5,338 research outputs found
Monolithically Patterned Wide-Narrow-Wide All-Graphene Devices
We investigate theoretically the performance advantages of all-graphene
nanoribbon field-effect transistors (GNRFETs) whose channel and source/drain
(contact) regions are patterned monolithically from a two-dimensional single
sheet of graphene. In our simulated devices, the source/drain and interconnect
regions are composed of wide graphene nanoribbon (GNR) sections that are
semimetallic, while the channel regions consist of narrow GNR sections that
open semiconducting bandgaps. Our simulation employs a fully atomistic model of
the device, contact and interfacial regions using tight-binding theory. The
electronic structures are coupled with a self-consistent three-dimensional
Poisson's equation to capture the nontrivial contact electrostatics, along with
a quantum kinetic formulation of transport based on non-equilibrium Green's
functions (NEGF). Although we only consider a specific device geometry, our
results establish several general performance advantages of such monolithic
devices (besides those related to fabrication and patterning), namely the
improved electrostatics, suppressed short-channel effects, and Ohmic contacts
at the narrow-to-wide interfaces.Comment: 9 pages, 11 figures, 2 table
Model of tunneling transistors based on graphene on SiC
Recent experiments shown that graphene epitaxially grown on Silicon Carbide
(SiC) can exhibit a energy gap of 0.26 eV, making it a promising material for
electronics. With an accurate model, we explore the design parameter space for
a fully ballistic graphene-on-SiC Tunnel Field-Effect Transistors (TFETs), and
assess the DC and high frequency figures of merit. The steep subthreshold
behavior can enable I_{ON}/I_{OFF} ratios exceeding 10^4 even with a low supply
voltage of 0.15 V, for devices with gatelength down to 30 nm. Intrinsic
transistor delays smaller than 1 ps are obtained. These factors make the device
an interesting candidate for low-power nanoelectronics beyond CMOS
Reconfigurable nanoelectronics using graphene based spintronic logic gates
This paper presents a novel design concept for spintronic nanoelectronics
that emphasizes a seamless integration of spin-based memory and logic circuits.
The building blocks are magneto-logic gates based on a hybrid
graphene/ferromagnet material system. We use network search engines as a
technology demonstration vehicle and present a spin-based circuit design with
smaller area, faster speed, and lower energy consumption than the
state-of-the-art CMOS counterparts. This design can also be applied in
applications such as data compression, coding and image recognition. In the
proposed scheme, over 100 spin-based logic operations are carried out before
any need for a spin-charge conversion. Consequently, supporting CMOS
electronics requires little power consumption. The spintronic-CMOS integrated
system can be implemented on a single 3-D chip. These nonvolatile logic
circuits hold potential for a paradigm shift in computing applications.Comment: 14 pages (single column), 6 figure
Hysteresis in As-Synthesized MoS2 Transistors: Origin and Sensing Perspectives
Two-dimensional materials, including molybdenum disulfide (MoS2), present promising
sensing and detecting capabilities thanks to their extreme sensitivity to changes in the environment.
Their reduced thickness also facilitates the electrostatic control of the channel and opens the door to
flexible electronic applications. However, these materials still exhibit integration difficulties with
complementary-MOS standardized processes and methods. The device reliability is compromised by
gate insulator selection and the quality of the metal/semiconductor and semiconductor/insulator
interfaces. Despite some improvements regarding mobility, hysteresis and Schottky barriers having
been reported thanks to metal engineering, vertically stacked heterostructures with compatible
thin-layers (such as hexagonal boron nitride or device encapsulation) variability is still an important
constraint to sensor performance. In this work, we fabricated and extensively characterized the
reliability of as-synthesized back-gated MoS2 transistors. Under atmospheric and room-temperature
conditions, these devices present a wide electrical hysteresis (up to 5 volts) in their transfer characteristics.
However, their performance is highly influenced by the temperature, light and pressure
conditions. The singular signature in the time response of the devices points to adsorbates and
contaminants inducing mobile charges and trapping/detrapping carrier phenomena as the mechanisms
responsible for time-dependent current degradation. Far from being only a reliability issue,
we demonstrated a method to exploit this device response to perform light, temperature and/or
pressure sensors in as-synthesized devices. Two orders of magnitude drain current level differences
were demonstrated by comparing device operation under light and dark conditions while a factor up
to 105 is observed at vacuum versus atmospheric pressure environments.European Union’s Horizon 2020 Research and Innovation Programme under the Marie Skłodowska-Curie grant agreement No 895322Spanish Government under Juan de la Cierva Formacion grant number FJC2018-038264-ISpanish Ministry of Economy, Industry and Competitivity under grant TEC2017-89800-RASCENT (EU Horizon 2020 GRANT 654384)Science Foundation Ireland through the AMBER 2 project (12/RC/2278-P2)UGR-MADOC CEMIX 2D-EDE
Development of electrochromic thin-film transistors on flexible substrate
This work documents the fabrication and characterization of electrochromic thin-film transistors (ECTFTs) based on tungsten oxide (WO3). The ECTFTs exhibit double functionality (optical and electrical modulation) and were deposited on Corning glass and polyethylene naphthalate (PEN) by radio-frequency (RF) magnetron sputtering in an argon-oxygen atmospherewith no intentional substrate heating. The resulting amorphous WO3film connects source and drain in a planar configuration with three different architectures(conventional, interdigital and back-electrode) and isgated by a drop-casted lithium-based polymer electrolyte (LiClO4:PC). EC films were characterized using X-ray diffraction (XRD), atomic force microscopy (AFM)andopto-electrochemical measurements, the electrolyte by electrochemicalimpedance spectroscopy (EIS) and the ECTFTs by static and dynamic electrical characterization. Thinner EC films (75 nm) evidenced lower optical density (ΔOD) and color efficiency (CE) of 0,26 and 21,85 cm2C-1, respectively, but faster EC reaction kinetics, with bleaching and coloration times (tband tc) of 1,8 and 3,8 seconds, respectively. In terms of electrical properties the best performing ECTFT architecture (interdigital) showed an ION/IOFFof 2,81x105and a transconductance of 2,24 mS. The back-electrode architecturehowever showed better ionic movement control in the channel(adjustable VON)with enhanced colorations, making ita better candidate for a two-in-one (pixel + transistor) solution for display applications
Fault Modeling of Graphene Nanoribbon FET Logic Circuits
[EN] Due to the increasing defect rates in highly scaled complementary metal-oxide-semiconductor (CMOS) devices, and the emergence of alternative nanotechnology devices, reliability challenges are of growing importance. Understanding and controlling the fault mechanisms associated with new materials and structures for both transistors and interconnection is a key issue in novel nanodevices. The graphene nanoribbon field-effect transistor (GNR FET) has revealed itself as a promising technology to design emerging research logic circuits, because of its outstanding potential speed and power properties. This work presents a study of fault causes, mechanisms, and models at the device level, as well as their impact on logic circuits based on GNR FETs. From a literature review of fault causes and mechanisms, fault propagation was analyzed, and fault models were derived for device and logic circuit levels. This study may be helpful for the prevention of faults in the design process of graphene nanodevices. In addition, it can help in the design and evaluation of defect- and fault-tolerant nanoarchitectures based on graphene circuits. Results are compared with other emerging devices, such as carbon nanotube (CNT) FET and nanowire (NW) FET.This work was supported in part by the Spanish Government under the research project TIN2016-81075-R and by Primeros Proyectos de Investigacion (PAID-06-18), Vicerrectorado de Investigacion, Innovacion y Transferencia de la Universitat Politecnica de Valencia (UPV), under the project 200190032.Gil Tomás, DA.; Gracia-Morán, J.; Saiz-Adalid, L.; Gil, P. (2019). Fault Modeling of Graphene Nanoribbon FET Logic Circuits. Electronics. 8(8):1-18. https://doi.org/10.3390/electronics8080851S11888International Technology Roadmap for Semiconductors (ITRS) 2013http://www.itrs2.net/2013-itrs.htmlSchuegraf, K., Abraham, M. C., Brand, A., Naik, M., & Thakur, R. (2013). Semiconductor Logic Technology Innovation to Achieve Sub-10 nm Manufacturing. IEEE Journal of the Electron Devices Society, 1(3), 66-75. doi:10.1109/jeds.2013.2271582International Technology Roadmap for Semiconductors (ITRS) 2015https://bit.ly/2xiiT8PNovoselov, K. S. (2004). Electric Field Effect in Atomically Thin Carbon Films. Science, 306(5696), 666-669. doi:10.1126/science.1102896Geim, A. K., & Novoselov, K. S. (2007). The rise of graphene. Nature Materials, 6(3), 183-191. doi:10.1038/nmat1849Wu, Y., Farmer, D. B., Xia, F., & Avouris, P. (2013). Graphene Electronics: Materials, Devices, and Circuits. Proceedings of the IEEE, 101(7), 1620-1637. doi:10.1109/jproc.2013.2260311Choudhury, M. R., Youngki Yoon, Jing Guo, & Mohanram, K. (2011). Graphene Nanoribbon FETs: Technology Exploration for Performance and Reliability. IEEE Transactions on Nanotechnology, 10(4), 727-736. doi:10.1109/tnano.2010.2073718Avouris, P. (2010). Graphene: Electronic and Photonic Properties and Devices. Nano Letters, 10(11), 4285-4294. doi:10.1021/nl102824hBanadaki, Y. M., & Srivastava, A. (2015). Scaling Effects on Static Metrics and Switching Attributes of Graphene Nanoribbon FET for Emerging Technology. IEEE Transactions on Emerging Topics in Computing, 3(4), 458-469. doi:10.1109/tetc.2015.2445104Avouris, P., Chen, Z., & Perebeinos, V. (2007). Carbon-based electronics. Nature Nanotechnology, 2(10), 605-615. doi:10.1038/nnano.2007.300Banerjee, S. K., Register, L. F., Tutuc, E., Basu, D., Kim, S., Reddy, D., & MacDonald, A. H. (2010). Graphene for CMOS and Beyond CMOS Applications. Proceedings of the IEEE, 98(12), 2032-2046. doi:10.1109/jproc.2010.2064151Schwierz, F. (2013). Graphene Transistors: Status, Prospects, and Problems. Proceedings of the IEEE, 101(7), 1567-1584. doi:10.1109/jproc.2013.2257633Fregonese, S., Magallo, M., Maneux, C., Happy, H., & Zimmer, T. (2013). Scalable Electrical Compact Modeling for Graphene FET Transistors. IEEE Transactions on Nanotechnology, 12(4), 539-546. doi:10.1109/tnano.2013.2257832Chen, Y.-Y., Sangai, A., Rogachev, A., Gholipour, M., Iannaccone, G., Fiori, G., & Chen, D. (2015). A SPICE-Compatible Model of MOS-Type Graphene Nano-Ribbon Field-Effect Transistors Enabling Gate- and Circuit-Level Delay and Power Analysis Under Process Variation. IEEE Transactions on Nanotechnology, 14(6), 1068-1082. doi:10.1109/tnano.2015.2469647Ferrari, A. C., Bonaccorso, F., Fal’ko, V., Novoselov, K. S., Roche, S., Bøggild, P., … Pugno, N. (2015). Science and technology roadmap for graphene, related two-dimensional crystals, and hybrid systems. Nanoscale, 7(11), 4598-4810. doi:10.1039/c4nr01600aHong, A. J., Song, E. B., Yu, H. S., Allen, M. J., Kim, J., Fowler, J. D., … Wang, K. L. (2011). Graphene Flash Memory. ACS Nano, 5(10), 7812-7817. doi:10.1021/nn201809kJeng, S.-L., Lu, J.-C., & Wang, K. (2007). 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A Millimeter-scale Single Charged Particle Dosimeter for Cancer Radiotherapy
This paper presents a millimeter-scale CMOS 6464 single charged
particle radiation detector system for external beam cancer radiotherapy. A
11 diode measures energy deposition by a single charged
particle in the depletion region, and the array design provides a large
detection area of 512512 . Instead of sensing the voltage drop
caused by radiation, the proposed system measures the pulse width, i.e., the
time it takes for the voltage to return to its baseline. This obviates the need
for using power-hungry and large analog-to-digital converters. A prototype ASIC
is fabricated in TSMC 65 nm LP CMOS process and consumes the average static
power of 0.535 mW under 1.2 V analog and digital power supply. The
functionality of the whole system is successfully verified in a clinical 67.5
MeV proton beam setting. To our' knowledge, this is the first work to
demonstrate single charged particle detection for implantable in-vivo
dosimetry
Modeling the Temperature Bias of Power Consumption for Nanometer-Scale CPUs in Application Processors
We introduce and experimentally validate a new macro-level model of the CPU
temperature/power relationship within nanometer-scale application processors or
system-on-chips. By adopting a holistic view, this model is able to take into
account many of the physical effects that occur within such systems. Together
with two algorithms described in the paper, our results can be used, for
instance by engineers designing power or thermal management units, to cancel
the temperature-induced bias on power measurements. This will help them gather
temperature-neutral power data while running multiple instance of their
benchmarks. Also power requirements and system failure rates can be decreased
by controlling the CPU's thermal behavior.
Even though it is usually assumed that the temperature/power relationship is
exponentially related, there is however a lack of publicly available physical
temperature/power measurements to back up this assumption, something our paper
corrects. Via measurements on two pertinent platforms sporting nanometer-scale
application processors, we show that the power/temperature relationship is
indeed very likely exponential over a 20{\deg}C to 85{\deg}C temperature range.
Our data suggest that, for application processors operating between 20{\deg}C
and 50{\deg}C, a quadratic model is still accurate and a linear approximation
is acceptable.Comment: Submitted to SAMOS 2014; International Conference on Embedded
Computer Systems: Architectures, Modeling, and Simulation (SAMOS XIV
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