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3 Oct 2005

Volume 87, Issue 14, Articles (14xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 87, 143902 (2005); http://dx.doi.org/10.1063/1.2077839 (3 pages)

Kaustubh D. Bhalerao, Edward Eteshola, Matthew Keener, and Stephen C. Lee
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Synthesis and ferroelectric properties of multiferroic BiFeO3 nanotube arrays

X. Y. Zhang, C. W. Lai, X. Zhao, D. Y. Wang, and J. Y. Dai

Appl. Phys. Lett. 87, 143102 (2005); http://dx.doi.org/10.1063/1.2076437 (3 pages) | Cited 48 times

Online Publication Date: 26 September 2005

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We report the synthesis and characterization of ordered multiferroic BiFeO3 (BFO) nanotube arrays. BFO nanotubes with diameters of about 250 nm and lengths of about 6 μm were fabricated by means of a sol-gel method utilizing nanochannel alumina templates. After postannealing at 700 °C, the BFO nanotubes exhibited a polycrystalline microstructure, and x-ray diffraction and transmission electron microscopy study revealed that they are of a perovskite crystal structure. Significant ferroelectric and piezoelectric characteristics of BFO nanotubes have been demonstrated by means of piezoresponse force microscopy measurement.
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77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
81.07.De Nanotubes
77.65.-j Piezoelectricity and electromechanical effects
77.80.-e Ferroelectricity and antiferroelectricity
61.46.-w Structure of nanoscale materials
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)
81.40.Gh Other heat and thermomechanical treatments

Patterning of nanostructured thin films by structured light illumination

E. Haro-Poniatowski, E. Fort, J. P. Lacharme, and C. Ricolleau

Appl. Phys. Lett. 87, 143103 (2005); http://dx.doi.org/10.1063/1.2061857 (3 pages) | Cited 13 times

Online Publication Date: 26 September 2005

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Light-induced reshaping of silver nanostructured films near the percolation threshold are investigated using a KrF excimer laser emitting at 248 nm. Depending on the laser intensity and the number of pulses, striking effects are observed for which the irregular particles melt and transform into spherical shaped particles. We show that the laser-induced modifications can be spatially designed by irradiating through masks and gratings taking advantage of their respective diffractive properties. This permits an easy and well controlled way to produce a variety of submicron patterning. The induced patterns accurately coincide with the intensity variations of the illumination field.
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81.16.Rf Micro- and nanoscale pattern formation
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
42.62.-b Laser applications

Electric-field-aligned vertical growth and field emission properties of In2O3 nanowires

S. Q. Li, Y. X. Liang, and T. H. Wang

Appl. Phys. Lett. 87, 143104 (2005); http://dx.doi.org/10.1063/1.2076438 (3 pages) | Cited 18 times

Online Publication Date: 27 September 2005

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Vertically aligned In2O3 nanowires are grown on InAs substrates by an electric field in the plasma sheath. The In2O3 nanowires are single crystalline with diameters less than 10 nm. Field emission results show that the aligned In2O3 nanowires have lower turn-on and threshold electric fields than nonaligned ones. This is discussed in terms of orientation, emitter shapes, and density of the In2O3 nanowires.
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79.70.+q Field emission, ionization, evaporation, and desorption
61.46.-w Structure of nanoscale materials
81.10.Bk Growth from vapor

Evidence of an enhanced interband absorption in Au nanoparticles: Size-dependent electronic structure and optical properties

B. Balamurugan and Toshiro Maruyama

Appl. Phys. Lett. 87, 143105 (2005); http://dx.doi.org/10.1063/1.2077834 (3 pages) | Cited 36 times

Online Publication Date: 27 September 2005

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The present study reports clear evidence and physical significance of an interband transition due to the transition from the d band to an empty state in the conduction band in the optical absorption spectra of Au nanoparticles. The optical absorption due to interband transitions has been observed to dominate the plasmon absorption on decreasing the particle size. X-ray photoelectron spectroscopy and optical absorption studies reveal the metallic nature even for smaller sizes of 2.5 nm.
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78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
61.46.-w Structure of nanoscale materials
73.22.-f Electronic structure of nanoscale materials and related systems
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons
79.60.Jv Interfaces; heterostructures; nanostructures

Atomic structure of epitaxial SrTiO3–GaAs(001) heterojunctions

R. F. Klie, Y. Zhu, E. I. Altman, and Y. Liang

Appl. Phys. Lett. 87, 143106 (2005); http://dx.doi.org/10.1063/1.2077837 (3 pages) | Cited 13 times

Online Publication Date: 28 September 2005

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We have examined the atomic and electronic structures of epitaxial SrTiO3 thin films on GaAs (001) deposited under different growth conditions in order to understand the interfacial structure-property relationships. High-resolution Z-contrast images show an atomically sharp heterointerface with SrTiO3[110] in perfect registry with GaAs [100] and the interfacial structure remains unchanged if a submonolayer of Ti was deposited prior to the SrTiO3 film growth. X-ray photoelectron spectroscopy shows that the Fermi level was pinned during the initial stage of growth when a submonolayer of Ti was deposited on As-terminated GaAs(001); subsequent SrTiO3 growth alleviated this pinning. These results indicate a self-driven interfacial atomic structure formation, independent of the initial stage of growth.
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71.20.Ps Other inorganic compounds
68.35.Ct Interface structure and roughness
68.55.A- Nucleation and growth
79.60.Jv Interfaces; heterostructures; nanostructures

Field emission from high aspect ratio tubular carbon cones grown on gold wire

J. J. Li, C. Z. Gu, Q. Wang, P. Xu, Z. L. Wang, Z. Xu, and X. D. Bai

Appl. Phys. Lett. 87, 143107 (2005); http://dx.doi.org/10.1063/1.2081127 (3 pages) | Cited 17 times

Online Publication Date: 29 September 2005

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Tubular carbon cones (TCCs) with nanometer-sized tips and micrometer-sized roots, having a herringbone hollow interior surrounded by helical sheets of graphite coiling around, were grown on Au wires by hot filament chemical vapor deposition (HFCVD). These TCCs exhibit excellent field emission properties with a very low threshold field of 0.27 V/μm and a corresponding current density of about 1 μA/cm2; and a stable emitting current density of 1.9 mA/cm2 can be obtained at only 0.6 V/μm. Their low effective work function of ∼ 0.0056 eV and their conical bases—which effectively reduce the screening effect due to sufficient distance between adjacent tubular cones—are both favorable to field emission enhancement.
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81.05.U- Carbon/carbon-based materials
79.70.+q Field emission, ionization, evaporation, and desorption
73.30.+y Surface double layers, Schottky barriers, and work functions
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Near-field spectroscopy of bimodal size distribution of InAs/AlGaAs single quantum dots

Young-Jun Yu, In-Taek Jeong, Jong-Chun Woo, and Wonho Jhe

Appl. Phys. Lett. 87, 143108 (2005); http://dx.doi.org/10.1063/1.2081129 (3 pages) | Cited 6 times

Online Publication Date: 29 September 2005

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We report on high-resolution photoluminescence (PL) spectroscopy of size distribution of InAs/AlGaAs quantum dots (QDs) by using a near-field scanning optical microscope (NSOM). The double-peaked distribution of PL spectra is clearly observed, which is associated with the bimodal size distribution of single QDs. In particular, the size difference of single QDs, represented by the doublet spectral distribution, is directly observed by the NSOM images of PL.
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68.37.Uv Near-field scanning microscopy and spectroscopy
78.55.Cr III-V semiconductors
78.67.Hc Quantum dots

Self-organized nanostripe arrays on ZnO (10-10) surfaces formed during laser molecular-beam-epitaxy growth

Hiroaki Matsui and Hitoshi Tabata

Appl. Phys. Lett. 87, 143109 (2005); http://dx.doi.org/10.1063/1.2081133 (3 pages) | Cited 17 times

Online Publication Date: 29 September 2005

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Nanostripe arrays with high density in the orders of 10−5 cm−1 were naturally formed on ZnO (10-10) surfaces during laser molecular-beam-epitaxy (laser-MBE) growth. The nanostripe arrays were elongated above 5 μm with a few branches along the [0001] direction. Transmittance electron microscopy showed that the nanostripe arrays were triangular-shaped in the cross section and two side bonding facets were composed of high-index [(31-40) and (4-1-30)] planes. The growth origin of the nanostripe arrays was derived from a step-faceting mechanism and nonthermal equilibrium growth by laser-MBE. The step faceting could be controlled by various growth conditions relating to the surface diffusion length of the ablated active species. It was found that the highly anisotropic surfaces dramatically affected electron transport of the ZnO (10-10) layers with Hall mobility parallel to the nanostripe edges more than two orders of magnitude larger than that perpendicular to the edges.
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81.07.-b Nanoscale materials and structures: fabrication and characterization
81.05.Dz II-VI semiconductors
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.16.Dn Self-assembly
81.07.Bc Nanocrystalline materials
61.46.-w Structure of nanoscale materials
81.16.Mk Laser-assisted deposition
68.37.Lp Transmission electron microscopy (TEM)
68.35.Fx Diffusion; interface formation
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)

Chemical turnstile

W. T. Lee and E. K. H. Salje

Appl. Phys. Lett. 87, 143110 (2005); http://dx.doi.org/10.1063/1.2084339 (2 pages) | Cited 2 times

Online Publication Date: 29 September 2005

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A chemical turnstile is a device for transporting small, well-characterized doses of atoms from one location to another. A working turnstile has yet to be built, despite the numerous technological applications available for such a device. The key difficulty in manufacturing a chemical turnstile is finding a medium which will trap and transport atoms. Here we propose that ferroelastic twin walls are suitable for this role. Previous work shows that twin walls can act as two-dimensional trapping planes within which atomic transport is fast. We report simulations showing that a stress-induced reorientation of a twin wall can occur. This behavior is ideal for chemical turnstile applications.
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81.16.Ta Atom manipulation

InGaN nanorings and nanodots by selective area epitaxy

P. Chen, S. J. Chua, Y. D. Wang, M. D. Sander, and C. G. Fonstad

Appl. Phys. Lett. 87, 143111 (2005); http://dx.doi.org/10.1063/1.2056584 (3 pages) | Cited 12 times

Online Publication Date: 30 September 2005

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An integrated process to fabricate controllable arrays of semiconductor nanorings and nanodots on patterned surfaces is presented. This approach is based on pattern transfer of nanopores to a SiO2 layer, followed by selective epitaxial growth of InGaN onto an underlying GaN substrate using metalorganic chemical vapor deposition. Using this approach, crystalline InGaN nanorings and nanodots ∼ 80 nm in diameter have been grown on GaN surfaces. The formation mechanism of the nanorings and nanodots is described based on the initial stage of selective growth and restricted atom migration in a confined hole. Strong photoluminescence obtained at room temperature from the noncapped nanorings indicates strong confinement of the excitons in the nanostructures. This approach enables fabrication of dense, uniform arrays of epitaxial nanostructures and is potentially applicable to a variety of materials systems.
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81.05.Ea III-V semiconductors
81.07.Ta Quantum dots
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
61.46.-w Structure of nanoscale materials
71.35.-y Excitons and related phenomena

Synthesis of silicon nanocones using rf microplasma at atmospheric pressure

H. Shirai, T. Kobayashi, and Y. Hasegawa

Appl. Phys. Lett. 87, 143112 (2005); http://dx.doi.org/10.1063/1.2084342 (3 pages) | Cited 20 times

Online Publication Date: 30 September 2005

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We report the synthesis of silicon nanocones using the rf microplasma discharge at atmospheric pressure. The products formed underneath the tube electrode on Fe-coated crystalline silicon were constituted mainly of silicon and silicon oxide despite the use of a methane-argon mixture. Carbon nanotubes and silicon nanowires were also formed around the silicon nanocones. The number density and average size of silicon nanocones increased with the plasma exposure time accompanied by the enlargement of their surface distribution. The growth mechanism of silicon nanocones is discussed in terms of the catalytic growth via diffusion of silicon with nanocrystalline Si particle through FeSix nanoclusters, and enhanced Si oxidation by the plasma heating.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
61.46.-w Structure of nanoscale materials
52.77.-j Plasma applications
81.16.-c Methods of micro- and nanofabrication and processing

Influence of oxygen on optical properties of Si nanocrystallites

L. E. Ramos, J. Furthmüller, and F. Bechstedt

Appl. Phys. Lett. 87, 143113 (2005); http://dx.doi.org/10.1063/1.2084325 (3 pages) | Cited 12 times

Online Publication Date: 30 September 2005

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The influence of oxygen on optical absorption spectra, radiative lifetimes, and localization of states is analyzed within the quasiparticle formalism based on the GW approximation for defect-free Si nanocrystallites. Passivation with hydroxyls and oxide coverage have significant influence on the spatial distribution of the highest-occupied and lowest-unoccupied molecular orbitals as well as on the radiative lifetimes. Oxidation blueshifts the onset of absorption, whereas oxide coverage and passivation with hydroxyls tend to redshift it. The indirect-gap nature of the optical transitions in Si bulk is transferred to the Si nanocrystallites independently of the oxygen contents.
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78.55.Ap Elemental semiconductors
61.46.-w Structure of nanoscale materials
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
81.65.Rv Passivation
81.65.Mq Oxidation
71.20.Mq Elemental semiconductors
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High-power SiO2/AlGaN/GaN metal-oxide-semiconductor heterostructure field-effect transistors

P. Kordoš, G. Heidelberger, J. Bernát, A. Fox, M. Marso, and H. Lüth

Appl. Phys. Lett. 87, 143501 (2005); http://dx.doi.org/10.1063/1.2058206 (3 pages) | Cited 30 times

Online Publication Date: 26 September 2005

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We report on SiO2/AlGaN/GaN metal-oxide-semiconductor heterostructure field-effect transistors (MOSHFETs), which exhibit a 6.7 W/mm power density at 7 GHz. Unpassivated and SiO2-passivated heterostructure field-effect transistors (HFETs) were also investigated for comparison. Deposited 12 nm thick SiO2 yielded an increase of the sheet carrier density from 7.6×1012 to 9.2×1012 cm−2 and a subsequent increase of the static drain saturation current from 0.75 to 1.09 A/mm. The small-signal rf characterization of the MOSHFETs showed an extrinsic current gain cutoff frequency fT of 24 GHz and a maximum frequency of oscillation fmax of 40 GHz. The output power of 6.7 W/mm of the MOSHFETs measured at 7 GHz is about two times larger than that of HFETs. The results obtained demonstrate the suitability of GaN-based MOSHFETs for high-power electronics.
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85.30.Tv Field effect devices

Polymer bulk homojunction photonic devices

Corey Tracy and Jun Gao

Appl. Phys. Lett. 87, 143502 (2005); http://dx.doi.org/10.1063/1.2077852 (3 pages) | Cited 7 times

Online Publication Date: 27 September 2005

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We demonstrate polymer photonic devices based on the formation of multiple p-n junctions within the bulk of the active polymer film. By simple mixing of metallic particles into an electrolyte/electroluminescent composite polymer film, thousands of tiny light-emitting p-n junctions are formed in situ by electrochemical p- and n-doping. This bulk homojunction device exhibits a large active light-emitting area, as well as a giant open-circuit voltage of 25.5 V, when operated as a photovoltaic cell. All devices are constructed in an extremely large planar configuration that can be directly imaged with a digital camera.
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85.60.Jb Light-emitting devices
82.45.Gj Electrolytes
61.72.up Other materials
85.60.-q Optoelectronic devices

Influence of indium tin oxide electrodes deposited at room temperature on the properties of organic light-emitting devices

Toshikazu Satoh, Hisayoshi Fujikawa, and Yasunori Taga

Appl. Phys. Lett. 87, 143503 (2005); http://dx.doi.org/10.1063/1.2077835 (3 pages) | Cited 6 times

Online Publication Date: 27 September 2005

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The influence of indium tin oxide (ITO) electrodes deposited at room temperature (ITO-RT) on the properties of organic light-emitting devices (OLEDs) has been studied. The OLED on the ITO-RT showed an obvious shorter lifetime and higher operating voltage than that on the conventional ITO electrode deposited at 573 K. The result of an in situ x-ray photoelectron spectroscopy analysis of the ITO electrode and the organic layer suggested that many of the hydroxyl groups that originate in the amorphous structure of the ITO-RT electrode oxidize the organic layer. The performance of the OLED on the ITO-RT is able to be explained by the oxidation of the organic layer.
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85.60.Jb Light-emitting devices
79.60.-i Photoemission and photoelectron spectra
81.15.Cd Deposition by sputtering

Mobility enhancement of polycrystalline-Si thin-film transistors using nanowire channels by pattern-dependent metal-induced lateral crystallization

Yung-Chun Wu, Ting-Chang Chang, Po-Tsun Liu, Yuan-Chun Wu, Cheng-Wei Chou, Chun-Hao Tu, Jen-Chung Lou, and Chun-Yen Chang

Appl. Phys. Lett. 87, 143504 (2005); http://dx.doi.org/10.1063/1.2076436 (3 pages) | Cited 8 times

Online Publication Date: 28 September 2005

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This work presents a method for enhancing the mobility of polycrystalline-Si (poly-Si) thin-film transistors (TFTs) by pattern-dependent metal-induced-lateral-crystallization (PDMILC) using nanowire channels. Experimental results indicate that the field-effect mobility of PDMILC TFT was enhanced as the channel width decreased, because the lateral length of the poly-Si grains increased. The PDMILC poly-Si TFT with ten nanowire channels (M10) had the greatest field-effect mobility, 109.34 cm2/V s and the lowest subthreshold swing, 0.23 V/dec, at a gate length of 2 μm. The field-effect mobility also increased as the gate length in the M10 PDMILC poly-Si TFT device declined, because the number of poly-Si grain-boundary defects was reduced.
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85.30.Tv Field effect devices

Varistors made of indium tin oxide/Si multilayers on p-type GaN substrates

S. Y. Yang, P. P. Su, Y. C. Chiu, Chin-Yih Hong, H. C. Yang, W. H. Liu, and B. J. Lee

Appl. Phys. Lett. 87, 143505 (2005); http://dx.doi.org/10.1063/1.2081119 (3 pages)

Online Publication Date: 28 September 2005

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Varistors are important devices in the prevention of electric circuits from electric surges or in the stabilization of the operation current. Instead of the conventional granular type, varistors consisting of conductor/semiconductor multilayers grown on p-type semiconductor substrates are developed. In this work, the conductor used is indium tin oxide (ITO), the semiconductor is Si and the substrate is of p-type GaN. It was found that symmetric and nonlinear current-voltage curves are available by cascading two (ITO/Si)N/p-GaN films with a bridging Ag film. Furthermore, the current-voltage characteristics can be manipulated by depositing various periods of ITO/Si multilayers on the p-type GaN substrates. The details of the design principle and the characterizations of the cascading (ITO/Si)N/p-GaN thin-film varistors are also discussed.
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85.30.-z Semiconductor devices

Fabrication of C60 field-effect transistors with polyimide and Ba0.4Sr0.6Ti0.96O3 gate insulators

Yoshihiro Kubozono, Takayuki Nagano, Yusuke Haruyama, Eiji Kuwahara, Toshio Takayanagi, Kenji Ochi, and Akihiko Fujiwara

Appl. Phys. Lett. 87, 143506 (2005); http://dx.doi.org/10.1063/1.2081134 (3 pages) | Cited 17 times

Online Publication Date: 29 September 2005

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A flexible C60 field-effect transistor (FET) device has been fabricated with a polyimide gate insulator on the poly(ethylene terephthalate) substrate, and n-channel normally off FET properties are observed in this FET device. The field-effect mobility, μ, is estimated to be ∼ 10−2 cm2 V−1 s−1 at 300 K. Furthermore, the C60 FET has been fabricated with a high-dielectric Ba0.4Sr0.6Ti0.96O3 (BST) gate insulator, showing n-channel properties; the μ value is estimated to be ∼ 10−4 cm2 V−1 s−1 at 300 K. The FET device operates at very low gate voltage, VG, and low drain-source voltage, VDS. Thus these C60 FET devices possess flexibility and low-voltage operation characteristic of polyimide and BST gate insulators, respectively.
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85.65.+h Molecular electronic devices

High-contrast top-emitting organic light-emitting devices for active-matrix displays

Chih-Jen Yang, Chun-Liang Lin, Chung-Chih Wu, Yung-Hui Yeh, Chun-Cheng Cheng, Yen-Hsun Kuo, and Tai-Hong Chen

Appl. Phys. Lett. 87, 143507 (2005); http://dx.doi.org/10.1063/1.2081137 (3 pages) | Cited 30 times

Online Publication Date: 29 September 2005

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Unlike previous high-contrast devices that all involve inserting extra layer(s) with optical purposes (e.g., absorption and interference) into the active region of devices, in this-letter we report a high-contrast top-emitting organic light-emitting device (OLED) that utilizes only optical characteristics of electrodes and anti-reflection coatings deposited outside the active region, thus reducing the complexity of devices. Furthermore, the device has an inherent microcavity which is beneficial to electroluminescence efficiency. The devices are readily compatible with the processing of active-matrix backplanes, and active-matrix OLED displays incorporating such high-contrast top-emitting devices were demonstrated to have improved readability under a strong lighting environment.
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85.60.Jb Light-emitting devices
42.79.Kr Display devices, liquid-crystal devices

ZnO extended-gate field-effect transistors as pH sensors

P. D. Batista and M. Mulato

Appl. Phys. Lett. 87, 143508 (2005); http://dx.doi.org/10.1063/1.2084319 (3 pages) | Cited 28 times

Online Publication Date: 29 September 2005

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The objective of this work is the study and characterization of zinc oxide (ZnO) as pH sensor. We used an extended-gate field-effect transistor (EGFET) to obtain the response of ZnO as a function of pH. Sol-gel was used for the production of ZnO films because this is a low cost and easy fabrication procedure. The ZnO powder was obtained at different temperatures of calcination, from 150 up to 500 ° C. The samples were investigated by x-ray diffraction, infrared spectroscopy, thermogravimetric analysis and differential thermal analysis. The films were investigated as pH sensors (range 2–12) and the ZnO EGFET shows a sensitivity of 38 mV/pH.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
85.30.Tv Field effect devices
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Optical detection of deoxyribonucleic acid hybridization using an anchoring transition of liquid crystal alignment

Hak-Rin Kim, Jae-Hoon Kim, Tae-Sun Kim, Sang-Wook Oh, and Eui-Yul Choi

Appl. Phys. Lett. 87, 143901 (2005); http://dx.doi.org/10.1063/1.2077859 (3 pages) | Cited 10 times

Online Publication Date: 27 September 2005

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We demonstrate an optical method for detecting specific binding events in an oligo deoxyribonucleic acid (DNA) chip using an anchoring transition of a nematic liquid crystal (NLC) as a result of DNA hybridization. A homeotropic orientation of the NLC supported by oligoDNA changes to a random planar orientation after hybridization. Such DNA hybridization and subsequent NLC reorientation are easily observable with a simple detection system via long-range orientational order and large optical anisotropy of the NLC.
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87.14.G- Nucleic acids
87.80.-y Biophysical techniques (research methods)
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing

Nanodevice design through the functional abstraction of biological macromolecules

Kaustubh D. Bhalerao, Edward Eteshola, Matthew Keener, and Stephen C. Lee

Appl. Phys. Lett. 87, 143902 (2005); http://dx.doi.org/10.1063/1.2077839 (3 pages)

Online Publication Date: 27 September 2005

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Biologic macromolecules are prefabricated, functional nanocomponents readily incorporated into nanodevices. Semibiologic nanodevice design typically depends on knowledge of specific biomolecules by individual biologist designers, so individual devices seldom take full advantage of available biodiversity and are poorly optimized. Available informational resources (proteomic and genomic databases) were built to reflect evolutionary relationships between organisms, molecules, and biologic systems, and are lacking in their explicit functional properties. This limits their direct utility in nanodevice design. We discuss the need, and possible structure for an information framework that captures the function of biological macromolecules to enable rational nanodevice design and optimization.
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87.80.-y Biophysical techniques (research methods)
87.14.E- Proteins
89.20.Hh World Wide Web, Internet
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Adaptation of flexible polymer fabrication to cellular mechanics study

Yi Zhao and Xin Zhang

Appl. Phys. Lett. 87, 144101 (2005); http://dx.doi.org/10.1063/1.2061861 (3 pages) | Cited 10 times

Online Publication Date: 26 September 2005

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Polymeric material has been utilized as mechanical sensors to measure microscopic cellular forces. Since many polymers are not readily compatible with conventional lithography, fabrication of numerous molds is inevitably a part of the process, compromising low cost and process simplicity. In this letter, we apply a flexible fabrication process to manufacture polymeric mechanical sensors with various aspect ratios from a single rigid mold. A proof-of-principle measurement was carried out in isolated cardiac myocytes. The results conform to the physiologic behavior. This approach has the potential for evaluation of mechanical interaction between various biological units and the substrates while minimizing the fabrication cost and complexity.
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87.15.La Mechanical properties
87.17.-d Cell processes
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
87.80.-y Biophysical techniques (research methods)

Surface enhanced infrared absorption by coupling phonon and plasma resonance

Mark S. Anderson

Appl. Phys. Lett. 87, 144102 (2005); http://dx.doi.org/10.1063/1.2077838 (3 pages) | Cited 9 times

Online Publication Date: 28 September 2005

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A gold and silicon carbide particle matrix is presented that concentrates light to its surface using a combination of phonon and plasmon resonance mechanisms. The enhanced infrared absorption spectrum of absorbed molecules is used to probe the coupled phonon and plasmon surface resonances. Sensitive molecular detection is achieved by measuring the enhanced infrared absorption or the frequency shift in the surface modes of the coated matrix. This work demonstrates that hybrid polariton resonance structures using metallic and polar dielectric materials are feasible for applications in near-field microscopy, nano-optical devices, and trace chemical sensing.
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73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
73.22.Lp Collective excitations
63.20.kk Phonon interactions with other quasiparticles
78.30.Hv Other nonmetallic inorganics
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
61.46.-w Structure of nanoscale materials

Smart membranes: A physical model for a circadian behavior

R. Rodríguez and V. M. Castaño

Appl. Phys. Lett. 87, 144103 (2005); http://dx.doi.org/10.1063/1.2084320 (3 pages)

Online Publication Date: 29 September 2005

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Synthetic “smart” membranes, able to adjust their pore sizes, from 1 to 50 μm, depending on the physical and/or chemical environment, are presented. Their oscillatory behavior, resembling that of many living systems, is accurately reproduced by a model based on the two competing phenomena in the membrane: elastic forces and steric interactions.
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87.16.D- Membranes, bilayers, and vesicles
87.10.-e General theory and mathematical aspects
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