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9 Jan 2012

Volume 100, Issue 2, Articles (02xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 100, 023701 (2012); http://dx.doi.org/10.1063/1.3673335 (3 pages)

Biswarup Pathak, Henrik Löfås, Jariyanee Prasongkit, Anton Grigoriev, Rajeev Ahuja, and Ralph H. Scheicher
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Excellent carrier mobility of 0.24 cm2/Vs in regioregular poly(3-hexylthiophene) based field-effect transistor by employing octadecyltrimethoxysilane treated gate insulator

Yi-Da Jiang, Tzu-Hao Jen, and Show-An Chen

Appl. Phys. Lett. 100, 023304 (2012); http://dx.doi.org/10.1063/1.3676444 (4 pages) | Cited 2 times

Online Publication Date: 11 January 2012

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The polymer field-effect transistor based on regioregular poly(3-hexylthiophene) (rr-P3HT) with excellent field-effect mobility up to 0.24 cm2/V s is demonstrated by spin-coating rr-P3HT onto octadecyltrimethoxysilane treated gate insulator followed by thermal annealing of rr-P3HT at 180 °C. This mobility is practically applicable in driving circuits of liquid crystal displays (greater than 0.1 cm2/V s) and close to the highest reported value (0.28 cm2/V s) for rr-P3HT but there a different coating method or dual dielectric layers was used. This impressive mobility can be attributed to the increase in structural ordering of rr-P3HT molecules as supported by x-ray diffraction measurement.
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85.30.Tv Field effect devices
72.20.Fr Low-field transport and mobility; piezoresistance
81.40.Tv Optical and dielectric properties related to treatment conditions
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Remanent polarization in a cryptand-polyanion bilayer implemented in an organic field effect transistor

Xiaodong Wang, Ari Laiho, Magnus Berggren, and Xavier Crispin

Appl. Phys. Lett. 100, 023305 (2012); http://dx.doi.org/10.1063/1.3677663 (3 pages)

Online Publication Date: 11 January 2012

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We investigate the possibility to maintain an electric polarization in an organic bilayer via ion trapping, i.e., without any external bias. In the cryptand-polyanion bilayer, ions of specific size can be strongly coordinated with organic macrocyclic molecules. Cations move from the polyanion layer to the cryptand layer upon applying a bias and are trapped in this layer. As a result, the voltage dependence of the polarization displays a hysteresis. The bilayer is then advantageously used as an electronic insulating layer in an organic field effect transistor. The ions trapping and de-trapping can be followed by the amplitude of the threshold voltage (Vth) shift as well as its temporal evolution.
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85.30.Tv Field effect devices
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Local charge transfer doping in suspended graphene nanojunctions

Jeffrey H. Worne, Hemtej Gullapalli, Charudatta Galande, Pulickel M. Ajayan, and Douglas Natelson

Appl. Phys. Lett. 100, 023306 (2012); http://dx.doi.org/10.1063/1.3677686 (4 pages) | Cited 1 time

Online Publication Date: 11 January 2012

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We report electronic transport measurements in nanoscale graphene transistors with gold and platinum electrodes whose channel lengths are shorter than 100 nm and compare them with transistors with channel lengths from 1 μm to 50 μm. We find a large positive gate voltage shift in charge neutrality point (NP) for transistors made with platinum electrodes but negligible shift for devices made with gold electrodes. This is consistent with the transfer of electrons from graphene into the platinum electrodes. As the channel length increases, the disparity between the measured NP using gold and platinum electrodes disappears.
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85.65.+h Molecular electronic devices
85.30.-z Semiconductor devices
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Organic photovoltaic cells based on unconventional electron donor fullerene and electron acceptor copper hexadecafluorophthalocyanine

J. L. Yang, P. Sullivan, S. Schumann, I. Hancox, and T. S. Jones

Appl. Phys. Lett. 100, 023307 (2012); http://dx.doi.org/10.1063/1.3671181 (3 pages) | Cited 1 time

Online Publication Date: 12 January 2012

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We demonstrate organic discrete heterojunction photovoltaic cells based on fullerene (C60) and copper hexadecafluorophthalocyanine (F16CuPc), in which the C60 and F16CuPc act as the electron donor and the electron acceptor, respectively. The C60/F16CuPc cells fabricated with conventional and inverted architectures both exhibit comparable power conversion efficiencies. Furthermore, we show that the photocurrent in both cells is generated by a conventional exciton dissociation mechanism rather than the exciton recombination mechanism recently proposed for a similar C60/F16ZnPc system [Song et al., J. Am. Chem. Soc. 132, 4554 (2010)]. These results demonstrate that new unconventional material systems are a potential way to fabricate organic photovoltaic cells with inverted as well as conventional architectures.
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84.60.Jt Photoelectric conversion
72.40.+w Photoconduction and photovoltaic effects
71.35.-y Excitons and related phenomena
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Charge transport in dual-gate organic field-effect transistors

J. J. Brondijk, M. Spijkman, F. Torricelli, P. W. M. Blom, and D. M. de Leeuw

Appl. Phys. Lett. 100, 023308 (2012); http://dx.doi.org/10.1063/1.3677676 (4 pages) | Cited 4 times

Online Publication Date: 13 January 2012

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The charge carrier distribution in dual-gate field-effect transistors is investigated as a function of semiconductor thickness. A good agreement with 2-dimensional numerically calculated transfer curves is obtained. For semiconductor thicknesses larger than the accumulation width, two spatially separated channels are formed. The cross-over from accumulation into depletion of the two channels in combination with a carrier density dependent mobility causes a shoulder in the transfer characteristics. A semiconducting monolayer has only a single channel. The charge carrier density, and consequently the mobility, are virtually constant and change monotonically with applied gate biases, leading to transfer curves without a shoulder.
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85.30.Tv Field effect devices
72.20.Fr Low-field transport and mobility; piezoresistance
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Electron detrapping in thin hafnium silicate and nitrided hafnium silicate gate dielectric stacks

Heng-Sheng Huang, Piyas Samanta, Tsung-Jian Tzeng, Shuang-Yuan Chen, and Chuan-Hsi Liu

Appl. Phys. Lett. 100, 023501 (2012); http://dx.doi.org/10.1063/1.3675454 (4 pages) | Cited 1 time

Online Publication Date: 9 January 2012

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The kinetics of zero-field and field-induced detrapping of electrons trapped in HfSixOy and HfSiON after positive bias stress on n+-polycrystalline silicon (polySi) gate of n-type metal-oxide-semiconductor (nMOS) capacitors are experimentally investigated. The self detrapping follows a simple logarithmic relation with time while field-induced detrapping upon reversing the stress voltage obeys a simple first-order exponential decay suggesting mono energetic shallow traps associated with tunnel emission of trapped electrons. Finally, our investigation raises questions about the validity of the widely used distributed capture cross section model of electron traps to explain the threshold voltage instability in MOS devices with hafnium silicate gate stacks.
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84.32.Tt Capacitors

Work-function-tuned multilayer graphene as current spreading electrode in blue light-emitting diodes

S. Chandramohan, Ji Hye Kang, Y. S. Katharria, Nam Han, Yun Seon Beak, Kang Bok Ko, Jong Bae Park, Hyun Kyu Kim, Eun-Kyung Suh, and Chang-Hee Hong

Appl. Phys. Lett. 100, 023502 (2012); http://dx.doi.org/10.1063/1.3675631 (4 pages) | Cited 13 times

Online Publication Date: 9 January 2012

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This letter reports on the implementation of multilayer graphene (MLG) as a current spreading electrode in GaN-based blue light-emitting diodes. We demonstrate two facile strategies to maneuver the electrical coupling between p-GaN layer and MLG. Using a work-function-tuned MLG and a thin gold (Au) metal interlayer, the current spreading and thus the device forward voltage are considerably improved. We attribute these improvements to the diminution in work function difference between p-GaN and MLG, the decrease of specific contact resistance, and the enhancement in the conductivity of MLG film as a result of doping. In addition, rapid thermal annealing at elevated temperature is found to provide additional pathway for enhanced carrier injection.
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85.60.Jb Light-emitting devices
61.72.Cc Kinetics of defect formation and annealing
73.30.+y Surface double layers, Schottky barriers, and work functions
73.40.Cg Contact resistance, contact potential

Probing band-tail states in silicon metal-oxide-semiconductor heterostructures with electron spin resonance

R. M. Jock, S. Shankar, A. M. Tyryshkin, Jianhua He, K. Eng, K. D. Childs, L. A. Tracy, M. P. Lilly, M. S. Carroll, and S. A. Lyon

Appl. Phys. Lett. 100, 023503 (2012); http://dx.doi.org/10.1063/1.3675862 (3 pages) | Cited 2 times

Online Publication Date: 9 January 2012

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We present an electron spin resonance (ESR) approach to characterize shallow electron trapping in band-tail states at Si/SiO2 interfaces in metal-oxide-semiconductor (MOS) devices and demonstrate it on two MOS devices fabricated at different laboratories. Despite displaying similar low temperature (4.2 K) peak mobilities, our ESR data reveal a significant difference in the Si/SiO2 interface quality of these two devices, specifically an order of magnitude difference in the number of shallow trapped charges at the Si/SiO2 interfaces. Thus, our ESR method allows a quantitative evaluation of the Si/SiO2 interface quality at low electron densities, where conventional mobility measurements are not possible.
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85.30.Tv Field effect devices

Carrier mobility measurement across a single grain boundary in polycrystalline silicon using an organic gate thin-film transistor

Masaki Hashimoto, Kensaku Kanomata, Katsuaki Momiyama, Shigeru Kubota, and Fumihiko Hirose

Appl. Phys. Lett. 100, 023504 (2012); http://dx.doi.org/10.1063/1.3675863 (3 pages)

Online Publication Date: 9 January 2012

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In this study, we developed a measurement method for field-effect-carrier mobility across a single grain boundary in polycrystalline Si (poly Si) used for solar cell production by using an organic gate field-effect transistor (FET). To prevent precipitation and the diffusion of impurities affecting the electronic characteristics of the grain boundary, all the processing temperatures during FET fabrication were held below 150 °C. From the grain boundary, the field-effect mobility was measured at around 21.4 cm2/Vs at 297 K, and the temperature dependence of the field-effect mobility suggested the presence of a potential barrier of 0.22 eV at the boundary. The technique presented here is applicable for the monitoring of carrier conduction characteristics at the grain boundary in poly Si used for the production of solar cells.
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06.30.Ka Basic electromagnetic quantities
61.72.Mm Grain and twin boundaries
72.20.Fr Low-field transport and mobility; piezoresistance
85.30.Tv Field effect devices
88.40.jj Silicon solar cells

Effects of cooperative ionic motion on programming kinetics of conductive-bridge memory cells

John R. Jameson, Nad Gilbert, Foroozan Koushan, Juan Saenz, Janet Wang, Shane Hollmer, and Michael Kozicki

Appl. Phys. Lett. 100, 023505 (2012); http://dx.doi.org/10.1063/1.3675870 (4 pages) | Cited 2 times

Online Publication Date: 9 January 2012

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Cooperative ionic motion is identified as a key physical effect influencing the programming kinetics of Ag/GeS2/W conductive-bridge memory cells. Cooperative effects are suggested to cause the time required to program virgin cells to: (i) deviate from the exponential voltage dependence typically observed at high voltage if the GeS2 is very thin and (ii) increase dramatically at low voltage when programmed with a pulse train having a low duty cycle. A previously reported model is shown to account for both phenomena, and a kinetic Monte Carlo algorithm is described for making quantitative calculations.
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84.30.Sk Pulse and digital circuits
02.70.Uu Applications of Monte Carlo methods

Intrinsic parameter extraction of a-InGaZnO thin-film transistors by a gated-four-probe method

Jaewook Jeong, Joonwoo Kim, Gwang Jun Lee, and Byeong-Dae Choi

Appl. Phys. Lett. 100, 023506 (2012); http://dx.doi.org/10.1063/1.3675876 (4 pages) | Cited 2 times

Online Publication Date: 10 January 2012

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We analyzed the intrinsic electrical characteristics of amorphous InGaZnO (a-IGZO) thin-film transistors (TFTs) using a gated-four-probe method. Based on the back channel potential, the extraction of intrinsic field-effect mobility (μFEi) and parasitic resistance in source (Rs) and drain (Rd) electrodes was performed especially for low VGS and VDS conditions. The resulting μFEi showed typical VGS dependency of amorphous semiconductor TFTs. However, Rs and Rd showed that there can be non-uniformity in source/drain parasitic resistance, which indicates that a separate analysis of the parameters of each electrode is essential for further improvement of the performance of a-IGZO TFTs.
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85.30.Tv Field effect devices

Long-term retention in organic ferroelectric-graphene memories

Santosh Raghavan, Igor Stolichnov, Nava Setter, Jean-Savin Heron, Mahmut Tosun, and Andras Kis

Appl. Phys. Lett. 100, 023507 (2012); http://dx.doi.org/10.1063/1.3676055 (3 pages) | Cited 5 times

Online Publication Date: 11 January 2012

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Long-term stability of high- and low-resistance states in full-organic ferroelectrically gated graphene transistors is an essential prerequisite for memory applications. Here, we demonstrate high retention performance for both memory states with fully saturated time-dependence of the graphene channel resistance. This behavior is in contrast with ferroelectric-polymer-gated silicon field-effect-transistors, where the gap between the two memory states continuously decreases with time. Before reaching saturation, the current decays exponentially as predicted by the retention model based on the charge injection into the interface-adjacent layer. The drain current saturation attests to a high quality of the graphene/ferroelectric interface with low density of charge traps.
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84.30.Sk Pulse and digital circuits
85.30.Tv Field effect devices
85.50.Gk Non-volatile ferroelectric memories

Surface passivation of Cu(In,Ga)Se2 using atomic layer deposited Al2O3

W.-W. Hsu, J. Y. Chen, T.-H. Cheng, S. C. Lu, W.-S. Ho, Y.-Y. Chen, Y.-J. Chien, and C. W. Liu

Appl. Phys. Lett. 100, 023508 (2012); http://dx.doi.org/10.1063/1.3675849 (3 pages)

Online Publication Date: 11 January 2012

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With Al2O3 passivation on the surface of Cu(In,Ga)Se2, the integrated photoluminescence intensity can achieve two orders of magnitude enhancement due to the reduction of surface recombination velocity. The photoluminescence intensity increases with increasing Al2O3 thickness from 5 nm to 50 nm. The capacitance-voltage measurement indicates negative fixed charges in the film. Based on the first principles calculations, the deposition of Al2O3 can only reduce about 35% of interface defect density as compared to the unpassivated Cu(In,Ga)Se2. Therefore, the passivation effect is mainly caused by field effect where the surface carrier concentration is reduced by Coulomb repulsion.
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81.65.Rv Passivation
61.72.-y Defects and impurities in crystals; microstructure
68.35.Ct Interface structure and roughness
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
73.25.+i Surface conductivity and carrier phenomena
78.55.Hx Other solid inorganic materials

Identification of a silicon vacancy as an important defect in 4H SiC metal oxide semiconducting field effect transistor using spin dependent recombination

C. J. Cochrane, P. M. Lenahan, and A. J. Lelis

Appl. Phys. Lett. 100, 023509 (2012); http://dx.doi.org/10.1063/1.3675857 (3 pages) | Cited 5 times

Online Publication Date: 11 January 2012

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A spin dependent recombination (SDR) spectrum observed in a wide range of SiC metal oxide semiconducting field effect transistors (MOSFETs) has previously been only tentatively linked to a silicon vacancy or vacancy related defect. By resolving hyperfine interactions in SDR detected spectra with 13C nuclei, we provide an extremely strong argument identifying the SDR spectrum with a silicon vacancy. Since the silicon vacancy spectrum dominates the SDR response in a wide variety of SiC MOSFETs, silicon vacancies are quite important traps in this technology.
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85.30.Tv Field effect devices

Solid polyelectrolyte-gated surface conductive diamond field effect transistors

M. Dankerl, M. Tosun, M. Stutzmann, and J. A. Garrido

Appl. Phys. Lett. 100, 023510 (2012); http://dx.doi.org/10.1063/1.3676662 (3 pages) | Cited 2 times

Online Publication Date: 12 January 2012

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Solid polyelectrolytes have been used in transistor devices to achieve gating with high capacitance. We use a solid polyethylene oxide/LiClO4 electrolyte to replace aqueous electrolytes as a gate for surface-conductive diamond field-effect transistors (FET). The resulting transistor shows characteristics comparable to those of aqueous electrolyte-gated diamond FETs. We investigate the polyelectrolyte/diamond interface with impedance spectroscopy and cyclic voltammetry, showing the electrochemical stability of the interface and capacitive gating up to 100 Hz. Hall effect measurements on the polyelectrolyte-gated devices are compared to those with liquid gates. The solid and transparent polyelectrolyte gates promise further applications for surface-conductive diamond FETs.
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85.30.Tv Field effect devices
82.45.Gj Electrolytes
85.30.Fg Bulk semiconductor and conductivity oscillation devices (including Hall effect devices, space-charge-limited devices, and Gunn effect devices)
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Double-functionalized nanopore-embedded gold electrodes for rapid DNA sequencing

Biswarup Pathak, Henrik Löfås, Jariyanee Prasongkit, Anton Grigoriev, Rajeev Ahuja, and Ralph H. Scheicher

Appl. Phys. Lett. 100, 023701 (2012); http://dx.doi.org/10.1063/1.3673335 (3 pages) | Cited 2 times

Online Publication Date: 9 January 2012

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We have studied the effect of double-functionalization on gold electrodes for improving nanopore-based DNA sequencing. The functionalizing molecular probes are, respectively, capable of temporarily forming hydrogen bonds with both the nucleobase part and the phosphate group of the target DNA, thus potentially minimizing the structural fluctuations of a single-stranded DNA molecule passing between the gold electrodes. The results of our first-principles study indicate that the proposed setup yields current signals that differ by at least 1 order of magnitude for the four different nucleic acid bases, thus offering the possibility to electrically distinguish them.
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87.15.B- Structure of biomolecules
87.15.R- Reactions and kinetics
87.15.Ya Fluctuations
82.45.-h Electrochemistry and electrophoresis

Optical-resolution photoacoustic microscopy based on two-dimensional scanning galvanometer

Yi Yuan, Sihua Yang, and Da Xing

Appl. Phys. Lett. 100, 023702 (2012); http://dx.doi.org/10.1063/1.3675907 (3 pages) | Cited 9 times

Online Publication Date: 9 January 2012

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An optical-resolution photoacoustic microscopy system was designed and fabricated by integration of a two-dimensional scanning galvanometer, an objective lens, an unfocused ultrasound transducer, and a sample stage. The lateral resolution of the system was measured to be ∼500 nm. Ex vivo erythrocytes were used to test the imaging capability of the system, and a single erythrocyte was mapped with high contrast. Furthermore, invivo blood vessels of a mouse ear were clearly shown, and the injured blood vessels were also monitored. The experimental results demonstrate that galvanometer-based photoacoustic microscopy holds clinical potential in detecting lesion of erythrocyte and blood vessel.
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87.85.Ox Biomedical instrumentation and transducers, including micro-electro-mechanical systems (MEMS)
87.64.M- Optical microscopy

Label-free multiphoton imaging and photoablation of preinvasive cancer cells

Shuangmu Zhuo, Jianxin Chen, Guizhu Wu, Xiaoqin Zhu, Xingshan Jiang, and Shusen Xie

Appl. Phys. Lett. 100, 023703 (2012); http://dx.doi.org/10.1063/1.3676271 (4 pages) | Cited 1 time

Online Publication Date: 10 January 2012

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Detection and treatment of early lesions in epithelial tissue offer several possibilities for curing cancer, but it is challenging. Here, we present an optical technique, the combination of multiphoton imaging and absorption, to label-freely detect and ablate preinvasive cancer cells in epithelial tissue. We find that multiphoton imaging can label-freely visualize the principal features of nuclear atypia associated with epithelial precancerous lesions, and the spatial localization of multiphoton absorption can perform targeted ablation of preinvasive cancer cells with micrometer-sized volume precision. These results indicate that this optical technique has the capability to label-freely visualize and remove preinvasive cancer cells in epithelial tissue. This study highlights the potential of this technique as a “seek-and-treat” tool for early lesions in epithelial tissue.
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87.50.wf Biophysical mechanisms of interaction
87.63.L- Visual imaging
87.19.xj Cancer

Biomolecule detection based on Si single-electron transistors for highly sensitive integrated sensors on a single chip

Takashi Kudo and Anri Nakajima

Appl. Phys. Lett. 100, 023704 (2012); http://dx.doi.org/10.1063/1.3676664 (3 pages)

Online Publication Date: 12 January 2012

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Biomolecule detection was achieved using a Si single-electron transistor (SET) for highly-sensitive detection. A multiple-island channel-structure was used for the SET to enable room-temperature operation and to increase sensitivity. Coulomb oscillation shifted against the gate voltage due to biotin-streptavidin binding. Coulomb oscillation has a possibility to increase transconductance (gm), and a higher gm leads to greater sensitivity to a charged target. Since a Si structure is important for integrating label-free-biomolecule and/or ion sensors into large-scale-integrated circuits, a Si SET with multiple islands should enable the integration of a sensor system on a single chip for multiplexed detections and simultaneous diagnoses.
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87.85.-d Biomedical engineering
85.35.Gv Single electron devices
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Electronic and optical properties of CoX2O4 (X = Al, Ga, In) alloys

Chunbao Feng, Wan-Jian Yin, Jinlan Nie, Xiaotao Zu, Muhammad N. Huda, Su-Huai Wei, Mowafak M. Al-Jassim, John A. Turner, and Yanfa Yan

Appl. Phys. Lett. 100, 023901 (2012); http://dx.doi.org/10.1063/1.3676039 (4 pages) | Cited 1 time

Online Publication Date: 10 January 2012

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The electronic and optical properties of Co based spinel oxides, CoX2O4 (X = Al, Ga, In) are calculated using first-principle density functional theory. We show that the desirable properties for solar photoconversion can be obtained by controlling the alloy compositions. The ability to manipulate the electronic and optical properties is attributed to the different s-orbital energies and sizes of the cations. Our calculated bandgaps as function of composition provide detailed practical guidance for synthesizing Co based spinel oxides with electronic and optical properties necessary to achieve high efficiency photoelectrochemical decomposition of water for hydrogen production by sunlight.
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71.20.Ps Other inorganic compounds
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
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X-ray diagnostics of runaway electrons generated during nanosecond discharge in gas at elevated pressures

S. Yatom, D. Levko, J. Z. Gleizer, V. Vekselman, and Ya. E. Krasik

Appl. Phys. Lett. 100, 024101 (2012); http://dx.doi.org/10.1063/1.3675462 (3 pages)

Online Publication Date: 9 January 2012

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The properties of high-energy runaway electrons generated during a nanosecond discharge in an air filled diode at pressures up to 3 × 105 Pa were studied using x-ray absorption spectroscopy. The results of studies of the discharge at different pressures and with different lengths of cathode-anode gap allow an insight into the factors that influence the energy distribution of runaway electrons. Energy distribution functions for runaway electrons produced in particle-in-cell simulation were used to create the x-ray attenuation curves via a computer-assisted technique simulating the generation of x-ray by energetic electrons. The simulated attenuation curves were compared to experimental results.
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52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.80.-s Electric discharges
52.25.Fi Transport properties
52.75.Fk Magnetohydrodynamic generators and thermionic convertors; plasma diodes
52.70.La X-ray and γ-ray measurements

Coupling effects in inductive discharges with radio frequency substrate biasing

J. Schulze, E. Schüngel, and U. Czarnetzki

Appl. Phys. Lett. 100, 024102 (2012); http://dx.doi.org/10.1063/1.3675879 (3 pages) | Cited 6 times

Online Publication Date: 10 January 2012

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Low pressure inductively coupled plasmas (ICP) operated in neon at 27.12 MHz with capacitive substrate biasing (CCP) at 13.56 MHz are investigated by phase resolved optical emission spectroscopy, voltage, and current measurements. Three coupling mechanisms are found potentially limiting the separate control of ion energy and flux: (i) Sheath heating due to the substrate biasing affects the electron dynamics even at high ratios of ICP to CCP power. At fixed CCP power, (ii) the substrate sheath voltage and (iii) the amplitude as well as frequency of plasma series resonance oscillations of the RF current are affected by the ICP power.
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52.80.Pi High-frequency and RF discharges
52.25.Fi Transport properties
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.35.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)
52.40.Kh Plasma sheaths
52.70.Kz Optical (ultraviolet, visible, infrared) measurements

Performance of a piezoelectric energy harvester driven by air flow

C. A. Kitio Kwuimy, G. Litak, M. Borowiec, and C. Nataraj

Appl. Phys. Lett. 100, 024103 (2012); http://dx.doi.org/10.1063/1.3676272 (3 pages) | Cited 1 time

Online Publication Date: 11 January 2012

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A turbulent wind source for possible energy harvesting is considered. To increase the amplitude of vibration, we apply a magnetopiezoelastic oscillator having a double well Duffing potential. The output voltage response of the system for different level of wind excitations is analyzed. The energy harvesting appeared to be the most efficient for the conditions close to the stochastic resonance region where the potential barrier was overcame.
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84.60.-h Direct energy conversion and storage

Directed jetting from collapsing cavities exposed to focused ultrasound

B. Gerold, P. Glynne-Jones, C. McDougall, D. McGloin, S. Cochran, A. Melzer, and P. Prentice

Appl. Phys. Lett. 100, 024104 (2012); http://dx.doi.org/10.1063/1.3676414 (3 pages) | Cited 3 times

Online Publication Date: 11 January 2012

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multimedia

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We demonstrate directed jetting from pulsed laser-induced cavities subjected to a burst of focused ultrasound. Alignment of the ultrasound focus and the pressure amplitudes in the vicinity of the cavity dictate the direction and length of the resulting jet, respectively. We interpret our observations in terms of radiation forces exerted on the cavity, due to the pressure gradient introduced to the ultrasound focus by its presence. We support our hypothesis with a linear analysis of the force distribution across the cavity surface, at the moment of maximum inflation, which shows reasonable predictive agreement with the observed jet characteristics.
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43.35.Bf Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in liquids, liquid crystals, suspensions, and emulsions
43.35.Ei Acoustic cavitation in liquids
43.35.Pt Surface waves in solids and liquids
47.15.Uv Laminar jets

Acoustic dipole radiation based conductivity image reconstruction for magnetoacoustic tomography with magnetic induction

Xiaodong Sun, Feng Zhang, Qingyu Ma, Juan Tu, and Dong Zhang

Appl. Phys. Lett. 100, 024105 (2012); http://dx.doi.org/10.1063/1.3676446 (4 pages) | Cited 2 times

Online Publication Date: 11 January 2012

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Based on the acoustic dipole radiation theory, a tomograhic conductivity image reconstruction algorithm is developed for the magnetoacoustic tomography with magnetic induction (MAT-MI) in a cylindrical measurement configuration. It has been experimentally proved for a tissue-like phantom that not only the configuration but also the inner conductivity distribution can be reconstructed without any borderline stripe. Furthermore, the spatial resolution also can be improved without the limitation of acoustic vibration. The favorable results have provided solid verification for the feasibility of conductivity image reconstruction and suggested the potential applications of MAT-MI in the area of medical electrical impedance imaging.
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87.63.dh Ultrasonographic imaging
43.80.Qf Medical diagnosis with acoustics
87.63.Pn Electrical impedance tomography (EIT)
87.57.nf Reconstruction
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