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Nanotechnology, IEEE Transactions on

Issue 5 • Date Sept. 2007

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Displaying Results 1 - 21 of 21
  • Table of contents

    Page(s): C1
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  • IEEE Transactions on Nanotechnology publication information

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  • Co-Induced Low-Temperature Silicidation of Ni Germanosilicide Using NiPt Alloy and the Effect of Ge Ratio on Thermal Stability

    Page(s): 485 - 491
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1662 KB) |  | HTML iconHTML  

    In this paper, novel Ni germanosilicide technology using NiPt alloy and Co overlayer has been proposed. Using the Co overlayer after NiPt deposition on Si1-xGex, the formation temperature of low resistive Ni germanosilicide is lowered with high thermal stability. The thermal stability of Ni germanosilicide with different Ge fraction in is also characterized. The sheet resistance degrades as increasing the Ge fraction (x) in Si1-xGex when NiPt/TiN is used. However, using the Co overlayer, the sheet resistance property among Ni germanosilicide formed with different Ge fraction is improved greatly compared with those of NiPt/TiN case (without Co overlayer). Therefore, low-temperature formation of highly thermal robust Ni germanosilicide can be achieved through the NiPt/Co/TiN tri-layer. View full abstract»

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  • Temperature and Excitation Dependence of Photoluminescence Spectra of InAs/GaAs Quantum Dot Heterostructures

    Page(s): 492 - 496
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (392 KB) |  | HTML iconHTML  

    In this study we investigated the effects that the carrier dynamics have on the temperature- and excitation-intensity- dependent photoluminescence (PL) spectra of a self-assembled quantum dot heterostructure. A rate equation model is proposed to take into account the dot size distribution, the random population of density of states, state filling effects, and the important carrier transfer mechanisms for the quantum dot system, including carrier capture, relaxation, thermal emission, and retrapping. This model reproduces the PL spectra quite well. Our quantitative calculations of the behavior of the thermal emitting carriers under various incident power intensities within the temperature range 15 K-240 K explain the carrier transfer process quite reasonably for the quantum dot system. In addition, we discuss the thermal redistribution and state filling effects in detail in our analysis of the dependence of the PL spectra on the temperature and excitation power intensity applied to the sample. Index View full abstract»

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  • Chemical Synthesis of ZnO Nanocrystals

    Page(s): 497 - 503
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    A new chemical process to synthesize pure ZnO nanocrystal colloidal for bioimaging applications is reported. Zinc acetate dihydrate was dissolved and refluxed in a methanol solution at a low temperature (68degC) and ambient environment. Biocompatible surface capping agents were introduced to the synthesis process to control the particle nucleation and growth and, therefore, the particle size and its surface chemistry. Five types of capping agents were investigated for their effectiveness in limiting the particle growth. Three capping agents-3-amino- propyl trimethoxysilane (Am), tetraethyl orthosilicate (TEOS), and mercaptosuccinic acid (Ms)-were found effective in capping the ZnO nanoparticles and limiting the growth of the particles, while the other two-3-mercaptopropyl trimethoxysilane (Mp) and polyvinylpyrrolidone (Pv)-caused agglomeration or forming large clusters in the solutions. Particles synthesized were in the size range of 10-30 nm after capping, and grew to 60 nm and 100 nm in 3 weeks and 6 weeks respectively during storage at ambient conditions. Refluxing time was found to affect only the first precipitation time. Washing by ethanol and slow drying were found critical in converting Zn(OH)2 into ZnO. XRD analyses revealed forming of single phase ZnO Wurzite (P63mc) structure. TEM analysis determined the single crystal size of 6 nm. Photo- luminescence (PL) spectra showed high intensity in UV emission and low intensity in the visible emission, which imply a good surface morphology of the ZnO nanoparticles with few surface defects. Optical absorption spectra indicated absorption at the wavelength of 380 nm from the uncapped ZnO, corresponding to the bandgap of bulk ZnO. The capped ZnO absorbed at a shorter wavelength (350 nm) indicating a much smaller particle size. Capping effectiveness of each agent is discussed through possible capping mechanisms and chemical reactions. View full abstract»

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  • Steady-State and Transient Conductivity of Colloidal Solutions of Gold Nanobeads

    Page(s): 504 - 508
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    Steady-state and transient conductance measurements of gold nanobeads solutions deposited on top of interdigitated electrodes have been performed. It is shown that the application of an electric field of moderate value between electrodes during the drying process of the droplet makes the resulting steady-state conductance value to increase significantly. The dynamics of the gold nanobeads in the solution has been studied by means of transient current measurements during the drying process and the effects correlated to the changes in the morphology of the association of the gold nanobeads when they reach the substrate. It is seen that the application of the electric field foster the formation of gold beads monolayers, chains, and dendritic associations which, in combination with the humidity conditions of the sample surface, are believed to be the reasons for the conductance increase. View full abstract»

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  • Time-Resolved Evaporation Rate of Attoliter Glycerine Drops Using On-Chip CMOS Mass Sensors Based on Resonant Silicon Micro Cantilevers

    Page(s): 509 - 512
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    The time-resolved evaporation rate of small glycerine drops (in the attoliter range) is determined by means of a mass sensor based on a resonant cantilever integrated in a CMOS chip. The cantilever is fabricated on crystalline silicon, using silicon-on-insulator (SOI) substrates for the integration of the CMOS-MEMS. Glycerine drops are deposited at the free end of the cantilever. The high mass sensitivity of the sensor (8 ag/Hz) allows to determine the evaporation rate for glycerine drops smaller than 500 aL, which are found to be below 3.2 aL/s in volume or 4 fg/s in mass. View full abstract»

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  • Fabrication of Functional Nanofibrous Ammonia Sensor

    Page(s): 513 - 518
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    A nanofibrous sensor for ammonia gas is fabricated by electrospinning the composite of poly(diphenylamine) (PDPA) with poly(methyl methacrylate) (PMMA) onto the patterned interdigit electrode. The composite electrospun membrane shows interconnected fibrous morphology. Functional groups in PDPA and the high active surface area of the fibrous membrane make the device detect a lower concentration of ammonia with a good reproducibility. The sensing capability of the device is studied by monitoring the changes in resistance of the membrane with different concentrations of ammonia. The changes in resistance of the membrane shows linearity with the concentration of ammonia in the limit of 10 and 300 ppm. UV-visible spectroscopy reveals the mechanism of sensing ammonia by the membrane. View full abstract»

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  • Toward Carbon Nanotube-Based AFM Cantilevers

    Page(s): 519 - 523
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    The mechanical properties of carbon nanotubes have been widely employed to enhance the performance of atomic force microscopy (AFM) cantilever tips. Utilizing the electromechanical properties of carbon nanotubes, this paper investigates the potential of using carbon nanotubes as active strain sensing elements on AFM cantilevers. A batch microfabrication process was developed to construct silicon microcantilevers. Multiwalled carbon nanotubes were dielectrophoretically assembled between electrodes. Based on the characterization results of 12 devices, the CNT-based cantilevers demonstrated a linear relationship between resistance changes and externally applied strain. The gauge factor ranged from 78.84 to 134.40 for four different device configurations. View full abstract»

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  • Three-Dimensional Simulation of One-Dimensional Transport in Silicon Nanowire Transistors

    Page(s): 524 - 529
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (438 KB) |  | HTML iconHTML  

    We present a simulation study of silicon nanowire transistors, based on an in-house code providing the self-consistent solution of Poisson, Schrodinger, and continuity equations on a generic three-dimensional domain. The main assumption, based on the very small nanowire cross section considered, is that an adiabatic approximation can be applied to the Schrodinger equation, so that transport occurs along one-dimensional sub- bands. Different subband transport models are considered, such as ballistic transport, either including quantum tunneling or not, and drift-diffusion. We show that nanowire transistors exhibit good control of short channel effects, and that barrier tunneling is significant in the strong inversion regime even for longer devices, while it is significant in subthreshold only for the shortest channel lengths. Finally, we show that a subband-based transport model allows to reach a very good trade off between physical accuracy of the simulation and computing time. View full abstract»

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  • Origin of Conductivity Threshold in the Solid Electrolyte Glass System: ( Ag2 S)x( As2 S3)1−x

    Page(s): 530 - 535
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    The electrical conductivity of (Ag2S)x(As2S3)1-x glasses increases to display a step-like jump of nearly five orders of magnitude in the narrow composition range, 9% < x < 15% range. To elucidate the origin of this threshold behavior, we have now examined the molecular structure of these glasses in modulated-differential scanning calorimetry (MDSC) and Raman scattering experiments. Our MDSC results reveal bimodal glass transition temperatures (Tgs), a low-Tg and a high-Tg in the 7% < x < 40% range but unimodal ones outside this range. The low-Tg phase bears a similarity to that of the stoichiometric glass at x = 1/2, or AgAsS2, and we identify it with a Ag-rich phase formed in these glasses once x > 7%. The Ag-rich phase is thought to percolate near x ~ 9%, and to contribute to the large jump in conductivity of the glasses. The high-Tg phase represents a semiconducting As2S3 glass phase alloyed with a few mole percent of Ag2S, and it displays a reversibility window in the 8% < x < 13% range. The semiconducting phase becomes elastically flexible once x > 13%. Softening of the high-Tg phase lowers Ag+ ion migration energies and also contributes to the conductivity threshold. View full abstract»

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  • Theory of High Bias Coulomb Blockade in Ultrashort Molecules

    Page(s): 536 - 544
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    We point out that single electron charging effects such as coulomb blockade (CB) and high-bias staircases play a crucial role in transport through single ultrashort molecules. A treatment of CB through a prototypical molecule, benzene, is developed using a master-equation in its complete many-electron Fock space, evaluated through exact diagonalization or full configuration interaction (CI). This approach can explain a whole class of nontrivial experimental features including vanishing zero bias conductances, sharp current onsets followed by ohmic current rises, and gateable current levels and conductance structures, most of which cannot be captured even qualitatively within the traditional self-consistent field (SCF) approach coupled with perturbative transport theories. By comparing the two approaches, namely SCF and CB, in the limit of weak coupling to the electrode, we establish that the inclusion of strong correlations within the molecule becomes critical in addressing the above experiments. Our approach includes on-bridge correlations fully, and is therefore well-suited for describing transport through short molecules in the limit of weak coupling to electrodes. View full abstract»

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  • Single-Walled Carbon Nanotubes as a Chemical Sensor for SO2 Detection

    Page(s): 545 - 548
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (529 KB) |  | HTML iconHTML  

    Single-walled carbon nanotubes (SWNTs) are Introduced as a chemical sensor for the detection of sulfur dioxide (SO2) molecules. For a single bundle of SWNTs, current-voltage (I-V) curves were measured for a series of different temperatures under adsorption of SO2 molecules. The I-V characteristics for a "MAT"-type thin film SWNTs, with respect to the amount of SO2 adsorbed, were measured at room temperature and compared directly with O2 adsorption. The change in current upon the adsorption of SO2 is distinctly higher than that of O2, and is also reversible for adsorption and successive evacuation. Thus, the results strongly suggested that a thin film of SWNTs can be used as a chemical sensor in the nanometer scale devices. View full abstract»

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  • Enhanced Thermoplasmonic Oscillations in Metallic Nanostructured Particles for the Realization of Nanofluidic Sensors

    Page(s): 549 - 555
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    We theoretically investigate the intense tunable nanofocusing of light in certain families of metallo-dielectric nanograin particles and topologically defected nanocylinders, mediated by thermoplasmonic resonances. By using versatile numerical algorithms, based on either exact 3-D electromagnetic scattering from canonical geometries, or discrete dipole approximation modeling for particles with arbitrary shapes, associated with the spectral as well as the thermooptical response of the proposed classes of plasmonic nanostructures, we identify the mechanisms responsible for the enhanced tunable thermoplasmonic resonances, by varying the ambient temperature. In addition it is found that the plasmonic resonances are also sensitive to the electric properties of the host medium, thus enabling this novel class of plasmonic nanoparticles to be used as fluidic (liquid/gas) sensors. Our investigation is expected to remove an essential obstacle in the development of nanosensing platforms with high sensitiveness to temperature fluctuations and ultracompact size, thus making the proposed plasmonic resonators excellent candidates for future nanoplasmonic sensing systems. View full abstract»

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  • Selective Filling and Sintering of Copper Nanoclusters for Interconnect

    Page(s): 556 - 560
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    In copper interconnect technology, dielectric trenches are patterned, filled with copper, and polished. We report a cluster-based deposition technology that provides efficient trench filling and excellent selectivity between trenches and plateaus on damascene structures. The selectivity arises due to the propensity for reflection of clusters from the planar surfaces between trenches. Trenches of sub-200 nm widths, with various diffusion barriers and seed layers, and up to 5:1 aspect ratios have been completely filled with copper clusters. We also show that copper clusters can be sintered into a seed layer using hydrogen annealing. Thus, dense copper films within trenches are obtained. Preliminary results from planar samples show that the resistivity is around 2.3 times 10-8 Omegam. View full abstract»

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  • A Theoretical Study of the Electrochemical Gate Effect in an STM-Based Biomolecular Transistor

    Page(s): 561 - 570
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    Electrochemical scanning tunneling microscopy (ECSTM) is gaining popularity as a tool to implement a proof-of-concept single (bio)molecular transistor. The understanding of such systems requires a discussion of the mechanism of the electrochemical current gating, which is intimately related to the electrostatic potential distribution in the tip-substrate gap where the redox active adsorbate is placed. We derive a relation that connects the local standard potential of the redox molecule in the tunneling junction with the applied electrode potentials, and we compare it with previously proposed relations. In particular, we show that a linear dependence of the local standard potential on the applied bias does not necessarily imply a monotonous potential drop between the electrodes. In addition, we calculate the electrostatic potential distribution and the parameters entering the derived relation for ECSTM on a redox metalloprotein (Azurin from P. Aeruginosa), for which experimental results exist. Finally, we give an estimate of the gating efficiency when the ECSTM setup including Azurin is interpreted as a single biomolecular wet transistor, confirming the effectiveness of the electrochemical gating for this system. View full abstract»

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  • Ultralow-Power Alcohol Vapor Sensors Using Chemically Functionalized Multiwalled Carbon Nanotubes

    Page(s): 571 - 577
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    Alcohol sensors, batch fabricated by forming bundles of chemically functionalized multiwalled carbon nanotubes (f-CNTs) across Au electrodes on SiO2/Si substrates using an AC electrophoretic technique, were developed for alcohol vapor detection using an ultralow input power of ~ 0.01 - 1 muW, which is lower than the power required for most commercially available alcohol sensors by more than four orders of magnitude. The multiwalled carbon nanotubes (MWCNTs) have been chemically functionalized with the COOH groups by oxidation. We found that the sensors are selective with respect to flow from air, water vapor, and alcohol vapor. The sensor response is linear for alcohol vapor concentrations from 1 to 21 ppm with a detection limit of 0.9 ppm. The transient response of these sensors is experimentally shown to be ~1 s and the variation of the responses at each concentration is within 10% for all of the tested sensors. The sensors could also easily be reset to their initial states by annealing the f-CNTs sensing elements at a current of 100-200 muA within ~ 100-200 s. We demonstrated that the response of the sensors can be increased by one order of magnitude after adding the functional group COOH onto the nanotubes, i.e., from ~0.9% of a bare MWCNTs sensor to ~9.6% of an f-CNTs sensor with a dose of 21 ppm alcohol vapor. View full abstract»

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  • In Situ One-Step Grown Fe/Suspended Single-Wall Carbon Nanotube/Fe Junction and Their Controllable Carrier Transport Properties

    Page(s): 578 - 582
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    We demonstrated the in situ one-step fabrication of suspended single wall carbon nanotube transistors with Fe/Al bi- layered film electrodes for practical integrated quantum phase devices. At 300 K, the devices show field effect transistor operation with an excellent subthreshold swing of S ~ 90 mV/decade for a long channel of 3 mum. In the low temperature regime, we observed four clear peaks corresponding to the four-fold degeneracy of the quantum energy levels at 3.7 K. These four clear peaks indicated that both of the contacts between the SWNT and Fe/Al are highly transparent and that a high-quality SWNT bridge is formed. The dl/dV characteristics under an applied external magnetic field indicate that the modulation of the bandgap of the nanotube with the oscillation of the conductance can be achieved by varying the magnetic field, due to the quantum interference of the electrons. In summary, the simple one-step grown SWNT junction between Fe electrodes can be utilized as a promising element for integrated quantum electronic devices. View full abstract»

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  • IEEE copyright form

    Page(s): 583 - 584
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  • IEEE Transactions on Nanotechnology information for authors

    Page(s): C3
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  • Blank page [back cover]

    Page(s): C4
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The IEEE Transactions on Nanotechnology is devoted to the publication of manuscripts of archival value in the general area of nanotechnology, which is rapidly emerging as one of the fastest growing and most promising new technological developments for the next generation and beyond.

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