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Nanotechnology, IEEE Transactions on

Issue 6 • Date Nov. 2007

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Displaying Results 1 - 25 of 27
  • Table of contents

    Publication Year: 2007 , Page(s): C1 - C4
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  • IEEE Transactions on Nanotechnology publication information

    Publication Year: 2007 , Page(s): C2
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  • Editorial

    Publication Year: 2007 , Page(s): 585 - 588
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  • Formation and Characterization of 1.5-Monolayer Self-Assembled InAs/GaAs Quantum Dots Using Postgrowth Annealing

    Publication Year: 2007 , Page(s): 589 - 594
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1304 KB) |  | HTML iconHTML  

    In this paper, we report that low-density InAs/GaAs quantum dots (QDs) can be formed by postgrowth annealing the samples with 1.5-monolayer (ML) InAs coverage, which is thinner than the critical layer thickness for the Stranski-Krastanov growth. The annealing procedure was performed immediately after the deposition of the InAs layer. The effects of annealing time and annealing temperature on the dot density, dot size, and optical characteristics of the QDs were investigated. The optimum annealing conditions to obtain low-density QDs are longer than 60 s and higher than 500degC . Meanwhile, no luminescence can be observed for the wetting-layer, which may suggest that the postgrowth annealing will make the wetting layer thinner and thus reduce the effects of wetting layer on carrier relaxation and recombination. On the other hand, we observe that a decrease of the PL intensity at the annealing conditions of 60 s and 515degC , which is possibly due to the increasing surface dislocations resulted from the In adatom desorption at higher annealing temperature. View full abstract»

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  • Crabwise ZnO Nanowire UV Photodetector Prepared on ZnO : Ga/Glass Template

    Publication Year: 2007 , Page(s): 595 - 600
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2881 KB) |  | HTML iconHTML  

    Vertical well-aligned and crabwise ZnO nanowires were prepared on patterned ZnO:Ga/glass substrates by reactive evaporation method under different growth conditions. The average length and diameter of vertical well-aligned ZnO nanowires were around 1 mum and 50-100 nm, respectively. In contrast, the average length and diameter of crabwise ZnO nanowires were around 5 mum and 30 nm, respectively. Upon illumination with UV light (lambda = 362 nm), it was found that measured responsivities were 0.015 and 0.03 A/W for the crabwise ZnO nanowire photodetector biased at 10 and 15 V, respectively. Furthermore, a rejection ratio of approximately 10 was obtained for the crabwise ZnO nanowire photodetector with an applied bias of 10 V. View full abstract»

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  • Carbon Nanotubes Coated Acoustic and Optical VOCs Sensors: Towards the Tailoring of the Sensing Performances

    Publication Year: 2007 , Page(s): 601 - 612
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2452 KB) |  | HTML iconHTML  

    This work is focused on the room temperature sensitivities and response times analysis against aromatic volatile organic compounds of both silica optical fiber and quartz crystal microbalance sensors, coated by single-walled carbon nanotubes (SWCNTs) Langmuir-Blodgett multilayers as highly sensitive nanomaterials. The fabricated samples have been characterized by means of X-ray diffraction, high-resolution transmission electron microscopy and scanning electron microscopy, silica optical fiber, and quartz crystal microbalance transducers have been simultaneously exposed at room temperature to toluene and xylene individual vapors in the ppm range. For each transducer type, a time division multiplexing approach has been exploited, enabling the simultaneous interrogation of up to 8 optical and 6 acoustic probes, respectively. The results obtained indicate that both optical and acoustic sensors provide very high reproducibility and sensitivity either towards toluene or xylene, with a resolution of few hundreds of ppb. Furthermore, sensitivities and response times turned out to be dependent on the particular analytes used for the vapors testing. Both transducer types demonstrate a similar response time, while with regard the recovery time, the optical detection seems to be significantly faster than the electrical counterpart. The effect of the SWCNTs monolayers number on sensors sensitivity and response time has also been investigated, demonstrating the possibility to enhance the performances of the proposed transducers by tailoring the geometric properties of the sensitive nanomaterial. View full abstract»

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  • Conventional Technological Boosters for Injection Velocity in Ultrathin-Body MOSFETs

    Publication Year: 2007 , Page(s): 613 - 621
    Cited by:  Papers (9)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (620 KB) |  | HTML iconHTML  

    To meet ITRS requirements, highly scaled MOSFETs will have to operate close to the quasi-ballistic regime and to exhibit enhanced injection velocity. Good performances may be achieved thanks to high transport materials such as germanium or III-V semiconductors. However their integration is still very challenging. Following a different approach, this paper proposes to examine how to improve the injection in conventional (100) silicon ultrathin-body (UTB) MOSFETs. A systematic investigation of the impact of the different usual technological parameters highlights that SG and DG exhibit comparable performances and that no improvement in the injection velocity is expected with the silicon thickness thinning down to 4 nm. Moreover the degradation of the injection velocity with the integration of high- dielectrics is shown. Finally, a significant improvement of the injection velocity due to a higher confinement in asymmetrical double gate MOSFET has been found. Similarly, it is shown that, single gate UTB MOSFETs with thin buried oxide (BOX) exhibit an enhanced injection velocity. In conclusion, only the reduction of the BOX thickness and the integration of strained channel have been found to be realistic and significant boosters of the injection velocity in silicon (100) MOSFETs. Prediction of the evolution of the injection velocity along the roadmap, using a pragmatic strategy of scaling, confirms that these two parameters will play a significant role in improving highly scaled (100) silicon devices performances. View full abstract»

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  • Grating Couplers Fabricated by Electron-Beam Lithography for Coupling Free-Space Light Into Nanophotonic Devices

    Publication Year: 2007 , Page(s): 622 - 626
    Cited by:  Papers (4)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1053 KB) |  | HTML iconHTML  

    Grating couplers with nanoscale periodicity have been fabricated on silicon-on-insulator (SOI) substrates by electron beam lithography and reactive ion etching. A versatile experimental apparatus has been implemented to measure the efficiency of these gratings in coupling free-space radiation into planar waveguides. This coupling efficiency has been measured as a function of grating depth and the angle and wavelength of incident radiation. Coupling efficiencies of at least 5% and as high as 20% are demonstrated for wavelengths in the vicinity of 1550 nm and incident angles around 45deg. View full abstract»

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  • Plasmon Resonances of Nanoshells of Spheroidal Shape

    Publication Year: 2007 , Page(s): 627 - 638
    Cited by:  Papers (3)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (585 KB) |  | HTML iconHTML  

    Plasmon resonances are computed for nanoshells of prolate and oblate spheroidal shape. Both longitudinal and transverse resonances are investigated as a function of aspect ratio and shell thickness. Formulas for the surface charge density on the outside and inside shell surfaces are derived. View full abstract»

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  • Pattern Generation by Using Multistep Room-Temperature Nanoimprint Lithography

    Publication Year: 2007 , Page(s): 639 - 644
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1954 KB) |  | HTML iconHTML  

    We have demonstrated multistep room-temperature nanoimprint lithography (RTNIL) using polystyrene (PS, average molecular weight 97 kg/mol) as the imprint polymer layer on a silicon substrate for imprinting complex patterns. Single, double, and multiple (up to ten) sequential imprint steps were performed at imprint pressures between 1 to 30 MPa in separate experiments. We also transferred the imprinted patterns from the PS layer into the silicon substrate by means of an reactive-ion etching (RIE) process. To accomplish this demonstration, we designed and built a tool that controllably and repeatedly translated and pressed a sample into a stationary mold. The demonstrated interstep alignment accuracy of this tool ranged between 80 nm and 380 nm. These experiments revealed that polymer deformation results when nanoimprint is used to further deform a previously structured surface. The molds used in these experiments consisted of 400-nm-period diffraction gratings, as well as of rectangular structures of varying aspect ratios, ranging from 150 to 300 nm wide. View full abstract»

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  • Microwave Reflectivity From Gold Sputtered Nanolayer

    Publication Year: 2007 , Page(s): 645 - 651
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (185 KB) |  | HTML iconHTML  

    This paper deals with reflectivity of a gold layer of nanometer-scale thickness sputtered on a dielectric foil at microwave frequencies. A model of nanometer-scale spheres characterizes the behavior of the layer. For short sputtering times, these spheres are separated, and later they touch each other to form a continuous layer. The structure is analyzed in several ways. The first model, as suggested in the literature, replaces the spheres by their electric dipole moments, while the second, newly proposed model replaces them by their mutual capacities. The structure is also being investigated by the CST Microwave Studio software. The data provided by the models is compared with the data obtained from measurements carried out and published by the authors previously. The reduction in effective conductivity of the layer due to microscopic phenomena in thin films is taken into account in the models. The measured conductivity is compared with values taken from the literature, and the differences are discussed. View full abstract»

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  • Role of Doping in Carbon Nanotube Transistors With Source/Drain Underlaps

    Publication Year: 2007 , Page(s): 652 - 658
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (341 KB) |  | HTML iconHTML  

    The effects of doping on the performance of coaxially gated carbon nanotube (CNT) field-effect transistors for both zero Schottky-barrier (SB) and doped carbon nanotube contacts are theoretically investigated. For ultrascaled CNTFETs in which the source/drain metal contacts lie 50 nm apart, there is no MOSFET-like contact CNTFET (C-CNTFET) with an acceptable on/off current ratio using a CNT of diameter ges1.5 nm and a source/drain voltage ges0.4 V. For CNTFETs with source/drain metal contacts either 50 nm or 100 nm apart, there is an optimal doping concentration of 10-3 dopants per atom. The maximum on/off current ratios for the 50 nm CNT/5 nm gate and the 100 nm CNT/10 nm gate SB-CNTFETs are 5 times 104 and 6 times 105, respectively. Performance metrics of delay time, cutoff frequency, and LC frequency are presented and compared. View full abstract»

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  • Coupled Mechanical and 3-D Monte Carlo Simulation of Silicon Nanowire MOSFETs

    Publication Year: 2007 , Page(s): 659 - 666
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1986 KB) |  | HTML iconHTML  

    In this paper we report on a general methodology to investigate nanowire MOSFETs based on the coupling of mechanical simulation with 3-D real-space Monte Carlo simulation. The Monte Carlo transport model accounts for both strain silicon and quantum mechanical effects. Mechanical strain effects are accounted for through an appropriate change of the anisotropic band structure computed with the empirical pseudopotential method. Quantum effects are instead included by means of a quantum mechanical correction of the potential coming from the self-consistent solution of the Schrodinger equation. This methodology has been then applied to the simulation of a test case silicon nanowire n-MOSFET. Impact of mechanical strain and quantum effects on the drive current is investigated. It is shown that only the inclusion of strain and quantum mechanical effects allows a good agreement with experimental data, demonstrating the validity of the proposed methodology for ultimate devices. View full abstract»

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  • Design of a Robust Analog-to-Digital Converter Based on Complementary SET/CMOS Hybrid Amplifier

    Publication Year: 2007 , Page(s): 667 - 675
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (672 KB) |  | HTML iconHTML  

    As a solution to the high speed, ultralow power, and extremely compact ADC circuit block, a complementary single-electron transistor (SET)/CMOS hybrid amplifier-based analog-to-digital converter (ADC) is proposed. It is implemented with a physics-based SPICE model including nonideal effects in real Si-based SETs such as the tunnel barrier lowering effect, parasitic MOSFETs operation, and the phase shift of Coulomb oscillation by the bias of a gate other than a main control gate. Its core scheme is the combination of both the amplification of SET current by MOSFETs and the suppression of a Coulomb blockade oscillation valley current by the differential amplification. In addition, the transient operation of SET/CMOS hybrid circuit-based ADCs fully accounting for nonideal effects of real SETs is successfully demonstrated for the first time. Compared with the previous SET-based ADCs, our ADC makes features of the immunity to nonideal effects, large voltage swing of the output signal, and high load drivability. View full abstract»

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  • Characterization and Electrical Properties of Individual Au–NiO–Au Heterojunction Nanowires

    Publication Year: 2007 , Page(s): 676 - 681
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1876 KB) |  | HTML iconHTML  

    High-definition metal-oxide-metal (MOM) heterojunction nanowires in the Au-NiO-Au system have been synthesized using a template-based method. These nanowires are 70 nm in diameter and in total length, with a 100 to 300 nm wide NiO segment sandwiched between the Au nanowires axially. Detailed electron-microscopy characterization studies of these nanowires show that the oxide segment is primarily cubic NiO and nanocrystalline, and that both the Au-NiO interfaces are well-defined. These Au-NiO-Au nanowires have been incorporated into high-quality single-nanowire devices, fabricated using a direct-write method. The current-voltage responses of individual Au-NiO-Au nanowires have been measured as a function of temperature in the range 298 to 573 K. While the - response at room temperature has been found to be nonlinear, it becomes more linear and less resistive with increasing temperature. These types of MOM nanowires are likely to offer certain advantages over all-oxide nanowires in fundamental size-effect studies, and they could be potentially useful as nanoscale building blocks for multifunctional nanoelectronics of the future. View full abstract»

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  • Theoretical Investigations on Thermal Light Emission From Metallic Carbon Nanotubes

    Publication Year: 2007 , Page(s): 682 - 687
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (729 KB) |  | HTML iconHTML  

    Electrically driven thermal light emission (TLE) from individual metallic single-walled carbon nanotubes (mCNTs) is theoretically investigated by detailed simulations and compared to a recent experiment (Mann et al., Nature Nanotech.., vol. 2, p. 33, 2007). The electrical and thermal properties are determined by carrier transport in the metallic subband, which has a zero dipole matrix element and does not experience radiative carrier recombination. The light emission, however, is contributed by the semiconducting subbands, which are populated by a thermal process. The simulation results indicate that due to diameter-dependent thermal effects, the maximum current of suspended mCNTs has a much stronger dependence on the CNT diameter than in non suspended CNTs. The size and shape of the light spot are sensitive to the measured photon energy range. Although the temperature profile along the CNT is approximately parabolic, the light emission profile has a much sharper peak at the middle of the CNT, which is in good agreement with the experiment and confirms the thermal nature of the light emission. The light emission spectrum at high energies is affected by the subband and energy dependences of the radiative recombination lifetime. View full abstract»

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  • Structural and Electrical Characterization of Carbon Nanofibers for Interconnect Via Applications

    Publication Year: 2007 , Page(s): 688 - 695
    Cited by:  Papers (26)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2466 KB) |  | HTML iconHTML  

    We present temperature-dependent electrical characteristics of vertically aligned carbon nanofiber (CNF) arrays for on-chip interconnect applications. The study consists of three parts. First, the electron transport mechanisms in these structures are investigated using I-V measurements over a broad temperature range (4.4 K to 350 K). The measured resistivity in CNF arrays is modeled based on known graphite two-dimensional hopping electron conduction mechanism. The model is used because of the disordered graphite structure observed during high-resolution scanning transmission electron microscopy (STEM) of the CNF and CNF-metal interface. Second, electrical reliability measurements are performed at different temperatures to demonstrate the robust nature of CNFs for interconnect applications. Finally, some guidance in catalyst material selection is presented to improve the nanostructure of CNFs, making the morphology similar to multiwall nanotubes. View full abstract»

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  • Reconfigurable Hybrid CMOS/Nanodevice Circuits for Image Processing

    Publication Year: 2007 , Page(s): 696 - 710
    Cited by:  Papers (19)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2308 KB) |  | HTML iconHTML  

    We have analyzed two options of using hybrid CMOS/nanodevice circuits with area-distributed (CMOL) interface for the low-level image processing tasks, on the simplest example of 2-D image convolution with a sizable filter window. The first option is to use digital, DSP-like circuits based on a reconfigurable CMOL fabric, while the second one is based on mixed-signal CMOL circuits with the analog presentation of input and output data and the binary presentation of the filter function. Estimates of the circuit performance have been carried out for the 45-nm CMOS technology and the 4.5-nm nanowire half-pitch, and the power consumption fixed at a manageable, ITRS-specified level. In the digital case, the circuit area per pixel is about 25times25 , and the time necessary for convolving a 1024times1024-pixel, 12-bit-accurate image with a 3232-pixel window function of similar accuracy is close to 25 , much shorter than that estimated for purely CMOS circuits with the same minimum feature size on 45 nm. For a mixed-signal CMOL circuit, the corresponding numbers are much better ( ~1 mum2 and 1mus, respectively), but this option requires a very high (~1%) reproducibility of on currents of the necessary crosspoint devices (programmable diodes), which has not yet been reached experimentally. View full abstract»

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  • Regional Signal-Delay Analysis Applied to High-Frequency Carbon Nanotube FETs

    Publication Year: 2007 , Page(s): 711 - 717
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (715 KB) |  | HTML iconHTML  

    A regional signal-delay analysis is presented for field-effect transistors intended for operation at very high frequencies. For the example used here of a doped-contact carbon nanotube field-effect transistor, the analysis reveals that tunneling into the channel region of the device, and modulation of the space-charge regions in the source and drain adjacent to the channel, are the principal contributors to the overall delay. A recently proposed lower limit to the signal delay time in the channel is critically examined via the introduction of a local signal velocity. View full abstract»

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  • Temperature Dependence of Coulomb Oscillations on DNA-Mediated Au Nanoparticle Assembly

    Publication Year: 2007 , Page(s): 718 - 721
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (973 KB) |  | HTML iconHTML  

    We fabricated a single-electron transistor using DNA-assisted assembly of Au nanoparticles. Most devices exhibited clear Coulomb blockade and oscillations. In contrast to conventional single-electron transistors, however, the period of Coulomb oscillations was observed to depend on the temperature. This temperature dependence is probably ascribed to the temperature dependence of gate capacitance. View full abstract»

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  • Multishell Carrier Transport in Multiwalled Carbon Nanotubes

    Publication Year: 2007 , Page(s): 722 - 726
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (433 KB) |  | HTML iconHTML  

    Understanding carrier transport in carbon nanotubes (CNTs) and their networks is important for harnessing CNTs for device applications. Here, we report multishell carrier transport in individual multiwalled CNTs, and films of randomly dispersed multiwalled CNTs, as a function of electric field and temperature. Electrical measurements and first-principles density functional theory calculations indicate transport across CNT shells. Intershell conduction occurs across an energy barrier range of 60-250 meV in individual CNTs, and ~ 60 meV in CNT networks. In both cases, the conductance behavior can be explained based upon field-enhanced carrier injection and defect-enhanced transport, as described by the Poole-Frenkel model. View full abstract»

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  • Controlled Vacuum Breakdown in Carbon Nanotube Field Emission

    Publication Year: 2007 , Page(s): 727 - 733
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2317 KB) |  | HTML iconHTML  

    We report a physical mechanism of controlling vacuum breakdown in field emission from carbon nanotubes (CNTs). The thermal evaporation or runaway of CNT emitters is considered to be responsible for destructive vacuum breakdowns due to an overcurrent through electronically shorted circuits, where misaligned or irregularly long CNT emitters were found. The occurrence of the destructive breakdown, however, could be under control after an electrical treatment using soft breakdowns. Significant improvements of field emission stability and uniformity were achieved by optimally controlled soft breakdowns, which eliminated the short circuits and recovered the field emission with no destruction of electrodes. View full abstract»

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  • Rapid Extension of Single and Double Stranded DNA on Atomically Flat Conductive Surfaces

    Publication Year: 2007 , Page(s): 734 - 736
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2154 KB) |  | HTML iconHTML  

    We report a simple method for extending DNA on atomically flat conductive graphite and gold surfaces employing molecular combing and using either coordinating ions on graphite or self-assembled molecular monolayers on gold. Extended DNA molecules on conductive surfaces can be used as platforms for building nanoscale electronic devices or used for direct electronic sequencing. View full abstract»

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  • Nanowire Transistors: Modeling, Device Design and Technology

    Publication Year: 2007 , Page(s): 737 - 738
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    Freely Available from IEEE
  • 2007 Index IEEE Transactions on Nanotechnology Vol. 6

    Publication Year: 2007 , Page(s): 739 - 759
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    Freely Available from IEEE

Aims & Scope

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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Meet Our Editors

Editor-in-Chief
Fabrizio Lombardi
Dept. of ECE
Northeastern Univ.