Showing papers in "IEEE Transactions on Nanotechnology in 2016"
TL;DR: A novel resistive memory-the transpose memory is presented, which adds additional functionality to the memristive memory, and a case study of an adder is presented to demonstrate the design issues discussed in this paper.
Abstract: Realizing logic operations within passive crossbar memory arrays is a promising approach to enable novel computer architectures, different from conventional von Neumann architecture. Attractive candidates to enable such architectures are memristors, nonvolatile memory elements commonly used within a crossbar, that can also perform logic operations. In such novel architectures, data are stored and processed within the same entity, which we term as memristive memory processing unit (MPU). In this paper, Memristor-Aided loGIC (MAGIC) family is discussed with various design considerations and novel techniques to execute logic within an MPU. We present a novel resistive memory-the transpose memory, which adds additional functionality to the memristive memory, and compare it with a conventional memristive memory. A case study of an adder is presented to demonstrate the design issues discussed in this paper. We compare the proposed design techniques with the memristive IMPLY logic in terms of speed, area, and energy. Our evaluation shows that the proposed MAGIC design is 2.4 × faster and consumes 66.3% less energy as compared with the IMPLY-based computing for N-bit addition within memristive crossbar memory. Additionally, we compare the proposed design with IMPLY logic family on ISCAS-85 benchmarks, which shows significant improvements in speed (2×) and energy (10×), with similar area.
258 citations
TL;DR: The model proposed is generic and could be incorporated into variants of threshold-based memristor models in which apparent variations in the output hysteresis convey the switching threshold shift, and paves the way for novel approaches in the fields of neuromorphic engineering circuits design.
Abstract: Diverse models have been proposed over the past years to explain the exhibiting behavior of memristors, the fourth fundamental circuit element. The models varied in complexity ranging from a description of physical mechanisms to a more generalized mathematical modeling. Nonetheless, stochasticity, a widespread observed phenomenon, has been immensely overlooked from the modeling perspective. This inherent variability within the operation of the memristor is a vital feature for the integration of this nonlinear device into the stochastic electronics realm of study. In this paper, experimentally observed innate stochasticity is modeled in a circuit compatible format. The model proposed is generic and could be incorporated into variants of threshold-based memristor models in which apparent variations in the output hysteresis convey the switching threshold shift. Further application as a noise injection alternative paves the way for novel approaches in the fields of neuromorphic engineering circuits design. On the other hand, extra caution needs to be paid to variability intolerant digital designs based on nondeterministic memristor logic.
87 citations
TL;DR: In this article, the effects of using high-k oxides and gate stacks on the performance of ultrascaled metal oxide semiconductor field effect transistors ( mosfet s) are analyzed.
Abstract: A widely used technique to mitigate gate leakage in ultrascaled metal oxide semiconductor field effect transistors ( mosfet s) is the use of high-k dielectrics, which provide the same equivalent oxide thickness (EOT) as $\rm SiO_2$ , but thicker physical layers. However, using a thicker physical dielectric for the same EOT has a negative effect on the device performance due to the degradation of 2D electrostatics. In this paper, the effects of high-k oxides on double-gate (DG) mosfet with gate length under 20 nm are studied. All the devices are modeled using an effective mass quantum transport approach based on the quantum transmitting boundary method, where only ballistic transport is considered. We find that there is an optimum physical oxide thickness ( $\rm T_{OX}$ ) to achieve the best performance in terms of on-current for each gate stack, including $\rm SiO_2$ interface layer and one high-k material. For the same EOT, $\rm Al_2O_3$ (k = 9) over 3- $\mathring{\mathrm{A}}$ $\rm SiO_2$ provides the best performance, while for $\rm HfO_2$ (k = 22) and $\rm La_2O_3$ (k = 30), $\rm SiO_2$ thicknesses should be 5 $\mathring{\mathrm{A}}$ and 7 $\mathring{\mathrm{A}}$ , respectively. The effects of using high-k oxides and gate stacks on the performance of ultrascaled mosfet s are analyzed. While thin oxide thickness increases the gate leakage, the thick oxide layer reduces the gate control on the channel. Therefore, the physical thicknesses of gate stack should be optimized to achieve the best performance.
65 citations
TL;DR: In this paper, a comparative study of the ultraviolet (UV) detection properties of n-TiO2/p-Si heterojunction devices fabricated using two different deposition techniques namely the electron-beam evaporation (EBE) and sol-gel (SG) methods is presented.
Abstract: This paper reports a comparative study of the ultraviolet (UV) detection properties of n-TiO2/p-Si heterojunction devices fabricated using two different deposition techniques namely the electron-beam evaporation (EBE) and sol–gel (SG) methods. A systematic study has also been carried out to investigate the structural, electrical, and optical properties of the as deposited TiO2 thin films on p-Si substrates by the EBE and SG methods. The electrical parameters of both the n-TiO2/p-Si heterojunction photodiodes have been measured and compared under dark and UV illumination conditions. The SG based n-TiO2/p-Si heterojunction photodiodes are observed with an excellent contrast ratio of ∼83911 at −5.2 V bias voltage, which is ∼6445 times higher than the EBE-based device. The measured responsivities of the EBE and SG based devices are ∼0.69 and ∼1.25 A/W at a bias voltage of −10 V ( P opt = 650 μW and λ = 365 nm), respectively. Thus, the n-TiO2/p-Si heterojunction diodes with SG derived TiO2 films are considered to be a better choice over the EBE-based n-TiO2/p-Si diodes for UV detection applications.
57 citations
TL;DR: In this article, the surface roughness of metal waveguides has been investigated at the nanoscale using microfabrication techniques, and two significant examples are considered: a 0.346-THz backward wave tube oscillator and an 0.263-thz traveling wave tube.
Abstract: Vacuum electron devices are the most promising solution for the generation of watt-level power at millimeter wave and terahertz frequencies. However, the three-dimensional nature of metal structures required to provide an effective interaction between an electron beam and THz signal poses significant fabrication challenges. At increasing frequency, losses present a serious detrimental effect on performance. In particular, the skin depth, on the order of one hundred nanometers or less, constrains the maximum acceptable surface roughness of the metal surfaces to be below those values. Microfabrication techniques have proven, in principle, to achieve values of surface roughness at the nanometer scale; however, the use of different metals and affordable microfabrication techniques requires further investigation for a repeatable quality of the metal surfaces. This paper compares, for the first time, the nanoscale surface roughness of metal THz waveguides realized by the main microfabrication techniques. In particular, two significant examples are considered: a 0.346-THz backward wave tube oscillator and a 0.263-THz traveling wave tube.
55 citations
TL;DR: In this paper, the impact of surface and bulk traps on two-dimensional electron gas, device characteristics, and gate leakage is accounted for, and a new approach to accurately model the forward gate leakage in Schottky gate devices is proposed.
Abstract: This paper for the first time presents a comprehensive computational modeling approach for AlGaN/GaN high electron mobility transistors. Impact of the polarization charge at different material interfaces on the energy band profile as well as parasitic charge across the epitaxial stack is modeled and studied. Furthermore, impact of surface and bulk traps on two-dimensional electron gas, device characteristics, and gate leakage is accounted in this paper. For the first time, surface states modeled as donor type traps were correlated with gate leakage. Moreover, a new approach to accurately model the forward gate leakage in Schottky gate devices is proposed. Finally, impact of lattice and carrier heating is studied, while highlighting the relevance of carrier heating, lattice heating, and bulk traps over the device characteristics. In addition to this, modeling strategy for other critical aspects like parasitic charges, quantum effects, S/D Schottky contacts, and high field effects is presented.
51 citations
TL;DR: In this paper, a distributed circuit model for a pair of coupled MLGNR interconnects is provided, with both capacitive and inductive coupling taken into account, and validated against the Spice results and the predicted experiment results in frequency and time domains.
Abstract: Multi-layer graphene nanoribbons (MLGNRs) material has been a potential solution to replace conventional Cu for next-generation on-chip interconnects. Based on equivalent single conductor model, this paper extracts the equivalent resistance-inductance-capacitance parameters for MLGNRs with consideration of edge roughness and Fermi level. A distributed circuit model for a pair of coupled MLGNR interconnects is provided, with both capacitive and inductive coupling taken into account, and validated against the Spice results and the predicted experiment results in frequency and time domains. Using the proposed model, the impact of various dimensional and technology parameters on the transfer gain and crosstalk delay is investigated for the global MLGNR interconnects at different phase modes. It is demonstrated that MLGNR interconnects with smooth edge exhibit higher transfer gain and lower crosstalk delay in comparison to its Cu counterpart at same dimension. However, edge roughness in the present fabrication technologies is inevitable that significantly deteriorates the propagation performance and the performance difference due to edge roughness is relatively less in wider MLGNR interconnects. Moreover, it is shown that side contact MLGNR interconnects have better electrical performance than that of top contact MLGNR interconnects at short interconnect length in comparison to that at long interconnects due to the domination of in-layer resistance. The results presented in this paper would be helpful to fully understand the propagation characteristics and provide guidelines for signal integrity analysis of MLGNR interconnects.
49 citations
TL;DR: In this paper, a high performance piezoelectric-pyroelectric hybrid nanogenerator based on P(VDF-TrFE) nanowire array that is capable of simultaneously harvesting mechanical and thermal energies is presented.
Abstract: The piezoelectric and pyroelectric effects are well known and have been widely used for energy harvesting and self-powered sensing systems. This paper presents a high performance piezoelectric-pyroelectric hybrid nanogenerator based on P(VDF-TrFE) nanowire array that is capable of simultaneously harvesting mechanical and thermal energies. The nanowire array was synthesized by nanoimprinting P(VDF-TrFE) polymer into anodic aluminum oxide (AAO). The ferroelectric β crystalline phase of the aligned P(VDF-TrFE) nanowires has been demonstrated by Fourier transform infrared spectrum and X-ray diffraction measurements. Under periodic mechanical bending, electric signals are repeatedly generated from the hybrid nanogenerator and the measured piezoelectric output reach 4.0 V/65 nA. The cyclic bending–releasing process and impacts of strain rate on the electrical outputs are thoroughly characterized and analyzed. Besides, upon exposure of heat–cool condition with a temperature range of 8 K around room temperature, pyroelectric output up to 3.2 V/52 nA was obtained. There is a linear relationship between the output and the temperature difference across the device. Because the fast response time of 90 ms and high detected sensitivity of 0.8 K, the hybrid nanogenerator can also use as a self-powered temperature sensor. Finally, the piezoelectric and pyroelectric output voltages were successfully integrated together to obtain an enhanced output. These results demonstrate the great potential of the flexible hybrid nanogenerator for self-powered electronic devices.
46 citations
TL;DR: This paper proposes a hybrid structure to implement the CNN with magnetic components and CMOS peripherals with a complete driving and sensing circuitry and proposes a digitally programmable magnetic synapse that can achieve both positive and negative values of the templates.
Abstract: Due to the massive parallel computing capability and outstanding image and signal processing performance, cellular neural network (CNN) is one promising type of non-Boolean computing system that can outperform the traditional digital logic computation and mitigate the physical scaling limit of the conventional CMOS technology. The CNN was originally implemented by VLSI analog technologies with operational amplifiers and operational transconductance amplifiers as neurons and synapses, respectively, which are power and area consuming. In this paper, we propose a hybrid structure to implement the CNN with magnetic components and CMOS peripherals with a complete driving and sensing circuitry. In addition, we propose a digitally programmable magnetic synapse that can achieve both positive and negative values of the templates. After rigorous performance analyses and comparisons, optimal energy is achieved based on various design parameters, including the driving voltage and the CMOS driving size. At a comparable footprint area and operation speed, a spintronic CNN is projected to achieve about one order of magnitude energy reduction per operation compared to its CMOS counterpart.
45 citations
TL;DR: In this paper, the SiGe/Si hetero-material system is applied to the n-channel ETL tunnel FET to suppress the low electric field BTBT by the ETL band engineering.
Abstract: Tunnel field-effect transistor (FET) is a promising candidate in ultralow-power applications due to its distinct operation mechanism, namely band-to-band tunneling (BTBT). The integration of different low-bandgap materials is explored extensively to improve the ON-state BTBT current of the tunnel FETs. The epitaxial tunnel layer (ETL) tunnel FET integrated with the hetero-material system is a promising structure due to its process compatibility with CMOS technologies. In the scenario of n-channel operation, the concept of the suppression of the low electric field BTBT is proposed. The SiGe/Si hetero-material system is applied to the n-channel ETL tunnel FET to suppress the low electric field BTBT by the ETL band engineering. The optimized ETL tunnel FET exhibits a high ON-state BTBT current due to the low bandgap material in the ETL. The average SS behavior is also further improved by suppressing the low electric field BTBT. In this study, the design concept and the device parameters of the n-channel ETL tunnel FET are discussed in detail. The performances of the complementary ETL tunnel FETs using the SiGe/Si hetero-material system are also provided to enrich the value of the ETL tunnel FET in the circuit applications.
45 citations
TL;DR: In this article, the authors investigated the mechanism of the high-optoacoustic conversion efficiency exhibited by the composite and proposed a thermal-acoustic coupling model for analyzing the performance of the composite.
Abstract: As a novel composite material for laser ultrasound transducer, candle soot nanoparticles polydimethylsiloxane (CSPs-PDMS) has been demonstrated to generate high frequency, broadband, and high-amplitude ultrasound waves. In this study, we investigated the mechanism of the high-optoacoustic conversion efficiency exhibited by the composite. A thermal-acoustic coupling model was proposed for analyzing the performance of the composite. The theoretical result matches well with the experimental observation. The acoustic beam profile was compared with Field II simulation results. The 4.41 × 10−3 energy conversion coefficient and 21 MHz-–6 dB frequency bandwidth of the composite suggest that CSPs-PDMS composites is promising for a broad range of ultrasound therapy and non-destructive testing applications.
TL;DR: This paper presents a set of complementary resistive switching (CRS)-based stateful logic operations that use material implication to provide the basic logic functionalities needed to realize logic circuits.
Abstract: Memristors are considered among the most promising future building blocks of next-generation digital systems. This paper focuses on specific ways to implement logic and arithmetic unit using memristors. In particular, we present a set of complementary resistive switching (CRS)-based stateful logic operations that use material implication to provide the basic logic functionalities needed to realize logic circuits. The proposed solution benefits from the exponential reduction in sneak path current in crossbar implemented logic. This paper also presents a closed-form expression for sneak current and analyzes the impact of device variation on the behavior of the proposed logic blocks. Our technique, as other similar techniques proposed in the literature, requires several sequential steps to perform the computation. However, in this paper, we show that only three steps are required for implementing N input nand gate, whereas previously proposed memristor-based stateful logic needs N + 1 steps. We validated the effectiveness of our solution through cadence spectre circuit simulator on a number of logic circuits. Finally, we extended this approach for arithmetic circuits with an 8-bit adder and a 4-bit multiplier.
TL;DR: In this article, a new high-output, flexible and transparent nanogenerator using chemical vapor deposition grown graphene as one of the friction layer is presented, which is low cost, simple, and robust approach for harvesting ambient vibration energy.
Abstract: This paper presents a new high-output, flexible and transparent nanogenerator using chemical vapor deposition grown graphene as one of the friction layer. Graphene on copper is transferred onto polyethylene terephthalate by wet transfer method makes graphene-based triboelectric nanogenerator (TENG) have electrical conductivity and high optical transmittance. We have fabricated plasma treated thin layer of polydimethylsiloxane structure as another layer to improve the output performance of nanogenerator. Using this graphene-based TENG, maximum output voltage 650 V and current 12 μA is achieved at 4.3 Hz frequency. As a power source, LCD and 50 commercial blue light-emitting diodes are lighted up. It is low cost, simple, and robust approach for harvesting ambient vibration energy.
TL;DR: In this paper, the performance of the current-mode signaling (CMS) scheme in carbon nanomaterial based multiwall carbon nanotube (MWCNT) bundle on-chip interconnect using finite-difference time-domain (FDTD) technique is investigated.
Abstract: The performance of current-mode signaling (CMS) scheme in carbon nanomaterial based multiwall carbon nanotube (MWCNT) bundle on-chip interconnect using finite-difference time-domain (FDTD) technique is investigated in the present paper. A very comprehensive model that analyzes both the traditional copper and the next-generation MWCNT bundle interconnects is presented. Further, this model is applicable for both the conventional voltage-mode signaling (VMS) and the delay-efficient CMS schemes. The number of MWCNT shells in a bundle interconnect is varied, and it is analyzed that MWCNTs with larger number of shells have better performance than both MWCNTs consisting of lesser number of shells and the copper interconnects. It is analyzed that CMS scheme has superior performance than VMS scheme in terms of smaller propagation delay and reduced crosstalk-induced delay. Various analyses have been performed for 32-nm technology node and are validated using SPICE simulations. The results obtained from the proposed FDTD based model and SPICE are found to be in close agreement, and the maximum error is within 3%.
TL;DR: Results indicate that HNTs are a promising carriers for polyphenol delivery and release, while curcumin is highly toxic for cancer cells.
Abstract: Halloysite is a nanostructured clay mineral with hollow tubular structure, which has recently found an important role as delivery system for drugs or other active molecules. One of these is curcumin, main constituent in the rhizome of the plant Curcuma Longa, with a series of useful pharmacological activities, hindered by its poor bioavalaibility and solubility in water. In this study, Halloysite clay nanotubes (HNTs) were characterized in terms of both structure and biocompatibility and they were used for curcumin delivery to cancer cells. The performed 3-(4, 5-dimethythiazol-2-yl)-2, 5-diphenyl-tetrazolium bromide (MTT) assay showed that HNTs have a high biocompatibility, also when coated with polymers, while curcumin is highly toxic for cancer cells. The release kinetics of curcumin from HNTs was investigated by the dialysis bag method, showing a slow and constant release of the drug, which can be further controlled by adding layers of polyelectrolytes to the external surface of the tubes. Successful polymer coating was followed by Zeta potential. The Trypan Blue assay showed a cytotoxic effect of loaded HNTs, proportional to the concentration of tubes and the incubation time. Successful HNTs uptake by breast cancer cells was demonstrated by Confocal Laser Scanning Microscopy images. All results indicate that HNTs are a promising carriers for polyphenol delivery and release.
TL;DR: In this article, the authors analyzed the frequency and intensity of ultrasound signals required to power an embedded nanosensor subject to medical safety limits, absorption by human tissue and reflection from interfaces.
Abstract: Embedded nanosensors will be a key feature of emerging medical monitoring systems. Power for these sensors could be harvested from ultrasonic vibrations generated by portable miniature sources and converted to electrical energy by piezoelectric nanowires. This letter analyzes the frequency and intensity of ultrasounds required to power an embedded nanosensor subject to medical safety limits, absorption by human tissue and reflection from interfaces. We calculate input and output power at different levels of energy conversion efficiency. Our analysis suggests that ultrasounds can be a viable source for energy harvesting of in-body nanosensors.
TL;DR: In this article, a semi-classical and a semiquantum current transport model for p-i-n n-type armchair graphene nanoribbon tunnel field effect transistor (TFET) is studied analytically.
Abstract: A semi-classical and a semi-quantum current transport model for p-i-n n-type armchair graphene nanoribbon tunnel field effect transistor (TFET) are studied analytically. The results are compared with the numerical quantum transport simulation method using an atomistic Schrodinger–Poisson solver within the non-equilibrium Green function (NEGF) formalism. The channel length and width are 20 and 4.9 nm and a-GNR band gap is 0.289 eV. Current ratio ${\rm I_{ON}}/{\rm I_{OFF}}$ at 0.1 V supply voltage is calculated as follows: 122, 16.3 and 116 with a subthreshold slopes 26, 69 and 27.4 mV/decade from semi-classical, semi-quantum and NEGF simulation, respectively. Performance of a-GNR TFET is also studied analytically and numerically considering a-GNR width variation. Voltage transfer characteristics of a-GNR TFET inverter are computed for 0.1 V and 0.2 supply voltages using three current transport models which are in close agreement.
TL;DR: Cheung et al. as discussed by the authors presented a comprehensive study on the electrical characteristics of Pt/ZnO thin film Schottky contacts fabricated on n-Si substrates by RF sputtering, and its application as a hydrogen sensor.
Abstract: This paper presents a comprehensive study on the electrical characteristics of Pt/ZnO thin film Schottky contacts fabricated on n-Si substrates by RF sputtering, and its application as a Hydrogen sensor. The basic structural, surface morphological, and optical properties of the ZnO thin film were also been explored. Pt/ZnO thin film junction was characterized using current–voltage (I–V) and capacitance–voltage (C–V) measurements at room temperature, exhibiting rectifying behavior with barrier height, ideality factor and series resistance of 0.71 eV (I–V) /0.996 eV (C–V), 2.5 and ∼95 Ω respectively. The lack of congruence between the values of Schottky barrier heights calculated from I–V and C–V measurements is interpreted. Cheung's method and modified Norde's functions were employed along with the conventional thermionic emission model, to incorporate the impact of series resistance in the calculation of diode parameters. We unveiled, the Hydrogen sensing characteristics displayed by the Pt/ZnO thin film-based sensor to different concentrations (200–1000 ppm) of Hydrogen at 350 °C. The sensor has exhibited good recoverable transient characteristics under a series of Hydrogen exposure cycles with a maximum sensitivity of 57% at 1000 ppm of Hydrogen.
TL;DR: In this paper, the authors discussed enhancements of solar energy conversion by photovoltaic (PV) cells using thermoelectric (TE) generators harvesting the heat released by the PV cell.
Abstract: This paper discusses enhancements of solar energy conversion by photovoltaic (PV) cells using thermoelectric (TE) generators harvesting the heat released by the PV cell. To optimize the TE–PV coupling, PV efficiency losses are analyzed by decoupling source- and absorber-dependent losses. This shows that the implementation of a tandem PV–TE device leads to a substantial increase of available power densities depending on the PV material. We further show that a major increase of the conversion efficiency can be achieved by adding an intermediate layer between the PV and the TE stage capable of absorbing the under-the-gap fraction of the solar spectrum. This increase of efficiency is discussed and commented upon also in view of the constraints PV–TE coupling imposes to the TE generator layout and to its material characteristics. The critical importance of effective heat dissipation will also be addressed. The conclusion is reached that not only could tandem PV–TE cells improve the conversion rate of existing solar cells but also that they could enable the use of lower cost PV materials, currently not considered because of their marginal PV efficiency.
TL;DR: In this paper, the authors proposed a spin circuit with spin Hall effect (SHE) and spin Hall magnetoresistance (SME) based on the diffusion equation, which can be used as a building block to analyze any arbitrarily shaped GSHE material.
Abstract: Spin circuits with four component voltages and currents have been developed and used in the past to analyze various structures, which include non-collinear ferromagnets. Recent demonstrations of large spin orbit torques in heavy metals like Pt, Ta, and W open up new possibilities in spintronic applications by providing an alternative way to write information into a magnet. Here, we extend the four component (one charge and three spins) conductance matrix to include materials with spin Hall effect based on the standard diffusion equation. Our proposed spin circuit successfully reproduces standard results like spin Hall effect (SHE), inverse spin Hall effect, and spin Hall magnetoresistance. This circuit representation also makes it straightforward to analyze new configurations. We present two examples, namely, 1) the possibility of spin injection using giant SHE (GSHE) materials into semiconductors without tunneling barriers, and 2) the effect of spin ground on one surface to enhance spin current injection from the opposite surface in a thin GSHE sample. Finally, we provide an elemental conductance matrix for a small cubic structure which can be used as a building block to analyze any arbitrarily shaped GSHE material.
TL;DR: An analog-to-stochastic converter using a magnetic tunnel junction (MTJ) device for vision chips based on stochastic computation and is designed in 90-nm CMOS and 100-nm MTJ technologies and verified using a SPICE simulator that handles both transistors and MTJ devices.
Abstract: This paper introduces an analog-to-stochastic converter using a magnetic tunnel junction (MTJ) device for vision chips based on stochastic computation. Stochastic computation has been recently exploited for area-efficient hardware implementation, such as low-density parity-check decoders and image processors. However, power-and-area hungry two-step (analog-to-digital and digital-to-stochastic) converters are required for the analog to stochastic signal conversion. To realize a one-step conversion, an MTJ device is used as it inherently exhibits a probabilistic switching behavior between two resistance states. Exploiting the device-based probabilistic behavior, analog signals can be directly and area efficiently converted to stochastic signals to mitigate the signal-conversion overhead. The analog-to-stochastic signal conversion is theoretically described and the conversion characteristic is evaluated using device and circuit parameters. In addition, the resistance variability of the MTJ device is considered in order to compensate the variability effect on the signal conversion. Based on the theoretical analysis, the analog-to-stochastic converter is designed in 90-nm CMOS and 100-nm MTJ technologies and is verified using a SPICE simulator (NS-SPICE) that handles both transistors and MTJ devices.
TL;DR: In this paper, the characterization efforts on resistive switching devices to date, with emphasis on direct transmission electron microscopy observations on conducting filament formation and growth dynamics, are discussed and challenges to be addressed and advances that are needed to further our understanding of dynamic ionic, electronic, and structural effects involved in the RS process.
Abstract: Characterizations of resistive switching (RS) devices, especially through direct, in situ methodologies, provide valuable information that could lead to improved insights into the device switching mechanism and device design and optimization. Here, we discuss the characterization efforts on resistive switching devices to date, with emphasis on direct transmission electron microscopy observations on conducting filament formation and growth dynamics. Other characterization techniques used in filament analysis such as spectroscopic and topographic characterizations will also be covered. In the end, we will discuss challenges to be addressed and advances that are needed to further our understanding of dynamic ionic, electronic, and structural effects involved in the RS process.
TL;DR: It is shown that the proposed simplified single-gate (SG) RFET achieves the same functionality and dc characteristics as the more complex DG-RFET, and has the additional advantage of being scalable to smaller channel length and thus achieving higher operating speed.
Abstract: Reconfigurable field-effect transistors (RFETs) are of interest as devices for dynamically switching between n- and p-type polarity which enables different logic computations using the same hardware. So far, RFETs have been realized with one or even two additional program gates for accomplishing reconfigurability. This paper presents an RFET design with just one single-gate on a silicon nanowire channel. Based on measured and device simulation data of a double-gate (DG) RFET, it is shown that the proposed simplified single-gate (SG) RFET achieves the same functionality and dc characteristics as the more complex DG-RFET. Besides reducing the wiring for the program gate(s), the SG-RFET has the additional advantage of being scalable to smaller channel length and thus achieving higher operating speed.
TL;DR: In this article, a distributed transmission line model of a mixed carbon nanotube bundle (MCB) built signal-ground-signal-type differential through silicon via (TSV) is established and validated against the multiconductor transmission line (MTL) results and predictive experiment results over a wide frequency range.
Abstract: Based on the extracted equivalent parasitic parameters, the distributed transmission line model of a mixed carbon nanotube bundle (MCB) built signal-ground-signal-type differential through silicon via (TSV) is established and validated against the multiconductor transmission line model (MTL) results and predictive experiment results over a wide frequency range. Using the proposed model, the effect of various dimensional parameters and material properties on the signal loss and characteristic impedances of the differential TSV interconnect is investigated for odd- and even-mode signal propagation, respectively. It is observed that dielectric thickness is the most important factor affecting the transmission characteristics of TSV interconnects for the proposed TSV configuration. Moreover, various electrical performances of the proposed differential TSV, such as insertion loss, eye opening area, characteristic impedances, and 50% time delay are evaluated and compared to that of a signal-ground-type single ended TSV interconnect. The results presented in this paper will be helpful to fully understand the CNT-TSV electrical characterization and provide some signal integrity-aware guidelines for circuit designers in early planning stage.
TL;DR: In this article, a comparative study of different nanogap-based FETs was conducted using numerical analysis to evaluate their performance metrics including response, sensitivity, detection limit, and dynamic range.
Abstract: A comparative study of biosensors based on a field effect transistor (FET) configuration is conducted using numerical analysis. A conventional back-gated device and three different nanogap-based structures are evaluated in terms of their performance metrics including response, sensitivity, detection limit, and dynamic range. An electrostatic model is used to address the sensing principle. The biochemical reaction is emulated simply by a change in the negative charge density and permittivity. The back-gated silicon nanoribbon FET (SiNR-FET) is used as a reference for comparison. The SiNR-FET is not affected by the permittivity change due to the biochemical reaction, whereas other nanogap-based structures are influenced by both the charge density and the permittivity shifts. Among the nanogap-based structures, a dielectric modulated FET (DM-FET) exhibits the widest dynamic range and a strong permittivity dependency. An underlap gate FET (UG-FET) and a fingered gate FET (FG-FET) show the highest sensitivity and detection limit. But the dynamic ranges of the UG-FET and FG-FET are narrower than that of the DM-FET. Nevertheless, by the nature of independent controllability of two gates, the FG-FET allows a tunable dynamic range. This comparative study offers application-specific guidelines for making appropriate choices for the sensor structure.
TL;DR: A thorough analysis of the clock signal added to the molecular QCA cell based on an ad hoc synthesized bisferrocene molecule is performed, demonstrating when and how much the presence of clock signal enhances or hinders the interactions between QCA molecules.
Abstract: Molecular quantum-dot cellular automata (mQCA) is found to be the most promising among all emerging technologies. It is expected to show remarkable operating frequencies (THz), high device densities, noncryogenic working temperature, and reduced power consumption. The computation relies on a new paradigm based on the interaction between nearby molecular QCA cells. This computation requires the aid of an external signal normally referred to as clock that enables/inhibits the molecular activity. The influence of clock on realistic molecules has never been deeply studied. In this paper, we performed a thorough analysis of the clock signal added to the molecular QCA cell based on an ad hoc synthesized bisferrocene molecule. Ab-initio simulations and further postprocessing of data have been used for characterizing the performance of bisferrocene molecule under the influence of a clock signal. Quantitative results on the molecule in terms of newly defined figures of merits, i.e., aggregated charge , equivalent voltage, and Vin-Vout trans-characteristic have been shown. Meanwhile, we demonstrate when and how much the presence of clock signal enhances or hinders the interactions between QCA molecules. These unprecedented data give a fundamental improvement to the knowledge on how information can be propagated through QCA devices. The results suggest directions to chemists, technologists, and engineers on how to proceed in the next steps for this promising technology.
TL;DR: In this article, the authors present an integration strategy to rationally design materials and processes to report flexible inorganic lithium-ion microbattery with no restrictions on the materials used, which shows an enhanced normalized capacity of 147μAh/cm2 when bent.
Abstract: Wearable electronics need miniaturized, safe, and flexible power sources. Lithium-ion battery is a strong candidate as high performance flexible battery. The development of flexible materials for battery electrodes suffers from the limited material choices. In this paper, we present integration strategy to rationally design materials and processes to report flexible inorganic lithium-ion microbattery with no restrictions on the materials used. The battery shows an enhanced normalized capacity of 147 μAh/cm2 when bent.
TL;DR: In this paper, the perovskite layer was grown using a two-step deposition technique, and the Bode analysis showed a bandwidth of 108 KHz with a high responsivity value of 0.35 A/W.
Abstract: Mesoscopic photodiodes were fabricated with hybrid organic/inorganic perovskite as absorber layer and Spiro-OMeTAD as hole transport Layer. The perovskite layer was grown using a two-step deposition technique. Our photodiode in addition to a good rectification behavior (three orders of magnitude, range −1 to 1 V) shows a small noise current (< 1 pA/(Hz)1/2), a high responsivity value (0.35 A/W) at 500 nanometers, and a good spectral response in the entire visible range. The Bode analysis shows a bandwidth of 108 KHz.
TL;DR: This paper presents the design of a pipelined Euclidean distance processor along with its various applications and develops a new model and methodology to design massively parallel memristor-CMOS hybrid datapath architectures at a system level.
Abstract: Continued dimensional scaling of CMOS processes is approaching fundamental limits and, therefore, alternate new devices and microarchitectures are explored to address the growing need of area scaling and performance gain. New nanotechnologies, such as memristors, emerge. Memristors can be used to perform stateful logic with nanowire crossbars, which allows for implementation of very large binary networks. This paper involves the design of a memristor-based massively parallel datapath for various applications, specifically single instruction multiple data and parallel pipelines. The innovation of our approach is that the datapath design is based on space-time diagrams that use stateful IMPLY gates built from binary memristors. The paper also develops a new model and methodology to design massively parallel memristor-CMOS hybrid datapath architectures at a system level. This methodology is based on an innovative concept of two interacting subsystems: 1) a controller composed of a memristive RAM, MsRAM, to act as a pulse generator, along with a finite-state machine realized in CMOS, a CMOS counter, CMOS multiplexers, and CMOS decoders; 2) massively parallel pipelined datapath realized with a new variant of a CMOL-like nanowire crossbar array, memristive stateful CMOL with binary stateful memristor-based IMPLY gates. In contrast to previous memristor-based FPGA, our proposed memristive stateful logic field programmable gate array uses memristors for both memory and combinational logic implementation. With a regular structure of square abutting blocks of memristive nanowire crossbars and their short connections, our architecture is highly reconfigurable. We present the design of a pipelined Euclidean distance processor along with its various applications. Euclidean distance calculation is widely used by many neural network and similar algorithms.
TL;DR: In this article, a new concept concerning dielectric engineering is presented aiming at a net improvement of the performance of Dielectric layers in RF MEMS capacitive switches with electrostatic actuation and an increase of their reliability.
Abstract: A new concept concerning dielectric engineering is presented in this study aiming at a net improvement of the performance of dielectric layers in RF MEMS capacitive switches with electrostatic actuation and an increase of their reliability. Instead of synthesis of new dielectric materials, we have developed a new class of dielectric layers that gain their performance from design rather than from composition. Two kinds of nanostructured dielectrics are presented. They consist of 1) silicon oxynitride layers (SiOxNy:H) with gradual variation of their properties (discrete or continuous) and 2) organosilicon (SiOxCy:H) and/or silica (SiO 2) layers with tailored interfaces; a single layer of silver nanoparticles (AgNPs) is embedded in the vicinity of the dielectric free surface. The nanostructured dielectric layers were deposited in a plasma process. They were structurally characterized and tested under electrical stress and environmental conditions typical for RF MEMS operation. The charge injection and decay dynamics were probed by Kelvin force microscopy. Modulation of the conductive properties of the nanostructured layers over seven orders of magnitude is achieved. Compared to dielectric monolayers, the nanostructured ones exhibit much shorter charge retention times. They appear to be promising candidates for implementation in RF MEMS capacitive switches with electrostatic actuation, and more generally for applications where surface charging must be avoided.