[show abstract][hide abstract] ABSTRACT: Optoelectronic nonvolatile memory elements based on polymer-coated carbon nanotube devices can serve as building blocks in programmable circuits. Although essential for improving the circuit performances, the details of the charge trapping mechanism in these mixed organic/inorganic optoelectronic devices are not fully elucidated. The detailed mechanism was investigated by intercalating layers of a hydrophobic organic dielectric (parylene) at different interfaces in the device structure. A thin parylene layer separating the SiO2/nanotube interface from the photosensitive polymer coating is presented as an optimized solution in terms of charging, stability, and robustness.
[show abstract][hide abstract] ABSTRACT: We present an original method to implement neuro-inspired supervised learning for a synaptic array based on carbon nanotube devices. The device characteristics required to implement on chip learning within a crossbar of carbon nanotube field effect transistors (CNTFETs) as synaptic arrays were experimentally demonstrated and accurately modeled through a specific electrical compact model. We performed electrical simulations of learning for an array of 24 nanotube memory devices corresponding to a 3 input × 3 output neural layer that revealed successful learning of separable logic functions within very few epochs, even when a realistic variability of nanotube diameter was taken into account. Such a learning approach opens the way to the use of high-density synaptic arrays as generic logic blocks in configurable circuits.
Circuits and Systems I: Regular Papers, IEEE Transactions on 10/2011; · 2.24 Impact Factor
[show abstract][hide abstract] ABSTRACT: We show that thin horizontal arrays of single wall carbon nanotubes (SWNTs) suspended above the channel of silicon MOSFETs can be used as vibrating gate electrodes. This new class of nano-electromechanical system (NEMS) combines the unique mechanical and electronic properties of SWNTs with an integrated silicon-based motion detection. Its electrical response exhibits a clear signature of the mechanical resonance of SWNT arrays (120-150 MHz) showing that these thin horizontal arrays behave as a cohesive, rigid and elastic body membrane with a Young's modulus in the order of 1-10 GPa and ultra-low mass. The resonant frequency can be tuned by the gate voltage and its dependence is well understood within the continuum mechanics framework.
[show abstract][hide abstract] ABSTRACT: We show that optic ally-gated carbon nanotube field effect transistors can be used as 2-terminal like devices with light sensitivity and memory capabilities. In particular, their channel resistivity can be adjusted precisely, within a large range and memorized. These devices can thus be used as synapses in neural network type of circuits. We demonstrate experimentally these properties, build a device model and propose a circuit architecture, which allows very efficient parallel learning.
Circuits and Systems (ISCAS), Proceedings of 2010 IEEE International Symposium on; 07/2010
[show abstract][hide abstract] ABSTRACT: Nanoscale devices such as carbon nanotube and nanowires based transistors, memristors and molecular devices are expected to play an important role in the development of new computing architectures. While their size represents a decisive advantage in terms of integration density, it also raises the critical question of how to efficiently address large numbers of densely integrated nanodevices without the need for complex multi-layer interconnection topologies similar to those used in CMOS technology. Two-terminal programmable devices in crossbar geometry seem particularly attractive, but suffer from severe addressing difficulties due to cross-talk, which implies complex programming procedures. Three-terminal devices can be easily addressed individually, but with limited gain in terms of interconnect integration. We show how optically gated carbon nanotube devices enable efficient individual addressing when arranged in a crossbar geometry with shared gate electrodes. This topology is particularly well suited for parallel programming or learning in the context of neuromorphic computing architectures.
[show abstract][hide abstract] ABSTRACT: Carbon nanotubes are intrinsically high impedance objects. The high frequency (HF) characterization of these nano-objects is crucial for applications such as interconnects in future integrated circuits, but still represents a daunting challenge. This letter presents HF characterization of an individual metallic single walled carbon nanotube up to 7 GHz. The equivalent circuit values are directly extracted from these HF measurements without numerical procedure, thus proving that the intrinsic transport parameters of a single carbon nanotube can be determined up to gigahertz frequencies.
[show abstract][hide abstract] ABSTRACT: In this paper we report the first experimental demonstration of Micro-Electro-Mechanical resonator based on a Carbon Nanotube-Array-Suspended-Gate-Field-Effect-Transistor (CNT-SGFET). A dense array of single-walled CNT aligned by ac-dielectrophoresis technique forms the suspended gate electrode of a conventional silicon based FET. Resonance frequency of 120 MHz is reported. An equivalent electrical model has been developed for the resonator.
[show abstract][hide abstract] ABSTRACT: In this paper we explore the possibility of using the equations of a well known compact model for CMOS transistors as a parameterized compact model for a variety of FET based nano-technology devices. This can turn out to be a practical preliminary solution for system level architectural researchers, who could simulate behaviourally large scale systems, while more physically based models become available for each new device. We have used a four parameter version of the EKV model equations and verified that fitting errors are similar to those when using them for standard CMOS FET transistors. The model has been used for fitting measured data from three types of FET nano-technology devices obeying different physics, for different fabrication steps, and under different programming conditions.
[show abstract][hide abstract] ABSTRACT: This paper presents the high frequency performance of single-walled carbon nanotube (SWNT) field-effect transistors, with channel consisting of dense networks of high purity semiconducting SWNTs. Using SWNT samples containing 99% pure semiconducting SWNTs, we achieved operating frequencies above 80 GHz. This record frequency does not require aligned SWNTs, thus demonstrating the remarkable potential of random networks of sorted SWNTs for high frequency electronics.
[show abstract][hide abstract] ABSTRACT: We investigate high frequency electrical and mechanical performances of
carbon nanotube based devices. Using configurations with multiple
single-wall nanotubes in parallel, we show that HF nanotube transistors
with intrinsic cut-off frequencies as high as 30 GHz can be obtained on
rigid substrates. Adapting our process to plastic substrates, we also
obtained highly flexible HF transistors showing constant
transconductances up to at least 6 GHz, as-measured cut-off frequencies
as high as 1 GHz (5-8 GHz after de-embedding) and stable DC performances
upon bending. We probed electromechanical properties of individual
suspended carbon multiwall nanotubes by using a modified AFM. DC
deflection measurements on different devices are in agreement with a
continuum model prediction and consistent with a Young's modulus of 0.4
TPa. Preliminary HF measurements on a doubly clamped device showed a
resonant frequency of 200MHz consistent with a Young's modulus of 0.43
TPa. This implies that built-in mechanical stress in the case of MWNTs
[show abstract][hide abstract] ABSTRACT: We report for the first time to our knowledge large-signal measurements performed at 600 MHz and in time domain on carbon nanotube field-effect transistors (CNFETs) using a large-signal network analyzer. To overcome the very high mismatch between the high CNFET impedance and the basic 50-Omega configuration of the setup, the output impedance was matched with the help of an experimental active load-pull configuration. Hence, we were able to observe under large-signal conditions the nonlinear behavior of CNFETs. Static measurements and continuous-wave S <sub>ij</sub> -parameter measurements were made for many different biases. They were used in order to determine a nonlinear electrical model that has been validated thanks to the nonlinear measurements. The developed model opens the way for electrical CNFET circuit simulation and nonlinear applications of these devices.
IEEE Transactions on Microwave Theory and Techniques 08/2008; · 2.23 Impact Factor
[show abstract][hide abstract] ABSTRACT: Carbon Nanotube Field Effect Transistors (CN- FETs) seem to be very promising candidates for the future microwave frequency applications. However, these components present high impedance values which make very difficult the characterization using usual characteristic impedance of microwave instrumentations (50Omega). To determine CNFET microwave capabilities, special techniques of measurements must be developed such as for example heterodyne detection, or two-tone measurements with the observation of the inter- modulation products. In our case we propose an original method using a Large Signal Network Analyser (LSNA) associated with an active load pull configuration. The aim of this active load pull is to reduce the mismatch between the CNFET output impedance and the 50Omega load and hence increase the measurements accuracy of these nano- devices. Moreover these samples can be characterize in linear but also non linear conditions.
[show abstract][hide abstract] ABSTRACT: We investigate the high frequency performances of flexible field-effect transistors based on carbon nanotubes. A large density of mostly aligned carbon nanotubes deposited on a flexible substrate by dielectrophoresis serves as the channel. The transistors display a constant transconductance up to at least 6 GHz and a current gain cutoff frequency (fT) as high as 1 GHz at VDS = −700 mV. Bending tests show that the devices can withstand a high degree of flexion characterized by a constant transconductance for radius of curvature as small as 3.3 mm.
[show abstract][hide abstract] ABSTRACT: High frequency capabilities of carbon nanotube field-effect transistors (CNTFETs) are investigated. Structures with a large number of single-walled carbon nanotubes were fabricated using dielecrophoresis to increase the density of nanotubes in the device channel. The authors obtained an intrinsic current gain cutoff frequency of 30 GHz establishing state-of-the-art high frequency (hf) potentialities of CNTFETs. The device also showed a maximum stable gain above 10 dB at 20 GHz. Finally, the parameters of an equivalent circuit model of multitube CNTFET at 20 GHz are determined, which open the route to the modeling of nanotubes-based hf electronics.
[show abstract][hide abstract] ABSTRACT: Chemically and biochemically-directed assembly of nanotubes (NT) for electronics is reviewed. Examples of new field-effect devices prepared this way either for high frequency (40GHz) operation or for applications to an optoelectronics multilevel memory are presented. A route towards (bio)molecular interconnects for NTs is outlined
Electron Devices Meeting, 2006. IEDM '06. International; 01/2007
[show abstract][hide abstract] ABSTRACT: In this letter, the authors report on the high-frequency (HF) performance of self-assembled carbon nanotube field-effect transistors. HF device structures including a large number of single-wall carbon nanotubes have been designed and optimized in order to establish a new state of the art. The device exhibits a current gain (|H<sub>21</sub>| <sup>2</sup>) cutoff frequency (f<sub>t</sub>) of 8 GHz and a maximum stable gain value of 10 dB at 1 GHz, after de-embedding the access pads. Considering such results, nanotube-based circuits with gigahertz performance are now conceivable
IEEE Electron Device Letters 09/2006; · 2.79 Impact Factor
[show abstract][hide abstract] ABSTRACT: AC performances of carbon nanotube field-effect transistors (CNT-FETs) are analyzed by means of scattering parameters measurements. The active ac properties of CNT-FETs are clearly demonstrated up to 80 MHz and indications of active behavior are obtained up to 1 GHz. From these measurements, a small signal equivalent circuit is proposed and validated up to 10 MHz. The extraction procedure and the determination of the intrinsic ac elements of CNT-FETs are pointed out
IEEE Transactions on Nanotechnology 08/2006; · 1.80 Impact Factor