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17 Jun 2002

Volume 80, Issue 24, pp. 4483-4665

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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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Rotors produced and driven in laser tweezers with reversed direction of rotation

Péter Galajda and Pál Ormos

Appl. Phys. Lett. 80, 4653 (2002); http://dx.doi.org/10.1063/1.1480885 (3 pages) | Cited 36 times

Online Publication Date: 10 June 2002

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Micrometer size rotors are produced by light induced polymerization of light curing resin. The propeller shaped rotors trapped in laser tweezers are rotated by the trapping light. A rotor is built that changes the direction of rotation by changing its position relative to the focus. The design is based on the very high numerical aperture of the focused light in the tweezers: the light has a large average component of momentum pointing perpendicular to the optical axis, in the opposite direction before and behind the focus. This perpendicular component drives the rotation and the direction changes when the rotor is moving around the focus. © 2002 American Institute of Physics.
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37.10.Vz Mechanical effects of light on atoms, molecules, and ions
78.20.Fm Birefringence
78.20.Ek Optical activity
42.25.Ja Polarization
82.35.Ej Nonlinear optics with polymers

Flat panel imagers with pixel level amplifiers based on polycrystalline silicon thin-film transistor technology

J. P. Lu, K. Van Schuylenbergh, J. Ho, Y. Wang, J. B. Boyce, and R. A. Street

Appl. Phys. Lett. 80, 4656 (2002); http://dx.doi.org/10.1063/1.1481788 (3 pages) | Cited 14 times

Online Publication Date: 10 June 2002

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We report here the realization of a large-area compatible, flat panel imager with pixel level amplifiers. The imager is based on excimer-laser crystallized, polycrystalline silicon (poly-Si) thin-film transistors. By incorporating pixel level amplification, flat panel imagers are expected to be able to achieve unprecedented noise performance, with the hope of achieving single photon detection. We have demonstrated good noise performance of 1300 erms, exceeding the commonly accepted industry standard of 2000 erms. We also briefly discuss the source of the extra noise, as well as the possibility of further reducing the noise level. © 2002 American Institute of Physics.
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07.85.-m X- and γ-ray instruments
85.30.Tv Field effect devices

Improvement of hole injection in phenyl-substituted electroluminescent devices by reduction of oxygen deficiency near the indium tin oxide surface

Beeling Low, Furong Zhu, Keran Zhang, and Soojin Chua

Appl. Phys. Lett. 80, 4659 (2002); http://dx.doi.org/10.1063/1.1484544 (3 pages) | Cited 21 times

Online Publication Date: 10 June 2002

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We report the use of an in situ four-point probe method to investigate the relation between oxygen plasma treatment on indium tin oxide (ITO) and the variation in its sheet resistance. Analyses on the ITO surface composition made with time-of-flight secondary ion mass spectroscopy probe a dual-layer parallel resistor model for oxygen plasma-treated ITO anodes. We have shown that the increase in the ITO sheet resistance can be attributed to the reduction of oxygen deficiency near the surface. The improvement in carrier injection in phenyl-substituted poly(p-phenylenevinylene)-based light-emitting diodes correlates directly with a layer of low conductivity, several nanometers thick. This was induced on the ITO surface and serves as an efficient hole injecting anode. © 2002 American Institute of Physics.
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78.60.Fi Electroluminescence
85.60.Jb Light-emitting devices
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Measurement of electronic stopping power of swift heavy ions using high-resolution time-of-flight spectrometer

Y. Zhang, G. Possnert, and W. J. Weber

Appl. Phys. Lett. 80, 4662 (2002); http://dx.doi.org/10.1063/1.1486042 (3 pages) | Cited 8 times

Online Publication Date: 10 June 2002

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Using only time of flight data to determine energy loss, an analysis procedure has been developed to improve the precision of simultaneously measuring electronic stopping powers of swift heavy ions from a continuous energy spectrum provided by a typical elastic recoil detection analysis geometry. This procedure eliminates the well-known calibration problem of Si detectors when used with heavy ions. Consequently, the stopping powers and the energy dependence are determined with higher precision. This approach is demonstrated by measuring the stopping powers of Be, C, Si, and Br in amorphous C over a continuous range of energies. The results exhibit good agreement with limited existing data but indicate some deviations from the predicted theoretical values. © 2002 American Institute of Physics.
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07.75.+h Mass spectrometers
61.85.+p Channeling phenomena (blocking, energy loss, etc.)
61.80.Jh Ion radiation effects
61.82.-d Radiation effects on specific materials
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Erratum: “Analytic method for evaluation of the field of a charge traversing a geometric discontinuity” [Appl. Phys. Lett. 80, 2842 (2002)]

S. Banna and L. Schächter

Appl. Phys. Lett. 80, 4665 (2002); http://dx.doi.org/10.1063/1.1488135 (1 page)

Online Publication Date: 10 June 2002

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Abstract Unavailable
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41.60.-m Radiation by moving charges
99.10.Cd Errata
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