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16 Apr 2012

Volume 100, Issue 16, Articles (16xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 100, 164101 (2012); http://dx.doi.org/10.1063/1.3702579 (4 pages)

Cheol-Ho Yun, Leslie Y. Yeo, James R. Friend, and Bernard Yan
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Composition dependent bilayer atomic ordering in AlxGa1−xN films examined by polarization-dependent extended x-ray absorption fine structure

J. C. Woicik, K. F. Ludwig, Jr., and T. D. Moustakas

Appl. Phys. Lett. 100, 162105 (2012); http://dx.doi.org/10.1063/1.4704678 (4 pages)

Online Publication Date: 17 April 2012

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Extended x-ray absorption fine structure has been used to study the local structure of ordered AlxGa1−xN films with nominal concentrations of x = 0.20 and x = 0.45. Strong cation ordering is found in alternating (0001) planes for both samples, with the 20% sample exhibiting nearly ideal local order compared to the 45% sample. Significant distortions in the nearest-neighbor Ga-N distances compared to the virtual crystal approximation are observed, although these distortions are found to be smaller than for disordered films. This result is counter to current theoretical predictions.
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68.55.Nq Composition and phase identification
78.70.Dm X-ray absorption spectra

Laser energy tuning of carrier effective mass and thermopower in epitaxial oxide thin films

A. I. Abutaha, S. R. Sarath Kumar, and H. N. Alshareef

Appl. Phys. Lett. 100, 162106 (2012); http://dx.doi.org/10.1063/1.4704183 (4 pages) | Cited 1 time

Online Publication Date: 18 April 2012

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The effect of the laser fluence on high temperature thermoelectric properties of the La doped SrTiO3 (SLTO) thin films epitaxially grown on LaAlO3 〈100〉 substrates by pulsed laser deposition is clarified. It is shown that oxygen vacancies that influence the effective mass of carriers in SLTO films can be tuned by varying the laser energy. The highest power factor of 0.433 W K−1 m−1 has been achieved at 636 K for a film deposited using the highest laser fluence of 7 J cm−2 pulse−1.
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81.15.Fg Pulsed laser ablation deposition
61.72.jd Vacancies
68.55.ag Semiconductors
72.20.Pa Thermoelectric and thermomagnetic effects
73.50.Lw Thermoelectric effects
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor

Semipolar {nmath01} InGaN/GaN ridge quantum wells (n = 1−3) fabricated by a regrowth technique

Mitsuru Funato, Teruhisa Kotani, Takeshi Kondou, and Yoichi Kawakami

Appl. Phys. Lett. 100, 162107 (2012); http://dx.doi.org/10.1063/1.4704779 (4 pages) | Cited 1 time

Online Publication Date: 19 April 2012

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Semipolar {nmath01} InGaN/GaN quantum wells (QWs) (n = 1−3) are fabricated on top of GaN microstructures, which consist of semipolar {1math01} facets. Semipolar planes are obtained via regrowth of three-dimensional structures on (0001) GaN templates under controlled growth conditions. Compared to QWs on {1math01} facets, {nmath01} ridge QWs show an intense emission at ∼ 440 nm. Time resolved photoluminescence reveals that the radiative lifetime of excitons in {nmath01} InGaN ridge QWs at 13 K is 310 ps, which is comparable to that in {1math01} QWs. The estimated internal quantum efficiency at room temperature is as high as 57%.
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81.07.St Quantum wells
78.47.jd Time resolved luminescence
71.35.-y Excitons and related phenomena
73.21.Fg Quantum wells
78.55.Cr III-V semiconductors
78.67.De Quantum wells

Improvement in the device performance of tin-doped indium oxide transistor by oxygen high pressure annealing at 150 °C

Se Yeob Park, Kwang Hwan Ji, Hong Yoon Jung, Ji-In Kim, Rino Choi, Kyoung Seok Son, Myung Kwan Ryu, Sangyoon Lee, and Jae Kyeong Jeong

Appl. Phys. Lett. 100, 162108 (2012); http://dx.doi.org/10.1063/1.4704926 (4 pages) | Cited 4 times

Online Publication Date: 19 April 2012

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This study examined the effect of oxygen (O2) high pressure annealing (HPA) on tin-doped indium oxide (ITO) thin film transistors (TFTs). The HPA-treated TFT at 150 °C exhibited a high saturation mobility (μSAT), low subthreshold gate swing (SS), threshold voltage, and Ion/off of 25.8 cm2/Vs, 0.14 V/decade, 0.6 V, and 2 × 108, respectively. In contrast, the ambient-annealed device suffered from a lower μSAT and high SS value of 5.2 cm2/Vs and 0.58 V/decade, respectively. This improvement can be attributed to the decreased concentration of oxygen vacancy defects in the ITO channel layer during the effective O2 HPA treatment, which also resulted in smaller hysteresis and less degradation of the drain current under positive bias stress conditions.
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85.30.Tv Field effect devices

Spatially modulated photoluminescence properties in dynamically strained GaAs/AlAs quantum wells by surface acoustic wave

Tetsuomi Sogawa, Haruki Sanada, Hideki Gotoh, Hiroshi Yamaguchi, and Paulo V. Santos

Appl. Phys. Lett. 100, 162109 (2012); http://dx.doi.org/10.1063/1.3703309 (4 pages) | Cited 3 times

Online Publication Date: 20 April 2012

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Spatially resolved photoluminescence (PL) spectra and polarization anisotropy were investigated in GaAs/AlAs dynamic wires, which were formed by applying a surface acoustic wave (SAW) on GaAs/AlAs quantum wells along the [110] or [1-10] direction. A synchronized excitation method clearly demonstrates that the band gap energies are spatially modulated by the travelling-SAW-induced strain. It is found that both the spatial PL modulation and anisotropic polarization properties depend on the SAW direction. The spatial modulation of the polarization anisotropies and their dependence on the strain-induced valence band mixing are also discussed theoretically.
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78.55.Cr III-V semiconductors
78.67.De Quantum wells
68.65.Fg Quantum wells

Structural and electrical properties of epitaxial Bi2Se3 thin films grown by hybrid physical-chemical vapor deposition

Joseph E. Brom, Yue Ke, Renzhong Du, Dongjin Won, Xiaojun Weng, Kalissa Andre, Jarod C. Gagnon, Suzanne E. Mohney, Qi Li, Ke Chen, X. X. Xi, and Joan M. Redwing

Appl. Phys. Lett. 100, 162110 (2012); http://dx.doi.org/10.1063/1.4704680 (4 pages) | Cited 1 time

Online Publication Date: 20 April 2012

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We report the epitaxial growth of Bi2Se3 thin films on (0001) Al2O3 substrates by hybrid physical-chemical vapor deposition (HPCVD). The HPCVD technique combines the thermal decomposition of trimethylbismuth with the thermal evaporation of Se and leads to a high Se partial pressure in the growth ambient. The Bi2Se3 films are highly c-axis oriented on sapphire but contain planar defects including stacking faults and twin boundaries. Variable-temperature Hall-effect measurements demonstrate a carrier concentration of 5.8 × 1018 cm−3 and a mobility of 900 cm2/Vs at 4.2 K. These results demonstrate the potential of HPCVD for producing high quality Bi2Se3 films for topological insulator studies.
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68.55.ag Semiconductors
61.72.Nn Stacking faults and other planar or extended defects
72.20.My Galvanomagnetic and other magnetotransport effects
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
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Stability of spinmotive force in perpendicularly magnetized nanowires under high magnetic fields

Y. Yamane, J. Ieda, and S. Maekawa

Appl. Phys. Lett. 100, 162401 (2012); http://dx.doi.org/10.1063/1.4703933 (3 pages) | Cited 1 time

Online Publication Date: 16 April 2012

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Spinmotive force induced by domain wall motion in perpendicularly magnetized nanowires is numerically demonstrated. We show that using nanowires with large magnetic anisotropy can lead to a high stability of spinmotive force under strong magnetic fields. We observe spinmotive force in the order of tens of μV in a multilayered Co/Ni nanowire and several hundreds of μV in a L10-ordered FePt nanowire; the latter is two orders of magnitude greater than that in permalloy nanowires reported previously. The narrow structure and low mobility of a domain wall under magnetic fields in perpendicularly magnetized nanowires permits downsizing of spinmotive force devices.
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75.75.Fk Domain structures in nanoparticles
75.78.Fg Dynamics of domain structures
75.60.Ch Domain walls and domain structure
75.30.Gw Magnetic anisotropy
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
72.25.Ba Spin polarized transport in metals

Co/Au multilayers with graded magnetic anisotropy for magnetic field sensing

M. Matczak, P. Kuświk, B. Szymański, M. Urbaniak, M. Schmidt, J. Aleksiejew, F. Stobiecki, and A. Ehresmann

Appl. Phys. Lett. 100, 162402 (2012); http://dx.doi.org/10.1063/1.4704176 (3 pages) | Cited 2 times

Online Publication Date: 17 April 2012

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A concept of a magnetoresistive sensor for magnetic fields based on a Au/Co-wedge/Au/Co/Au multilayer is proposed. The wedged Co layer is characterized by a laterally changing coercivity resulting from a gradient of perpendicular magnetic anisotropy. Its magnetization reversal in a perpendicular magnetic field takes place by movement of a single domain wall in the direction parallel to the anisotropy gradient. The magnetization reversal of the multilayer has been investigated by magnetooptical and magnetoresistive measurements. The resistance of the proposed film system correlates well with the position of the domain wall and thus it can be used to sense magnetic fields.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.70.Kw Domain structure (including magnetic bubbles and vortices)
75.30.Gw Magnetic anisotropy
75.50.Vv High coercivity materials
72.15.Gd Galvanomagnetic and other magnetotransport effects
07.55.Ge Magnetometers for magnetic field measurements

Magnetoresistance and its relation to magnetization in Ni50Mn35Sn15 shape-memory epitaxial films

J. Dubowik, K. Załȩski, I. Gościańska, H. Głowiński, and A. Ehresmann

Appl. Phys. Lett. 100, 162403 (2012); http://dx.doi.org/10.1063/1.4704562 (4 pages)

Online Publication Date: 17 April 2012

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The magnetoresistance (MR) of Heusler alloy Ni50Mn35Sn15 epitaxial films on MgO substrates is studied as a function of temperature T and magnetic field H. The large negative MR extends over martensitic transformation with maximum of −22% at 110 K. In martensitic and austenitic phase, the MR is −3% and −5%, respectively. We show that the MR is governed mainly by magnetization paraprocess at high magnetic fields and scales as the square of magnetization Δm(H,T)2.
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72.15.Gd Galvanomagnetic and other magnetotransport effects
75.30.Sg Magnetocaloric effect, magnetic cooling
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.70.Ak Magnetic properties of monolayers and thin films
81.30.Kf Martensitic transformations
64.70.kd Metals and alloys

Reliable nucleation of isolated magnetic antivortices

Matthias Pues, Michael Martens, Thomas Kamionka, and Guido Meier

Appl. Phys. Lett. 100, 162404 (2012); http://dx.doi.org/10.1063/1.3698150 (3 pages) | Cited 1 time

Online Publication Date: 18 April 2012

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Individual magnetic antivortices are reliably generated in φ-shaped microstructures using a specific remagnetization sequence of in-plane fields. The process of antivortex creation is understood by means of micromagnetic simulations and is experimentally demonstrated by magnetic force microscopy on multiple microstructures. The probability of antivortex nucleation is optimized by the variation of the structure geometry and the nucleation field strength. The presented method opens the path to radio frequency absorption measurements which rely on the resonant excitation of an ensemble of antivortices.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.78.Cd Micromagnetic simulations
68.37.Rt Magnetic force microscopy (MFM)

NO-assisted molecular-beam epitaxial growth of nitrogen substituted EuO

R. Wicks, S. G. Altendorf, C. Caspers, H. Kierspel, R. Sutarto, L. H. Tjeng, and A. Damascelli

Appl. Phys. Lett. 100, 162405 (2012); http://dx.doi.org/10.1063/1.3701589 (4 pages)

Online Publication Date: 18 April 2012

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We have investigated a method for substituting oxygen with nitrogen in EuO thin films, which is based on molecular beam epitaxy distillation with NO gas as the oxidizer. By varying the NO gas pressure, we produce crystalline, epitaxial EuO1-xNx films with good control over the films’ nitrogen concentration. In situ x-ray photoemission spectroscopy reveals that nitrogen substitution is connected to the formation Eu3+4f6 and a corresponding decrease in the number of Eu2+4f7, indicating that nitrogen is being incorporated in its 3− oxidation state. While small amounts of Eu3+ in over-oxidized Eu1-δO thin films lead to a drastic suppression of the ferromagnetism, the formation of Eu3+ in EuO1-xNx still allows the ferromagnetic phase to exist with an unaffected Tc, thus providing an ideal model system to study the interplay between the magnetic f7 (J = 7/2) and the non-magnetic f6 (J = 0) states close to the Fermi level.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.ag Semiconductors
75.50.Dd Nonmetallic ferromagnetic materials
75.50.Pp Magnetic semiconductors
75.70.Ak Magnetic properties of monolayers and thin films
79.60.Bm Clean metal, semiconductor, and insulator surfaces

Spin-torque nano-emitters for magnonic applications

H. Ulrichs, V. E. Demidov, S. O. Demokritov, and S. Urazhdin

Appl. Phys. Lett. 100, 162406 (2012); http://dx.doi.org/10.1063/1.4704563 (4 pages) | Cited 2 times

Online Publication Date: 19 April 2012

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In the emerging field of magnonics, spin waves are utilized as a medium for high-speed transmission and processing of electrical signals on the nanometer scale. The implementation of high-performance magnonic devices requires efficient nano-scaled sources of spin waves. Here, we demonstrate experimentally that this goal can be accomplished by utilizing a modified design of spin-torque devices, in which the internal dipolar field is compensated in the active device area by a built-in micromagnet. We show experimentally that the proposed device geometry enables efficient emission of spin waves with a large propagation length for practical implementation of integrated magnonic circuits.
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85.70.Ay Magnetic device characterization, design, and modeling
84.40.-x Radiowave and microwave (including millimeter wave) technology

Collective spin waves in a bicomponent two-dimensional magnonic crystal

G. Gubbiotti, S. Tacchi, M. Madami, G. Carlotti, S. Jain, A. O. Adeyeye, and M. P. Kostylev

Appl. Phys. Lett. 100, 162407 (2012); http://dx.doi.org/10.1063/1.4704659 (5 pages) | Cited 4 times

Online Publication Date: 19 April 2012

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Spin waves propagating in a bicomponent magnonic crystal consisting of a two-dimensional array of alternated NiFe and Co nanodots have been investigated. The frequency dispersion of collective modes, measured by Brillouin light scattering, is compared with the band diagram obtained by numerically solving the eigenvalue problem derived from the linearized Landau-Lifshitz magnetic torque equation. It is shown that the modes which are active in Brillouin experiment are characterized by the simplest modal profiles within the NiFe dots. For such excitations, the Co dots act as mediators of dipole coupling between the NiFe dots.
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75.30.Ds Spin waves
75.50.Tt Fine-particle systems; nanocrystalline materials
78.35.+c Brillouin and Rayleigh scattering; other light scattering
75.75.-c Magnetic properties of nanostructures

Lateral spin transport through bulk silicon

Jing Li and Ian Appelbaum

Appl. Phys. Lett. 100, 162408 (2012); http://dx.doi.org/10.1063/1.4704802 (3 pages) | Cited 2 times

Online Publication Date: 19 April 2012

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Using ballistic hot electron techniques, we demonstrate lateral spin transport through a bulk Si wafer. Despite a wide spin transport time distribution caused by transport path variation in the 400 μm-thick Si channel, the absence of a buried interface in close proximity increases the observed spin lifetime to approximately 100 ns at 61 K. The relative insensitivity of this lifetime to temperature variation (and its absolute magnitude) indicates a contribution from an extrinsic depolarization mechanism such as disorder and defects at the exposed air/Si interface in the transport region between injector and detector.
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72.25.Dc Spin polarized transport in semiconductors
72.80.Cw Elemental semiconductors
73.23.Ad Ballistic transport

Spin-dependent tunneling transport in a ferromagnetic GaMnAs and un-doped GaAs double-quantum-well heterostructure

Iriya Muneta, Shinobu Ohya, and Masaaki Tanaka

Appl. Phys. Lett. 100, 162409 (2012); http://dx.doi.org/10.1063/1.4704154 (3 pages)

Online Publication Date: 20 April 2012

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We investigate the spin-dependent tunneling transport in a ferromagnetic GaMnAs and un-doped GaAs double-quantum-well heterostructure. Clear tunneling magnetoresistance (TMR) and negative differential resistance due to the strong resonant tunneling in the GaAs quantum well (QW) are demonstrated in this device. We show that TMR oscillates as a function of the bias voltage following the dI/dV-V characteristics, and TMR becomes negative at biases where resonant tunneling occurs. These results can be explained by the difference of the potential drops in the magnetic tunnel junction composed of the top GaMnAs/AlAs/GaMnAs-QW between parallel and anti-parallel magnetization.
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73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
72.20.My Galvanomagnetic and other magnetotransport effects
75.47.Pq Other materials
75.50.Dd Nonmetallic ferromagnetic materials
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FeNi-based magnetoimpedance multilayers: Tailoring of the softness by magnetic spacers

A. V. Svalov, E. Fernandez, A. Garcia-Arribas, J. Alonso, M. L. Fdez-Gubieda, and G. V. Kurlyandskaya

Appl. Phys. Lett. 100, 162410 (2012); http://dx.doi.org/10.1063/1.4704984 (4 pages) | Cited 3 times

Online Publication Date: 20 April 2012

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The microstructure and magnetic properties of sputtered permalloy films and FeNi(170 nm)/X/FeNi(170 nm) (X = Co, Fe, Gd, Gd-Co) sandwiches were studied. Laminating of the thick FeNi film with various spacers was done in order to control the magnetic softness of FeNi-based multilayers. In contrast to the Co and Fe spacers, Gd and Gd-Co magnetic spacers improved the softness of the FeNi/X/FeNi sandwiches. The magnetoimpedance responses were measured for [FeNi/Ti(6 nm)]2/FeNi and [FeNi/Gd(2 nm)]2/FeNi multilayers in a frequency range of 1–500 MHz: for all frequencies under consideration the highest magnetoimpedance variation was observed for [FeNi/Gd(2 nm)]2/FeNi multilayers.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
68.55.-a Thin film structure and morphology
75.70.Ak Magnetic properties of monolayers and thin films
61.72.-y Defects and impurities in crystals; microstructure
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Microwave-induced excess quasiparticles in superconducting resonators measured through correlated conductivity fluctuations

P. J. de Visser, J. J. A. Baselmans, S. J. C. Yates, P. Diener, A. Endo, and T. M. Klapwijk

Appl. Phys. Lett. 100, 162601 (2012); http://dx.doi.org/10.1063/1.4704151 (4 pages) | Cited 3 times

Online Publication Date: 19 April 2012

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We have measured the number of quasiparticles and their lifetime in aluminium superconducting microwave resonators. The number of excess quasiparticles below 160 mK decreases from 72 to 17 μm−3 with a 6 dB decrease of the microwave power. The quasiparticle lifetime increases accordingly from 1.4 to 3.5 ms. These properties of the superconductor were measured through the spectrum of correlated fluctuations in the quasiparticle system and condensate of the superconductor, which show up in the resonator amplitude and phase, respectively. Because uncorrelated noise sources vanish, fluctuations in the superconductor can be studied with a sensitivity close to the vacuum noise.
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85.25.-j Superconducting devices
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Vacancy-driven ferromagnetism in ferroelectric PbTiO3

Takahiro Shimada, Yoshitaka Uratani, and Takayuki Kitamura

Appl. Phys. Lett. 100, 162901 (2012); http://dx.doi.org/10.1063/1.4704362 (3 pages) | Cited 3 times

Online Publication Date: 16 April 2012

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The possible origin of ferromagnetism in PbTiO3 containing vacancies is investigated by performing first-principles calculations. We demonstrate that O and Ti vacancies both induce ferromagnetism but by different mechanisms: the ferromagnetism driven by the O vacancy originates from the spin-polarized eg state of the nearest Ti atom, whereas that driven by the Ti vacancy is due to the half-metallic px state of the nearest O atom. The results presented here provide fundamental insights into the design of multiferroics in conventional ferroelectrics.
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75.50.-y Studies of specific magnetic materials
75.85.+t Magnetoelectric effects, multiferroics
61.72.jd Vacancies
75.50.Dd Nonmetallic ferromagnetic materials
77.80.-e Ferroelectricity and antiferroelectricity
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Tunable thermal rectification in graphene nanoribbons through defect engineering: A molecular dynamics study

Yan Wang, Siyu Chen, and Xiulin Ruan

Appl. Phys. Lett. 100, 163101 (2012); http://dx.doi.org/10.1063/1.3703756 (3 pages) | Cited 3 times

Online Publication Date: 16 April 2012

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Using non-equilibrium molecular dynamics, we show that asymmetrically defected graphene nanoribbons (GNR) are promising thermal rectifiers. The optimum conditions for thermal rectification (TR) include low temperature, high temperature bias, ∼1% concentration of single-vacancy or substitutional silicon defects, and a moderate partition of the pristine and defected regions. TR ratio of ∼80% is found in a 14-nm long and 4-nm wide GNR at a temperature of 200 K and bias of 90 K, where heat conduction is in the ballistic regime since the bulk effective phonon mean-free-path is around 775 nm. As the GNR length increases towards the diffusive regime, the TR ratio decreases and eventually stabilizes at a length-independent value of about 3%–5%. This work extends defect engineering to 2D materials for achieving TR.
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66.70.Lm Other systems such as ionic crystals, molecular crystals, nanotubes, etc.
66.30.Lw Diffusion of other defects
61.72.jd Vacancies
61.48.Gh Structure of graphene
63.22.Rc Phonons in graphene

Chiral tunneling in trilayer graphene

S. Bala Kumar and Jing Guo

Appl. Phys. Lett. 100, 163102 (2012); http://dx.doi.org/10.1063/1.3703758 (4 pages) | Cited 7 times

Online Publication Date: 16 April 2012

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We study the effect of chiral-tunneling in Bernal and rhombohedral stacked trilayer-graphene (3LG). Based on the chirality of the electronic bands, at the K-point, (rhombohedral) Bernal-3LG exhibits 100% (50%) transparency across a heterojunction. Utilizing this property, we further investigate the effect of electron collimation in 3LG. Due to the difference in the Berry’s phase, we show that, rhombohedral-3LG is a better electron collimator, compared to monolayer and Bernal-bilayer graphene. Since, Bernal-3LG can be decomposed into two separate channels consisting of a monolayer and a modified Bernal-bilayer graphene; the Bernal-3LG is weaker electron collimator, compared to rhombohedral-3LG.
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73.40.Gk Tunneling
73.22.Pr Electronic structure of graphene
73.63.-b Electronic transport in nanoscale materials and structures
71.15.Ap Basis sets (LCAO, plane-wave, APW, etc.) and related methodology (scattering methods, ASA, linearized methods, etc.)

A core/shell mechanism for stacking-fault generation in GaAs nanowires

Zaoshi Yuan, Ken-ichi Nomura, and Aiichiro Nakano

Appl. Phys. Lett. 100, 163103 (2012); http://dx.doi.org/10.1063/1.3703765 (3 pages)

Online Publication Date: 16 April 2012

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Generation of stacking faults (SFs) during the growth of nanowires (NWs) is a major concern for the efficiency of NW-based devices such as solar cells. Here, molecular-dynamics simulation of a [111]-oriented gallium arsenide NW reveals an atomistic mechanism of SF generation. Spatial distribution of the adatom energy on the (111)B top surface exhibits a core/shell structure due to the contraction of atomic bonds at the sidewall surfaces, where SFs are preferentially nucleated in the shell. A nucleation growth model incorporating the core/shell mechanism suggests a size and growth-condition controlled approach for SF-free growth of NWs.
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81.07.Gf Nanowires
61.72.Nn Stacking faults and other planar or extended defects
81.05.Ea III-V semiconductors
81.16.-c Methods of micro- and nanofabrication and processing
68.65.La Quantum wires (patterned in quantum wells)
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)

Imaging of subatomic electron cloud interactions: Effect of higher harmonics processing in noncontact atomic force microscopy

C. Alan Wright and Santiago D. Solares

Appl. Phys. Lett. 100, 163104 (2012); http://dx.doi.org/10.1063/1.3703767 (4 pages) | Cited 1 time

Online Publication Date: 16 April 2012

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In a previous study of higher harmonics atomic force microscopy imaging of graphite using a tungsten tip [Hembacher et al., Science 305, 380 (2004)], the authors interpreted the observed subatomic features as the signature of tip apex electron bonding lobes. We explore here their higher harmonics processing and filtering methods. We do not find any imaging artifacts inherent to the filtering process, but we find that the harmonics averaging approach used is not appropriate due to non-uniform harmonics ratios across the surface. A promising alternative may be the individual mapping of the first two harmonics.
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07.79.Lh Atomic force microscopes
68.37.Ps Atomic force microscopy (AFM)

Electrothermal phenomena in zinc oxide nanowires and contacts

Saniya LeBlanc, Sujay Phadke, Takashi Kodama, Alberto Salleo, and Kenneth E. Goodson

Appl. Phys. Lett. 100, 163105 (2012); http://dx.doi.org/10.1063/1.4703935 (5 pages) | Cited 1 time

Online Publication Date: 16 April 2012

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Heat generation along nanowires and near their electrical contacts influences the feasibility of energy conversion devices. This work presents ZnO nanowire electrical resistivity data and models electrothermal transport accounting for heat generation at metal-semiconductor contacts, axial thermal conduction, and substrate heat losses. The current-voltage relationships and electron microscopy indicate that sample degradation is caused by the interplay of heat generation at contacts and within the nanowire volume. The model is used to interpret literature data for Si, GaN, and ZnO nanowires. This work assists with electrothermal nanowire measurements and highlights practical implications of utilizing solution-synthesized nanowires.
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73.40.Ns Metal-nonmetal contacts
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)

Growth of triangle-shape graphene on Cu(111) surface

Xiu Chen, Shuyi Liu, Lacheng Liu, Xiaoqing Liu, Xiaoming Liu, and Li Wang

Appl. Phys. Lett. 100, 163106 (2012); http://dx.doi.org/10.1063/1.4704149 (3 pages) | Cited 4 times

Online Publication Date: 17 April 2012

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Triangle-shape graphene has been grown on Cu(111) surface by thermal decomposition of 1,1′-ferrocenedicarboxylic acid molecules in an ultrahigh vacuum chamber. The observations of Moiré patterns and honeycomb structure unambiguously reveal that such triangle-shape graphene is a single-crystalline one-layer domain with zigzag edge structure. Graphene islands can extend up to 17 nm until the growth process is hindered by the edges of the atomic terraces.
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81.05.ue Graphene
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
61.48.Gh Structure of graphene

Visualization of hybridization states with atomic resolution using electron energy loss spectroscopy mapping

M. Haruta, K. Kurashima, T. Nagai, H. Komatsu, Y. Shimakawa, H. Kurata, and K. Kimoto

Appl. Phys. Lett. 100, 163107 (2012); http://dx.doi.org/10.1063/1.4704558 (4 pages) | Cited 2 times

Online Publication Date: 17 April 2012

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Show Abstract
Hybridization state mapping with atomic resolution was demonstrated using electron energy loss spectroscopy combined with scanning transmission electron microscopy. The O 2p states hybridized with Sn 5s and Cu 3d in a layered double perovskite La2CuSnO6 were individually distinguished by significant contrast differences in the oxygen K-edge energy-loss near-edge structure. The anisotropic oxygen intensity in the distorted CuO6 octahedron resulting from the Jahn-Teller effect could also be observed. The localized Cu 3d hole in the bc plane was indirectly imaged in real space using two-dimensional oxygen mapping.
Show PACS
79.20.Uv Electron energy loss spectroscopy
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Lp Transmission electron microscopy (TEM)
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
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