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24 Oct 2005

Volume 87, Issue 17, Articles (17xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 87, 172506 (2005); http://dx.doi.org/10.1063/1.2120911 (3 pages)

T. Kimura, Y. Otani, and J. Hamrle
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Electrical contacts to carbon nanotubes down to 1 nm in diameter

Woong Kim, Ali Javey, Ryan Tu, Jien Cao, Qian Wang, and Hongjie Dai

Appl. Phys. Lett. 87, 173101 (2005); http://dx.doi.org/10.1063/1.2108127 (3 pages) | Cited 75 times

Online Publication Date: 17 October 2005

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Rhodium (Rh) is found similar to Palladium (Pd) in making near-Ohmic electrical contacts to single-walled carbon nanotubes (SWNTs) with diameters d> ∼ 1.6 nm. Non-negligible positive Schottky barriers (SBs) exist between Rh or Pd and semiconducting SWNTs (S-SWNTs) with d< ∼ 1.6 nm. With Rh and Pd contacts, the characteristics of SWNT field-effect transistors and SB heights at the contacts are largely predictable based on the SWNT diameters, without random variations among devices. Surprisingly, electrical contacts to metallic SWNTs (M-SWNTs) also appear to be diameter dependent especially for small SWNTs. Ohmic contacts are difficult for M-SWNTs with diameters ⩽ ∼ 1.0 nm possibly due to tunnel barriers resulted from large perturbation of contacting metal to very small diameter SWNTs due to high chemical reactivity of the latter.
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85.30.Tv Field effect devices
73.30.+y Surface double layers, Schottky barriers, and work functions
61.46.-w Structure of nanoscale materials
73.40.Ns Metal-nonmetal contacts

Coupling of photon energy via a multiwalled carbon nanotube array

Qi Lu, Rahul Rao, Bindu Sadanadan, William Que, Apparao M. Rao, and Pu Chun Ke

Appl. Phys. Lett. 87, 173102 (2005); http://dx.doi.org/10.1063/1.2112206 (3 pages) | Cited 5 times

Online Publication Date: 17 October 2005

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Fluorescent beads were excited by a laser beam coupled through a multiwalled carbon nanotube array. The images of the fluorescent beads showed a distinctive dependence on the polarization direction of the laser beam owing to the surface plasmons induced from the metallic property of the array. The thickness of the array is 2 μm as compared to the metallic films of tens of nanometers in thickness that are conventionally used for surface plasmon excitation. This remarkable photon coupling capacity of a multiwalled carbon nanotube array is attributed to the confinement of electrons in its outermost tube shells and ballistic transport.
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78.67.Ch Nanotubes
73.63.Fg Nanotubes
73.22.Lp Collective excitations
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
78.68.+m Optical properties of surfaces
73.23.Ad Ballistic transport

Nanostructuring of Bi(0001) surfaces with the scanning tunneling microscope: Writing of periodic Bi structures by bias voltage pulsing

A. Turchanin and W. Freyland

Appl. Phys. Lett. 87, 173103 (2005); http://dx.doi.org/10.1063/1.2112182 (3 pages)

Online Publication Date: 18 October 2005

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Employing the scanning-tunneling-microscope pulse technique with a tungsten tip, we studied the nanostructuring of Bi (0001) surfaces at room temperature. A controlled extraction of Bi and its reversible deposition is demonstrated by simply changing the pulse polarity. Periodic nanostructures of dots, holes, lines, and grooves were written in the point and line mode of the scanner which exhibit a relatively high stability over a period of up to 22 days. Our data indicate that during the nanostructuring a Bi nanobridge forms between tungsten tip and substrate on a time scale of ∼ 100 μs.
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81.16.Ta Atom manipulation
81.07.Bc Nanocrystalline materials
61.46.-w Structure of nanoscale materials

Application of carbon nanotube field emission effect to an ionization gauge

In-Mook Choi and Sam-Yong Woo

Appl. Phys. Lett. 87, 173104 (2005); http://dx.doi.org/10.1063/1.2112184 (3 pages) | Cited 15 times

Online Publication Date: 18 October 2005

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Using the field emission effect of a carbon nanotube (CNT), we characterized a new type of technology for detecting low pressure. The fabricated low pressure sensor is of a triode type, consisting of a cathode (carbon nanotubes field emitter arrays), a grid, and a collector. The gauge described here has a triode configuration similar to that of a conventional hot cathode ionization gauge but also has a cold emission source. Due to the excellent field emission characteristics of CNT, it is possible to make a cost effective cold cathode type ionization gauge. For an effective CNT cathode, we used the screen-printing method and also, we controlled the collector and the grid potentials in order to obtain a high ionization current. We found that the ratio of the ionization current to the CNT cathode current changes according to the pressure in the chamber. In short, we elaborate the various metrological characteristics of a home-made pressure sensor that uses CNTs.
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85.35.Kt Nanotube devices
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
07.30.Dz Vacuum gauges
79.70.+q Field emission, ionization, evaporation, and desorption

Dynamic lateral force microscopy with true atomic resolution

Shigeki Kawai, Shin-ichi Kitamura, Dai Kobayashi, and Hideki Kawakatsu

Appl. Phys. Lett. 87, 173105 (2005); http://dx.doi.org/10.1063/1.2112203 (3 pages) | Cited 15 times

Online Publication Date: 18 October 2005

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We present frequency modulation dynamic lateral force microscopy with true atomic resolution. Torsional resonance mode of a commercially available rectangular cantilever was used to detect interaction lateral force gradients caused between the tip and the sample surface. A slight negative frequency shift of the torsional resonance frequency was observed before contact to the silicon surface. Individual adatoms in a unit cell of the Si(111)-7×7 reconstructed surface were imaged with the constant frequency shift mode. Two sets of the neighboring corner adatoms and one set of the center adatoms on the dithering direction of the tip were connected on the image. This method has a great potential to observe friction between single atoms.
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68.47.Fg Semiconductor surfaces
07.79.Sp Friction force microscopes
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.43.Mn Adsorption kinetics

Structural control of vertically aligned multiwalled carbon nanotubes by radio-frequency plasmas

Jitendra Menda, Benjamin Ulmen, Lakshman K. Vanga, Vijaya K. Kayastha, Yoke Khin Yap, Zhengwei Pan, Ilia N. Ivanov, Alex A. Puretzky, and David B. Geohegan

Appl. Phys. Lett. 87, 173106 (2005); http://dx.doi.org/10.1063/1.2115068 (3 pages) | Cited 6 times

Online Publication Date: 18 October 2005

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Plasma-enhanced chemical vapor deposition is the only technique for growing individual vertically aligned multiwalled carbon nanotubes (VA-MWCNTs) at desired locations. Inferior graphitic order has been a long-standing issue that has prevented realistic applications of these VA-MWCNTs. Previously, these VA-MWCNTs were grown by a one-plasma approach. Here, we demonstrate the capability of controlling graphitic order and diameters of VA-MWCNTs by decoupling the functions of the conventional single plasma into a dual-plasma configuration. Our results indicate that the ionic flux and kinetic energy of the growth species are important for improving graphitic order of VA-MWCMTs.
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81.07.De Nanotubes
61.46.-w Structure of nanoscale materials

Charge storage in nitrided nanocrystalline silicon dots

Shaoyun Huang and Shunri Oda

Appl. Phys. Lett. 87, 173107 (2005); http://dx.doi.org/10.1063/1.2115069 (3 pages) | Cited 17 times

Online Publication Date: 18 October 2005

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Nitrided nanocrystalline silicon (nc-Si) dots are proposed to be a candidate of memory nodes for nonvolatile memory device applications to make good use of advantages of both silicon quantum dots and silicon nitride films. The stored charges in the memory nodes are identified not only in nc-Si dots (electron delocalized states) but also in defect states at the nc-Si/silicon-nitride interface (electron localized states) by current-voltage (I-V) spectrum. Temperature dependences of the I-V characteristics demonstrate an evolution of stored charges in the combined system and clarify its storage mechanisms.
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73.21.La Quantum dots
71.55.Cn Elemental semiconductors

Imaging suspended carbon nanotubes in field-effect transistors configured with microfabricated slits for transmission electron microscopy

Taekyung Kim, Jian-Min Zuo, Eric A. Olson, and Ivan Petrov

Appl. Phys. Lett. 87, 173108 (2005); http://dx.doi.org/10.1063/1.2115070 (3 pages) | Cited 10 times

Online Publication Date: 18 October 2005

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Field-effect transistors with carbon nanotubes (CNTs) suspended across etched slits and fabricated by chemical vapor deposition have been characterized by electrical measurements and transmission electron microscopy. Two devices are examined here: One is semiconducting from two single-wall CNTs, and the other is semiconducting and metallic, with a large off current, that comes from multiple nanotubes. The study highlights the importance of structural characterization in understanding the performance of CNT devices.
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85.30.Tv Field effect devices
85.35.Kt Nanotube devices

First-principles study of band-gap change in deformed nanotubes

Bin Shan, Gregory W. Lakatos, Shu Peng, and Kyeongjae Cho

Appl. Phys. Lett. 87, 173109 (2005); http://dx.doi.org/10.1063/1.2067697 (3 pages) | Cited 21 times

Online Publication Date: 18 October 2005

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The effects of cross-sectional deformation and bending on the electronic structures of single-wall carbon nanotubes (SWNTs) are examined. Upon increasing the deformation, semiconducting SWNTs undergo semiconductor-metal transition, and the conduction band and valence band show asymmetric response to the deformation. The metallic tubes’ electronic structures are relatively insensitive to similar mechanical deformation. Using the properties of deformed nanotubes, we propose a conceptual design of SWNT-based single-electron quantum-well devices.
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73.20.At Surface states, band structure, electron density of states
71.15.-m Methods of electronic structure calculations
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity

Cylindrical nanopores in NiO induced by swift heavy ions

B. Schattat, W. Bolse, S. Klaumünzer, I. Zizak, and R. Scholz

Appl. Phys. Lett. 87, 173110 (2005); http://dx.doi.org/10.1063/1.2115084 (3 pages) | Cited 6 times

Online Publication Date: 18 October 2005

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NiO single crystals and polycrystalline films of about 100 nm thickness have been irradiated at liquid-nitrogen temperature with 90 MeV Ar, 140 MeV Kr, 230 MeV Xe, and 350 MeV Au ions. After bombardment with Xe or Au ions, transmission electron microscopy and small angle x-ray scattering reveal empty ion tracks with diameters between 2 and 4 nm. These nanopores extend through the specimens and are terminated by spherical nanoparticles containing the material which is missing in the pores.
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81.07.Bc Nanocrystalline materials
61.43.Gt Powders, porous materials
61.46.-w Structure of nanoscale materials
61.80.Jh Ion radiation effects
61.82.Ms Insulators
68.37.Lp Transmission electron microscopy (TEM)
78.70.Ck X-ray scattering

GaN nanowire lasers with low lasing thresholds

Silvija Gradečak, Fang Qian, Yat Li, Hong-Gyu Park, and Charles M. Lieber

Appl. Phys. Lett. 87, 173111 (2005); http://dx.doi.org/10.1063/1.2115087 (3 pages) | Cited 128 times

Online Publication Date: 18 October 2005

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We report optically pumped room-temperature lasing in GaN nanowires grown by metalorganic chemical vapor deposition (MOCVD). Electron microscopy images reveal that the nanowires grow along a nonpolar ⟨11-20⟩ direction, have single-crystal structures and triangular cross sections. The nanowires function as free-standing Fabry–Pérot cavities with cavity mode spacings that depend inversely on length. Optical excitation studies demonstrate thresholds for stimulated emission of 22 kW/cm2 that are substantially lower than other previously reported GaN nanowires. Key contributions to low threshold lasing in these MOCVD GaN nanowire cavities and the development of electrically pumped GaN nanowire lasers are discussed.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
68.65.La Quantum wires (patterned in quantum wells)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Direct contact buckling of electrochemically grown gold nanowires

W. J. Kim, S. M. Carr, and M. N. Wybourne

Appl. Phys. Lett. 87, 173112 (2005); http://dx.doi.org/10.1063/1.2117618 (3 pages) | Cited 3 times

Online Publication Date: 20 October 2005

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We report the electrochemical growth and direct probing of near-vertical gold nanowires several micrometers long that are attached at one end to a substrate. Controllable contact is made to the wires using a straightforward tip-probe arrangement inside a scanning electron microscope. The contact allowed us to perform mechanical and electrical measurements. Through elastic nanowire buckling, we have observed dynamic low-frequency parametric pumping caused by small vibrations of the probe. A numerical simulation of the recorded motion is consistent with an estimated value of Young’s modulus of about 80 GPa, which is close to that of bulk gold.
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81.40.Lm Deformation, plasticity, and creep
61.46.-w Structure of nanoscale materials
62.20.F- Deformation and plasticity
82.45.Yz Nanostructured materials in electrochemistry
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.D- Elasticity

Mid-infrared intersublevel absorption of vertically electronically coupled InAs quantum dots

C. Kammerer, S. Sauvage, G. Fishman, P. Boucaud, G. Patriarche, and A. Lemaître

Appl. Phys. Lett. 87, 173113 (2005); http://dx.doi.org/10.1063/1.2117621 (3 pages) | Cited 13 times

Online Publication Date: 20 October 2005

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We have studied mid-infrared intersublevel absorption of samples containing two layers of vertically self-aligned, self-assembled InAs quantum dots separated by a thin GaAs barrier. Samples with coupled quantum dots exhibiting different average size between the two layers are investigated. The electronically coupled quantum dot absorption is compared with the absorption of a reference sample containing uncoupled quantum dots. Electronically coupled quantum dots present a spectrally narrow absorption line ( ∼ 20 meV full width at half maximum) mainly polarized along the growth axis in the range 110–150 meV. This absorption is attributed to the bound-to-bound transition between bonding (symmetric-like) and antibonding (antisymmetric-like) s state combinations of the double quantum dot structure. This assignment is supported by the electronic structure of the coupled quantum dots as calculated by the three-dimensional resolution of the Schrödinger equation written in the 8-band k.p envelope function formalism.
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78.30.Fs III-V and II-VI semiconductors
68.65.Hb Quantum dots (patterned in quantum wells)
73.21.La Quantum dots
78.67.Hc Quantum dots

Strong visible light emission from well-aligned multiwalled carbon nanotube films under infrared laser irradiation

Yong Zhang, Tao Gong, Wenjin Liu, Xianfeng Zhang, Jianguo Chang, Kunlin Wang, and Dehai Wu

Appl. Phys. Lett. 87, 173114 (2005); http://dx.doi.org/10.1063/1.2117627 (3 pages) | Cited 7 times

Online Publication Date: 20 October 2005

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We report strong and brilliant visible light emission from well-aligned multiwalled carbon nanotube (AMWNT) films under infrared (IR) laser irradiation with wavelength at 1.06 and 10.6 μm, respectively. The AMWNT film shows a high durability against laser irradiation and achieved a conversion from IR laser to visible light. It is a good candidate for optical converter. Light emission spectra versus different wavelengths and various powers were found to have similar line shapes. It could be explained as combination of laser-induced photoluminescence and resistive heating.
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78.67.Ch Nanotubes
78.55.Hx Other solid inorganic materials
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)

Patterning lyotropic liquid crystals as precursors for carbon nanotube arrays

M. E. Sousa, S. G. Cloutier, K. Q. Jian, B. S. Weissman, R. H. Hurt, and G. P. Crawford

Appl. Phys. Lett. 87, 173115 (2005); http://dx.doi.org/10.1063/1.2108111 (3 pages) | Cited 2 times

Online Publication Date: 20 October 2005

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We report on a simple patterning technique using lyotropic liquid-crystal solutions to fabricate organized arrays of high aspect ratio carbon nanostructures. An automated pen writing system is used in conjunction with nanochannel alumina templates to produce ordered arrays of nanotubes and nanofibers in a variety of shapes, widths, and carbon crystal structures set by surface anchoring phenomena. The nanostructure arrays are characterized with optical and electron microscopy and Raman spectroscopy to establish the morphology and crystal structures of the carbon nanoform arrays.
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81.16.Rf Micro- and nanoscale pattern formation
61.46.-w Structure of nanoscale materials
68.37.-d Microscopy of surfaces, interfaces, and thin films
61.50.-f Structure of bulk crystals
78.30.Hv Other nonmetallic inorganics

Long-range ordered nanoaperture array with uniform diameter and interpore spacing

Ming-Nung Lin, Minn-Tsong Lin, C. Y. Liu, M. Y. Lai, N. W. Liu, C. Y. Peng, H. H. Wang, and Y. L. Wang

Appl. Phys. Lett. 87, 173116 (2005); http://dx.doi.org/10.1063/1.2117608 (3 pages) | Cited 8 times

Online Publication Date: 20 October 2005

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In application of focused-ion-beam lithography and grazing Ar+ milling on the U-shape barrier layer of anodic alumina nanochannels, we fabricated a hexagonally symmetry aperture array with nominal diameter of 12±2 nm and interspacing of 100±2 nm. Besides long-range spatial ordering, the focused-ion-beam guided-grown process has also significantly improved uniformity of both the interpore spacing and the aperture size. This aperture array membrane can be applied to the fabrication of nanostructures, such as a lithographic contact mask for ordered quantum-dot array.
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61.46.-w Structure of nanoscale materials
81.16.Nd Micro- and nanolithography

Lasing action in colloidal CdS/CdSe/CdS quantum wells

Jianfeng Xu and Min Xiao

Appl. Phys. Lett. 87, 173117 (2005); http://dx.doi.org/10.1063/1.2119423 (3 pages) | Cited 11 times

Online Publication Date: 20 October 2005

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Lasing action is observed in random medium of colloidal CdS/CdSe/CdS quantum wells (QWs) at 77 K. Sharp lasing peaks appear over a broad spectral range as pumping power increases. The lasing threshold is around 3 W/cm2, which is much lower than that of other random or nanocrystal laser systems. Such improvement in lasing threshold opens the door to practical applications of QW random laser. The characteristic cavity length is determined by the Fourier transform of the lasing spectrum.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
82.70.Dd Colloids

Water reaction with chlorine-terminated silicon (111) and (100) surfaces

Sandrine Rivillon, Rhett T. Brewer, and Yves J. Chabal

Appl. Phys. Lett. 87, 173118 (2005); http://dx.doi.org/10.1063/1.2119426 (3 pages) | Cited 5 times

Online Publication Date: 20 October 2005

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Hydroxylation of chlorine-terminated silicon (111) and (100) by water vapor exposure has been studied as a function of substrate temperature using in situ infrared absorption spectroscopy. No hydroxyl is observed, as would have been expected from the surface reaction: Si–Cl(ads)+H2O(g)→Si–OH(ads)+HCl(g) (ads referring to adsorbed surface species). Instead, silicon oxide is formed upon removal of the Si–Cl bond at ∼ 325 °C. This indicates that, while hydroxylation of the Cl-terminated silicon surface may occur, the hydroxylated surface formed by this reaction is not stable at the temperature necessary for the reaction.
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68.47.Fg Semiconductor surfaces
78.66.Db Elemental semiconductors and insulators
82.40.Np Temporal and spatial patterns in surface reactions
78.30.Am Elemental semiconductors and insulators
68.43.Mn Adsorption kinetics

Room-temperature ferromagnetic Co-doped ZnO nanoneedle array prepared by pulsed laser deposition

J. J. Chen, M. H. Yu, W. L. Zhou, K. Sun, and L. M. Wang

Appl. Phys. Lett. 87, 173119 (2005); http://dx.doi.org/10.1063/1.2119415 (3 pages) | Cited 29 times

Online Publication Date: 20 October 2005

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A Co-doped ZnO nanoneedle array with room-temperature ferromagnetic properties was successfully fabricated by pulsed laser deposition (PLD) method. Detailed nanostructures were studied by transmission electron microscopy (TEM) and x-ray diffraction (XRD). High resolution TEM images and selected area electron diffraction (SAD) patterns showed nanoneedles grew along c-axis of ZnO with a preferential growth perpendicular to Si (100) substrate, which is also confirmed by XRD. Uneven surface and stacking faults along the nanoneedles were observed, which implies lattice distortion due to the Co doping. Electron energy loss spectroscopy (EELS) analysis of different positions along the growth direction of nanoneedles shows homogeneous distribution of the Co dopant. No segregated clusters of impurity phase were detected by TEM. Superconducting quantum interference device (SQUID) magnetometer measurements show room temperature ferromagnetic ordering, which is attributed to the Co substitution for Zn in the ZnO nanoneedle.
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75.50.Tt Fine-particle systems; nanocrystalline materials
75.50.Dd Nonmetallic ferromagnetic materials
81.05.Dz II-VI semiconductors
61.46.-w Structure of nanoscale materials
81.07.Bc Nanocrystalline materials
75.50.Pp Magnetic semiconductors
68.37.Lp Transmission electron microscopy (TEM)
68.47.Fg Semiconductor surfaces
61.72.uj III-V and II-VI semiconductors
79.20.Uv Electron energy loss spectroscopy
81.16.-c Methods of micro- and nanofabrication and processing

Simultaneously B- and P-doped silicon nanoclusters: Formation energies and electronic properties

S. Ossicini, E. Degoli, F. Iori, E. Luppi, R. Magri, G. Cantele, F. Trani, and D. Ninno

Appl. Phys. Lett. 87, 173120 (2005); http://dx.doi.org/10.1063/1.2119424 (3 pages) | Cited 30 times

Online Publication Date: 21 October 2005

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The effects of B and P codoping on the impurity formation energies and electronic properties of Si nanocrystals (Si-nc) are calculated by a first-principles method. We show that, if carriers in the Si-nc are perfectly compensated by simultaneous doping with n- and p-type impurities, the Si-nc undergo a minor structural distortion around the impurities and that the formation energies are always smaller than those for the corresponding single-doped cases. The band gap of the codoped Si-nc is strongly reduced with respect to the gap of the pure ones showing the possibility of an impurity based engineering of the photoluminescence properties of Si-nc.
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71.55.Cn Elemental semiconductors
71.20.Mq Elemental semiconductors
61.72.uf Ge and Si
61.46.-w Structure of nanoscale materials
71.15.-m Methods of electronic structure calculations
73.22.-f Electronic structure of nanoscale materials and related systems

Acoustic modes and elastic properties of polymeric nanostructures

R. D. Hartschuh, A. Kisliuk, V. Novikov, A. P. Sokolov, P. R. Heyliger, C. M. Flannery, W. L. Johnson, C. L. Soles, and W.-L. Wu

Appl. Phys. Lett. 87, 173121 (2005); http://dx.doi.org/10.1063/1.2119414 (3 pages) | Cited 13 times

Online Publication Date: 21 October 2005

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Phonon spectra of polymeric linear nanostructures have been characterized using Brillouin light scattering. In addition to phonon modes similar to those present in uniform thin films, the phonon spectra of the nanolines reveal a new mode with a lower frequency that depends on the width of the nanolines. Classic wave theory and finite element analysis were combined to identify this new mode as a flexural vibration of the nanolines. Analysis of the phonon spectra gave estimates of elastic constants in the nanostructures and indicated that there is no significant deviation from bulk mechanical properties and no mechanical anisotropy in structures as small as 88 nm.
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63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
81.40.Jj Elasticity and anelasticity, stress-strain relations
81.40.Lm Deformation, plasticity, and creep
62.25.-g Mechanical properties of nanoscale systems
62.20.D- Elasticity
62.20.F- Deformation and plasticity
61.46.-w Structure of nanoscale materials
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
78.35.+c Brillouin and Rayleigh scattering; other light scattering

Synthesis and characterization of crystalline microporous cobalt phosphite nanowires

R. C. Che, L.-M. Peng, and W. Z. Zhou

Appl. Phys. Lett. 87, 173122 (2005); http://dx.doi.org/10.1063/1.2084327 (3 pages) | Cited 5 times

Online Publication Date: 21 October 2005

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Crystalline microporous Co11(HPO3)8(OH)6 nanowires have been synthesized through a soft hydrothermal reaction between red phosphor, KOH, and metal halides. These nanowires were found to have their main hexagonal channels along the long axis and a narrow distribution around 30–40 nm in diameter. The growth of the nanowires were found to initiate at Co(OH)2 nuclei. The length of the nanowires depends mainly on the hydrothermal reaction time and the amount of Co(OH)2 available at the nuclei to feed the growth of the nanowires. Blue shift of up to 85 nm was observed in UV-visible absorption spectra from the Co11(HPO3)8(OH)6 nanowires in comparing with that from the micro-size particle sample, giving an absorption edge deep in the ultraviolet region at about 255 nm or a bandgap Eg ∼ 4.9 eV.
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81.07.Bc Nanocrystalline materials
81.07.Vb Quantum wires
81.05.Rm Porous materials; granular materials
61.46.-w Structure of nanoscale materials
68.65.La Quantum wires (patterned in quantum wells)
73.21.Hb Quantum wires
73.22.-f Electronic structure of nanoscale materials and related systems
78.67.-n Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures
61.43.Gt Powders, porous materials
81.16.Be Chemical synthesis methods
81.10.Dn Growth from solutions
78.40.Ha Other nonmetallic inorganics
61.66.Fn Inorganic compounds
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