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19 Mar 2012

Volume 100, Issue 12, Articles (12xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 100, 121101 (2012); http://dx.doi.org/10.1063/1.3693413 (4 pages)

Jolly Xavier, Raktim Dasgupta, Sunita Ahlawat, Joby Joseph, and Pradeep Kumar Gupta
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Breakdown by magnetic field in a La0.7Sr0.3MnO3/MgO/Fe spin valve

Xiaojie Wu, Zhenzhong Zhang, and Jian Meng

Appl. Phys. Lett. 100, 122408 (2012); http://dx.doi.org/10.1063/1.3696670 (3 pages)

Online Publication Date: 22 March 2012

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A La0.7Sr0.3MnO3/MgO/Fe spin valve with inverse tunneling magnetoresistance (TMR) was fabricated on a (100) SrTiO3 substrate by radio frequency magnetron sputtering. Giant TMR ratios up to 540% were obtained. The breakdown of the spin valve was observed at high magnetic field, which was attributed to the joint action of the invalidation of MgO barrier and the shift of Fermi energy in La0.7Sr0.3MnO3 at high magnetic field.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.47.De Giant magnetoresistance
81.15.Cd Deposition by sputtering

Tailoring interfacial exchange coupling with low-energy ion beam bombardment: Tuning the interface roughness

K.-W. Lin, M. Mirza, C. Shueh, H.-R. Huang, H.-F. Hsu, and J. van Lierop

Appl. Phys. Lett. 100, 122409 (2012); http://dx.doi.org/10.1063/1.3697405 (4 pages) | Cited 7 times

Online Publication Date: 22 March 2012

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By ascertaining NiO surface roughness in a Ni80Fe20/NiO film system, we were able to correlate the effects of altered interface roughness from low-energy ion-beam bombardment of the NiO layer and the different thermal instabilities in the NiO nanocrystallites. From experiment and by modelling the temperature dependence of the exchange bias field and coercivity, we have found that reducing the interface roughness and changing the interface texture from an irregular to striped conformation enhanced the exchange coupling strength. Our results were in good agreement with recent simulations using the domain state model that incorporated interface mixing.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.50.Tt Fine-particle systems; nanocrystalline materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Et Exchange and superexchange interactions
61.80.Jh Ion radiation effects
68.35.Ct Interface structure and roughness

Manipulation of magnetic anisotropy of Fe/graphene by charge injection

S. J. Gong, Chun-Gang Duan, Zi-Qiang Zhu, and Jun-Hao Chu

Appl. Phys. Lett. 100, 122410 (2012); http://dx.doi.org/10.1063/1.3697627 (3 pages) | Cited 2 times

Online Publication Date: 23 March 2012

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We propose that charge injection can be used to tune the magnetic anisotropy of transition metal monolayer adsorbed on graphene substrate. Using relativistic density-functional calculations, we calculate magnetocrystalline anisotropy energy (MAE) of freestanding Fe monolayer and Fe/graphene complex system. We find MAE of Fe atom is drastically changed, from meV/atom in freestanding Fe monolayer to μeV/atom in Fe/graphene system. The more interesting finding is, through charge injection, the suppressed MAE of Fe atoms in Fe/graphene system can be restored back, which provides an effective approach to control MAE. We expect such strategy would be beneficial to graphene based spintronic devices.
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75.30.Gw Magnetic anisotropy
68.43.Mn Adsorption kinetics
68.43.-h Chemisorption/physisorption: adsorbates on surfaces
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
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Multiple Andreev reflection in MgB2/MgO/MgB2 Josephson junctions

Ke Chen, Daniel Cunnane, Yi Shen, X. X. Xi, Alan W. Kleinsasser, and John M. Rowell

Appl. Phys. Lett. 100, 122601 (2012); http://dx.doi.org/10.1063/1.3695159 (4 pages)

Online Publication Date: 19 March 2012

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The current-voltage and conductance-voltage characteristics of MgB2/MgO/MgB2 junctions made with MgB2 electrodes grown by hybrid physical-chemical vapor deposition were systematically analyzed. In the junctions with different sizes and critical current densities, we found excess current and subharmonic gap structure indicative of multiple Andreev reflection. An apparent link between multiple Andreev reflection and substantial Josephson current at high temperatures suggests that the barrier is dominated by high-transparency channels.
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74.50.+r Tunneling phenomena; Josephson effects
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
74.25.F- Transport properties
74.25.Sv Critical currents

The influence of the buffer layer architecture on transport properties for BaFe1.8Co0.2As2 films on technical substrates

S. Trommler, R. Hühne, J. Hänisch, E. Reich, K. Iida, S. Haindl, V. Matias, L. Schultz, and B. Holzapfel

Appl. Phys. Lett. 100, 122602 (2012); http://dx.doi.org/10.1063/1.3696888 (4 pages) | Cited 3 times

Online Publication Date: 21 March 2012

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A low and almost temperature independent resistance in the normal state and an anomalous peak effect within the normal-superconducting transition have been observed in BaFe1.8Co0.2As2/Fe bilayers, prepared on ion beam assisted deposition-MgO/Y2O3 buffered technical substrates. A resistor network array sufficiently reproduces this effect, assuming an increase of the electrical conductance between tape and film with decreasing buffer layer thickness. Based on this model, we evaluated the influence of this effect on the critical current density and successfully reconstructed the superconducting transition of the bilayer.
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74.25.fc Electric and thermal conductivity
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition
74.78.Fk Multilayers, superlattices, heterostructures
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Low magnetic field reversal of electric polarization in a Y-type hexaferrite

Fen Wang, Tao Zou, Li-Qin Yan, Yi Liu, and Young Sun

Appl. Phys. Lett. 100, 122901 (2012); http://dx.doi.org/10.1063/1.3697636 (5 pages) | Cited 1 time

Online Publication Date: 19 March 2012

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We report on the magnetically tunable ferroelectricity and giant magnetoelectric sensitivity up to 250 K in a Y-type hexaferrite, BaSrCoZnFe11AlO22. Not only the magnitude but also the sign of electric polarization can be effectively controlled by applying low magnetic fields (a few hundreds of Oe) that modifies the spiral magnetic structures. The magnetically induced ferroelectricity is stabilized even in zero magnetic field. Decayless reproducible flipping of electric polarization by oscillating low magnetic fields is shown. The maximum linear magnetoelectric coefficient reaches a high value of ∼3.0 × 103 ps/m at 200 K.
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77.22.Ej Polarization and depolarization
77.80.-e Ferroelectricity and antiferroelectricity
75.85.+t Magnetoelectric effects, multiferroics
75.50.Gg Ferrimagnetics

Electric field induced intermediate phase and polarization rotation path in alkaline niobate based piezoceramics close to the rhombohedral and tetragonal phase boundary

Jian Fu, Ruzhong Zuo, S. C. Wu, J. Z. Jiang, L. Li, T. Y. Yang, Xiaohui Wang, and Longtu Li

Appl. Phys. Lett. 100, 122902 (2012); http://dx.doi.org/10.1063/1.3696071 (5 pages) | Cited 3 times

Online Publication Date: 20 March 2012

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High resolution synchrotron x-ray and dielectric measurements on unpoled and poled (Na,K)(Nb,Sb)O3-LiTaO3-xBaZrO3 lead-free ceramics close to the rhombohedral-tetragonal (R-T) phase boundary have suggested an additional lattice distortion induced by poling field. This intermediate phase (IP) is consistent with the orthorhombic (O) symmetry but lower symmetries cannot be discarded. As a result, a modified polarization rotation path along R-IP-T in poled ceramics would be responsible for their high piezoelectric activity owing to the effect of the IP bridging the R and T phases. Simultaneously, the electric field induced phase transition would probably contribute to the observed large piezoelectric strains.
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77.22.Ej Polarization and depolarization
77.65.Ly Strain-induced piezoelectric fields
77.22.Ch Permittivity (dielectric function)

Direct observation of ferroelectric polarization-modulated band bending at oxide interfaces

B. C. Huang, Y. T. Chen, Y. P. Chiu, Y. C. Huang, J. C. Yang, Y. C. Chen, and Y. H. Chu

Appl. Phys. Lett. 100, 122903 (2012); http://dx.doi.org/10.1063/1.3691615 (4 pages) | Cited 2 times

Online Publication Date: 20 March 2012

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This study presents a direct visualization of the influences of ferroelectric polarization on the electronic properties of the Schottky contact at the Nb-SrTiO3/BiFeO3 hetero-interface using scanning tunneling microscopy and spectroscopy (STM/S). The evolution of the local density of states across the Nb-SrTiO3/BiFeO3 interface reveals the interfacial band alignment and the characteristic quantities of the metal/ferroelectric contact. The unique combination of STM and STS in this study delivers an approach to obtain critical information on the interfacial electronic configurations of ferroelectric oxide interfaces and also their variation with ferroelectric polarization switching.
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77.84.-s Dielectric, piezoelectric, ferroelectric, and antiferroelectric materials
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
73.30.+y Surface double layers, Schottky barriers, and work functions
77.80.-e Ferroelectricity and antiferroelectricity

Microwave dielectric dispersion in a multiferroic Pb(Fe1/2Nb1/2)O3 thin film

R. Sobiestianskas, W. Peng, N. Lemée, M. Karkut, J. Banys, J. Holc, and M. Kosec

Appl. Phys. Lett. 100, 122904 (2012); http://dx.doi.org/10.1063/1.3696043 (4 pages) | Cited 1 time

Online Publication Date: 21 March 2012

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We present the dielectric dispersion in a Pb(Fe1/2Nb1/2)O3 (PFN) thin film grown on (001) SrTiO3 substrate from 20 MHz to 20 GHz in the temperature range of 270 to 340 K. In the radio frequency region, the hopping charge transport and associated polar nanoregion and/or domain-wall motion contribute to the spectrum. In the microwave region, relaxational dispersion was observed with a dielectric contribution of Δε ≈ 600 at room temperature having a characteristic frequency (fm)0.4 = 9.8 · (T−T0) Hz, where T0 is 660 K. It is associated with possible mode-softening behavior, related to the onset of polar nanoregions at T0. The dielectric permittivity shows similarities with 1-dimensional Ising model behaviour.
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77.22.Ch Permittivity (dielectric function)
77.22.Gm Dielectric loss and relaxation
77.55.fj Niobate- and tantalate-based films
77.55.Nv Multiferroic/magnetoelectric films
77.84.Ek Niobates and tantalates
77.80.Dj Domain structure; hysteresis

Mapping of the epitaxial stabilization of quasi-tetragonal BiFeO3 with deposition temperature

N. Dix, R. Muralidharan, M. Varela, J. Fontcuberta, and F. Sánchez

Appl. Phys. Lett. 100, 122905 (2012); http://dx.doi.org/10.1063/1.3696048 (4 pages) | Cited 1 time

Online Publication Date: 22 March 2012

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Quasi-tetragonal BiFeO3 (T-BFO) multiferroic oxide is receiving much attention due to prospects of enhanced ferroelectric polarization and close-to-room-temperature phase transitions. Here, we report on the role of deposition temperature on the stabilization of the T-BFO phase on LaAlO3(001) substrates. T-BFO has only been obtained in a narrow temperature window. We will show that competitive formation of rhombohedral BFO and thermal decomposition at lower and higher temperatures, respectively, bounds the stability range of T-BFO. However, we show that addition of a secondary spinel phase, creating vertical interfaces, extends the formation range of T-BFO.
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81.15.Fg Pulsed laser ablation deposition
81.15.Kk Vapor phase epitaxy; growth from vapor phase
77.80.bg Compositional effects
77.22.Ej Polarization and depolarization
77.55.fp Other ferroelectric films
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.

Spectroscopic evaluation of band alignment of atomic layer deposited BeO on Si(100)

Ming Lei, J. H. Yum, J. Price, Todd W. Hudnall, C. W. Bielawski, S. K. Banerjee, P. S. Lysaght, G. Bersuker, and M. C. Downer

Appl. Phys. Lett. 100, 122906 (2012); http://dx.doi.org/10.1063/1.3697646 (4 pages) | Cited 2 times

Online Publication Date: 22 March 2012

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We report optical characterization of the conduction band offset (CBO) between atomic-layer-deposited single crystal BeO and Si using internal photoemission (IPE) and internal multi-photon photoemission (IMPE), and of the valence band offset (VBO) using synchrotron x-ray photoelectron spectroscopy. The IPE/IMPE measurements indicate a CBO of 2.31 ± 0.1 eV for 10 nm thick as-deposited oxides. For samples subjected to post-deposition anneal in N2 at 600 °C and 900 °C, it increases to 2.54 ± 0.1 eV and 2.61 ± 0.1 eV, respectively. The VBO is stable at 4.14 ± 0.2 eV for both as-deposited and annealed samples.
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78.66.Nk Insulators
79.60.Dp Adsorbed layers and thin films
71.20.Ps Other inorganic compounds
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.40.Gh Other heat and thermomechanical treatments
79.60.Bm Clean metal, semiconductor, and insulator surfaces

Band alignment of HfO2 on SiO2/Si structure

Xiaolei Wang, Kai Han, Wenwu Wang, Jinjuan Xiang, Hong Yang, Jing Zhang, Xueli Ma, Chao Zhao, Dapeng Chen, and Tianchun Ye

Appl. Phys. Lett. 100, 122907 (2012); http://dx.doi.org/10.1063/1.3694274 (4 pages)

Online Publication Date: 23 March 2012

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Band alignment of HfO2 with various thicknesses on SiO2/Si structure is investigated by x-ray photoelectron spectroscopy (XPS). Band bending of HfO2/SiO2/Si system is found to vary with HfO2 thickness. Band alignment of entire HfO2/SiO2/Si is demonstrated using concepts of interfacial or surface gap states and charge neutrality level (CNL). The XPS results are interpreted and attributed to lower CNL of HfO2 than SiO2/Si which induces electron transfer from SiO2/Si to HfO2, resulting in band bending upward for SiO2/Si. These further confirm feasibility of gap state based theory in investigating band alignments of oxide/semiconductor and oxide/oxide interfaces.
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73.20.At Surface states, band structure, electron density of states
79.60.Jv Interfaces; heterostructures; nanostructures
71.20.Ps Other inorganic compounds
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Reversible bistability of conductance on graphene/CuOx/Cu nanojunction

Sangku Kwon, Hyungtak Seo, Hyunsoo Lee, Ki-Joon Jeon, and Jeong Young Park

Appl. Phys. Lett. 100, 123101 (2012); http://dx.doi.org/10.1063/1.3694754 (4 pages) | Cited 3 times

Online Publication Date: 19 March 2012

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We report that a nanojunction composed of graphene, copper oxide, and Cu substrate exhibits resistive switching behavior, revealed with conductive probe atomic force microscopy at ultrahigh vacuum. The current-voltage curve measured between the titanium nitride-coated tip and the nanojunction exhibited reversible bistable resistance states. We propose that the switching behavior is controlled by the migration of oxygen ions in the copper oxide layer, leading to the reversible formation/disruption of a CuOx-associated charge tunneling barrier, which is consistent with glancing-angle x-ray photoelectron spectroscopy analysis.
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61.48.Gh Structure of graphene
73.40.Gk Tunneling
68.37.Ps Atomic force microscopy (AFM)

Construction of nanostructured electrodes on flexible substrates using pre-treated building blocks

Fuzhi Huang, Dehong Chen, Qi Li, Rachel A. Caruso, and Yi-Bing Cheng

Appl. Phys. Lett. 100, 123102 (2012); http://dx.doi.org/10.1063/1.3695080 (4 pages) | Cited 2 times

Online Publication Date: 19 March 2012

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A “building block” concept is introduced for the construction of electrodes for dye-sensitized solar cells (DSCs). The building blocks are prefabricated submicrometer- to micrometer-sized clusters, such as nanostructured mesoporous TiO2 spheres. This concept makes a number of approaches possible that are difficult to achieve through the conventional nanoparticle route for the preparation of flexible DSCs. Significantly, the building blocks can be physically and chemically pre-treated prior to electrode fabrication. Thus some of the intrinsic limitations of using plastic substrates can be overcome, such as applying heat treatment and TiCl4 treatment, affording a high power conversion efficiency of 7.5%.
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81.07.-b Nanoscale materials and structures: fabrication and characterization
81.40.Gh Other heat and thermomechanical treatments
88.40.jr Organic photovoltaics
81.05.Rm Porous materials; granular materials
61.46.-w Structure of nanoscale materials
61.43.Gt Powders, porous materials

Emission stability enhancement of a tip-type carbon-nanotube-based field emitter via hafnium interlayer deposition and thermal treatment

Jong-Pil Kim, Han-Beet Chang, Bu-Jong Kim, and Jin-Seok Park

Appl. Phys. Lett. 100, 123103 (2012); http://dx.doi.org/10.1063/1.3695173 (3 pages)

Online Publication Date: 20 March 2012

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Carbon nanotubes (CNTs) were deposited on a tip-type tungsten substrate via electrophoretic deposition, in which a hafnium thin film was used as an interlayer. The long-term (up to 24 h) emission stability of the CNT-based field emitter was remarkably enhanced when the hafnium interlayer was coated and thermally treated. This is attributed to the enhanced adhesion between the substrate and the CNTs. An x-ray photoelectron spectroscopy study and nano-scratch measurement provided a convincing evidence of the increase in the adhesive force.
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85.35.Kt Nanotube devices
81.15.Pq Electrodeposition, electroplating

Electrical characterization of back-gated bi-layer MoS2 field-effect transistors and the effect of ambient on their performances

Hao Qiu (邱浩), Lijia Pan (潘力佳), Zongni Yao (姚宗妮), Junjie Li (李俊杰), Yi Shi (施毅), and Xinran Wang (王欣然)

Appl. Phys. Lett. 100, 123104 (2012); http://dx.doi.org/10.1063/1.3696045 (3 pages) | Cited 16 times

Online Publication Date: 21 March 2012

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Two-dimensional transition-metal dichalcogenides such as MoS2 are promising channel materials for transistor scaling. Here, we report the performance and environmental effects on back-gated bi-layer MoS2 field-effect transistors. The devices exhibit Ohmic contacts with titanium at room temperature, on/off ratio higher than 107, and current saturation. Furthermore, we show that the devices are sensitive to oxygen and water in the ambient. Exposure to ambient dramatically reduces the on-state current by up to 2 orders of magnitude likely due to additional scattering centers from chemisorption on the defect sites of MoS2. We demonstrate that vacuum annealing can effectively remove the absorbates and reversibly recover the device performances. This method significantly reduces the large variations in MoS2 device caused by extrinsic factors.
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85.30.Tv Field effect devices
84.32.Dd Connectors, relays, and switches
61.72.Cc Kinetics of defect formation and annealing

Enhanced atomic corrugation in dynamic force microscopy—The role of repulsive forces

L. Lichtenstein, C. Büchner, S. Stuckenholz, M. Heyde, and H.-J. Freund

Appl. Phys. Lett. 100, 123105 (2012); http://dx.doi.org/10.1063/1.3696039 (3 pages) | Cited 2 times

Online Publication Date: 22 March 2012

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Full range two dimensional (2D) force mapping was performed by means of low temperature dynamic force microscopy (DFM) on a highly complex surface structure. For this purpose, we used a thin film of vitreous silica on a Ru(0001)-support, which is a 2D structural equivalent to silica glass. The 2D spectroscopy shows that the contrast generating shift in vertical distance between two sites on the surface is twice as large on the repulsive branch of the frequency shift-distance curve as compared to the attractive branch. The results give insight into the origin of the formation of atomic resolution in DFM.
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68.35.bj Amorphous semiconductors, glasses
61.43.Fs Glasses
68.55.aj Insulators
68.37.Ps Atomic force microscopy (AFM)

Fabrication of submicron devices on the (011) cleave surface of a cleaved-edge-overgrowth GaAs/AlGaAs crystal

A. M. Chang, Hao Zhang, L. N. Pfeiffer, and K. W. West

Appl. Phys. Lett. 100, 123106 (2012); http://dx.doi.org/10.1063/1.3694052 (4 pages)

Online Publication Date: 22 March 2012

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We describe the fabrication of submicron devices on the (011) cleave surface of a GaAs heterostructure crystal, in which this surface is extremely narrow. Special purpose devices are produced, which take advantage of the unique characteristics of cleaved-edge-overgrowth. The successful fabrication relies on understanding the surface tension of the electron beam polymethyl methacrylate resist, the workable degree of variation in resist thickness, and on gluing the crystal onto a backing substrate to increase structural strength. We demonstrate functional gate-controlled quantum point contact constrictions placed 9 μm from one edge of the cleave surface.
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85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Effect of bending stress on structures and quantum conduction of Cu nanowires

C. He, W. X. Zhang, Z. Q. Shi, J. P. Wang, and H. Pan

Appl. Phys. Lett. 100, 123107 (2012); http://dx.doi.org/10.1063/1.3696052 (3 pages)

Online Publication Date: 23 March 2012

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The ballistic transport properties of Cu nanowires under different bending stresses are investigated for future application in flexible displays and flexible solar cell using first-principles density-function theory. The stability and quantum conduction of both nonhelical and helical atomic strands are reduced by applying a bending stress f. With increasing of f, the helical wire becomes disorder, suffering a phase transition to similar nonhelical one and collapsing eventually. Our calculations show that the maximum bearable bending stress is fmax = 3 nN for the helical atomic strands while is more stable than fmax = 2.5 nN for the nonhelical atomic strands.
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73.23.Ad Ballistic transport
72.20.Ht High-field and nonlinear effects
73.63.Nm Quantum wires
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity

Ultrahigh efficient single-crystalline TiO2 nanorod photoconductors

R. S. Chen, C. A. Chen, H. Y. Tsai, W. C. Wang, and Y. S. Huang

Appl. Phys. Lett. 100, 123108 (2012); http://dx.doi.org/10.1063/1.3694926 (4 pages) | Cited 5 times

Online Publication Date: 23 March 2012

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Photoconductive gain and normalized gain, which determine the device and material properties on photoconduction, respectively, have been defined for single-crystalline titanium dioxide (TiO2) nanorods (NRs) with various diameter sizes. The gain values of the NR photodetectors can reach 105 easily at a low bias of 0.1 V. By excluding the contributions of experimental parameters, the optimal normalized gain of the indirect-bandgap TiO2 NRs at 5.4 × 10−5 m2V−1 is comparable with that estimated from the direct-bandgap ZnO nanowires. The average normalized gain value at 3.3 ± 2.2 × 10−5 m2V−1 obtained from eight individual TiO2 NRs with diameters ranging from 120 to 1250 nm is also over three orders of magnitude higher than the polycrystalline nanotube counterpart. The results demonstrate the superior photoconductivity efficiency in boundary-free titania one-dimensional nanostructure, which is crucial for ultraviolet photodetector, dye-sensitized solar cell, and photochemical device applications.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
72.40.+w Photoconduction and photovoltaic effects
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Anisotropic charge transport and contact resistance of 6,13-bis(triisopropylsilylethynyl) pentacene field-effect transistors fabricated by a modified flow-coating method

Kenji Sakamoto, Junichi Ueno, Kirill Bulgarevich, and Kazushi Miki

Appl. Phys. Lett. 100, 123301 (2012); http://dx.doi.org/10.1063/1.3695169 (4 pages) | Cited 1 time

Online Publication Date: 19 March 2012

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Using a modified flow-coating method, bottom-gate/bottom-contact type organic field-effect transistors (OFETs) with a highly oriented active layer of 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-pentacene) were fabricated. The flow-coated TIPS-pentacene films were fairly uniform and consisted of arrays of needle-shaped crystals along the flow-coating direction. The uniformity allowed us to determine the contact resistance by a transfer line method. The usefulness of the modified flow-coating method for fabricating high performance OFETs has been demonstrated, and we found that not only the field-effect mobility but also the contact resistance significantly depends on the channel current direction with respect to the flow-coating direction.
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85.30.Tv Field effect devices
FREE

Evidence for different origins of the magnetic field effect on current and electroluminescence in organic light-emitting diodes

Andreas Buchschuster, Tobias D. Schmidt, and Wolfgang Brütting

Appl. Phys. Lett. 100, 123302 (2012); http://dx.doi.org/10.1063/1.3696051 (4 pages) | Cited 6 times

Online Publication Date: 20 March 2012

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An external magnetic field can change the current through an organic light-emitting diode and the luminance it emits. Existing models predict that both phenomena have the same behaviour and, therefore, a common origin; however, there are indications that they are not completely linked. As a direct proof, we measured the magnetic field effect in multilayer organic light-emitting diodes using Alq3 as emission layer. After successively adding blocking layers, we found a decrease of the magnetic field effect on the current, whereas the effect on the luminance remained at the same level. Thus, both effects can be separated from each other.
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85.60.Jb Light-emitting devices
FREE

Organic integrated complementary inverters with ink-jet printed source/drain electrodes and sub-micron channels

E. Gili, M. Caironi, and H. Sirringhaus

Appl. Phys. Lett. 100, 123303 (2012); http://dx.doi.org/10.1063/1.3696487 (4 pages) | Cited 3 times

Online Publication Date: 22 March 2012

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We have demonstrated device operation of down-scaled n-type field effect transistors (FETs) with ink-jet printed source/drain contacts and sub-μm channel length, using the P(NDI2OD-T2) semiconducting polymer as active material. We integrated these devices with down-scaled p-type FETs made with bis(triisopropylsilylethynyl)pentacene to fabricate complementary inverter gates, in which both transistors and the printed interconnections were implemented on the same substrate. The devices operate at 10 V supply voltage, achieve noise margin values of 56% of math and a gain higher than 10. They are therefore suitable for printed, high performance organic integrated circuits with low supply voltage.
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85.30.Tv Field effect devices
FREE

Field-induced evolution of metallic nano-tips in indium tin oxide-tris-(8-hydroxyquinoline) aluminum-aluminum device

Y. T. You, Q. Zeng, Y. Yao, M. L. Wang, B. Wu, Y. He, Y. M. Hu, C. Q. Wu, and X. Y. Hou

Appl. Phys. Lett. 100, 123304 (2012); http://dx.doi.org/10.1063/1.3697829 (4 pages) | Cited 1 time

Online Publication Date: 23 March 2012

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The effect of electric field and temperature on bistable characteristics of indium tin oxide/tris-(8-hydroxyquinoline) aluminum (Alq3)/aluminum (Al) device has been investigated. The switching time, during which the device turns from a high resistive (OFF) state to a low resistive (ON) state, increases with decreasing field and temperature. The observed phenomena are accounted for by a phenomenological model that metallic nano-tips may evolve under the influence of the electric field and temperature.
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85.35.-p Nanoelectronic devices
85.30.De Semiconductor-device characterization, design, and modeling
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Plasmon resonant excitation in grating-gated AlN barrier transistors at terahertz frequency

Lin Wang, Weida Hu, Jun Wang, Xiaodong Wang, Shaowei Wang, Xiaoshuang Chen, and Wei Lu

Appl. Phys. Lett. 100, 123501 (2012); http://dx.doi.org/10.1063/1.3695154 (5 pages) | Cited 5 times

Online Publication Date: 19 March 2012

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This paper describes the plasmon resonances in AlN/GaN high electron mobility transistors. It is shown that wide tunable resonances with the frequency located at terahertz band can be obtained in this material system. The results originate from the ultra-high electron density induced by the polarization effect and higher order plasmon excitation. At room temperature, the dielectric response caused by phonon-polariton interactions obliterates the higher order plasmon resonances at frequency higher than 10 THz. However, the viscosity contribution to the damping of plasmons is very small in these devices. Our results also show the potential of this device for terahertz applications.
Show PACS
85.30.Tv Field effect devices
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