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9 Oct 2006

Volume 89, Issue 15, Articles (15xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 89, 151920 (2006); http://dx.doi.org/10.1063/1.2360906 (3 pages)

Aycan Yurtsever, Matthew Weyland, and David A. Muller
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Ultraviolet photodetectors with ZnO nanowires prepared on ZnO:Ga/glass templates

Chien-Yuan Lu, Shoou-Jinn Chang, Sheng-Po Chang, Ching-Ting Lee, Che-Fu Kuo, Hong-Ming Chang, Yu-Zung Chiou, Cheng-Liang Hsu, and I-Cherng Chen

Appl. Phys. Lett. 89, 153101 (2006); http://dx.doi.org/10.1063/1.2360219 (3 pages) | Cited 25 times

Online Publication Date: 9 October 2006

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Vertically well-aligned ZnO nanowire ultraviolet (UV) photodetectors were fabricated by spin-on-glass technology on ZnO:Ga/glass templates. With 2 V applied bias, it was found that dark current density of the fabricated device was only 2.0×10−7 A/cm2. It was also found that UV-to-visible rejection ratio and quantum efficiency of the fabricated ZnO nanowire photodetectors were more than 1000 and 12.6%, respectively.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
81.07.Vb Quantum wires
73.63.Nm Quantum wires
78.67.Lt Quantum wires
72.40.+w Photoconduction and photovoltaic effects
81.16.-c Methods of micro- and nanofabrication and processing

Large area, dense silicon nanowire array chemical sensors

A. Alec Talin, Luke L. Hunter, François Léonard, and Bhavin Rokad

Appl. Phys. Lett. 89, 153102 (2006); http://dx.doi.org/10.1063/1.2358214 (3 pages) | Cited 34 times

Online Publication Date: 9 October 2006

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The authors present a simple top-down approach based on nanoimprint lithography to create dense arrays of silicon nanowires over large areas. Metallic contacts to the nanowires and a bottom gate allow the operation of the array as a field-effect transistor with very large on/off ratios. When exposed to ammonia gas or cyclohexane solutions containing nitrobenzene or phenol, the threshold voltage of the field-effect transistor is shifted, a signature of charge transfer between the analytes and the nanowires. The threshold voltage shift is proportional to the Hammett parameter and the concentration of the nitrobenzene and phenol analytes.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
85.30.Tv Field effect devices
85.40.Hp Lithography, masks and pattern transfer
82.30.Fi Ion-molecule, ion-ion, and charge-transfer reactions

Strain-controlled correlation effects in self-assembled quantum dot stacks

R. Kunert and E. Schöll

Appl. Phys. Lett. 89, 153103 (2006); http://dx.doi.org/10.1063/1.2354476 (3 pages) | Cited 5 times

Online Publication Date: 9 October 2006

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The authors show that elastic interactions of an array of self-assembled quantum dots in a parent material matrix are markedly distinct from the elastic field created by a single point defect and can explain the observed abrupt correlation-anticorrelation transition in semiconductor quantum dot stacks. Finite volume effects of the quantum dots are shown to lead to sharper transitions. Their analysis also predicts the inclination angle under which the alignment in successive quantum dot layers occurs in dependence on the material anisotropy.
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81.07.Ta Quantum dots
81.05.Ea III-V semiconductors
68.65.Hb Quantum dots (patterned in quantum wells)
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.D- Elasticity
61.72.J- Point defects and defect clusters

Transition-metal-doping-enhanced hydrogen storage in boron nitride systems

S. A. Shevlin and Z. X. Guo

Appl. Phys. Lett. 89, 153104 (2006); http://dx.doi.org/10.1063/1.2360232 (3 pages) | Cited 23 times

Online Publication Date: 9 October 2006

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The authors perform spin-polarized density functional theory simulations on the 3d transition metal (TM) series (Sc to Fe) doped system borazine (B3N3H6). The Sc and Ti bind most strongly to borazine but Cr and Mn do not bind at all. With increasing hydrogen content the bound hydrogen species becomes molecular. The maximum amount of hydrogen that can be stored is 4H2 per TM atom for Sc, Ti, and V dopants ( ∼ 6 wt % bound hydrogen). The binding energy of hydrogen in these systems is of the order of −0.3 to −0.7 eV/H2, desirable for practical hydrogen storage applications. The optimum dopant is titanium.
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84.60.-h Direct energy conversion and storage
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
71.15.Nc Total energy and cohesive energy calculations

Spin-polarized inelastic electron tunneling spectroscopy of a molecular magnetic tunnel junction

Wenyong Wang and Curt A. Richter

Appl. Phys. Lett. 89, 153105 (2006); http://dx.doi.org/10.1063/1.2360908 (3 pages) | Cited 12 times

Online Publication Date: 9 October 2006

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Molecular electronic devices with spin-dependent tunneling transport behavior offer an innovative and extremely enticing direction towards spin electronics, both from fundamental and technological points of view. In this work, inelastic electron tunneling spectroscopy provides unambiguous experimental evidence of the existence of molecular species in the fabricated molecular magnetic tunnel devices. Tunneling spectroscopy is also utilized to investigate the spin-polarized inelastic electron tunneling processes in the molecular device. The results show that inelastic scattering due to molecular vibrations, instead of magnon excitations, may be the main cause of the observed junction magnetoresistance bias dependence.
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85.75.Mm Spin polarized resonant tunnel junctions
85.65.+h Molecular electronic devices

Excitation-dependent photoluminescence in Ge/Si Stranski-Krastanov nanostructures

B. V. Kamenev, E.-K. Lee, H.-Y. Chang, H. Han, H. Grebel, L. Tsybeskov, and T. I. Kamins

Appl. Phys. Lett. 89, 153106 (2006); http://dx.doi.org/10.1063/1.2361198 (3 pages) | Cited 8 times

Online Publication Date: 9 October 2006

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In Ge/Si Stranski-Krastanov nanostructures grown by chemical vapor deposition, the authors find ∼ 30 meV/decade photoluminescence (PL) spectral shift toward greater photon energies as excitation intensity increases from 0.1 to 104 W/cm2. The PL lifetime exhibits strong spectral dependence, and it decreases from ∼ 20 μs at 0.77 eV to 200 ns at 0.89 eV. The authros attribute the observed PL spectral shift and shorter PL lifetime at higher photon energies to an increasing contribution from recombination between holes populating excited Ge cluster energy states and electrons in SiGe alloy cluster regions.
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81.05.Cy Elemental semiconductors
81.07.Bc Nanocrystalline materials
78.55.Ap Elemental semiconductors
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
73.63.Bd Nanocrystalline materials
61.46.Hk Nanocrystals

Effects of nanoparticle deposition on surface wettability influencing boiling heat transfer in nanofluids

S. J. Kim, I. C. Bang, J. Buongiorno, and L. W. Hu

Appl. Phys. Lett. 89, 153107 (2006); http://dx.doi.org/10.1063/1.2360892 (3 pages) | Cited 50 times

Online Publication Date: 10 October 2006

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Buildup of a porous layer of nanoparticles on the heated surface occurs upon boiling of nanofluids containing alumina, zirconia, or silica nanoparticles. This layer significantly improves the surface wettability, as shown by a reduction of the static contact angle on the nanofluid-boiled surfaces compared with the pure-water-boiled surfaces. The contact angle reduction is attributed to changes in surface energy and surface morphology brought about by the presence of the nanoparticle layer. The high surface wettability can plausibly explain the boiling critical heat flux enhancement in nanofluids.
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47.27.te Turbulent convective heat transfer
47.55.dp Cavitation and boiling
47.57.J- Colloidal systems
68.03.Cd Surface tension and related phenomena

Elongation of InAs/GaAs quantum dots from magnetophotoluminescence measurements

V. Křápek, K. Kuldová, J. Oswald, A. Hospodková, E. Hulicius, and J. Humlíček

Appl. Phys. Lett. 89, 153108 (2006); http://dx.doi.org/10.1063/1.2358845 (3 pages) | Cited 2 times

Online Publication Date: 10 October 2006

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The authors have used magnetophotoluminescence for the determination of the lateral anisotropy of buried quantum dots. While the calculated shifts of the energies of higher radiative transitions in magnetic field are found to be sensitive to the lateral elongation, the shift of the lowest transition is determined mainly by the exciton effective mass. This behavior can be used for a fairly reliable determination both the effective mass and the elongation from spectra containing at least two resolved bands.
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81.07.Ta Quantum dots
78.67.Hc Quantum dots
78.55.Cr III-V semiconductors
68.65.Hb Quantum dots (patterned in quantum wells)
78.20.Ls Magneto-optical effects
71.35.-y Excitons and related phenomena

Growth and characteristics of ultralow threshold 1.45 μm metamorphic InAs tunnel injection quantum dot lasers on GaAs

Z. Mi, P. Bhattacharya, and J. Yang

Appl. Phys. Lett. 89, 153109 (2006); http://dx.doi.org/10.1063/1.2358847 (3 pages) | Cited 23 times

Online Publication Date: 10 October 2006

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The molecular beam epitaxial growth and characteristics of 1.45 μm metamorphic InAs quantum dot tunnel injection lasers on GaAs have been studied. Under optimized growth conditions, the quantum dots exhibit photoluminescence linewidths ∼ 30 meV and high intensity at room temperature. The lasers are characterized by ultralow threshold current (63 A/cm2), large frequency response (f−3 dB = 8 GHz), and near-zero α parameter and chirp.
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42.60.By Design of specific laser systems
42.55.Px Semiconductor lasers; laser diodes
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
42.60.Fc Modulation, tuning, and mode locking

Theoretical analysis of electric field effect on Young’s modulus of nanowires

Xiaojing Zheng and Linli Zhu

Appl. Phys. Lett. 89, 153110 (2006); http://dx.doi.org/10.1063/1.2358848 (3 pages) | Cited 9 times

Online Publication Date: 10 October 2006

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The effect of an applied electric field on Young’s modulus of nanowires is investigated in this letter. The exact and analytical expressions of the transverse and axial Young moduli of a nanowire in an applied electric field are derived with the aid of the surface energy arising from the charges distributed on the surfaces of the nanowire. The results reveal that the transverse and axial Young moduli of a nanowire in an applied electric field are different from those of a nanowire in the absence of the field. The effect of the electric field on Young modulus is related to the intensity of the field, the size of the wire, and the direction of the wire.
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81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.D- Elasticity
68.35.Md Surface thermodynamics, surface energies
62.25.-g Mechanical properties of nanoscale systems

Controlled growth of Co nanoparticle assembly on nanostructured template Al2O3/NiAl(100)

Wen-Chin Lin, Shen-Shing Wong, Po-Chun Huang, Chii-Bin Wu, Bin-Rui Xu, Cheng-Tien Chiang, Hong-Yu Yen, and Minn-Tsong Lin

Appl. Phys. Lett. 89, 153111 (2006); http://dx.doi.org/10.1063/1.2358926 (3 pages) | Cited 8 times

Online Publication Date: 10 October 2006

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Based on the systematic studies of the growth temperature, deposition rate, and annealing effects, the control of Co nanoparticle density, size, and alignment is demonstrated to be feasible on a nanostructured template Al2O3/NiAl(100). At 140–170 K, a slow deposition rate (0.027 ML/min) promises both the linear alignment and the high particle density. 1.5 ML Co nanoparticle assembly sustains the density of ∼ 260/104 nm2 even after 800–1090 K annealing. This study also indicates the possibilities of the controlled growth for nanoparticles of different materials.
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81.07.Bc Nanocrystalline materials
81.05.Bx Metals, semimetals, and alloys
81.16.-c Methods of micro- and nanofabrication and processing
81.40.Gh Other heat and thermomechanical treatments
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)

Nonlinear absorption of femtosecond laser on a metal surface embedded by metallic nanoparticles

Amir Ahmad and V. K. Tripathi

Appl. Phys. Lett. 89, 153112 (2006); http://dx.doi.org/10.1063/1.2358937 (2 pages) | Cited 2 times

Online Publication Date: 10 October 2006

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Metal surface with nanosize roughness is modeled as a plane surface embedded with clusters. A high power femtosecond laser pulse normally incident on the metal surface undergoes field enhancement when laser frequency equals the frequency of surface charge oscillations of the clusters. The enhanced field causes increased absorption of the laser pulse. The model suggests that the increase in absorption decreases with the increase of the laser power. The results are in line with recent observations.
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78.47.-p Spectroscopy of solid state dynamics
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.47.De Metallic surfaces

Quadraxial probe for high resolution near-field scanning rf/microwave microscopy

A. Karbassi, C. A. Paulson, A. B. Kozyrev, M. Banerjee, Y. Wang, and D. W. van der Weide

Appl. Phys. Lett. 89, 153113 (2006); http://dx.doi.org/10.1063/1.2358945 (3 pages) | Cited 3 times

Online Publication Date: 10 October 2006

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The authors propose and demonstrate a miniaturized quadraxial probe that employs a differential feed technique for use in near-field rf/microwave transmission microscopy. Their quadraxial probe’s electric field measurements show higher electric field localization than a conventional coaxial (monopole) probe. The improved spatial resolution and more sensitive phase measurement of the quadraxial probe versus coaxial probe are further validated by a metal line scan experiment.
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07.79.-v Scanning probe microscopes and components
68.37.-d Microscopy of surfaces, interfaces, and thin films

Electronic delocalization and resonant transmission in symmetric metallic nanowires

R. L. Zhang, R. W. Peng, L. S. Cao, Z. Wang, Z. H. Tang, X. F. Zhang, Mu Wang, and A. Hu

Appl. Phys. Lett. 89, 153114 (2006); http://dx.doi.org/10.1063/1.2357875 (3 pages) | Cited 2 times

Online Publication Date: 10 October 2006

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We report here the theoretical studies on electronic delocalization and resonant transmission in symmetric metallic nanowires (SMNs). Resonant transmissions, which are characterized by multiple perfect transmission peaks, have been found in the electronic band gap. The resonant energy and the number of modes of resonant transmission therein can be manipulated, and the quality factor of the perfect transmission peak can be exponentially increased. We suggest that the resonant transmission originates from the electronic delocalization in SMNs, which is characterized by the extended wave function of electrons around the resonant energy. These features open a unique way to control quantum transport in nanodevices.
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73.21.Hb Quantum wires
73.63.Nm Quantum wires

Enhanced compositional sensitivity in atomic force microscopy by the excitation of the first two flexural modes

N. F. Martinez, S. Patil, J. R. Lozano, and R. Garcia

Appl. Phys. Lett. 89, 153115 (2006); http://dx.doi.org/10.1063/1.2360894 (3 pages) | Cited 52 times

Online Publication Date: 11 October 2006

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The authors demonstrate that the compositional sensitivity of an atomic force microscope is enhanced by the simultaneous excitation of its first two flexural eigenmodes. The coupling of those modes by the nonlinear probe-surface interactions enables to map compositional changes in several conjugated molecular materials with a phase shift sensitivity that is about one order of magnitude higher than the one achieved in amplitude modulation atomic force microscopy.
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07.79.Lh Atomic force microscopes
68.37.Ps Atomic force microscopy (AFM)
68.35.B- Structure of clean surfaces (and surface reconstruction)

Influence of Ag particle size on ethanol sensing of SnO1.8:Ag nanoparticle films: A method to develop parts per billion level gas sensors

Rakesh K. Joshi and F. Einar Kruis

Appl. Phys. Lett. 89, 153116 (2006); http://dx.doi.org/10.1063/1.2360245 (3 pages) | Cited 20 times

Online Publication Date: 12 October 2006

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The influence of Ag particle size on ethanol sensing of SnO1.8:Ag films composed of size-selected nanoparticles with independently controlled size and concentration of Ag is reported in the present study. The study shows that Ag nanoparticles are acting as catalyst for chemical sensitization through a spillover effect. The catalyst particles are observed to be more active on decreasing their size, resulting into an improved sensor response. A response time of 2 s for 1000 ppm ethanol has been achieved. Detection of 100 ppb ethanol in air has been demonstrated using this well-defined technique.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
82.80.-d Chemical analysis and related physical methods of analysis
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)

High negative differential resistance in silicon quantum dot metal-insulator-semiconductor structure

Nae-Man Park, Sang Hyeob Kim, Sunglyul Maeng, and Seong-Ju Park

Appl. Phys. Lett. 89, 153117 (2006); http://dx.doi.org/10.1063/1.2360888 (3 pages) | Cited 9 times

Online Publication Date: 12 October 2006

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Metal-insulator-semiconductor structures, comprised of silicon quantum dot films grown by plasma-enhanced chemical vapor deposition, were fabricated on Si wafers. The devices showed a negative differential resistance, as a result of the resonant tunneling and the very high peak-to-valley current ratios of 2240 under illumination and 390 in the dark at room temperature, which are much higher than the corresponding values of other Si tunneling devices. The peak voltage was reduced down to 1.9 V by increasing the doping concentration of the wafer and reducing the device area. The structure shows promise for use in solid-state switch applications.
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85.30.Tv Field effect devices
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
85.40.Ry Impurity doping, diffusion and ion implantation technology

Co–Au core-shell nanocrystals formed by sequential ion implantation into SiO2

P. Kluth, B. Hoy, B. Johannessen, S. G. Dunn, G. J. Foran, and M. C. Ridgway

Appl. Phys. Lett. 89, 153118 (2006); http://dx.doi.org/10.1063/1.2360891 (3 pages) | Cited 3 times

Online Publication Date: 12 October 2006

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Co–Au core-shell nanocrystals (NCs) were formed by sequential ion implantation of Au and Co into thin SiO2. The NCs were investigated by means of transmission electron microscopy and extended x-ray absorption fine structure spectroscopy. The latter reveals a bond length expansion in the Co core compared to monatomic Co NCs. Concomitantly, a significant contraction of the bond length and a significant reduction of the effective Au–Au coordination number were observed in the Au shells. Increased Debye-Waller factors indicate significant strain in the NCs. These experimental results verify recent theoretical predictions.
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61.46.Hk Nanocrystals
61.80.Jh Ion radiation effects
61.72.up Other materials
68.37.Lp Transmission electron microscopy (TEM)
78.70.Dm X-ray absorption spectra
63.70.+h Statistical mechanics of lattice vibrations and displacive phase transitions

Rapid hot-electron capture in self-assembled quantum dots via phonon processes

J.-Z. Zhang and I. Galbraith

Appl. Phys. Lett. 89, 153119 (2006); http://dx.doi.org/10.1063/1.2360913 (3 pages) | Cited 2 times

Online Publication Date: 12 October 2006

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Electron capture induced by carrier heating in InAs/GaAs quantum dots is studied theoretically. Room temperature capture rates due to single longitudinal-optical (LO) phonons, LO phonons plus acoustic phonons, and two LO phonons are compared. Due to energy broadening from carrier-carrier scattering, single LO-phonon processes are the fastest capture channel. Screening from wetting-layer (WL) carriers is studied comprehensively using a number of screening models. Due to the dispersion of the WL electron-hole plasma and dynamic effects of screening, antiscreening occurs expediting rather than slowing down electron capture, with capture times of several picoseconds when the carrier temperature is 100–200 K above room temperature.
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73.63.Kv Quantum dots
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.30.+q High-frequency effects; plasma effects
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials

Optimized plasmonic nanoparticle distributions for solar spectrum harvesting

Joseph R. Cole and N. J. Halas

Appl. Phys. Lett. 89, 153120 (2006); http://dx.doi.org/10.1063/1.2360918 (3 pages) | Cited 50 times

Online Publication Date: 12 October 2006

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The large optical cross sections of metallic nanoparticles at wavelengths corresponding to their plasmon resonance make them highly attractive for harvesting solar energy for a variety of applications. Here the authors determine ideal distributions of spherical metallic nanoparticles, both nanospheres and nanoshells, that match the AM 1.5 solar spectrum in a mixed component, submonolayer geometry. Both absorbing and scattering distributions are determined and their properties compared to conventional broad spectrum absorbing and scattering media.
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78.40.Kc Metals, semimetals, and alloys
78.30.Er Solid metals and alloys
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
96.60.Tf Solar electromagnetic emission

Alkylsiloxane self-assembled monolayer formation guided by nanoimprinted Si and SiO2 templates

Amir A. Yasseri, Shashank Sharma, Theodore I. Kamins, Qiangfei Xia, Stephen Y. Chou, and R. Fabian W. Pease

Appl. Phys. Lett. 89, 153121 (2006); http://dx.doi.org/10.1063/1.2360920 (3 pages) | Cited 2 times

Online Publication Date: 12 October 2006

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Alkylsiloxane self-assembled monolayers (SAMs) were formed on surface relief created by nanoimprinting and etching recesses into Si and SiO2. Rather than exhibiting the isolated domains seen on unpatterned surfaces after limited formation time, the SAM on nanoimprinted surfaces became continuous and uniform after only a short ( ∼ 5–10 min) reaction time. The hydrocarbon chains are densely packed and nearly vertically oriented. X-ray photoemission spectroscopy indicates complete hydrolysis and elimination of Cl from the octadecyltrichlorosilane precursor. The results suggest that the pattern edges enhance the nucleation rate, leading to the rapid coverage, and provide in-plane order within the SAM.
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81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.Nd Micro- and nanolithography
81.16.Dn Self-assembly
79.60.Fr Polymers; organic compounds

Simultaneous formation of SiC and Si nanostructures on silicon by local ion implantation and electron beam annealing

A. Markwitz, S. Johnson, and M. Rudolphi

Appl. Phys. Lett. 89, 153122 (2006); http://dx.doi.org/10.1063/1.2361162 (3 pages) | Cited 3 times

Online Publication Date: 12 October 2006

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The authors demonstrate the fabrication of SiC nanocrystals on silicon by carbon ion implantation into silicon followed by electron beam annealing at 1000 °C. A continuous asymmetric, pyramidal ridge around 20 nm in height is observed at the boundary between the implanted and unimplanted regions. Adjacent to the ridge within the implanted region appears a trough which is continuous around the perimeter of the implanted/unimplanted boundary. The surface of the unimplanted region consists of pyramidal structures with an average height of 5–10 nm which cover the entire surface.
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81.07.-b Nanoscale materials and structures: fabrication and characterization
81.05.Cy Elemental semiconductors
61.46.-w Structure of nanoscale materials
61.80.Jh Ion radiation effects
61.72.Cc Kinetics of defect formation and annealing
61.80.Fe Electron and positron radiation effects

Nanoscale resolution microchannel flow velocimetry by atomic force microscopy

Brian Piorek, Ádám Mechler, Ratnesh Lal, Patrick Freudenthal, Carl Meinhart, and Sanjoy Banerjee

Appl. Phys. Lett. 89, 153123 (2006); http://dx.doi.org/10.1063/1.2358966 (3 pages) | Cited 7 times

Online Publication Date: 12 October 2006

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The velocity of a microchannel flow was determined by atomic force microscopy (AFM) using a 50 nm wide “whisker,” which was partially submerged and scanned transverse to the flow while drag was recorded. A peaked, near parabolic, flow velocity profile was found. Particle image velocity (PIV) measurements using 70 nm diameter quantum-dot-coated polystyrene spheres confirmed the shape of the AFM-measured velocity profile. AFM-based nanometer resolution velocimetry confirms that the drag-velocity relationship for the whisker remains consistent over a wide range of shear values and appears to successfully resolve submicron scale flows, which are beyond the limits of conventional PIV measurements.
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47.60.-i Flow phenomena in quasi-one-dimensional systems
47.80.Cb Velocity measurements
47.50.Ef Measurements
47.85.Np Fluidics
07.10.Cm Micromechanical devices and systems

Noble metal nanoparticle patterning deposition using pulsed-laser deposition in liquid for surface-enhanced Raman scattering

H. Cui, P. Liu, and G. W. Yang

Appl. Phys. Lett. 89, 153124 (2006); http://dx.doi.org/10.1063/1.2359289 (3 pages) | Cited 6 times

Online Publication Date: 12 October 2006

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Show Abstract
Deposition of noble metal nanoparticle patterning via pulsed-laser deposition in liquid for use as surface-enhanced Raman scattering substrates has been reported. The silver nanoparticle patterning has been deposited on a glass surface in contact with water by the pulsed-laser ablation of a silver target in water, and then found to be a highly effective surface-enhanced Raman scattering substrate. Three advantages of this technique are, respectively, positioning of nanoparticle patterning in devices with limited accessibility for optical sensing by surface-enhanced Raman scattering, chemically simple, and clean for nanoparticle patterning fabrications.
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81.07.Wx Nanopowders
81.16.Rf Micro- and nanoscale pattern formation
81.16.Mk Laser-assisted deposition
81.15.Fg Pulsed laser ablation deposition
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
78.30.Er Solid metals and alloys

Thermionic cooling in cylindrical semiconductor nanostructures

Pin Lyu and Chao Zhang

Appl. Phys. Lett. 89, 153125 (2006); http://dx.doi.org/10.1063/1.2361263 (3 pages)

Online Publication Date: 12 October 2006

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The authors analyzed the thermionic cooling efficiency of the cylindrical semiconductor nanostructures. It is shown that due to the reduced emission current from the inner electrode, the cooling efficiency can be enhanced if the outer cylinder is the cold electrode. The threshold voltage for thermionic cooling is lower in cylindrical devices as compared to that in planar devices. The competition between the heat transport by electrons and the heat conduction by phonons is responsible for the efficiency enhancement and the voltage reduction.
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66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves
63.20.-e Phonons in crystal lattices
79.40.+z Thermionic emission
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