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16 Apr 2012

Volume 100, Issue 16, Articles (16xxxx)

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Appl. Phys. Lett. 100, 164101 (2012); http://dx.doi.org/10.1063/1.3702579 (4 pages)

Cheol-Ho Yun, Leslie Y. Yeo, James R. Friend, and Bernard Yan
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Multi-degree-of-freedom ultrasonic micromotor for guidewire and catheter navigation: The NeuroGlide actuator

Cheol-Ho Yun, Leslie Y. Yeo, James R. Friend, and Bernard Yan

Appl. Phys. Lett. 100, 164101 (2012); http://dx.doi.org/10.1063/1.3702579 (4 pages) | Cited 1 time

Online Publication Date: 16 April 2012

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A 240-μm diameter ultrasonic micromotor is presented as a potential solution for an especially difficult task in minimally invasive neurosurgery, navigating a guidewire to an injury in the neurovasculature as the first step of surgery. The peak no-load angular velocity and maximum torque were 600 rad/s and 1.6 nN-m, respectively, and we obtained rotation about all three axes. By using a burst drive scheme, open-loop position and speed control were achieved. The construction method and control scheme proposed in this study remove most of the current limitations in minimally invasive, catheter-based actuation, enabling minimally invasive vascular surgery concepts to be pursued for a broad variety of applications.
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87.85.Ox Biomedical instrumentation and transducers, including micro-electro-mechanical systems (MEMS)
87.85.Wc Neural engineering
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
87.85.D- Applied neuroscience

Photoacoustic effect in a sinusoidally modulated structure

Binbin Wu and Gerald J. Diebold

Appl. Phys. Lett. 100, 164102 (2012); http://dx.doi.org/10.1063/1.3703606 (4 pages) | Cited 4 times

Online Publication Date: 16 April 2012

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We derive solutions to an inhomogeneous Mathieu equation that describes the photoacoustic effect in a one-dimensional phononic structure whose acoustic properties vary sinusoidally in space. Solutions show splitting of resonances, the space equivalent of subharmonic generation, and spatial confinement. Properties of the photoacoustic effect including the damping of waves inside the band gaps, the dispersion relation, the positions and widths of the gaps, the frequencies of resonances, and the space dependence of the acoustic waves can be found in closed form from known properties of Mathieu functions.
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43.35.Ud Thermoacoustics, high temperature acoustics, photoacoustic effect
43.40.-r Structural acoustics and vibration

In-situ small-angle x-ray scattering study of nanoparticles in the plasma plume induced by pulsed laser irradiation of metallic targets

L. Lavisse, J.-L. Le Garrec, L. Hallo, J.-M. Jouvard, S. Carles, J. Perez, J. B. A. Mitchell, J. Decloux, M. Girault, V. Potin, H. Andrzejewski, M. C. Marco de Lucas, and S. Bourgeois

Appl. Phys. Lett. 100, 164103 (2012); http://dx.doi.org/10.1063/1.4703930 (3 pages) | Cited 8 times

Online Publication Date: 16 April 2012

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Small angle x-ray scattering was used to probe in-situ the formation of nanoparticles in the plasma plume generated by pulsed laser irradiation of a titanium metal surface under atmospheric conditions. The size and morphology of the nanoparticles were characterized as function of laser irradiance. Two families of nanoparticles were identified with sizes on the order of 10 and 70 nm, respectively. These results were confirmed by ex-situ transmission electron microscopy experiments.
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78.70.Ck X-ray scattering
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
52.77.-j Plasma applications
68.35.B- Structure of clean surfaces (and surface reconstruction)
79.20.Ds Laser-beam impact phenomena

Measurement of an inverse Compton scattering source local spectrum using k-edge filters

Bruno Golosio, Marco Endrizzi, Piernicola Oliva, Pasquale Delogu, Massimo Carpinelli, Igor Pogorelsky, and Vitaly Yakimenko

Appl. Phys. Lett. 100, 164104 (2012); http://dx.doi.org/10.1063/1.4703932 (4 pages) | Cited 2 times

Online Publication Date: 16 April 2012

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X-ray sources based on the inverse Compton scattering process are attracting a growing interest among scientists, due to their extremely fast pulse, quasi-monochromatic spectrum, and relatively high intensity. The energy spectrum of the x-ray beam produced by inverse Compton scattering sources in a fixed observation direction is a quasi-monochromatic approximately Gaussian distribution. The mean value of this distribution varies with the scattering polar angle between the electron beam direction and the x-ray beam observation direction. Previous works reported experimental measurements of the mean energy as a function of the polar angle. This work introduces a method for the measurement of the whole local energy spectrum (i.e., the spectrum in a fixed observation direction) of the x-ray beam yielded by inverse Compton scattering sources, based on a k-edge filtering technique.
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07.85.Fv X- and γ-ray sources, mirrors, gratings, and detectors
07.85.Nc X-ray and γ-ray spectrometers
29.30.Kv X- and γ-ray spectroscopy

Ge atom distribution in buried dome islands

A. Portavoce, K. Hoummada, I. Berbezier, A. Ronda, and D. Mangelinck

Appl. Phys. Lett. 100, 164105 (2012); http://dx.doi.org/10.1063/1.4704150 (4 pages)

Online Publication Date: 17 April 2012

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Laser-assisted atom probe tomography microscopy is used to provide direct and quantitative compositional measurements of tri-dimensional Ge distribution in Ge dome islands buried by Si. Sub-nanometer spatial resolution 3D imaging shows that islands keep their facets after deposition of the Si cap, and that the island/substrate/Si cap interfaces are abrupt. The core of the domes contains 55% of Ge, while the island shell exhibits a constant composition of 15% of Ge. The {113} facets of the islands present a Ge enrichment up to 35%. The wetting layer composition is not homogeneous, varying from 9.5% to 30% of Ge.
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68.55.ag Semiconductors
68.47.Fg Semiconductor surfaces
81.05.Cy Elemental semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Precision quantization of Hall resistance in transferred graphene

M. Woszczyna, M. Friedemann, M. Götz, E. Pesel, K. Pierz, T. Weimann, and F. J. Ahlers

Appl. Phys. Lett. 100, 164106 (2012); http://dx.doi.org/10.1063/1.4704190 (3 pages) | Cited 2 times

Online Publication Date: 18 April 2012

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We show that quantum resistance standards made of transferred graphene reach the uncertainty of semiconductor devices, the current reference system in metrology. A large graphene device (150 × 30 μm2), exfoliated and transferred onto GaAs revealed a quantization with a precision of ( − 5.1 ± 6.3) · 10−9 accompanied by a vanishing longitudinal resistance at current levels exceeding 10 μA. While such performance had previously only been achieved with epitaxially grown graphene, our experiments demonstrate that transfer steps, inevitable for exfoliated graphene or graphene grown by chemical vapor deposition, are compatible with the requirements of high quality quantum resistance standards.
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72.20.My Galvanomagnetic and other magnetotransport effects
81.05.ue Graphene
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Effect of helium on spatial plasma parameters in low pressure argon-helium plasma

Jin-Young Bang, Duksun Han, Sung-Won Cho, and Chin-Wook Chung

Appl. Phys. Lett. 100, 164107 (2012); http://dx.doi.org/10.1063/1.3703608 (5 pages)

Online Publication Date: 20 April 2012

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Spatial distributions of the electron energy probability function were measured using a Langmuir probe in side-type argon-helium inductively coupled plasma. Collisional dominated electron heating and a concave shape of plasma density profile were observed at 10 mTorr pure argon. As the helium proportion increased, the electron heating and density profile changed to collisionless dominated heating and a convex shape respectively, and the same tendency was shown when the pressure decreased in the pure argon plasma. These changes were due to the decrease in the e-n collision frequency and the expansion of the electron power dissipation region.
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52.25.Fi Transport properties
52.20.Fs Electron collisions
52.20.Hv Atomic, molecular, ion, and heavy-particle collisions
52.50.Dg Plasma sources
52.70.Ds Electric and magnetic measurements
02.50.Cw Probability theory

Negative normal stress differences in graphene/polycarbonate composites

Sang Il Jun and Heon Sang Lee

Appl. Phys. Lett. 100, 164108 (2012); http://dx.doi.org/10.1063/1.4704929 (3 pages)

Online Publication Date: 20 April 2012

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We measured the negative normal stress differences in graphene (0.5 wt. %)/polycarbonate composites during shear flow. The Peclet number in graphene/PC melt is estimated to be 105 ∼ 108, indicating the graphene sheets are non-Brownian. The negative normal stress is related with the deformations of gel-like structure of graphene sheets in PC. The storage modulus of graphene/PC composite melts approaches to a solid-like plateau in the terminal region at low concentration of 0.05 ∼ 0.70 wt. % graphene.
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62.10.+s Mechanical properties of liquids
82.70.Gg Gels and sols
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