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28 Nov 2005

Volume 87, Issue 22, Articles (22xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 87, 221108 (2005); http://dx.doi.org/10.1063/1.2137458 (3 pages)

V. Barna, S. Ferjani, A. De Luca, R. Caputo, N. Scaramuzza, C. Versace, and G. Strangi
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Kinetic control of Ge(Si)/Si(100) dome cluster composition

E. P. McDaniel, Qian Jiang, P. A. Crozier, Jeff Drucker, and David J. Smith

Appl. Phys. Lett. 87, 223101 (2005); http://dx.doi.org/10.1063/1.2135870 (3 pages) | Cited 8 times

Online Publication Date: 21 November 2005

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The Ge content of dome clusters grown by molecular beam epitaxy of pure Ge onto Si(100) rises with increasing deposition rate. The rising Ge content is manifested by a decrease in the volume at which clusters change shape from pyramids to domes and is quantitatively confirmed using nm spatial resolution electron-energy-loss spectroscopy in a scanning transmission electron microscope. The areal density of dome clusters is controlled by the ratio between the deposition and surface diffusion rates whereas their composition is controlled by the ratio between the deposition and Si interdiffusion rates.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
68.43.Hn Structure of assemblies of adsorbates (two- and three-dimensional clustering)
81.05.Cy Elemental semiconductors
68.47.Fg Semiconductor surfaces
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.49.Jk Electron scattering from surfaces
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.35.Fx Diffusion; interface formation
66.30.Ny Chemical interdiffusion; diffusion barriers

Formation and evolution of self-assembled crystalline Si nanorings on (001) Si mediated by Au nanodots

J. H. He, W. W. Wu, Y. L. Chueh, C. L. Hsin, L. J. Chen, and L. J. Chou

Appl. Phys. Lett. 87, 223102 (2005); http://dx.doi.org/10.1063/1.2136219 (3 pages) | Cited 10 times

Online Publication Date: 21 November 2005

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The growth of high-density Si nanorings has been achieved on ultrathin Au films on silicon substrate. Nanorings, which are gold-free and epitaxially grown on (001) Si, had a narrow distribution of height and diameter of 1.4±0.3 and 24.9±4.0 nm, with a density of 4.3×1010 cm−2. In situ ultrahigh-vacuum transmission electron microscopy revealed that the formation of nanorings involves a mechanism mediated by Au nanodots and evaporation of Au-Si eutectic liquid droplets at high temperature. The process promises to be an effective nanofabrication technique to produce high-density and uniform-sized nanorings.
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81.16.Dn Self-assembly
61.46.-w Structure of nanoscale materials

Reversible electromechanical characteristics of individual multiwall carbon nanotubes

V. Semet, Vu Thien Binh, D. Guillot, K. B. K. Teo, M. Chhowalla, G. A. J. Amaratunga, W. I. Milne, P. Legagneux, and D. Pribat

Appl. Phys. Lett. 87, 223103 (2005); http://dx.doi.org/10.1063/1.2136229 (3 pages) | Cited 16 times

Online Publication Date: 21 November 2005

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Here we report the reversible change in the nonlinear conductance of a multiwall carbon nanotube (MWNT) when it is bent longitudinally. As the nanotube is compressed and bent, its resistance decreases dramatically. This behavior is fully recoverable. The observed drop in resistance during bending must be the result of increasing number of conduction channels in the nanotube and parallel transport through them. Using this concept of parallel transport, we show that it is indeed possible to electrically model the behavior of the MWNT under compression. The reversible electrical characteristics of a MWNT under bending opens new possibilities for these structures to be applied as nanoscale displacement sensors.
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81.07.De Nanotubes
73.63.Fg Nanotubes
62.25.-g Mechanical properties of nanoscale systems
77.65.-j Piezoelectricity and electromechanical effects
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity

Fabrication and characterization of electrostatic Si/SiGe quantum dots with an integrated read-out channel

M. R. Sakr, H. W. Jiang, E. Yablonovitch, and E. T. Croke

Appl. Phys. Lett. 87, 223104 (2005); http://dx.doi.org/10.1063/1.2136436 (3 pages) | Cited 28 times

Online Publication Date: 21 November 2005

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A nontraditional fabrication technique is used to produce quantum dots with read-out channels in silicon/silicon–germanium two-dimensional electron gases. The technique utilizes Schottky gates, placed on the sides of a shallow etched quantum dot, to control the electronic transport process. An adjacent quantum point contact gate is integrated to the side gates to define a read-out channel, and thus allow for noninvasive detection of the electronic occupation of the quantum dot. Reproducible and stable Coulomb oscillations and the corresponding jumps in the read-out channel resistance are observed at low temperatures. The fabricated dot combined with the read-out channel represents a step toward the spin-based quantum bit in Si/SiGe heterostructures.
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81.07.Ta Quantum dots
81.05.Cy Elemental semiconductors
81.05.Hd Other semiconductors
73.21.La Quantum dots
73.63.Kv Quantum dots
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.30.+y Surface double layers, Schottky barriers, and work functions
73.23.-b Electronic transport in mesoscopic systems
73.63.Rt Nanoscale contacts

On the capillary condensation of water in mesoporous silica films measured by x-ray reflectivity

Sandrine Dourdain and Alain Gibaud

Appl. Phys. Lett. 87, 223105 (2005); http://dx.doi.org/10.1063/1.2136412 (3 pages) | Cited 5 times

Online Publication Date: 21 November 2005

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X-ray reflectivity experiments have been used to monitor the capillary condensation of water in mesoporous silica thin films. We show that both the Bragg peak intensities and the film critical wave vector transfer are very sensitive to water intrusion or extrusion from the pores. Similarly to what is achieved during adsorption and desorption of gas, adsorption isotherms can be measured by monitoring the evolution of the average electron density of the film as a function of the relative humidity. The pore size distribution of mesoporous silica thin films is further determined from the isotherms.
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78.66.Nk Insulators
61.43.Gt Powders, porous materials
68.55.-a Thin film structure and morphology
73.61.Ng Insulators
72.20.-i Conductivity phenomena in semiconductors and insulators
68.43.Mn Adsorption kinetics

Surface compositional gradients of InAs/GaAs quantum dots

G. Biasiol, S. Heun, G. B. Golinelli, A. Locatelli, T. O. Mentes, F. Z. Guo, C. Hofer, C. Teichert, and L. Sorba

Appl. Phys. Lett. 87, 223106 (2005); http://dx.doi.org/10.1063/1.2135213 (3 pages) | Cited 16 times

Online Publication Date: 21 November 2005

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With laterally resolved photoemission spectroscopy, we obtained In and Ga surface concentration maps of InAs/GaAs quantum dots. Our data demonstrate that the dot composition is neither pure InAs nor homogeneous InxGa1−xAs, but presents an In concentration increasing from the borders to the center of the dots. Besides, our observations suggest strong In segregation (x ∼ 0.9) on the surface of the dots and of the surrounding wetting layer. Such segregation, well known for two-dimensional InAs/GaAs growth, had not been directly observed so far on the dots, and should be taken into account to model size and composition of GaAs-overgrown structures.
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68.35.Dv Composition, segregation; defects and impurities
78.67.Hc Quantum dots
79.60.Bm Clean metal, semiconductor, and insulator surfaces
68.47.Fg Semiconductor surfaces
78.66.Fd III-V semiconductors
64.75.-g Phase equilibria

Low frequency noise in silicon nanogaps

Jonas Berg, Per Lundgren, Peter Enoksson, and Stefan Bengtsson

Appl. Phys. Lett. 87, 223107 (2005); http://dx.doi.org/10.1063/1.2135215 (3 pages)

Online Publication Date: 21 November 2005

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Silicon nanogaps are contact structures for connecting organic molecules. An insulating layer is removed by etching, and this dramatically increases the current levels and the noise, which closely resembles a 1/f law and scales with the square of the current. After etching, the noise level at 30 Hz and 10 nA is in the order of 10−21 A2/Hz, which is more than two orders of magnitude larger than before etching. We model the noisy behavior by several percolation paths in parallel at the etched surface between the electrodes, and compare it with soft breakdown in thin oxide.
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72.70.+m Noise processes and phenomena
73.61.Cw Elemental semiconductors
73.63.Bd Nanocrystalline materials

Growth and field-emission property of tungsten oxide nanotip arrays

Jun Zhou, Li Gong, Shao Zhi Deng, Jun Chen, Jun Cong She, Ning Sheng Xu, Rusen Yang, and Zhong Lin Wang

Appl. Phys. Lett. 87, 223108 (2005); http://dx.doi.org/10.1063/1.2136006 (3 pages) | Cited 88 times

Online Publication Date: 21 November 2005

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Large-area, quasialigned nanotips of tungsten oxide have been grown by a two-step high-temperature, catalyst-free, physical evaporation deposition process. The tungsten oxide nanotips are single crystalline with growth direction of [010]. The tungsten oxide nanotips exhibit excellent field-emission properties with a low threshold field (for an emission current density of 10 mA/cm2) ∼ 4.37 MV/m and uniform emission from the entire arrays, as well as high time stability. These results make tungsten oxide nanotip arrays a competitive candidate for field-emission displays.
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81.07.Bc Nanocrystalline materials
79.70.+q Field emission, ionization, evaporation, and desorption

Fabrication and electron holography characterization of FePt alloy nanorods

R. C. Che, M. Takeguchi, M. Shimojo, W. Zhang, and K. Furuya

Appl. Phys. Lett. 87, 223109 (2005); http://dx.doi.org/10.1063/1.2136071 (3 pages) | Cited 15 times

Online Publication Date: 21 November 2005

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Well-aligned, ferromagnetic FePt nanorods have been fabricated by electron beam-induced deposition using an ultrahigh-vacuum scanning electron microscope. A mixture gas of iron pentacarbonyl and cyclopentadienylplatinum (IV) trimethyl was used as a precursor and post-annealing at 600 °C for 2 h was performed to accomplish the crystallization process. Each nanorod was composed of a chain of crystalline Fe-Pt alloy nanoparticles encapsulated within a carbon-containing sheath. The nanoparticles were identified to be face centered tetragonal (fct) FePt phase (L10,P4/mmm) by electron diffraction and high-resolution transmission electron microscopy (HRTEM). The residual magnetic flux density Br of the nanorods was evaluated to be about 1.53 T via off-axis electron holography, showing a strong ferromagnetic character.
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81.07.Bc Nanocrystalline materials
75.50.Bb Fe and its alloys
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
81.40.Gh Other heat and thermomechanical treatments
64.70.K- Solid-solid transitions
68.37.Lp Transmission electron microscopy (TEM)
42.40.Kw Holographic interferometry; other holographic techniques

Nonvolatile memory using Al2O3 film with an embedded Al-rich layer

Shunji Nakata, Kunio Saito, and Masaru Shimada

Appl. Phys. Lett. 87, 223110 (2005); http://dx.doi.org/10.1063/1.2137449 (3 pages) | Cited 13 times

Online Publication Date: 22 November 2005

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This letter describes the capacitance-voltage (C-V) characteristics of a new nonvolatile Al2O3 memory with nanoscale thin film deposited by electron-cyclotron-resonance sputtering. Al-rich Al2O3 was fabricated at a reduced oxygen gas flow rate and used as a charge storage layer of the Al2O3 memory, which is located between the tunnel insulator and blocking insulator. C-V characteristics show a large hysteresis window due to the Al-rich structure, but there is no hysteresis window in the case of stoichiometric Al2O3 structure. This memory will stay nonvolatile for several years or more. The number of electrons injected into the insulator in the case of nanoscale memory cell length is discussed. A discussion of the statistical Gaussian distribution indicates that about 50 localization sites are necessary in Al2O3 memory with 10 nm cell length for realizing a 1.8 V change of the threshold voltage, which corresponds to the control of ten electrons in the insulator. This structure is easily achieved by the proposed Al-rich Al2O3 memory.
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85.35.-p Nanoelectronic devices
84.30.Sk Pulse and digital circuits

Time-resolved photoluminescence from ZnO nanostructures

W. M. Kwok, A. B. Djurišić, Y. H. Leung, W. K. Chan, and D. L. Phillips

Appl. Phys. Lett. 87, 223111 (2005); http://dx.doi.org/10.1063/1.2137456 (3 pages) | Cited 26 times

Online Publication Date: 22 November 2005

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Different ZnO nanostructures (tetrapods, shells, rods, and highly faceted rods) were characterized by photoluminescence (PL) and time-resolved PL measurements. It was found that different nanostructures exhibit very different optical properties in terms of defect emission and decay times of the spontaneous emission. No correlation was found between the PL decay times and defect emission intensities and defect emission positions. The short decay times of the UV emission are most likely due to nonradiative defects that are correlated with the crystalline quality and do not contribute to the visible emission. Neither short PL decay times nor intense defect emissions rule out achievement of stimulated emission.
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78.55.Et II-VI semiconductors
78.47.-p Spectroscopy of solid state dynamics
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters

Unexpected polarization behavior at the aperture of hollow-pyramid near-field probes

P. Biagioni, D. Polli, M. Labardi, A. Pucci, G. Ruggeri, G. Cerullo, M. Finazzi, and L. Duò

Appl. Phys. Lett. 87, 223112 (2005); http://dx.doi.org/10.1063/1.2137891 (3 pages) | Cited 22 times

Online Publication Date: 22 November 2005

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Polarization in the proximity zone beyond the illuminated aperture of a near-field optical microscope is determined by means of a thin dichroic layer of fluorescent molecules used as a near-field polarization analyzer. Near-field probes of the hollow-pyramid type, with a metal coating and about 100 nm apertures, are used. Surprisingly, it is found that the input polarization is always maintained in the near field, independently of the aperture geometry, in spite of the behavior of the transmitted far field, which may result either isotropic or strongly dichroic depending on the ellipticity of the aperture.
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07.79.Fc Near-field scanning optical microscopes
33.50.Dq Fluorescence and phosphorescence spectra
33.55.+b Optical activity and dichroism
33.57.+c Magneto-optical and electro-optical spectra and effects

Synthesis and characterization of metallic TaSi2 nanowires

Y. L. Chueh, L. J. Chou, S. L. Cheng, L. J. Chen, C. J. Tsai, C. M. Hsu, and S. C. Kung

Appl. Phys. Lett. 87, 223113 (2005); http://dx.doi.org/10.1063/1.2132523 (3 pages) | Cited 12 times

Online Publication Date: 22 November 2005

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TaSi2 nanowires have been synthesized by annealing FeSi2 thin film and nanodots grown on a Si substrate in an ambient containing Ta vapor. The TaSi2 nanowires are formed in three steps; segregation of Si atoms from the FeSi2 underlayer to form Si base, growth of TaSi2 nanodots on Si base, and elongation of TaSi2 nanowire along the growth direction. Strong field-emission properties promise future electronics and optoelectronics applications.
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81.07.Bc Nanocrystalline materials
81.16.-c Methods of micro- and nanofabrication and processing
79.70.+q Field emission, ionization, evaporation, and desorption
64.75.-g Phase equilibria
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
81.40.Gh Other heat and thermomechanical treatments

Directed integration of ZnO nanobridge devices on a Si substrate

John F. Conley, Lisa Stecker, and Yoshi Ono

Appl. Phys. Lett. 87, 223114 (2005); http://dx.doi.org/10.1063/1.2136218 (3 pages) | Cited 40 times

Online Publication Date: 22 November 2005

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We demonstrate the directed assembly and integration of ZnO nanobridges into working devices on silicon-on-insulator substrates. The “pick and place” method of nanowire integration is avoided and metal catalysts are not used. ZnO nanowires (NWs) were grown selectively via a vapor-solid method using a patterned ZnO thin-film seed layer that was deposited on Si trench sidewalls via atomic layer deposition. ZnO NWs grew to span the trench and self-terminate on the opposing surface, effectively forming electrically accessible horizontal ZnO nanobridge devices. Vertical bridge devices were also constructed using undercut islands. Directly grown horizontal ZnO nanobridge devices were operated as gas and UV sensors, demonstrating that this method represents a significant step towards practical large-scale integration of nanodevices into Si microelectronics.
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81.16.-c Methods of micro- and nanofabrication and processing
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
85.60.Gz Photodetectors (including infrared and CCD detectors)
81.07.Vb Quantum wires
81.05.Dz II-VI semiconductors
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Self-assembled growth and green emission of gold nanowhiskers

T. Qiu, X. L. Wu, G. G. Siu, and Paul K. Chu

Appl. Phys. Lett. 87, 223115 (2005); http://dx.doi.org/10.1063/1.2138360 (3 pages) | Cited 9 times

Online Publication Date: 22 November 2005

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Unique structured Au nanowhiskers were fabricated via electroless metal deposition on Si wafer in KAuCl4–HF solution. A self-assembled localized microscopic electrochemical cell model and a diffusion-limited aggregation process are associated with the formation of Au nanowhiskers. A green photoluminescence (PL) band was recorded. Spectral analyses suggest the green PL arises from the radiative recombination of sp-band electrons with d-band holes in the Au nanowhiskers and its intensity enhancement is due to local electric field connected with the Au particle plasmons oscillation. A red PL band was also observed from long-time etched Si substrates and proposed to be related to Si nanocrystals in the surface layer of etched Si wafer. Its stability was considered to be owing to the formation of stable Si–Au bonds on the surfaces of Si nanocrystals.
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68.70.+w Whiskers and dendrites (growth, structure, and nonelectronic properties)
81.16.Dn Self-assembly
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
81.07.Bc Nanocrystalline materials
78.55.Hx Other solid inorganic materials
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons

Shape change of SiGe islands with initial Si capping

Y. Q. Wu, F. H. Li, J. Cui, J. H. Lin, R. Wu, J. Qin, C. Y. Zhu, Y. L. Fan, X. J. Yang, and Z. M. Jiang

Appl. Phys. Lett. 87, 223116 (2005); http://dx.doi.org/10.1063/1.2137307 (3 pages) | Cited 17 times

Online Publication Date: 22 November 2005

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The morphologies of self-assembled Ge/Si(001) islands with initial Si capping at a temperature of 640 °C are investigated by atomic force microscopy. Before Si capping, the islands show a metastable dome shape with very good size uniformity. This dome shape changes to a pyramid shape with {103} facets at a Si capping thickness of 0.32 nm, and then changes to pyramid shapes with {104} and {105} facets at Si capping thicknesses of 0.42 and 0.64 nm, respectively. Noteworthy is that islands with one side retained their dome shape while the other three sides that changed to {103} facets are observed at a Si capping thickness of 0.18 nm. These observations indicate that island shape change with Si capping is a kinetic rather than thermodynamic process. The atomic processes associated with this island shape change are kinetically limited at a low temperature of 400 °C, and no significant change in size and shape of islands is observed when Si capping layers are deposited at this temperature.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
68.37.Ps Atomic force microscopy (AFM)

Line and two-dimensional fractal analysis of micrographs obtained by atomic force microscopy of surface-immobilized oligonucleotide nano-aggregates

Prashant D. Sawant and Dan V. Nicolau

Appl. Phys. Lett. 87, 223117 (2005); http://dx.doi.org/10.1063/1.2132080 (3 pages) | Cited 5 times

Online Publication Date: 23 November 2005

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This study reports on the evaluation of the nanotopographies of DNA functionalized polymer surfaces, i.e., cyclo-olefine copolymer (COC) and polycarbonate (PC) using line, “Zmax” and two dimensional fractal dimension methods, i.e., power spectrum density algorithm (PSDA) and perimeter-area relationship (PAR), applied to atomic force microscopy (AFM) scans. A decrease in the fractal dimension after the immobilization of oligonucleotides suggests the prevalence of a vertical assembly of oligonucleotides, more significantly on COC than on PC.
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87.15.B- Structure of biomolecules
87.64.Dz Scanning tunneling and atomic force microscopy
87.14.G- Nucleic acids
87.10.-e General theory and mathematical aspects

Aggregated nanoparticle structures prepared by thermal decomposition of poly(vinyl)-N-pyrrolidone/Ag nanoparticle composite films

L. Rast and A. Stanishevsky

Appl. Phys. Lett. 87, 223118 (2005); http://dx.doi.org/10.1063/1.2137451 (3 pages) | Cited 5 times

Online Publication Date: 23 November 2005

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Silver nanoparticle layers were fabricated using spin coating and rapid thermal processing of poly(vinyl)-N-pyrrolidone/Ag nanoparticle composite thin films on glass. Fast thermal degradation of the polymeric matrix at 420 °C results in spontaneous aggregation of Ag nanoparticles, accompanied by strong enhancement and a shift toward longer wavelengths of the absorption peak due to surface plasmon resonance (SPR). Longer annealing times lead initially to fragmentation of the aggregates, and then to partial coalescence of the nanoparticles with a corresponding shift of SPR towards shorter wavelengths. We investigated the dependence of the shape, size, and absorbance spectra of these aggregates on the spin speed and the conditions of thermal processing.
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81.07.Bc Nanocrystalline materials
81.16.Be Chemical synthesis methods
81.05.Qk Reinforced polymers and polymer-based composites
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.40.Gh Other heat and thermomechanical treatments
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
78.40.Ha Other nonmetallic inorganics

Room-temperature excitonic absorption in quantum wires

Yasushi Takahashi, Yuhei Hayamizu, Hirotake Itoh, Masahiro Yoshita, Hidefumi Akiyama, Loren N. Pfeiffer, and Ken W. West

Appl. Phys. Lett. 87, 223119 (2005); http://dx.doi.org/10.1063/1.2135872 (3 pages) | Cited 9 times

Online Publication Date: 23 November 2005

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We measured the absorption spectra of T-shaped quantum wires at room temperature using waveguide-transmission spectroscopy. A strong and narrow room-temperature one-dimensional-exciton absorption peak was observed, which indicates a peak modal absorption coefficient of 160 cm−1 per 20 wires with a Γ-factor of 4.3×10−3, a width of 7.2 meV, and strong polarization anisotropy.
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78.67.Lt Quantum wires
73.21.Hb Quantum wires
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

Low-threshold-current operation of 1540 nm GaInAsP/InP distributed-feedback lasers with multiple-quantum-wire active regions

Hideki Yagi, Koji Miura, Yoshifumi Nishimoto, Dhanorm Plumwongrot, Kazuya Ohira, Takeo Maruyama, and Shigehisa Arai

Appl. Phys. Lett. 87, 223120 (2005); http://dx.doi.org/10.1063/1.2138789 (3 pages) | Cited 7 times

Online Publication Date: 23 November 2005

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1540 nm wavelength GaInAsP/InP distributed-feedback lasers consisting of multiple-quantum-wire active regions with the wire width of 24 nm were realized by electron-beam lithography, CH4/H2 reactive ion etching, and two-step organometallic vapor-phase-epitaxial growth processes. A threshold current as low as 2.7 mA (threshold current density = 270 A/cm2), a differential quantum efficiency of 19%/facet and a submode suppression ratio of 51 dB at a bias current of twice the threshold were achieved for the stripe width of 3.0 μm and the cavity length of 330 μm under a room-temperature continuous-wave condition.
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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
81.65.Cf Surface cleaning, etching, patterning
81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.05.Ea III-V semiconductors

Control the relative length of carbon nanotubes from site to site on one silicon substrate

Zhengjun Zhang, Ya Zhou, and Yang Yue

Appl. Phys. Lett. 87, 223121 (2005); http://dx.doi.org/10.1063/1.2138441 (3 pages) | Cited 7 times

Online Publication Date: 23 November 2005

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Carbon nanotubes were grown on silicon substrates by chemical vapor deposition with a mixture of ferrocene and xylene by suppressing the reaction of Fe with silicon. We also found a way to control the relative length of carbon nanotubes grown on one substrate by using Au thin films with different thickness (at the nanometer scale) as the block material, whose vaporization postponed the growth of carbon nanotubes. We can thus use Au films as a “shutter” to adjust the growth time of the nanotubes, leading to the control in the relative length of carbon nanotubes from site to site on one substrate.
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81.07.De Nanotubes
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