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5 Nov 2001

Volume 79, Issue 19, pp. 3017-3198

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Electric-field-directed growth of aligned single-walled carbon nanotubes

Yuegang Zhang, Aileen Chang, Jien Cao, Qian Wang, Woong Kim, Yiming Li, Nathan Morris, Erhan Yenilmez, Jing Kong, and Hongjie Dai

Appl. Phys. Lett. 79, 3155 (2001); http://dx.doi.org/10.1063/1.1415412 (3 pages) | Cited 215 times

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Electric-field-directed growth of single-walled carbon nanotubes by chemical-vapor deposition is demonstrated. The field-alignment effect originates from the high polarizability of single-walled nanotubes. Large induced dipole moments lead to large aligning torques and forces on the nanotube, and prevent randomization of nanotube orientation by thermal fluctuations and gas flows. The results shall open up possibilities in directed growth of ordered molecular-wire architectures and networks on surfaces. © 2001 American Institute of Physics.
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61.46.-w Structure of nanoscale materials
81.07.De Nanotubes
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)

Conducting tip atomic force microscopy analysis of aluminum oxide barrier defects decorated by electrodeposition

J. Carrey, K. Bouzehouane, J.-M. George, C. Ceneray, A. Fert, A. Vaurès, S. Kenane, and L. Piraux

Appl. Phys. Lett. 79, 3158 (2001); http://dx.doi.org/10.1063/1.1415775 (3 pages) | Cited 2 times

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We show that the electrodeposition of Ni80Fe20 on top of a thin aluminum oxide barrier leads to particle growth occurring on preferential nucleation centers. The particle sites are attributed to local defects in the aluminum oxide barrier. As a function of the thickness of the barrier, different growth modes can occur. For thinner barriers, new nucleation centers are created during electrodeposition. The resistance of the defects, characterized by conducting atomic force microscopy, ranges from less than 104 to greater than 1012 Ω. Various I(V) characteristics were also obtained, depending on the resistance of the defect. These results suggest that this experimental technique could be a very interesting one with which to fabricate nanoconstrictions dedicated to ballistic magnetoresistance studies.© 2001 American Institute of Physics.
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68.37.Ps Atomic force microscopy (AFM)
81.15.Pq Electrodeposition, electroplating
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
75.70.Ak Magnetic properties of monolayers and thin films

Enhanced hysteresis in the semiconductor-to-metal phase transition of VO2 precipitates formed in SiO2 by ion implantation

R. Lopez, L. A. Boatner, T. E. Haynes, R. F. Haglund, and L. C. Feldman

Appl. Phys. Lett. 79, 3161 (2001); http://dx.doi.org/10.1063/1.1415768 (3 pages) | Cited 32 times

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A strongly enhanced hysteresis with a width of >34 °C has been observed in the semiconductor-to-metal phase transition of submicron-scale VO2 precipitates formed in the near-surface region of amorphous SiO2 by the stoichiometric coimplantation of vanadium and oxygen and subsequent thermal processing. This width is approximately an order of magnitude larger than that reported previously for the phase transition of VO2 particles formed in Al2O3 by a similar technique. The phase transition is accompanied by a significant change in infrared transmission. The anomalously wide hysteresis loop observed here for the VO2/SiO2 system can be exploited in optical data storage and switching applications in the infrared region. © 2001 American Institute of Physics.
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72.60.+g Mixed conductivity and conductivity transitions
64.75.-g Phase equilibria
61.72.up Other materials
42.65.Pc Optical bistability, multistability, and switching, including local field effects
42.79.Vb Optical storage systems, optical disks

Tunable surface plasmon resonance silver films

W. A. Weimer and M. J. Dyer

Appl. Phys. Lett. 79, 3164 (2001); http://dx.doi.org/10.1063/1.1416473 (3 pages) | Cited 41 times

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Precise control of thermal evaporation deposition parameters allows the production of silver island films on glass substrates with tunable surface plasmon resonance wavelengths. Specific combinations of substrate temperature, deposition rate, and film thickness produce films exhibiting surface plasmon resonance wavelengths that can be adjusted throughout the visible and into the near-IR regions of the electromagnetic spectrum. These films are shown to be useful as substrates for surface enhanced Raman spectroscopy. © 2001 American Institute of Physics.
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73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
78.66.Bz Metals and metallic alloys
78.40.Kc Metals, semimetals, and alloys
78.30.Er Solid metals and alloys

Cluster glass structure in nanohybrids of nonstoichiometric zinc ferrite in silica matrix

Z. H. Zhou, J. Wang, J. M. Xue, and H. S. O. Chan

Appl. Phys. Lett. 79, 3167 (2001); http://dx.doi.org/10.1063/1.1415375 (3 pages) | Cited 3 times

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A cluster glass structure has been observed to occur in nanohybrids consisting of zinc ferrite in an amorphous silica matrix. Such a unique cluster glass structure has been supported by studies of x-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, and magnetic characterization. By increasing the Fe/Zn ratio in silica gel to 10, crystallites of zinc ferrite of partially inverted structure were nucleated and grown in amorphous iron oxide pockets dispersed in the silica network. The zinc ferrite crystallites, together with the confinement of silica matrix, suppress nucleation and crystallization of α-Fe2O3 to a temperature above 900 °C, preserving the cluster glass structure. The resulting cluster glass structure consists of amorphous iron oxide pockets of ∼ 10 nm in dimensions together with zinc ferrite crystallites of ∼ 3 nm in sizes, which are uniformly dispersed in the amorphous silica glass matrix.© 2001 American Institute of Physics.
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61.46.-w Structure of nanoscale materials
81.07.Bc Nanocrystalline materials
75.50.Gg Ferrimagnetics
75.50.Tt Fine-particle systems; nanocrystalline materials
78.35.+c Brillouin and Rayleigh scattering; other light scattering
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
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)

Direct quantitative measurement of compositional enrichment and variations in InyGa1−yAs quantum dots

P. A. Crozier, M. Catalano, R. Cingolani, and A. Passaseo

Appl. Phys. Lett. 79, 3170 (2001); http://dx.doi.org/10.1063/1.1415414 (3 pages) | Cited 12 times

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Assessment of the composition of quantum dots on the nanoscale is crucial for a deeper understanding of both the growth mechanisms and the properties of these materials. In this letter, we discuss a direct method to obtain a quantitative evaluation of the In variation across nanometer-sized InGaAs quantum dots embedded in a GaAs matrix, by means of electron energy-loss spectroscopy in a scanning transmission electron microscope. © 2001 American Institute of Physics.
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81.05.Ea III-V semiconductors
68.65.Hb Quantum dots (patterned in quantum wells)
79.20.Uv Electron energy loss spectroscopy

Elastic force analysis of functional polymer submicron oscillators

Hong-Bo Sun, Kenji Takada, and Satoshi Kawata

Appl. Phys. Lett. 79, 3173 (2001); http://dx.doi.org/10.1063/1.1418024 (3 pages) | Cited 59 times

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We report in this letter an elastic force analysis of two-photon-polymerized submicron oscillators with spiral radius of 150 nm. A laser trapping force was first utilized to mechanically drive the spring of this small size. An overdamped oscillation was observed, according to which, the spring constant was measured to approximately 10−8 N/m. This value was 5-order smaller than the one calculated using oscillator parameters. Both deviated from a more reliable result, 10−6 N/m, as was estimated from the laser trapping force. The significant discrepancies were attributed to scaling effects and to the difference of condensed states of the polymer related to exposure processes. © 2001 American Institute of Physics.
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07.10.Cm Micromechanical devices and systems
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
62.20.D- Elasticity
81.40.Jj Elasticity and anelasticity, stress-strain relations
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
82.35.-x Polymers: properties; reactions; polymerization
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials

Surface-modified CuO layer in size-stabilized single-phase Cu2O nanoparticles

B. Balamurugan, B. R. Mehta, and S. M. Shivaprasad

Appl. Phys. Lett. 79, 3176 (2001); http://dx.doi.org/10.1063/1.1416478 (3 pages) | Cited 52 times

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Activated reactive evaporation has been used to grow copper oxide nanoparticles in the size range of 8–100 nm. X-ray diffraction spectra clearly show the presence of a single Cu2O phase. Detailed x-ray photoelectron spectroscopy studies show an increase in the ionicity of the Cu2O system with decreasing particle size. Depth profiling and finger printing of x-ray photoelectron spectra reveal that the Cu2O nanoparticles are capped with a CuO surface layer of thickness ≈1.6 nm. This study strongly suggests that the stabilization of the cubic Cu2O nanophase is enhanced by the formation of a CuO surface layer. © 2001 American Institute of Physics.
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61.46.-w Structure of nanoscale materials
81.07.Bc Nanocrystalline materials
79.60.Bm Clean metal, semiconductor, and insulator surfaces

Electronic structure of the Fe-layer-catalyzed carbon nanotubes studied by x-ray-absorption spectroscopy

C. L. Yueh, J. C. Jan, J. W. Chiou, W. F. Pong, M.-H. Tsai, Y. K. Chang, Y. Y. Chen, Y. F. Lee, P. K. Tseng, S. L. Wei, C. Y. Wen, L. C. Chen, and K. H. Chen

Appl. Phys. Lett. 79, 3179 (2001); http://dx.doi.org/10.1063/1.1416165 (3 pages) | Cited 14 times

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X-ray-absorption near edge structure (XANES) measurements have been performed to investigate the local electronic structures of the Fe-catalyzed and stabilized carbon nanotubes (CNT) with various diameters. The intensities of the π∗- and σ∗-band and the interlayer-state features in the C K-edge XANES spectra of these CNTs vary with the diameter of the CNT. The white-line features at the C K- and Fe L3-edges suggest a strong hybridization between the C 2p and Fe 3d orbitals, which lead to an enhancement of the C K- and reduction of the Fe L3-edge features, respectively, indicative of a charge transfer from C 2p to Fe 3d orbitals. The Fe K-edge spectra reveal a p–d rehybridization effect that reduces p-orbital occupation at the Fe site. © 2001 American Institute of Physics.
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73.22.Dj Single particle states
78.70.Dm X-ray absorption spectra
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