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11 Dec 2006

Volume 89, Issue 24, Articles (24xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 89, 242109 (2006); http://dx.doi.org/10.1063/1.2405843 (3 pages)

Carlo R. da Cunha, Nobuyuki Aoki, Takahiro Morimoto, Yuichi Ochiai, Richard Akis, and David K. Ferry
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Random telegraph signals and noise behaviors in carbon nanotube transistors

Fei Liu, Kang L. Wang, Daihua Zhang, and Chongwu Zhou

Appl. Phys. Lett. 89, 243101 (2006); http://dx.doi.org/10.1063/1.2402224 (3 pages) | Cited 2 times

Online Publication Date: 11 December 2006

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A random telegraph signal appears at a smaller absolute gate bias for a larger absolute drain-source bias in a carbon nanotube transistor. Its mechanism is attributed to a defect located in the drain side of the Schottky barrier carbon nanotube transistor with Ti/Au as contact material. Furthermore, room temperature random telegraph signal is presented for both semiconducting and metallic carbon nanotubes, indicating the need to include random telegraph signal as a noise source for carbon nanotube transistors.
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85.35.Kt Nanotube devices
85.30.Tv Field effect devices

Time-resolved x-ray-excited optical luminescence characterization of one-dimensional Si–CdSe heterostructures

R. A. Rosenberg, G. K. Shenoy, X. H. Sun, and T. K. Sham

Appl. Phys. Lett. 89, 243102 (2006); http://dx.doi.org/10.1063/1.2402262 (3 pages) | Cited 4 times

Online Publication Date: 11 December 2006

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The authors have monitored the optical luminescence from one-dimensional Si–CdSe nanoheterostructures as a function of x-ray energy at the Se L3 edge ( ∼ 1430 eV). The wires consist of a diamond Si core encased in a wurtzite CdSe sheath. The time-resolved luminescence spectrum consists of a short-lifetime band centered at 637 nm and a long-lived band at 530 nm. By monitoring the intensities of these bands following excitation of a Se 2p3/2 electron, the authors are able to show that the 637 nm band is associated with the CdSe sheath while the 530 nm band emanates from the Si core.
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78.67.-n Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures
78.55.-m Photoluminescence, properties and materials
78.47.-p Spectroscopy of solid state dynamics
78.70.En X-ray emission spectra and fluorescence

Enhanced thermal stability and emission intensity of InAs quantum dots covered by an InGaAsSb strain-reducing layer

Wei-Sheng Liu, David M. T. Kuo, Jen-Inn Chyi, Wen-Yen Chen, Hsing-Szu Chang, and Tzu-Min Hsu

Appl. Phys. Lett. 89, 243103 (2006); http://dx.doi.org/10.1063/1.2405872 (3 pages) | Cited 8 times

Online Publication Date: 11 December 2006

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An InGaAsSb overgrown layer, i.e., strain-reducing layer (SRL), is adopted to increase the emission intensity of InAs quantum dots (QDs) and extend the emission wavelength to as long as 1.42 μm. InAs QDs capped with InGaAsSb SRL also exhibit a thermal activation energy of 534 meV, which is much higher than that of InAs QDs with an InGaAs SRL. The increase in luminescence efficiency and thermal stability is attributed to the improved carrier confinement of the GaAs/InAs/InGaAsSb heterostructure.
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78.67.Hc Quantum dots
78.55.Cr III-V semiconductors

All-carbon nanotube-based junction with virtual source and drain of carbon nanotubes by in situ one-step process for practical integrated nanoelectronics

Yun-Hi Lee, Je-Min Yoo, Jong-Hee Lee, and B. K. Ju

Appl. Phys. Lett. 89, 243104 (2006); http://dx.doi.org/10.1063/1.2403186 (3 pages)

Online Publication Date: 11 December 2006

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The authors propose a suspended in situ lateral grown all-carbon nanotube-based junction and report on the dc carrying behaviors of the carbon nanotube junction, especially with and after UV exposure. Also, the release of carriers of the junctions was studied by capacitance (C) measurements with ac excitation. The designed diluted magnetic impurity doped oxide film was adopted as catalyst in the fabrication of the junction. The suspended nanotube channel showed ambipolar function and almost the same low barrier height for the holes and electrons, which was determined by I-T(K) measurements. Subsequent measurements on the channel treated by low intensity UV resulted in a highly conductive channel with high current carrying behavior. Both their junction structure and analogy between dc I-V and capacitance can be applied to develop a practical and accessible system for forming reproducible integrated nanoelectronic junctions as well as to accelerate the realization of all low dimensional molecular devices.
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85.35.Kt Nanotube devices
85.30.Tv Field effect devices

Structure and photoluminescence properties of epitaxially oriented GaN nanorods grown on Si(111) by plasma-assisted molecular-beam epitaxy

Hung-Ying Chen, Hon-Way Lin, Chang-Hong Shen, and Shangjr Gwo

Appl. Phys. Lett. 89, 243105 (2006); http://dx.doi.org/10.1063/1.2404597 (3 pages) | Cited 42 times

Online Publication Date: 11 December 2006

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The authors show that vertically c-axis-aligned GaN nanorod arrays grown by plasma-assisted molecular-beam epitaxy are epitaxially oriented on Si(111) substrates and their crystal structure corresponds to a fully relaxed wurtzite lattice. At later growth stage, these GaN nanorods exhibit the tendency to coalesce into nanorod bundles. Low-temperature photoluminescence spectrum from 1-μm-long GaN nanorods consists of intense exciton lines of strain-free bulk GaN and additional lines at ∼ 3.21 and ∼ 3.42 eV (Y7 and Y2). The Y7 line is attributed to the excitons trapped along the dislocations at the boundaries of coalesced GaN nanorods, while the Y2 line has its origin in the interface defects at the GaN/Si(111) interfaces.
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61.46.Hk Nanocrystals
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
81.10.Bk Growth from vapor
78.55.Cr III-V semiconductors
61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)
71.35.-y Excitons and related phenomena

Modulating transmission properties of nanoscale transistors by dipoles near contacts

Li Yang, Jian Wu, Wenhui Duan, and Bing-Lin Gu

Appl. Phys. Lett. 89, 243106 (2006); http://dx.doi.org/10.1063/1.2405383 (3 pages)

Online Publication Date: 12 December 2006

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The authors theoretically demonstrate that dipole layers on the electrode can modulate the transmission properties of nanoscale devices by influencing the contact properties, through first principles simulations on carbon nanotube based field effect transistors. The dipole layers are realized by potassium adsorption on Au electrodes, which change the electrostatic potential at the near contact region significantly. The dipoles parallel to the direction of the bias voltage may act as a supplement to the effect of gate voltages, while the perpendicular dipoles modify the interface barrier of contacts.
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85.30.Tv Field effect devices
85.35.Kt Nanotube devices

Schottky barrier formation at a carbon nanotube—metal junction

Wenguang Zhu and Efthimios Kaxiras

Appl. Phys. Lett. 89, 243107 (2006); http://dx.doi.org/10.1063/1.2405393 (3 pages) | Cited 22 times

Online Publication Date: 12 December 2006

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The issue of Schottky barrier formation at carbon nanotube (CNT) contacts with metal leads is of crucial importance for nanotube-based electronic devices. The authors examine the electronic properties of a particular structure containing a metal/CNT contact that resembles experimental setups for CNT field-effect transistors. The model consists of a single-wall (8,0) CNT with its central section fully covered by a Pd ring, representing the metal electrode. Through first-principles total energy and electronic structure calculations within density functional theory, the authors establish that the junction between the metal-covered part and the bare part of the CNT is responsible for the experimentally measured Schottky barrier of ∼ 0.4 eV in CNT field-effect transistors.
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73.30.+y Surface double layers, Schottky barriers, and work functions
85.35.Kt Nanotube devices
85.30.Tv Field effect devices

Study of the size effect on the optical mode frequencies of ZnO nanoparticles with nearly uniform size

S. L. Zhang, Y. Zhang, Z. Fu, S. N. Wu, M. Gao, M. Liu, J. Chen, L. Niu, J. Z. Jiang, Y. Ling, Q. Wang, and H. Chen

Appl. Phys. Lett. 89, 243108 (2006); http://dx.doi.org/10.1063/1.2403925 (3 pages) | Cited 8 times

Online Publication Date: 12 December 2006

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It was found in ZnO nanoparticles of nearly uniform size that the Raman frequencies of both the polar A1(LO) and nonpolar E2(H) modes do not shift with particle sizes. This observation is in perfect agreement with previous theoretical prediction. The observed result is consistent with the prediction that the size insensitivity of optic vibration frequency in polar nanosemiconductors originates from the Fröhlich interaction, which exists only in polar nanosemiconductors.
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78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
78.30.Fs III-V and II-VI semiconductors
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials

Compact dye laser on a chip fabricated by ultraviolet nanoimprint lithography

Ch. Peroz, J-C. Galas, L. Le Gratiet, Y. Chen, and J. Shi

Appl. Phys. Lett. 89, 243109 (2006); http://dx.doi.org/10.1063/1.2404607 (3 pages) | Cited 8 times

Online Publication Date: 12 December 2006

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High aspect ratio and high resolution distributed feed back (DFB) gratings have been patterned on a fused silica plate by ultraviolet nanoimprint lithography and reactive ion etch techniques. Then, they were integrated into a microfluidic chip for optofluidic operations. The authors observed laser emission from organic dye solutions flowing through an optical resonator formed between two third order DFB gratings. Such a dye layer can operate with a picoliter dye solution. With rhodamine 6G dye molecules dissolved in ethanol and pumped by a frequency-doubled Nd:YAG pulsed laser, a laser emission of threshold of 12 μJ/mm2 has been found.
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42.55.Mv Dye lasers
42.60.By Design of specific laser systems
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.82.Cr Fabrication techniques; lithography, pattern transfer
81.16.Nd Micro- and nanolithography
47.85.Np Fluidics

Ab initio study of the effect of water adsorption on the carbon nanotube field-effect transistor

Dongchul Sung, Suklyun Hong, Yong-Hoon Kim, Noejung Park, Sanghyeob Kim, Sung Lyul Maeng, and Ki-Chul Kim

Appl. Phys. Lett. 89, 243110 (2006); http://dx.doi.org/10.1063/1.2397543 (3 pages) | Cited 16 times

Online Publication Date: 13 December 2006

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We perform density-functional calculations to investigate the effect of adsorbed water molecules on carbon nanotubes (CNTs). Noting that the H2O molecule has much wider energy gap than the CNT, we find that the charge transfer between them is negligible. We discuss that several recent publications, which claimed a substantial electron transfer from the water molecule to the CNT, have been based on incautious interpretations of the Mulliken population analysis. We suggest that the effect of humidity on nanotube devices may be attributed to various indirect effects enhanced by water vapors, rather than the carrier generations by the physisorbed H2O molecules.
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85.30.Tv Field effect devices
85.35.Kt Nanotube devices

Nanofabrication on ZnO nanowires

Jinhua Zhan, Yoshio Bando, Junqing Hu, and Dmitri Golberg

Appl. Phys. Lett. 89, 243111 (2006); http://dx.doi.org/10.1063/1.2404950 (3 pages) | Cited 13 times

Online Publication Date: 13 December 2006

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ZnO nanowires were subjected to convergent electron beam irradiation in a 300 kV transmission electron microscope. The size of perforated hexagonal pores generated by irradiation can vary with the beam size. An irradiated area is denuded layer by layer via removal of Zn and O atoms. The polar ZnO surfaces have a higher resistance to irradiation than the unpolar ones. Ultrathin nanobridges, ∼ 1 nm thick or less, were generated through deliberate removal of Zn and O atomic monolayers.
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81.16.Ta Atom manipulation
61.46.-w Structure of nanoscale materials
68.65.La Quantum wires (patterned in quantum wells)
61.80.Fe Electron and positron radiation effects
61.82.Fk Semiconductors

Nanofractal structure consisting of nanoparticles produced by ultrashort laser pulses

Kumiko Nishikawa, Kei Takano, Hidekazu Miyahara, Tohru Kawamura, Akitoshi Okino, Eiki Hotta, Takuya Nayuki, Yuji Oishi, Takashi Fujii, Xiaofang Wang, and Koshichi Nemoto

Appl. Phys. Lett. 89, 243112 (2006); http://dx.doi.org/10.1063/1.2402225 (3 pages) | Cited 3 times

Online Publication Date: 13 December 2006

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By irradiating subpicosecond laser onto an iron plate, a nanofibrous structure consisting of iron nanoparticles with diameters less than 12 nm was produced. The nanofibrous structure was found to be three-dimensional fractal, and its fractal dimension measured from field-emission scanning electron microscopy images conserved the same fractal dimension of 1.73 in the wide-scale range from 30 nm to 60 μm, and the smallest fractal structure was less than 10 nm. The growth of this fractal is related to the cluster-cluster aggregation model, and it suggests that the fractal structure grew by the attachment of clusters consisting of nanoparticles.
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61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.82.Bg Metals and alloys
61.82.Rx Nanocrystalline materials
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Size-dependent Schottky Barrier Height in self-assembled gold nanoparticles

F. Ruffino, M. G. Grimaldi, F. Giannazzo, F. Roccaforte, and V. Raineri

Appl. Phys. Lett. 89, 243113 (2006); http://dx.doi.org/10.1063/1.2405407 (3 pages) | Cited 12 times

Online Publication Date: 13 December 2006

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(Au nanocluster)/6H-SiC Schottky contacts were electrically characterized by conductive atomic force microscopy, collecting a high number of current-voltage (I-V) curves. The main observed result is the Schottky barrier height (SBH) dependence on the cluster size. The SBH increases from 1.35±0.01 to 1.77±0.01 eV when the cluster size increases from 1.5 to 6.8 nm and it tends, asymptotically, to the theoretical SBH of the macroscopic contact Au/SiC ( ∼ 1.9 eV). This behavior is interpreted considering the thermoionic transport theory through the Au cluster/SiC barrier coupled with the concept of ballistic transport within few electron quantum dots.
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73.30.+y Surface double layers, Schottky barriers, and work functions
73.40.Ns Metal-nonmetal contacts
73.63.Kv Quantum dots
73.23.Ad Ballistic transport

Synthesis of (K0.5Bi0.5)0.4Ba0.6TiO3 nanowires and ceramics by sol-gel–hydrothermal method

Yudong Hou, Lei Hou, Mankang Zhu, and Hui Yan

Appl. Phys. Lett. 89, 243114 (2006); http://dx.doi.org/10.1063/1.2405881 (3 pages) | Cited 6 times

Online Publication Date: 13 December 2006

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(K0.5Bi0.5)0.4Ba0.6TiO3 nanowires have been fabricated by a sol-gel–hydrothermal method at 200 °C. X-ray diffraction result shows that the nanowires have a tetragonal perovskite structure. Transmission electron microscopy investigations exhibit that the as-prepared nanowires are single crystalline grains with diameters of about 40 nm and lengths reaching up to 800 nm. The (K0.5Bi0.5)0.4Ba0.6TiO3 ceramics with a relative density of 97% can be fabricated from the high quality nanowires even by a conventional sintering process, which showed that typical characteristics of relaxor ferroelectrics, the indicator of degree of diffuseness γ and Curie temperature TC (100 kHz), were 1.65 and 220 °C, respectively.
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82.45.Un Dielectric materials in electrochemistry
81.10.Dn Growth from solutions
81.10.Fq Growth from melts; zone melting and refining
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
77.80.B- Phase transitions and Curie point
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation

Carbon nanotube diode fabricated by contact engineering with self-assembled molecules

Byoung-Kye Kim, Ju-Jin Kim, Hye-Mi So, Ki-jeong Kong, Hyunju Chang, Jeong-O Lee, and Noejung Park

Appl. Phys. Lett. 89, 243115 (2006); http://dx.doi.org/10.1063/1.2403929 (3 pages) | Cited 5 times

Online Publication Date: 13 December 2006

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The authors report the construction of carbon nanotube Schottky diodes by covering a selectively exposed area of the electrode with self-assembling molecules. Two self-assembling molecules with different polarities, 2-aminoethanethiol and 3-mercaptopropionic acid, were used to modify the Fermi level lineup at the selected contact. The devices showed p-type behavior with symmetric I-V showing clear rectifying behavior after treatment of one contact with 2-aminoethanethiol. Their experiment, in conjunction with the results of ab initio electronic structure calculations, suggests that the diode action stems from the asymmetric Fermi level lineup between the bare and engineered contacts.
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85.30.Kk Junction diodes
85.35.Kt Nanotube devices

Actuation of liquid crystal elastomers reprocessed with carbon nanoparticles

Martin Chambers, Boštjan Zalar, Maja Remškar, Slobodan Žumer, and Heino Finkelmann

Appl. Phys. Lett. 89, 243116 (2006); http://dx.doi.org/10.1063/1.2404952 (3 pages) | Cited 16 times

Online Publication Date: 14 December 2006

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Liquid crystal elastomers are currently of great interest due to their large thermally stimulated changes in shape. Here the authors show that by using an existing network and conducting carbon nanoparticles dispersed in a solvent with high swelling capability, a surface integrated layer can be created. This layer allows the effective resistivity to be reduced from highly insulating to usable values for electrical actuation and withstands large changes in geometrical shape both in contraction and expansion. Utilizing a resistive “Joule” heating effect, the reprocessed system shows a 150% length change and can be cycled beyond 10 kcycles.
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61.30.Vx Polymer liquid crystals
61.25.H- Macromolecular and polymers solutions; polymer melts

Sputter deposition onto ionic liquids: Simple and clean synthesis of highly dispersed ultrafine metal nanoparticles

Tsukasa Torimoto, Ken-ichi Okazaki, Tomonori Kiyama, Kaori Hirahara, Nobuo Tanaka, and Susumu Kuwabata

Appl. Phys. Lett. 89, 243117 (2006); http://dx.doi.org/10.1063/1.2404975 (3 pages) | Cited 82 times

Online Publication Date: 14 December 2006

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Sputter deposition of gold (Au) onto ionic liquids (ILs) resulted in the formation of highly dispersed Au nanoparticles without additional chemical species, such as reducing and∕or stabilizing agents. The Au nanoparticles in 1-ethyl-3-methylimidazolium tetrafluoroborate had an average diameter (dav) of 5.5 nm with a standard deviation (σ) of 0.86 nm, while sputter deposition onto N,N,N-trimethyl-N-propylammonium bis(trifluoromethanesulfonyl)imide resulted in the formation of much smaller Au nanoparticles with dav of 1.9 nm and σ of 0.46 nm. Prolongation of sputtering time results in a higher concentration of Au nanoparticles in ILs, but did not cause a remarkable change in their size.
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81.07.Wx Nanopowders
81.16.-c Methods of micro- and nanofabrication and processing
81.15.Cd Deposition by sputtering
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)

Adhesion and elasticity in nanoscale indentation

L. Sirghi and F. Rossi

Appl. Phys. Lett. 89, 243118 (2006); http://dx.doi.org/10.1063/1.2404981 (3 pages) | Cited 15 times

Online Publication Date: 14 December 2006

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The present work proposes an extension of Oliver-Pharr analysis [J. Mater. Res. 7, 1564 (1992) ] of unloading force-displacement data obtained in nanoscale indentation experiments to account for contact adhesion. The loading force is considered a sum of the contact elastic and adhesion forces. During the unloading, both forces suffer variations. For conical geometry, the unloading force-displacement curve is described by a sum of a quadratic term (accounting for the elastic force) and a linear term (accounting for adhesive force). Results of atomic force microscopy indentation experiments performed with sharpened silicon tips on poly(dimethylsiloxane) agreed well with the prediction of the proposed theoretical model.
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68.35.Np Adhesion
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.D- Elasticity
68.35.Gy Mechanical properties; surface strains
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
68.37.Ps Atomic force microscopy (AFM)

Element specific imaging by scanning tunneling microscopy combined with synchrotron radiation light

Toyoaki Eguchi, Taichi Okuda, Takeshi Matsushima, Akira Kataoka, Ayumi Harasawa, Kotone Akiyama, Toyohiko Kinoshita, Yukio Hasegawa, Masanori Kawamori, Yuichi Haruyama, and Shinji Matsui

Appl. Phys. Lett. 89, 243119 (2006); http://dx.doi.org/10.1063/1.2399348 (3 pages) | Cited 14 times

Online Publication Date: 14 December 2006

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Microscopic surface images showing a distribution of a designated element was obtained by scanning tunneling microscopy combined with synchrotron radiation light. A tip current induced by photoirradiation is found to increase when the photon energy is just above the absorption edge of a sample element. From the photoinduced current measured during the tip scanning over the surface, element specific images were obtained. An estimated spatial resolution of the chemical imaging is less than 20 nm, better than that achieved by photoemission electron microscopy.
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82.80.-d Chemical analysis and related physical methods of analysis
07.79.Cz Scanning tunneling microscopes

High efficiency 90° bending metal heterowaveguides for nanophotonic integration

Lin Chen, Bing Wang, and Guo Ping Wang

Appl. Phys. Lett. 89, 243120 (2006); http://dx.doi.org/10.1063/1.2404596 (3 pages) | Cited 15 times

Online Publication Date: 14 December 2006

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The propagation properties of surface plasmon polaritons (SPPs) along metal heterowaveguide (MHWG)-constructed bending nanowaveguides are investigated by finite-difference time-domain simulation. The results reveal that SPPs can pass through 90° sharp bending MHWGs with higher than 90% propagation efficiency. Further numerical demonstrations of the bending MHWGs in splitters and Mach-Zehnder interferometers imply that MHWGs may find significant applications in highly integrated nanophotonic networks.
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42.82.Et Waveguides, couplers, and arrays
42.79.Gn Optical waveguides and couplers
85.60.-q Optoelectronic devices

Dependence of photocurrent in single-crystalline boron nanobelts on atmosphere

Kazuhiro Kirihara, Kenji Kawaguchi, Yoshiki Shimizu, Takeshi Sasaki, Naoto Koshizaki, Kohei Soga, and Kaoru Kimura

Appl. Phys. Lett. 89, 243121 (2006); http://dx.doi.org/10.1063/1.2404609 (3 pages) | Cited 8 times

Online Publication Date: 14 December 2006

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This letter describes the dependence of photocurrent of single-crystalline boron nanobelts on the atmosphere. In ambient air, slow photoresponse under blue light illumination was observed. Rise and decay times exceeded three days. The magnitude of photoresponse in ambient air and oxygen was greater than that in hydrogen and argon atmospheres. In vacuum, a photoresistivity effect consisting of the continuous decrease of conductance under blue light illumination was observed. Variation of band bending of the nanobelt surface by adsorption or desorption of oxygen and water molecules appeared to switch the photoconduction on and off by the respective trapping and recombination of photoexcited carriers at the nanobelt core and surface.
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73.63.Bd Nanocrystalline materials
72.40.+w Photoconduction and photovoltaic effects
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
68.43.Mn Adsorption kinetics

Multisegmented one-dimensional hybrid structures of carbon nanotubes and metal nanowires

Fung Suong Ou, M. M. Shaijumon, Lijie Ci, Derek Benicewicz, Robert Vajtai, and P. M. Ajayan

Appl. Phys. Lett. 89, 243122 (2006); http://dx.doi.org/10.1063/1.2405390 (3 pages) | Cited 21 times

Online Publication Date: 15 December 2006

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Multisegmented one-dimensional hybrid structures of carbon nanotubes and metal nanowires were fabricated using the alumina templates. Metal nanowires are first grown inside part of the nanochannel using electrodeposition technique, which is followed by the growth of carbon nanotubes using chemical vapor deposition. Well-adhered interfaces formed between the carbon nanotubes and the metal nanowires. The hybrid structure reported here results in nanoscale metal contact with carbon nanotube and will provide a solution to problem of using carbon nanotubes in interconnects. Nanotube-nanowire interfaces for different metals have also been examined and are characterized using scanning electron microscopy and transmission electron microscopy.
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68.37.Lp Transmission electron microscopy (TEM)
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.07.Lk Nanocontacts
61.46.-w Structure of nanoscale materials
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)

Atomistic simulation of brittle to ductile transition in GaN nanotubes

Zhiguo Wang, Xiaotao Zu, Fei Gao, and William J. Weber

Appl. Phys. Lett. 89, 243123 (2006); http://dx.doi.org/10.1063/1.2405879 (3 pages) | Cited 9 times

Online Publication Date: 15 December 2006

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Molecular dynamics methods with a Stillinger-Weber [Phys. Rev. B 31, 5262 (1985) ] potential have been used to investigate the mechanical properties of wurtzite-type single-crystalline GaN nanotubes under applied tensile strains. At low temperatures, the nanotubes show brittle properties, whereas at high temperatures, they behave as ductile materials. The brittle to ductile transition (BDT) is systematically investigated and the corresponding transition temperatures have been determined in GaN nanotubes. The BDT temperature generally increases with increasing thickness of nanotubes and strain rate.
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68.35.Gy Mechanical properties; surface strains
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.M- Structural failure of materials

Photoluminescence of surface InAs quantum dot stacking on multilayer buried quantum dots

B. L. Liang, Zh. M. Wang, Yu. I. Mazur, and G. J. Salamo

Appl. Phys. Lett. 89, 243124 (2006); http://dx.doi.org/10.1063/1.2408653 (3 pages) | Cited 5 times

Online Publication Date: 15 December 2006

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Coupling between the surface and the buried quantum dots (QDs) is studied by photoluminescence (PL) measurement for a heterostructure with InAs surface QDs sitting above four layers of buried QDs. Temperature and excitation intensity dependences of the PL together with the PL temporal decay behavior reveal fast carrier transfer from the buried QDs to the surface QDs. The PL signals from the surface and buried QDs are shown to be closely correlated with each other and very surface sensitive. These features support the promise this heterostructure holds for sensor devices.
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78.67.Hc Quantum dots
78.55.Cr III-V semiconductors
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