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17 Jun 2002

Volume 80, Issue 24, pp. 4483-4665

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Independent optically addressable nanoparticle-polymer optomechanical composites

S. R. Sershen, S. L. Westcott, N. J. Halas, and J. L. West

Appl. Phys. Lett. 80, 4609 (2002); http://dx.doi.org/10.1063/1.1481536 (3 pages) | Cited 33 times

Online Publication Date: 10 June 2002

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We report the fabrication and characterization of optomechanically active composite materials consisting of a thermally responsive poly(NIPAAm-co-AAm) hydrogel matrix incorporating a dilute concentration of Au or silica-Au core-shell nanoparticles. Under optical illumination at the resonance absorption wavelength of the nanoparticle dopant, a dramatic volume collapse of the composite occurs due to local photothermal heating of the NIPAAm matrix. Nanoparticle dopants were chosen so that each composite was specifically optically addressable, exhibiting optomechanical behavior at independent wavelengths. Such materials can be useful as independently addressable remotely triggerable switches and gates in a wide variety of micromechanical applications. © 2002 American Institute of Physics.
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07.10.Cm Micromechanical devices and systems
81.05.Qk Reinforced polymers and polymer-based composites
61.82.Rx Nanocrystalline materials
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.46.-w Structure of nanoscale materials
62.25.-g Mechanical properties of nanoscale systems
65.80.-g Thermal properties of small particles, nanocrystals, nanotubes, and other related systems
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
81.07.Bc Nanocrystalline materials
82.35.Np Nanoparticles in polymers
78.20.N- Thermo-optic effects
78.20.nb Photothermal effects
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices

Room-temperature metallic behavior in nanophase polypyrrole

S. Bhattacharyya and S. K. Saha

Appl. Phys. Lett. 80, 4612 (2002); http://dx.doi.org/10.1063/1.1486475 (2 pages) | Cited 4 times

Online Publication Date: 10 June 2002

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An ultrathin layer of polypyrrole (PPy) phase has been grown on the pore wall of a nanoporous template using oxidation polymerization technique. This thin layer of PPy phase shows metallic behavior (positive temperature coefficient of resistance) up to room temperature (300 K) and a metal-insulator transition is observed at around room temperature. © 2002 American Institute of Physics.
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72.15.Nj Collective modes (e.g., in one-dimensional conductors)
73.61.Ph Polymers; organic compounds
71.30.+h Metal-insulator transitions and other electronic transitions
73.63.Bd Nanocrystalline materials
82.35.Cd Conducting polymers
61.46.-w Structure of nanoscale materials
81.07.Bc Nanocrystalline materials

Color-selective semiconductor nanocrystal laser

Hans-Jürgen Eisler, Vikram C. Sundar, Moungi G. Bawendi, Michael Walsh, Henry I. Smith, and Victor Klimov

Appl. Phys. Lett. 80, 4614 (2002); http://dx.doi.org/10.1063/1.1485125 (3 pages) | Cited 119 times

Online Publication Date: 10 June 2002

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Theoretical predictions of the benefits of three-dimensional quantum confinement have provided motivation for the development of quantum-dot lasers. Such lasers, developed in the case of self-assembled quantum dots, have not been successfully demonstrated with quantum-confined colloidal nanocrystals (NCs). Here, using recently developed NC-titania chemistry, we report the successful development of an optically pumped, NC-based distributed feedback laser, in which the narrow gain profiles of these nanoparticles have been matched with the feedback of a second-order distributed feedback laser. This laser, whose output color can be selected by choosing appropriately sized nanocrystals, operates at 80 K and at room temperature. © 2002 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
81.07.Bc Nanocrystalline materials
81.05.Dz II-VI semiconductors
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
78.55.Et II-VI semiconductors
61.46.-w Structure of nanoscale materials
42.60.By Design of specific laser systems
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
42.50.Nn Quantum optical phenomena in absorbing, amplifying, dispersive and conducting media; cooperative phenomena in quantum optical systems
78.45.+h Stimulated emission

Fabrication of Si single-electron transistors having double SiO2 barriers

Yuhei Ito, Tsuyoshi Hatano, Anri Nakajima, and Shin Yokoyama

Appl. Phys. Lett. 80, 4617 (2002); http://dx.doi.org/10.1063/1.1485306 (3 pages) | Cited 6 times

Online Publication Date: 10 June 2002

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We fabricated Si single-electron transistors (SETs) having double SiO2 barriers and a polycrystalline Si (poly-Si) dot. The fabrication method of this device is completely compatible with the complementary metal–oxide–semiconductor technology, and the position of the poly-Si dot is self-aligned between the source and drain regions. The device exhibits drain current (Id) oscillation against gate voltage. From the dot size dependence of the electrical characteristics, the Id oscillation is considered to be due to the Coulomb blockade effect caused by poly-Si grains in the poly-Si dot. The self-alignment of the poly-Si dot in the fabrication process also means that the SET is promising for practical use. © 2002 American Institute of Physics.
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85.35.Gv Single electron devices
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
73.63.Kv Quantum dots
73.23.Hk Coulomb blockade; single-electron tunneling
72.70.+m Noise processes and phenomena
81.05.Cy Elemental semiconductors
81.07.Ta Quantum dots

Temperature dependence of intersublevel absorption in InAs/GaAs self-assembled quantum dots

F. Bras, P. Boucaud, S. Sauvage, G. Fishman, and J.-M. Gérard

Appl. Phys. Lett. 80, 4620 (2002); http://dx.doi.org/10.1063/1.1487446 (3 pages) | Cited 21 times

Online Publication Date: 10 June 2002

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We have studied the temperature dependence of the intersublevel absorption in n-doped InAs/GaAs self-assembled quantum dots. The investigated intersublevel transition corresponds to the optical transition between the s-type conduction ground state to the p-type first excited states. These transitions, resonant between 20 and 22 μm, are in-plane polarized along the [110] and the [math10] directions. A redshift lower than 3 meV is observed for the transition resonance from low temperature to room temperature. While the effective barrier height from the ground state is around 150 meV, the integrated absorption amplitude decreases by a factor of 4 from low temperature to room temperature. This decrease is modeled by the thermionic emission of the carriers, taking into account the density of states of the two-dimensional wetting layer, the density of states of the three-dimensional bulk layer surrounding the dots and the existence of polaron states associated with the strong electron-phonon coupling in the dots. © 2002 American Institute of Physics.
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78.67.Hc Quantum dots
78.66.Fd III-V semiconductors
73.21.La Quantum dots
81.05.Ea III-V semiconductors
81.07.Ta Quantum dots
73.20.At Surface states, band structure, electron density of states
71.38.-k Polarons and electron-phonon interactions
63.20.K- Phonon interactions

Mechanical properties of high-aspect-ratio atomic-force microscope tips

G. Jänchen, P. Hoffmann, A. Kriele, H. Lorenz, A. J. Kulik, and G. Dietler

Appl. Phys. Lett. 80, 4623 (2002); http://dx.doi.org/10.1063/1.1485307 (3 pages) | Cited 7 times

Online Publication Date: 10 June 2002

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Focused-electron-beam-deposited carbon atomic-force microscope tips were characterized using flexural vibrations excited with piezoelectric transducers and observed directly inside a scanning electron microscope. Frequencies in the high-MHz range were measured and the elastic modulus was estimated to be 0.54±0.16 TPa. © 2002 American Institute of Physics.
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68.35.Gy Mechanical properties; surface strains
81.05.U- Carbon/carbon-based materials
07.79.Lh Atomic force microscopes
68.35.Ja Surface and interface dynamics and vibrations
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
62.20.D- Elasticity

Electrically isolated SiGe quantum dots

Emma Tevaarwerk, P. Rugheimer, O. M. Castellini, D. G. Keppel, S. T. Utley, D. E. Savage, M. G. Lagally, and M. A. Eriksson

Appl. Phys. Lett. 80, 4626 (2002); http://dx.doi.org/10.1063/1.1484251 (3 pages) | Cited 2 times

Online Publication Date: 10 June 2002

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A variation of electric force microscopy (EFM) is used to measure the electrical isolation of SiGe quantum dots (QDs). The SiGe QDs are grown on mesas of ultrathin silicon on insulator. Near the mesa edges, the thin silicon layer has been incorporated into the QDs, resulting in electrically isolated QDs. Away from the edges, the silicon layer is not incorporated and has a two-dimensional resistivity of less than 800 TΩ per sq, resulting in relatively short RC times for charge flow on the mesa. The EFM technique we use here is a powerful probe of samples and devices with floating-gate geometries. © 2002 American Institute of Physics.
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68.65.Hb Quantum dots (patterned in quantum wells)
81.16.Dn Self-assembly
73.63.Kv Quantum dots

Nanometer-sized optical waveguides fabricated by anodic oxidation using a scanning near-field optical microscope

T. Onuki, T. Tokizaki, Y. Watanabe, T. Tsuchiya, and T. Tani

Appl. Phys. Lett. 80, 4629 (2002); http://dx.doi.org/10.1063/1.1486479 (3 pages) | Cited 10 times

Online Publication Date: 10 June 2002

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We have fabricated an optical waveguide with a subwavelength cross section that propagates light. A metal–oxide core is partially embedded into a metal clad by anodic oxidation using the probe tip of a scanning near-field optical microscope (SNOM). Then, using the SNOM in transmission mode we have evidence of light propagating more than 5 μm in the waveguide whose core width and thickness are 300 and 70 nm, respectively. © 2002 American Institute of Physics.
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42.79.Gn Optical waveguides and couplers
42.86.+b Optical workshop techniques
81.16.Pr Micro- and nano-oxidation
07.79.Fc Near-field scanning optical microscopes

Carbon-nanotube-based resonant-circuit sensor for ammonia

S. Chopra, A. Pham, J. Gaillard, A. Parker, and A. M. Rao

Appl. Phys. Lett. 80, 4632 (2002); http://dx.doi.org/10.1063/1.1486481 (3 pages) | Cited 79 times

Online Publication Date: 10 June 2002

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We present the design and development of highly sensitive and fast-responsive microwave resonant sensors for monitoring the presence of ammonia gas. The sensor consists of a circular disk electromagnetic resonant circuit coated with either single- or multiwalled carbon nanotubes that are highly sensitive to adsorbed gas molecules. Upon exposure to ammonia, the electrical resonant frequency of the sensor exhibits a dramatic downshift of 4.375 MHz. The recovery and response times of these sensors are nominally 10 min. This technology is suitable for designing remote sensor systems to monitor gases inside sealed opaque packages and environmental conditions that do not allow physical wire connections. © 2002 American Institute of Physics.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
73.63.Fg Nanotubes
84.40.-x Radiowave and microwave (including millimeter wave) technology

Submicron liquid crystal pixels on a nanopatterned indium tin oxide surface

M. Behdani, A. Rastegar, S. H. Keshmiri, S. I. Missat, E. Vlieg, and Th. Rasing

Appl. Phys. Lett. 80, 4635 (2002); http://dx.doi.org/10.1063/1.1484556 (3 pages) | Cited 13 times

Online Publication Date: 10 June 2002

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We have prepared a grooved indium tin oxide (ITO) surface with groove widths of ∼40–90 nm and a variable groove separation up to 36 μm using atomic force microscopy nanolithography. Twisted nematic pixels with 4-n-pentyl-4-cyanobiphenly (5CB) liquid crystal were prepared using a rubbed polyimide counter plate. The 5CB molecules align along the direction of the grooves, but no pretilt angle was observed on the ITO surface. The surface anchoring energy appeared not to depend on the groove separation nor on the scan force. The lateral correlation length of 5CB on ITO was measured to be 2.2 μm. If a grooved surface is scanned in another direction, liquid crystal molecules follow the direction of the last scan. © 2002 American Institute of Physics.
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61.30.-v Liquid crystals
42.79.Kr Display devices, liquid-crystal devices
68.37.Ps Atomic force microscopy (AFM)
81.16.Nd Micro- and nanolithography
68.03.Cd Surface tension and related phenomena
42.70.Df Liquid crystals

Forming silicon carbon nitride crystals and silicon carbon nitride nanotubes by microwave plasma-enhanced chemical vapor deposition

Hui Lin Chang, Chih Ming Hsu, and Cheng Tzu Kuo

Appl. Phys. Lett. 80, 4638 (2002); http://dx.doi.org/10.1063/1.1487925 (3 pages) | Cited 9 times

Online Publication Date: 10 June 2002

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Catalyst-assisted silicon carbon nitride (SiCN) nanotubes and SiCN crystals are prepared. The SiCN nanotubes and SiCN crystals are formed by gaseous sources of CH4/N2/H2 and CH4/N2, respectively, and using solid Si columns arranged symmetrically around the specimen as additional Si sources. The formation of the tubular structure is related to the ambient of process that includes H2 gas, which is considered to delay the action of the so-called catalyst poisons and keep the tube end open during growth. Analysis shows that the SiCN crystals exhibit tetragonal or hexagonal shapes with sizes of about several microns, and multibonding structures. In contrast, the SiCN tubes are randomly orientated with various diameters, and graphitelike structure. The growth mechanisms of SiCN crystals and SiCN nanotubes are discussed. © 2002 American Institute of Physics.
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81.07.De Nanotubes
81.07.Bc Nanocrystalline materials
81.16.Hc Catalytic methods
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
61.46.-w Structure of nanoscale materials
52.77.Dq Plasma-based ion implantation and deposition
68.55.-a Thin film structure and morphology
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

SiC and its bicrystalline nanowires with uniform BN coatings

C. C. Tang, Y. Bando, T. Sato, K. Kurashima, X. X. Ding, Z. W. Gan, and S. R. Qi

Appl. Phys. Lett. 80, 4641 (2002); http://dx.doi.org/10.1063/1.1487926 (3 pages) | Cited 22 times

Online Publication Date: 10 June 2002

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Uniformly BN-coated SiC nanowires have been synthesized within the framework of vapor–liquid–solid growth mechanism. Nanoscale Ni–C alloy covering graphite sheet was used as catalysts and the mixture of boron and silica was heated to simultaneously generate B2O2 and SiO gas-phase precursors. 2 to 4 nm BN layers were found to coat the overall surface of the inside of the SiC nanowires with the diameters ranging from several nm to 80 nm. The bicrystalline structure of SiC nanowires with BN coating were also observed and had a [311] growth axis at least. The structures and possible coating mechanism have been studied by high-resolution transmission electron microscopy. © 2002 American Institute of Physics.
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81.07.Vb Quantum wires
61.46.-w Structure of nanoscale materials
81.07.Bc Nanocrystalline materials
68.65.La Quantum wires (patterned in quantum wells)
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
68.37.Lp Transmission electron microscopy (TEM)
81.16.Hc Catalytic methods

Hall magnetometry on a single iron nanoparticle

Yongqing Li, Peng Xiong, Stephan von Molnár, Steffen Wirth, Yuzo Ohno, and Hideo Ohno

Appl. Phys. Lett. 80, 4644 (2002); http://dx.doi.org/10.1063/1.1487921 (3 pages) | Cited 39 times

Online Publication Date: 10 June 2002

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High-sensitivity magnetometry over a wide temperature range has been achieved using submicron GaAs/GaAlAs Hall gradiometry. The sensitivity and versatility of the technique was demonstrated by the successful measurement of the magnetization switching of a single Fe nanoparticle with m ∼ 5×105 μB ( ∼ 5×10−15 emu) at temperatures as high as 75 K. © 2002 American Institute of Physics.
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75.50.Tt Fine-particle systems; nanocrystalline materials
75.50.Bb Fe and its alloys
72.15.Gd Galvanomagnetic and other magnetotransport effects
75.60.Jk Magnetization reversal mechanisms

Effects of nanotube waviness on the modulus of nanotube-reinforced polymers

F. T. Fisher, R. D. Bradshaw, and L. C. Brinson

Appl. Phys. Lett. 80, 4647 (2002); http://dx.doi.org/10.1063/1.1487900 (3 pages) | Cited 108 times

Online Publication Date: 10 June 2002

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Recent experimental results demonstrate that substantial improvements in the mechanical behavior of polymers can be obtained using very small amounts of carbon nanotubes as a reinforcing phase. Here, a method is developed to incorporate the typically observed curvature of the embedded nanotubes into traditional micromechanical methods for determination of the effective modulus of the nanotube-reinforced polymer. Using a combined finite element and micromechanical approach, it was determined that the nanotube curvature significantly reduces the effective reinforcement when compared to straight nanotubes. This model suggests that nanotube waviness may be an additional mechanism limiting the modulus enhancement of nanotube-reinforced polymers. © 2002 American Institute of Physics.
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81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.D- Elasticity
62.25.-g Mechanical properties of nanoscale systems
61.46.-w Structure of nanoscale materials
02.70.Dh Finite-element and Galerkin methods

Effects of rapid thermal annealing on the optical properties of 1.3 μm InGaAlAs multiquantum wells grown by digital-alloy molecular-beam epitaxy

Jin Dong Song, Jae Su Yu, Jong Min Kim, Seong Ju Bae, and Yong Tak Lee

Appl. Phys. Lett. 80, 4650 (2002); http://dx.doi.org/10.1063/1.1485132 (3 pages) | Cited 8 times

Online Publication Date: 10 June 2002

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We investigated the effect of rapid thermal annealing (RTA) on the optical properties of digital-alloy 1.3 μm InGaAlAs multiquantum-well structure grown by molecular-beam epitaxy at RTA temperature (TRTA) in the range of 400 °C–675 °C. Photoluminescence (PL) peak intensity taken at room temperature rose drastically at TRTA above 625 °C, which increased up to ∼ 500 times larger at TRTA of 650 °C and RTA time of 60 s than that of as-grown sample without any significant shift of PL peak wavelength. This extraordinary increase of PL peak intensity at TRTA ≥ 625 °C is attributed to the curing of nonradiative centers mainly in InAlAs grown at a lower temperature than its congruent temperature, and partially at the heterointerfaces between InGaAs/InAlAs short-period superlattices. © 2002 American Institute of Physics.
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81.07.St Quantum wells
81.40.Tv Optical and dielectric properties related to treatment conditions
78.67.De Quantum wells
78.55.Cr III-V semiconductors
81.05.Ea III-V semiconductors
78.66.Fd III-V semiconductors
68.65.Cd Superlattices
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.40.Gh Other heat and thermomechanical treatments
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