mechanisms and the two orders of magnitude drop in leakage current density.
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77.55.fp Other ferroelectric films
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.80.-e Ferroelectricity and antiferroelectricity
77.55.Px Epitaxial and superlattice films
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.40.Gh Other heat and thermomechanical treatments

Improved ferroelectric properties of Pb(Zr0.52,Ti0.48)O3 thin film on single crystal diamond using CaF2 layer

Meiyong Liao, Kiyomi Nakajima, Masataka Imura, and Yasuo Koide

Appl. Phys. Lett. 96, 012910 (2010); http://dx.doi.org/10.1063/1.3291056 (3 pages) | Cited 5 times

Online Publication Date: 8 January 2010

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The authors report the integration of perovskite Pb(Zr0.52,Ti0.48)O3 thin film on single crystal diamond by using a nonoxide single CaF2 buffer layer. The CaF2 buffer layer plays a dual role in the lead zirconate titanate Pb(Zr,Ti)O3 (PZT) film deposition. The first is that the CaF2 layer leads to a preferentially (100)-oriented PZT thin film on diamond, improving the ferroelectric properties significantly. The PZT film exhibits a remanent in-plane polarization of 2Pr = 68 μC/cm2 and a coercive field of 33 kV/cm. The remanent polarization is much larger than that of PZT films deposited on diamond by using SrTiO3/Al2O3 buffer layer. The second is that the CaF2 layer acts as an efficient energy barrier for the metal-ferroelectric-insulator-diamond capacitor due to its wide band gap. The leakage current in the capacitor is reduced to be lower than 10−6 A/cm2 in the forward bias mode.
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73.61.-r Electrical properties of specific thin films
77.80.-e Ferroelectricity and antiferroelectricity
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
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Assembly of gold nanoparticles of different diameters between nanogap electrodes

Donguk Cheon, Sanjeev Kumar, and Gil-Ho Kim

Appl. Phys. Lett. 96, 013101 (2010); http://dx.doi.org/10.1063/1.3280859 (3 pages) | Cited 6 times

Online Publication Date: 4 January 2010

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Gold nanoparticles (NPs) of different diameters i.e., 5, 10, and 20 nm, were assembled between 20 nm gap electrodes using ac dielectrophoresis (DEP) process. DEP parameters, such as frequency, trapping time, and voltage of value 1 MHz, 1 s, and 2–3 V, respectively, led to the pearl-chain assembly corresponding to each type of NPs between 20 nm gap electrodes. Mutual DEP could be attributed to the NPs chaining in low field regions and subsequently the DEP force directs these chains to the trapping region. Such controlled assembly of individual NPs may find application in fabricating devices for molecular electronics.
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81.07.Bc Nanocrystalline materials
81.05.Bx Metals, semimetals, and alloys
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
81.16.-c Methods of micro- and nanofabrication and processing
82.45.Fk Electrodes
85.35.-p Nanoelectronic devices

Exchange bias in large three dimensional iron oxide nanocomposites

J. R. Morales, S. Tanju, W. P. Beyermann, and J. E. Garay

Appl. Phys. Lett. 96, 013102 (2010); http://dx.doi.org/10.1063/1.3277147 (3 pages) | Cited 5 times

Online Publication Date: 4 January 2010

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A processing method is presented for the production of macroscopic nanocomposites that display antiferromagnetic/ferrimagnetic (AFM/fM) coupling. The technique takes advantage of the metastability of iron oxide phases and the fast densification of nanocrystalline powders. The total processing time is under 500s. It is possible to manipulate the composition of fM and AFM phases with processing temperature. The relatively high density of AFM/fM boundaries produces an exchange bias caused by coupling at the interfaces. The magnitude of the exchange field (Hex) is affected the composition as well as the grain size; the smaller grain size samples have the highest Hex.
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75.50.Tt Fine-particle systems; nanocrystalline materials
81.16.-c Methods of micro- and nanofabrication and processing
81.07.Wx Nanopowders
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
75.50.Gg Ferrimagnetics
75.50.Ee Antiferromagnetics

Characterization of the junction capacitance of metal-semiconductor carbon nanotube Schottky contacts

Yu-Chih Tseng and Jeffrey Bokor

Appl. Phys. Lett. 96, 013103 (2010); http://dx.doi.org/10.1063/1.3277182 (3 pages) | Cited 3 times

Online Publication Date: 5 January 2010

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Capacitance-voltage measurements have been performed on individual metal-carbon nanotube (CNT) Schottky diodes. The capacitance is found to agree in general with electrostatic simulations, taking into account the one-dimensional density of states of the CNT, and depends strongly on the Schottky barrier height and the diameter of the nanotube. The results indicate that the capacitance-voltage technique can be extended to characterize electrical junctions with very small area.
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73.30.+y Surface double layers, Schottky barriers, and work functions
73.40.Ns Metal-nonmetal contacts
73.22.-f Electronic structure of nanoscale materials and related systems

Monodispersed cation-disordered cubic AgInS2 nanocrystals with enhanced fluorescence

Zhenyu Feng, Pengcheng Dai, Xicheng Ma, Jinhua Zhan, and Zhaojun Lin

Appl. Phys. Lett. 96, 013104 (2010); http://dx.doi.org/10.1063/1.3280372 (3 pages) | Cited 8 times

Online Publication Date: 6 January 2010

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Monodispersed metastable cubic AgInS2 nanocrystals with an average size of around 2.5 nm are obtained via a solution-phase reaction. In contrast with the usual chalcopyrite and orthorhombic phase, Ag+ and In3+ cations in metastable cubic AgInS2 are randomly coordinated by four S2− anions. A phase transition from cation-disordered cubic to orthorhombic AgInS2 occurs with the increased reaction temperature or elongated reaction time. The photoluminescence quantum yield of cation-disordered cubic AgInS2 nanocrystals could reach 10% at room temperature, which is much higher than that of orthorhombic AgInS2 nanocrystals obtained via a similar approach.
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78.55.Hx Other solid inorganic materials
81.05.Hd Other semiconductors
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
64.70.kg Semiconductors
81.07.Bc Nanocrystalline materials

Strain-induced lateral self-organization in Si/SiO2 nanostructures

L. Tsybeskov, B. V. Kamenev, A. A. Sirenko, J. P. McCaffrey, and D. J. Lockwood

Appl. Phys. Lett. 96, 013105 (2010); http://dx.doi.org/10.1063/1.3290250 (3 pages) | Cited 1 time

Online Publication Date: 6 January 2010

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We show that strain, arising from the mismatch between Si and SiO2 thermal expansion coefficients, directs the thermal crystallization of amorphous Si along Si/SiO2 interfaces, and produces continuous, fully crystallized nanometer thick Si layers with a lateral-to-vertical aspect ratio close to 100:1. These Si nanolayers exhibit a low density of structural defects and are found to be elastically strained with respect to the crystal Si substrate.
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81.16.-c Methods of micro- and nanofabrication and processing
61.72.Mm Grain and twin boundaries
81.07.Bc Nanocrystalline materials
65.80.-g Thermal properties of small particles, nanocrystals, nanotubes, and other related systems
81.40.Jj Elasticity and anelasticity, stress-strain relations
64.70.dg Crystallization of specific substances

High efficiency green, yellow, and amber emission from InGaN/GaN dot-in-a-wire heterostructures on Si(111)

Y.-L. Chang, J. L. Wang, F. Li, and Z. Mi

Appl. Phys. Lett. 96, 013106 (2010); http://dx.doi.org/10.1063/1.3284660 (3 pages) | Cited 14 times

Online Publication Date: 6 January 2010

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The authors report on the achievement of nearly defect-free, vertically aligned InGaN/GaN dot-in-a-wire nanoscale heterostructures grown directly on Si(111) substrates by molecular beam epitaxy. Strong green, yellow, and amber emission, with a room temperature internal quantum efficiency of ∼ 45% of that measured at low temperature ( ∼ 10 K), was achieved. Detailed structural and optical studies further confirm that the emission characteristics are strongly influenced by the presence of In-rich nanoclusters, formed by phase segregation, in the InGaN dots.
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78.55.Cr III-V semiconductors
64.75.Qr Phase separation and segregation in semiconductors
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
78.67.Hc Quantum dots
78.67.Lt Quantum wires

Self-organized growth of high density magnetic Co nanodot arrays on a Moiré template

L. Fernández, M. Corso, F. Schiller, M. Ilyn, M. Holder, and J. E. Ortega

Appl. Phys. Lett. 96, 013107 (2010); http://dx.doi.org/10.1063/1.3280900 (3 pages) | Cited 3 times

Online Publication Date: 6 January 2010

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We report the self-organized growth of cobalt nanodot arrays using a Gd-Au Moiré superlattice as a template. After analyzing the influence of the Co flux and the substrate temperature, we obtain the suitable parameters to maximize nanodot density, homogeneity, and individual size. Depending on the growth conditions an areal density of up to 54 Teradots/inch2 can be achieved. Below the limit of lateral coalescence, independent nanodots made of ∼ 1000 Co atoms exhibit room temperature remanent magnetization.
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81.16.Dn Self-assembly
75.50.Tt Fine-particle systems; nanocrystalline materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.07.Bc Nanocrystalline materials
75.75.Cd Fabrication of magnetic nanostructures

Bimetallic Fe–V catalyzed magnesium films exhibiting rapid and cycleable hydrogenation at 200 °C

Beniamin Zahiri, Babak Shalchi Amirkhiz, Mohsen Danaie, and David Mitlin

Appl. Phys. Lett. 96, 013108 (2010); http://dx.doi.org/10.1063/1.3275864 (3 pages) | Cited 8 times

Online Publication Date: 7 January 2010

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We examined hydrogen sorption in 1.5 μm thick Mg–Fe–V films, using the binary alloys as baselines. At 200 °C both Mg–V and Mg–Fe–V absorb in tens of seconds, and desorb in tens of minutes. The ternary alloys show minimal kinetic or capacity degradation even after 105 absorption/desorption cycles. Pressure—composition isotherms yield the well-known enthalpies of α-MgH2 formation (decomposition), agreeing with x-ray diffraction results. The x-ray spectrum also shows a broad hump centered near (011) reflection of CsCl-type Fe–V phase. Our hypothesis is that a densely distributed nanoscale Fe–V acts both as a potent hydrogen dissociation catalyst and a heterogeneous nucleation site.
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82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
68.43.Nr Desorption kinetics
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
82.60.Cx Enthalpies of combustion, reaction, and formation
68.55.jd Thickness
82.60.Nh Thermodynamics of nucleation
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