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30 Dec 2002

Volume 81, Issue 27, pp. 5099-5257

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All-optical single-electron read-out devices based on GaN quantum dots

Irene D’Amico and Fausto Fossi

Appl. Phys. Lett. 81, 5213 (2002); http://dx.doi.org/10.1063/1.1532546 (3 pages) | Cited 16 times

Online Publication Date: 19 December 2002

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We study few-particle interactions in GaN-coupled quantum dots and discuss how the built-in field characteristic of these structures strongly reinforce dipole–dipole and dipole–monopole interactions. We introduce a semi-analytical model that allows for a rapid and easy estimate of the magnitude of few-particle interactions and whose predictions are closer than 10% to “exact” results. We apply our study to the design of an all-optical read-out device that exploits long-range dipole–monopole interactions and may be also used to monitor the charge status of a quantum dot system. © 2002 American Institute of Physics.
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85.35.Gv Single electron devices
73.63.Kv Quantum dots
78.67.Hc Quantum dots
85.60.-q Optoelectronic devices

Plasma deposition of Ultrathin polymer films on carbon nanotubes

Donglu Shi, Jie Lian, Peng He, L. M. Wang, Wim J. van Ooij, Mark Schulz, Yijun Liu, and David B. Mast

Appl. Phys. Lett. 81, 5216 (2002); http://dx.doi.org/10.1063/1.1527702 (3 pages) | Cited 39 times

Online Publication Date: 19 December 2002

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Ultrathin films of pyrrole were deposited on the surfaces of carbon nanotubes using a plasma polymerization treatment. High-resolution electron transmission microscopy images revealed that an extremely thin film of the polymer layer (2 ∼ 7 nm) was uniformly deposited on the outer and inner surfaces of the nanotubes. The nanotubes of all sizes exhibited equally uniform ultrathin films, indicating well-dispersed nanotubes in the fluidized bed reactor during the plasma treatment. In particular, the inner wall of the nanotube was also coated with a uniform ultrathin film of only ∼1–3 nm. Time-of-flight secondary ion mass spectroscopy experiments confirmed the highly branched and cross-linked polymer thin films on the carbon nanotubes. The plasma deposition mechanism is discussed in this letter. © 2002 American Institute of Physics.
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81.15.Jj Ion and electron beam-assisted deposition; ion plating
52.77.Dq Plasma-based ion implantation and deposition
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
81.07.De Nanotubes
82.35.Gh Polymers on surfaces; adhesion

Tip-gating effect in scanning impedance microscopy of nanoelectronic devices

Sergei V. Kalinin, Dawn A. Bonnell, Marcus Freitag, and A. T. Johnson

Appl. Phys. Lett. 81, 5219 (2002); http://dx.doi.org/10.1063/1.1531833 (3 pages) | Cited 14 times

Online Publication Date: 19 December 2002

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Electronic transport in semiconducting single-walled carbon nanotubes is studied by combined scanning gate microscopy and scanning impedance microscopy (SIM). Depending on the probe potential, SIM can be performed in both invasive and noninvasive modes. High-resolution imaging of the defects is achieved when the probe acts as a local gate and simultaneously as an electrostatic probe of local potential. A class of weak defects becomes observable even if they are located in the vicinity of strong defects. The imaging mechanism of tip-gating scanning impedance microscopy is discussed. © 2002 American Institute of Physics.
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73.63.Fg Nanotubes
85.35.Kt Nanotube devices
07.79.-v Scanning probe microscopes and components

Annealing-induced reversible change in optical absorption of Ag nanoparticles

Huijuan Bi, Weiping Cai, Lide Zhang, D. Martin, and F. Träger

Appl. Phys. Lett. 81, 5222 (2002); http://dx.doi.org/10.1063/1.1532757 (3 pages) | Cited 16 times

Online Publication Date: 19 December 2002

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Optical absorption of silver nanoparticles dispersed within pores of monolithic mesoporous silica was investigated after annealing in different atmospheres. It has been found that treatment in H2 or N2 induces a strong surface plasmon resonance (SPR) as usually expected, but air annealing results in the disappearance of the SPR, which is contrary to the fact that bulk metal silver is stable and not oxidized in air at above 200 °C. The absence and appearance of the SPR absorption can be controlled through alternate annealing in air and H2 (or N2). Thermodynamic analysis for oxidation of Ag nanoparticles, by additionally considering the surface and curvature effects of a particle, shows the existence of critical particle size. Only when a Ag particle size is smaller than the critical value is the oxidation possible in air at above 200 °C. The optical changes are attributed to the occurrence of the redox of the Ag particles in different atmospheres at a high temperature. © 2002 American Institute of Physics.
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78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
73.22.Lp Collective excitations
78.40.Kc Metals, semimetals, and alloys

Synthesis of boron nitride nanofibers and measurement of their hydrogen uptake capacity

Renzhi Ma, Yoshio Bando, Tadao Sato, Dmitri Golberg, Hongwei Zhu, Cailu Xu, and Dehai Wu

Appl. Phys. Lett. 81, 5225 (2002); http://dx.doi.org/10.1063/1.1534415 (3 pages) | Cited 18 times

Online Publication Date: 19 December 2002

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High-purity boron nitride (BN) nanofibers with diameters ranging from 30 to 100 nm were synthesized. Electron energy loss spectroscopy revealed that they have stoichiometric BN composition. The hydrogen uptake capacity measurements showed that the fibers could adsorb 2.9 wt % hydrogen under ∼10 MPa at room temperature. This hydrogen uptake capacity was compared with those of BN multiwalled or bamboo-like nanotubes under the same experimental conditions. It was suggested that the unique morphology of nanofibers, namely open-ended BN edge layers on the exterior surface, might facilitate hydrogen adsorption. © 2002 American Institute of Physics.
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84.60.Ve Energy storage systems, including capacitor banks
61.46.-w Structure of nanoscale materials
81.40.Vw Pressure treatment
68.43.Mn Adsorption kinetics
79.20.Uv Electron energy loss spectroscopy
81.07.Bc Nanocrystalline materials
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
62.50.-p High-pressure effects in solids and liquids

Electronic structure and interband transitions of metallic carbon nanotubes

P. N. D’yachkov, H. Hermann, and D. V. Kirin

Appl. Phys. Lett. 81, 5228 (2002); http://dx.doi.org/10.1063/1.1533858 (3 pages) | Cited 18 times

Online Publication Date: 19 December 2002

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Band structure of the metallic (n,n) carbon nanotubes (coefficients n are the indices of the two-dimensional primitive lattice vectors of the graphene lattice) is calculated in terms of a linear augmented cylindrical wave method. The results are used to correlate the minimum direct energy gaps E11 between the conduction and valence band singularities with the nanotube diameter d and optical absorption spectra. Significant deviations from the equation E11 ∼ d−1 are observed. The ππ∗ gap energy increases monotonically with 1/d, whereas the σπ∗ gap width shows a minimum at n = 10. In the (3, 3) tube, the conduction band singularity coincides with the Fermi level, resulting in a drastic increase of the density of states on this level. © 2002 American Institute of Physics.
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73.22.Dj Single particle states
78.67.Ch Nanotubes

Piezoresponse force microscopy of lead titanate nanograins possibly reaching the limit of ferroelectricity

A. Roelofs, T. Schneller, K. Szot, and R. Waser

Appl. Phys. Lett. 81, 5231 (2002); http://dx.doi.org/10.1063/1.1534412 (3 pages) | Cited 80 times

Online Publication Date: 19 December 2002

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Single ferroelectric lead titanate (PTO) grains down to 15 nm were fabricated by chemical solution deposition. Varying the dilution of the precursor solution leads to different grain sizes between 15 and 200 nm. The grain-size-dependent domain configuration was studied using three-dimensional piezoresponse force microscopy (PFM). It is found that the PTO grains in a dense film contain laminar 90° domain walls, whereas separated PTO grains show more complicated structures of mainly 180° domain walls. For grains smaller than 20 nm, no piezoresponse was observed and we suppose this could be due to the transition from the ferroelectric to the superparaelectric phase which has no spontaneous polarization. Recent calculations showed that the ferroelectricity of fine ferroelectric particles decrease with decreasing particle size. From these experiments the extrapolated critical size of PTO particles was found to be around 4–14 nm. © 2002 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.55.-g Dielectric thin films
77.80.Dj Domain structure; hysteresis
77.80.B- Phase transitions and Curie point
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
68.55.-a Thin film structure and morphology

Intrinsic electron transport properties of carbon nanotube Y-junctions

Vincent Meunier, Marco Buongiorno Nardelli, J. Bernholc, Thomas Zacharia, and Jean-Christophe Charlier

Appl. Phys. Lett. 81, 5234 (2002); http://dx.doi.org/10.1063/1.1533842 (3 pages) | Cited 37 times

Online Publication Date: 19 December 2002

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The electron transport properties of three-terminal carbon-nanotube junctions are investigated within the Landauer theory of quantum conductance. Using a realistic tight-binding Hamiltonian, we demonstrate that the experimentally observed rectifying behavior is not an intrinsic property of the junction, but rather of the contact geometry. When semiconducting nanotubes are connected to metallic leads, nontransmitting states are induced at the nanotube–metal interface, leading to asymmetric transmission curves and potentially rectifying behavior of the nanodevice. © 2002 American Institute of Physics.
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73.63.Fg Nanotubes
73.40.Ei Rectification
73.40.Ns Metal-nonmetal contacts

A glow-discharge approach for functionalization of carbon nanotubes

Bishun N. Khare, M. Meyyappan, Joel Kralj, Patrick Wilhite, Metagus Sisay, Hiroshi Imanaka, Jessica Koehne, and Charles W. Baushchlicher

Appl. Phys. Lett. 81, 5237 (2002); http://dx.doi.org/10.1063/1.1533859 (3 pages) | Cited 31 times

Online Publication Date: 19 December 2002

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We demonstrate the functionalization of single-walled carbon nanotubes (SWNTs) using a glow discharge for generating atomic or molecular radicals. A 30-s exposure to a cold plasma of H2 results in near-saturation coverage of SWNT with atomic hydrogen. Functionalization of SWNTs with atomic hydrogen is confirmed by an infrared band at 2924 cm−1, characteristic of C–H stretching mode. A corresponding decrease in the ultraviolet absorption is also observed, which is due to a loss of some conjugated C–C π bonds in hydrogen covered SWNTs. © 2002 American Institute of Physics.
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68.43.Pq Adsorbate vibrations
78.30.Na Fullerenes and related materials
78.40.Ri Fullerenes and related materials
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