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10 Oct 2005

Volume 87, Issue 15, Articles (15xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 87, 151103 (2005); http://dx.doi.org/10.1063/1.2089157 (3 pages)

Andrew B. Greytak, Carl J. Barrelet, Yat Li, and Charles M. Lieber
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1.55 μm emission from InAs quantum dots grown on GaAs

Tung-Po Hsieh, Pei-Chin Chiu, Jen-Inn Chyi, Nien-Tze Yeh, Wen-Jeng Ho, Wen-Hao Chang, and Tzu-Min Hsu

Appl. Phys. Lett. 87, 151903 (2005); http://dx.doi.org/10.1063/1.2099536 (3 pages) | Cited 15 times

Online Publication Date: 4 October 2005

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We report a comparative study on the growth of InAs quantum dots (QDs) on GaAs by metalorganic chemical vapor deposition using triethylgallium (TEGa) and trimethylgallium (TMGa) for the GaAs cap layer. QDs exhibit 1.3 μm photoluminescence (PL) at room temperature, as the GaAs cap layer is directly grown on the QDs. The PL emission can be extended to 1.49 μm when an In0.25Ga0.75As overgrown layer is inserted between the cap layer and the InAs QDs. The use of TMGa or TEGa for the growth of the GaAs cap layer is essential for a further increase in the emission wavelength of the InAs QDs. Strong PL emission at 1.55 μm with a linewidth of 28 meV can be obtained as the GaAs cap layer is grown by TEGa, while the optical properties degrade severely when using TMGa.
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78.55.Cr III-V semiconductors
78.67.Hc Quantum dots

Effect of Cu deficiency on the optical bowing of chalcopyrite CuIn1−xGaxSe2

Sung-Ho Han, Falah S. Hasoon, Joel W. Pankow, Allen M. Hermann, and Dean H. Levi

Appl. Phys. Lett. 87, 151904 (2005); http://dx.doi.org/10.1063/1.2089154 (3 pages) | Cited 7 times

Online Publication Date: 4 October 2005

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Optical bowing coefficients are used to describe the band gap variation of a composite semiconductor alloy. It is known to be related to the electronic structure and the lattice deformation in the semiconductor alloys. Spectroscopic ellipsometry study shows that the optical bowing coefficient of slightly Cu-poor polycrystalline Cu0.9In1−xGaxSe2 is larger than that of stoichiometric polycrystalline CuIn1−xGaxSe2 and band gaps are larger when Cu becomes poor. This can be explained by an increase in valence band offset due to reduced p-d coupling and an increase of perturbation potential ΔV due to lattice deformation.
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71.20.Nr Semiconductor compounds
78.66.Li Other semiconductors

Efficient pure blue electroluminescence from ter(9,9, 9″,9″-bihexyl-9′,9′-diphenyl)-fluorenes

Gang Cheng, Yingfang Zhang, Yi Zhao, Shiyong Liu, Shi Tang, and Yuguang Ma

Appl. Phys. Lett. 87, 151905 (2005); http://dx.doi.org/10.1063/1.2099539 (3 pages) | Cited 7 times

Online Publication Date: 4 October 2005

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An oligomer of polyfluorene, ter(9,9, 9″,9″-bihexyl-9′,9′-diphenyl)fluorenes (THPF), is used as a blue-emitting material to achieve efficient pure blue electroluminescence. Based on a 4,4′,4″-tri(N-carbazolyl)-triphenylamine hole-transporting layer, a 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline hole-blocking layer, an (8-hydroxyquinoline) aluminum electron-transporting layer, and a LiF/Al cathode, the device has two emission peaks at 404 and 424 nm, chromaticity coordinates at (0.18, 0.09), and a maximum efficiency of 1.27 cd/A. By using a submonolayer of 5,6,11,12-tetraphenylnaphthacene as a carrier detector, we demonstrate that THPF functions well as an electron-transporting layer, similar to Alq.
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78.60.Fi Electroluminescence

Air-bridged lateral growth of an Al0.98Ga0.02N layer by introduction of porosity in an AlN buffer

T. Wang, J. Bai, P. J. Parbrook, and A. G. Cullis

Appl. Phys. Lett. 87, 151906 (2005); http://dx.doi.org/10.1063/1.2089182 (3 pages) | Cited 21 times

Online Publication Date: 5 October 2005

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We demonstrated air-bridged lateral growth of an Al0.98Ga0.02N layer with significant dislocation reduction by introduction of a porous AlN buffer underneath via metalorganic chemical vapor deposition. By modifying growth conditions, a porous AlN layer and an atomically flat AlN layer have been obtained for comparison, confirmed by atomic force microscopy. An Al0.98Ga0.02N layer was subsequently grown on both the porous AlN layer and the atomically flat AlN layer under identical conditions. Significant dislocation reduction was achieved for the Al0.98Ga0.02N layer grown on the porous AlN buffer layer, compared to the layer grown on the atomically flat AlN layer, as observed by transmission electron microscopy. Clear bubbles from the layer grown on the porous AlN buffer layer have been observed, while in contrast, there was not any bubble from the layer on the flat AlN buffer, confirming the mechanism of lateral growth for dislocation reduction. Asymmetric x-ray diffraction studies also indicated that the crystal quality was dramatically improved using the porous AlN buffer layer.
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81.05.Ea III-V semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.55.A- Nucleation and growth
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Nanoscale multistep shear band formation by deformation-induced nanocrystallization in Zr-Al-Ni-Pd bulk metallic glass

Junji Saida, Albertus Deny Heri Setyawan, Hidemi Kato, and Akihisa Inoue

Appl. Phys. Lett. 87, 151907 (2005); http://dx.doi.org/10.1063/1.2081124 (3 pages) | Cited 64 times

Online Publication Date: 5 October 2005

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A single Zr65Al7.5Ni10Pd17.5 bulk metallic glass exhibits a large plastic strain of 6.6% during the compressive deformation process, which is attributed to the deformation mode with nanoscale multistep shear bands. We have observed that nanocrystals with a metastable fcc Zr2Ni structure containing several distorted icosahedral clusters are arranged in a “bandlike” formation in the glassy matrix around the multistep shear bands. This is recognized as direct evidence of the novel phenomenon of the restraint of shear band propagation owing to the dynamic precipitation of the nanocrystals.
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81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
61.43.Fs Glasses
61.46.-w Structure of nanoscale materials

Modeling of heterogeneous precipitation of iron in silicon

A. Haarahiltunen, H. Väinölä, O. Anttila, E. Saarnilehto, M. Yli-Koski, J. Storgårds, and J. Sinkkonen

Appl. Phys. Lett. 87, 151908 (2005); http://dx.doi.org/10.1063/1.2099531 (3 pages) | Cited 6 times

Online Publication Date: 6 October 2005

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A model is presented for the growth and dissolution of iron precipitates at oxygen-related defects in silicon during thermal processing. The heterogeneous nucleation of iron is taken into account by special growth and dissolution rates, which are inserted into a set of modified chemical rate equations. This approach allows us to calculate the size distribution of iron precipitates and the residual iron concentration. By comparing the simulated results with experimental ones, it is proven that this model can be used to estimate the internal gettering efficiency of iron under a variety of processing conditions.
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81.10.Aj Theory and models of crystal growth; physics and chemistry of crystal growth, crystal morphology, and orientation
81.05.Cy Elemental semiconductors
81.30.Mh Solid-phase precipitation
64.75.-g Phase equilibria

Far-infrared absorption due to electronic transitions of N–O complexes in Czochralski-grown silicon crystals: Influence of nitrogen and oxygen concentration

H. Ch. Alt, Y. V. Gomeniuk, F. Bittersberger, A. Kempf, and D. Zemke

Appl. Phys. Lett. 87, 151909 (2005); http://dx.doi.org/10.1063/1.2099517 (3 pages) | Cited 10 times

Online Publication Date: 6 October 2005

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Fourier-transform infrared absorption measurements have been carried out on nitrogen-doped Czochralski-grown silicon crystals after thermal annealing at 600 °C. The strength of the electronic transitions due to N–O related shallow donors shows a square root dependence on the nitrogen concentration and donor-specific power dependences on the interstitial oxygen concentration. Based on mass action laws, chemical compositions are discussed. It is found that the N–O complexes investigated all involve one nitrogen atom but three different numbers of oxygen atoms.
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78.30.Am Elemental semiconductors and insulators
61.72.uf Ge and Si
61.72.S- Impurities in crystals
61.72.J- Point defects and defect clusters
61.72.Cc Kinetics of defect formation and annealing
82.80.-d Chemical analysis and related physical methods of analysis

Photoluminescence from 8-hydroxy quinoline aluminum embedded in porous anodic alumina membrane

G. S. Huang, X. L. Wu, Y. Xie, F. Kong, Z. Y. Zhang, G. G. Siu, and Paul K. Chu

Appl. Phys. Lett. 87, 151910 (2005); http://dx.doi.org/10.1063/1.2099522 (3 pages) | Cited 12 times

Online Publication Date: 6 October 2005

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By immersing porous alumina membranes in 8-hydroxy quinoline aluminum (Alq3) solutions, we embed Alq3 molecules into the nanovoids of the membranes. Photoluminescence (PL) spectral examinations show that the Alq3 molecules embedded in the alumina membrane show a blueshifted luminescent spectrum compared to that of Alq3 solid film. Since the blueshift of ∼ 18 nm does not change with nanopore diameter, we consider it to be due to the confinement of nanovoids in the nanopore walls, which prevents Alq3 molecules from aggregation and thus weakens the interaction between them. Further spectral analyses suggest that the photogeneration of carriers takes place in oxygen vacancies at the surfaces of nanopore walls, whereas the radiative recombination occurs in the embedded Alq3 molecules. Förster energy transfer from oxygen vacancies to the embedded Alq3 molecules is proposed to be responsible for the enhancement of the PL intensity.
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78.55.Mb Porous materials
82.45.Wx Polymers and organic materials in electrochemistry
82.20.Rp State to state energy transfer

Electrically induced surface instability of a conductive thin film on a dielectric substrate

Rui Huang

Appl. Phys. Lett. 87, 151911 (2005); http://dx.doi.org/10.1063/1.2099526 (3 pages)

Online Publication Date: 6 October 2005

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The stability of a conductive thin film on a dielectric substrate subjected to a transverse electric field and a residual strain is analyzed. Under a uniform electric field, an equilibrium state exists with a constant thickness reduction of the substrate. The equilibrium state, however, can be unstable, depending on the intensity of the electric field, the stiffness, and Poisson’s ratio of the substrate, and on the residual strain in the film. Based on a linear perturbation analysis, the critical condition is determined, beyond which wrinkling of the film is expected.
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77.84.-s Dielectric, piezoelectric, ferroelectric, and antiferroelectric materials
77.55.-g Dielectric thin films
68.60.Bs Mechanical and acoustical properties
73.61.-r Electrical properties of specific thin films
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.D- Elasticity

Spatially resolved in situ measurements of the transport of organic molecules in a polycrystalline nanoporous membrane

Weontae Oh and Sankar Nair

Appl. Phys. Lett. 87, 151912 (2005); http://dx.doi.org/10.1063/1.2093918 (3 pages) | Cited 1 time

Online Publication Date: 7 October 2005

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We report spatially resolved, quantitative, in situ, nondestructive measurements of the transport of organic molecules through a polycrystalline, anisotropic, nanoporous molecular sieve membrane, with micron-scale resolution. A method based on photoacoustic spectroscopy experiments during permeation through a nanoporous membrane, combined with a physical model of photoacoustic signal generation from a heterogeneous membrane, allows extraction of concentration profiles in situ. In particular, we demonstrate the steady-state concentration profiling of the organic molecules p-xylene and n-hexane during their transport through a nanoporous zeolite silicalite membrane. The implications for elucidating structure-property relationships in membrane materials for separations, catalytic, or nanotechnology applications are discussed.
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82.75.Jn Measurements and modeling of molecule migration in zeolites
82.75.Mj Measurements and simulation of properties (optical, structural) of molecules in zeolites
43.35.Ud
62.65.+k Acoustical properties of solids
82.80.Kq Energy-conversion spectro-analytical methods (e.g., photoacoustic, photothermal, and optogalvanic spectroscopic methods)
61.43.Gt Powders, porous materials
61.46.-w Structure of nanoscale materials

Basal plane dislocation-free epitaxy of silicon carbide

Z. Zhang and T. S. Sudarshan

Appl. Phys. Lett. 87, 151913 (2005); http://dx.doi.org/10.1063/1.2093931 (3 pages) | Cited 16 times

Online Publication Date: 7 October 2005

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Molten KOH etching was implemented on SiC substrates before growing epilayers on them. It was found that the creation of basal plane dislocation (BPD) etch pits on the substrates can greatly enhance the conversion of BPDs to threading edge dislocations during epitaxy, and thus low BPD density and BPD-free SiC epilayers are obtained by this method. The reason why BPD etch pits can promote the earlier conversion is discussed. The SiC epilayer growth by this method is very promising in overcoming forward voltage drop degradation of SiC PiN diodes.
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81.05.Hd Other semiconductors
81.65.Cf Surface cleaning, etching, patterning
68.55.A- Nucleation and growth
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
61.72.Lk Linear defects: dislocations, disclinations
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High-mobility Sb-doped p-type ZnO by molecular-beam epitaxy

F. X. Xiu, Z. Yang, L. J. Mandalapu, D. T. Zhao, J. L. Liu, and W. P. Beyermann

Appl. Phys. Lett. 87, 152101 (2005); http://dx.doi.org/10.1063/1.2089183 (3 pages) | Cited 118 times

Online Publication Date: 4 October 2005

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Reproducible Sb-doped p-type ZnO films were grown on n-Si (100) by electron-cyclotron-resonance-assisted molecular-beam epitaxy. The existence of Sb in ZnO:Sb films was confirmed by low-temperature photoluminescence measurements. An acceptor-bound exciton (A°X) emission was observed at 3.358 eV at 8 K. The acceptor energy level of the Sb dopant is estimated to be 0.2 eV above the valence band. Temperature-dependent Hall measurements were performed on Sb-doped ZnO films. At room temperature, one Sb-doped ZnO sample exhibited a low resistivity of 0.2 Ω cm, high hole concentration of 1.7×1018 cm−3 and high mobility of 20.0 cm2/V s. This study suggests that Sb is an excellent dopant for reliable and reproducible p-type ZnO fabrication.
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73.61.Ga II-VI semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.55.Et II-VI semiconductors
71.35.-y Excitons and related phenomena
71.20.Nr Semiconductor compounds
72.20.My Galvanomagnetic and other magnetotransport effects
61.72.uj III-V and II-VI semiconductors

Carbon nanotube gated lateral resonant tunneling field-effect transistors

D. P. Wang, B. R. Perkins, A. J. Yin, A. Zaslavsky, J. M. Xu, R. Beresford, and G. L. Snider

Appl. Phys. Lett. 87, 152102 (2005); http://dx.doi.org/10.1063/1.2089177 (3 pages) | Cited 6 times

Online Publication Date: 4 October 2005

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We have produced a lateral resonant tunneling field-effect transistor using a Y-junction multiwalled carbon nanotube as the dual gate on a narrow channel etched from a modulation-doped GaAs/AlGaAs heterostructure. When the Y-junction nanotube is negatively biased, electrons traveling from source to drain along the channel face a voltage-tunable electrostatic double-barrier potential. We measured the three-terminal IDS(VDS,VGS) characteristics of the device at 4.2 K and observed gate-induced structure in the transconductance and negative differential resistance in the drain current. We interpret the data in terms of resonant tunneling through one-dimensional subbands confined by a self-consistently calculated electrostatic potential.
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85.30.Tv Field effect devices
85.35.Kt Nanotube devices

Radiation-induced trapping and charge transport in a smectic liquid crystal

Katherine Hudson, Brett Ellman, Volker Gettwert, Yulia Getmanenko, and Robert J. Twieg

Appl. Phys. Lett. 87, 152103 (2005); http://dx.doi.org/10.1063/1.2099543 (3 pages) | Cited 6 times

Online Publication Date: 4 October 2005

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We have studied changes in the hole transport properties of a smectic liquid crystalline semiconductor resulting from high-energy electron irradiation. The “radiation doping” results in sharply increased shallow trap densities and the onset of nearly trap-limited hopping conduction. A simple semiquantitative model provides estimates of the trap lifetime and the irradiation energy required to create a single trap. Experimental techniques to overcome parasitic effects due to increased molecular ion densities in irradiated samples are also discussed.
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72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.20.Ee Mobility edges; hopping transport
72.80.Le Polymers; organic compounds (including organic semiconductors)
72.80.Ph Liquid semiconductors
61.30.Eb Experimental determinations of smectic, nematic, cholesteric, and other structures
61.82.Fk Semiconductors
61.82.Pv Polymers, organic compounds
61.80.Fe Electron and positron radiation effects

Dependence of carrier mobility on grain mosaic spread in ⟨001⟩-oriented Si films grown on polycrystalline substrates

Woong Choi, Vladimir Matias, Jung-Kun Lee, and Alp T. Findikoglu

Appl. Phys. Lett. 87, 152104 (2005); http://dx.doi.org/10.1063/1.2103405 (3 pages) | Cited 7 times

Online Publication Date: 4 October 2005

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We studied the dependence of carrier mobility on grain mosaic spread for ⟨001⟩-oriented, 200-to-400-nm-thick Si thin films grown on polycrystalline metal substrates. The Hall mobility increased from 1% to 23% of that in bulk single-crystal Si with decreasing grain mosaic spread from 14° to 2°. For the same range of parameters, a model combining intragrain and grain boundary scattering yielded a decrease of the energy barrier height from 0.1 eV to less than 10−3 eV and an accompanying decrease of trap density from 6×1011 cm−2 to less than 3×1010 cm−2. These results demonstrate that, for polycrystalline Si films, improving the intergrain alignment is an effective and practical alternative to increasing the grain size to achieve enhanced mobility.
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73.61.Cw Elemental semiconductors
72.20.Ee Mobility edges; hopping transport
61.72.Mm Grain and twin boundaries

Influence of the dielectric constant of a polyvinyl phenol insulator on the field-effect mobility of a pentacene-based thin-film transistor

Yunseok Jang, Do Hwan Kim, Yeong Don Park, Jeong Ho Cho, Minkyu Hwang, and Kilwon Cho

Appl. Phys. Lett. 87, 152105 (2005); http://dx.doi.org/10.1063/1.2093940 (3 pages) | Cited 29 times

Online Publication Date: 5 October 2005

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The mobility of pentacene thin-film transistors (TFTs) is correlated with the dielectric properties of their insulators. We varied the dielectric properties of the poly(4-vinylphenol) insulators of such TFTs by changing the molar ratio of the prepolymer/cross-linking agent while keeping the surface potential of the insulator surface constant. It was found that the field-effect mobility of the pentacene TFTs increases with increases in the dielectric constant of the insulators. A small increase in the dielectric constant of the insulator (a 20% increase, 3.6–4.3) was found to result in a dramatic increase in the field-effect mobility of pentacene TFTs by a factor of 3 (0.26 to 0.81 cm2/V s).
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85.30.Tv Field effect devices
77.22.Ch Permittivity (dielectric function)

Improvement of the current-voltage characteristics of a tunneling dielectric by adopting a Si3N4/SiO2/Si3N4 multilayer for flash memory application

Sug Hun Hong, Jae Hyuck Jang, Tae Joo Park, Doo Seok Jeong, Miyoung Kim, Cheol Seong Hwang, and Jeong Yeon Won

Appl. Phys. Lett. 87, 152106 (2005); http://dx.doi.org/10.1063/1.2093932 (3 pages) | Cited 3 times

Online Publication Date: 7 October 2005

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Superior characteristics of an atomic-layer-deposited (ALD) Si3N4 layer and Si3N4/SiO2/Si3N4 stacked layers as a tunneling gate dielectric for nonvolatile flash memory application are reported. Compared to a single layer of SiO2 electric field-sensitive characteristics were obtained by barrier profile engineering with a stacked layer; a lower leakage current at a low field and a higher leakage current at a high field. The stacked dielectric layer showed Fowler–Nordheim tunneling. However, the interfacial potential barrier profile was somewhat smoothed by chemical interaction between the individual layers. The interfacial trap density of this dielectric with an ALD Si3N4 bottom layer was as low as 4×10−10/cm2 eV near the mid-gap energy state, but the reoxidation process degraded the interface quality. The degradation mechanism was studied.
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77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.55.-g Dielectric thin films
84.30.Sk Pulse and digital circuits
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Dendritic magnetic avalanches in carbon-free MgB2 thin films with and without a deposited Au layer

Eun-Mi Choi, Hyun-Sook Lee, Hyun Jung Kim, Byeongwon Kang, Sung-Ik Lee, A. A. F. Olsen, D. V. Shantsev, and T. H. Johansen

Appl. Phys. Lett. 87, 152501 (2005); http://dx.doi.org/10.1063/1.2084323 (3 pages) | Cited 22 times

Online Publication Date: 3 October 2005

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From magneto optic images (MOI), the dendritic magnetic avalanche is known to appear dominantly for thin films of the newly discovered MgB2. To clarify the origin of this phenomenon, we studied in detail the MOI of carbon-free MgB2 thin films with and without a deposited gold layer. The MOI indicated that carbon contamination was not the main source of the avalanche. The MOI clearly showed that the deposition of metallic gold on top of a MgB2 thin film improved its thermal stability and suppressed the sudden appearance of the dendritic flux avalanche. This is consistent with the previous observation of flux noise in the magnetization.
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74.25.Ha Magnetic properties including vortex structures and related phenomena
74.78.-w Superconducting films and low-dimensional structures
74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
68.70.+w Whiskers and dendrites (growth, structure, and nonelectronic properties)
74.25.Sv Critical currents

High-magnetic-moment core-shell-type FeCo–Au/Ag nanoparticles

Jianmin Bai and Jian-Ping Wang

Appl. Phys. Lett. 87, 152502 (2005); http://dx.doi.org/10.1063/1.2089171 (3 pages) | Cited 28 times

Online Publication Date: 4 October 2005

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We developed a physical technique combining an on-line sputtering/evaporation process with an integrated nanocluster deposition process to prepare core-shell-type nanoparticles. High-magnetic-moment (Fe60Co40)coreAushell and (Fe60Co40)coreAgshell superparamagnetic nanoparticles with controllable particle size of 10–20 nm and Au/Ag shell thickness of 1–3 nm were prepared by using this method. Au shell is not only functional for the potential biocompatibility but also the key to prevent the oxidation of FeCo nanoparticles. Saturation magnetization of (Fe60Co40)coreAushell nanoparticles was found three times higher than that of iron oxide nanoparticles. This technique enables us to control independently the dimensions of core and shell and select individually materials for core and shell for any other core-shell-type nanoparticles.
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75.50.Tt Fine-particle systems; nanocrystalline materials
75.30.Cr Saturation moments and magnetic susceptibilities
75.20.En Metals and alloys
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
61.46.-w Structure of nanoscale materials
81.07.Bc Nanocrystalline materials
81.16.Pr Micro- and nano-oxidation

X-ray ferromagnetic resonance spectroscopy

G. Boero, S. Rusponi, P. Bencok, R. S. Popovic, H. Brune, and P. Gambardella

Appl. Phys. Lett. 87, 152503 (2005); http://dx.doi.org/10.1063/1.2089180 (3 pages) | Cited 16 times

Online Publication Date: 5 October 2005

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We present a method to measure continuous-wave ferromagnetic resonance (FMR) spectra based on the core-level absorption of circularly polarized x rays. The technique is demonstrated by using a monochromatic x-ray beam incident on an yttrium–iron–garnet sample excited by a microwave field at 2.47 GHz. FMR spectra are obtained by monitoring the x-ray absorption intensity at the photon energy corresponding to the maximum of the magnetic circular dichroism effect at the iron L2,3 edges as a function of applied magnetic field. The x-ray FMR signal is shown to be energy dependent, which makes the technique element sensitive and opens up new possibilities to perform element-resolved FMR in magnetic alloys and multilayers.
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07.57.Pt Submillimeter wave, microwave and radiowave spectrometers; magnetic resonance spectrometers, auxiliary equipment, and techniques
07.85.Nc X-ray and γ-ray spectrometers
75.50.Gg Ferrimagnetics
76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance
78.70.Dm X-ray absorption spectra
75.50.Dd Nonmetallic ferromagnetic materials
73.20.At Surface states, band structure, electron density of states
78.20.Ls Magneto-optical effects

Current-induced asymmetric transport in La0.8Ca0.2MnO3 epitaxial thin films

F. X. Hu and J. Gao

Appl. Phys. Lett. 87, 152504 (2005); http://dx.doi.org/10.1063/1.2093934 (3 pages) | Cited 14 times

Online Publication Date: 5 October 2005

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We investigated the influence of a dc current on the transport properties in La0.8Ca0.2MnO3 epitaxial thin films grown on SrTiO3 substrates. A prominent finding is the appearance of asymmetric transport properties, like the behavior of p-n junctions, in a wide temperature range from 10 K to 300 K after the films were applied by a dc current over a threshold value. The asymmetric behavior resulted from a relative weak excitation is unstable and even spontaneously disappears. By optimizing excitation condition, the rectifyinglike behavior turns to be more significant and stable. Applying a small ac current could make the asymmetric transport collapse, subsequently, conventional symmetric transport behaviors appear. Phase separation and the coexistent ferromagnetic phases with different orbital order are taken into account in the interpretation of the observed phenomena.
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75.47.Lx Magnetic oxides
75.47.Gk Colossal magnetoresistance
75.50.Dd Nonmetallic ferromagnetic materials
71.27.+a Strongly correlated electron systems; heavy fermions
75.70.Ak Magnetic properties of monolayers and thin films

Large induced magnetic anisotropy in manganese spinel ferrite films

Xu Zuo, Aria Yang, Soack-Dae Yoon, Joseph A. Christodoulides, Vincent G. Harris, and Carmine Vittoria

Appl. Phys. Lett. 87, 152505 (2005); http://dx.doi.org/10.1063/1.2084341 (3 pages) | Cited 17 times

Online Publication Date: 7 October 2005

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The oxygen pressure dependence of magnetic anisotropy in pulse laser deposited manganese ferrite (MnFe2O4) films was investigated. Magnetic anisotropy fields (Ha) are shown to exceed 5 kOe when films were processed at oxygen pressures below 5 mTorr. Further, it is shown that the magnetically preferred direction of Ha can be aligned either along the film plane (pO2<8 mTorr) or perpendicular to it (pO2>8 mTorr). The ability to induce large perpendicular magnetic anisotropy in spinel ferrites allows for new applications (i.e., phase shifters, filters, isolators, and circulators) near or above X-band frequencies to be considered.
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75.30.Gw Magnetic anisotropy
75.50.Gg Ferrimagnetics
75.70.Ak Magnetic properties of monolayers and thin films
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Large dielectric tunability and microwave properties of Mn-doped (Ba,Sr)TiO3 thin films

Z. Yuan, Y. Lin, J. Weaver, X. Chen, C. L. Chen, G. Subramanyam, J. C. Jiang, and E. I. Meletis

Appl. Phys. Lett. 87, 152901 (2005); http://dx.doi.org/10.1063/1.2089181 (3 pages) | Cited 47 times

Online Publication Date: 5 October 2005

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Ferroelectric Ba0.6Sr0.4TiO3 thin films with 2% Mn additional doping were grown on (001) MgO by pulsed laser deposition. The microstructural studies from x-ray diffraction and transmission electron microscopy indicate that the films are highly epitaxial with c-axis oriented and atomic sharp interface. Dielectric property measurements at 1 MHz and room temperature reveal that the as-grown films have outstanding dielectric properties with large tunability of 80% at 40 KV/cm, very large dielectric constant value of 3800, and extra low dielectric loss of only 0.001. The high frequency (10–30 GHz) dielectric measurements demonstrate that the films are excellent in both dielectric property and very low dielectric insertion loss. Compared with the pure BSTO films or traditional doping, the additional doping of Mn in BSTO thin films can significantly improve the dielectric property of the as-grown films.
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77.55.-g Dielectric thin films
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.22.Ch Permittivity (dielectric function)
77.22.Gm Dielectric loss and relaxation
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Exclusive-OR gate using a two-input single-electron transistor in single-wall carbon nanotubes

D. Tsuya, M. Suzuki, Y. Aoyagi, and K. Ishibashi

Appl. Phys. Lett. 87, 153101 (2005); http://dx.doi.org/10.1063/1.2089149 (3 pages) | Cited 10 times

Online Publication Date: 3 October 2005

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We demonstrated a two-input exclusive-OR (XOR) gate using a single-electron transistor with two similar side gates in single-wall carbon nanotubes. Coulomb peaks were adjusted to have a half phase difference by a high input voltage to one of the two gates. The output current was in a low level when the same voltages, high or low, were applied to both gates, while it was in a high level when different voltages were applied to each gate, a XOR behavior. The present device operated up to ∼ 30 K.
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85.35.Gv Single electron devices
85.35.Kt Nanotube devices
85.35.Ds Quantum interference devices
84.30.Sk Pulse and digital circuits

Electrochemical capacitance from manganese oxide nanowire structure synthesized by cyclic voltammetric electrodeposition

Mao-Sung Wu

Appl. Phys. Lett. 87, 153102 (2005); http://dx.doi.org/10.1063/1.2089169 (3 pages) | Cited 32 times

Online Publication Date: 3 October 2005

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Manganese oxide electrodes of nanowire structure are electrochemically synthesized by cyclic voltammetric electrodeposition at room temperature without surfactant, catalyst, or template. Electrode morphology depends on the deposition potential, which greatly influences the electrochemical performances of the capacitor. When the deposition potential is the range of 0.1–0.6 V versus saturated calomel electrode, electrode morphology changes from nanorod (15–35 nm in diameter) to nanowire structure (8–16 nm in diameter). Specific capacitance of the electrode reaches 350 Fg−1 and the electrode shows a good high-rate charge/discharge capability in aqueous Na2SO4 solution. Manganese oxide electrode of nanowire structure is therefore a suitable candidate for electrochemical capacitor use.
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82.47.Uv Electrochemical capacitors; supercapacitors
84.32.Tt Capacitors
82.45.Fk Electrodes
61.46.-w Structure of nanoscale materials
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.15.Pq Electrodeposition, electroplating
82.45.Qr Electrodeposition and electrodissolution
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