Channel Devices Research Articles

Identifying the Microscopic Nature of Two Level System Loss Channels in Acoustic Devices Using X-ray Photoelectron Spectroscopy and Atomic Force Microscopy.

Identifying the Microscopic Nature of Two Level System Loss Channels in Acoustic Devices Using X-ray Photoelectron Spectroscopy and Atomic Force Microscopy.

3D SRAM Macro Design in 3D Nanofabric Process Technology

In this paper, we introduce a novel design of a 3D static random-access memory (SRAM) macro in a 3D Nanofabric process technology. The 3D Nanofabric technology is based on enabling the processing of N stack of identical layers simultaneously regardless of the number of stacked layers which consequently reduces the fabrication cost as well as the footprint of SRAM macros. To enable simultaneous patterning of stacked layers, 3D Nanofabric requires circuit topology and layout that rely on a single layer where the device channel, poly, and metal wires are all embedded without any other crossing than the gate on top of the device channel. Accordingly, we modify the layouts of the conventional SRAM bit-cell and periphery circuits which are complex and contain several metal crossings. Furthermore, we propose a new overall organization of the 3D SRAM macro that incorporates a stack of multiple identical layers each consisting of an equal size 2D array of bit-cells and the periphery circuits. We show that the proposed 3D Nanofabric SRAM macro offers 71.2% footprint gain and 36.3% read access speed improvement compared to equal size 2D SRAM macro in 3 nm FinFET.

Numerical Analysis Study of The Effects of Backscattering Coefficient on Electrical Performance of Double-Gate nano-MOSFET

The simulated and computed electrical characteristics, with and without carriers backscattering, of 10 nm double-gate (DG) nano-MOSFET have been investigated and compared in this paper. The electrical parameters thus studied include Ballistic Enhancement Factor (BEF), on-state ballistic drain current Id, 2D electron density Qi and electron velocity v. BEF values with and without backscattering coefficients are 2.065 and 2.149, respectively because injection velocity reduced when considering backscattering. Average electron velocity near the beginning of the device channel has been found to reduce from 4.131x105 ms-1 to 1.186x105 ms-1 with the inclusion of backscattering phenomenon. The 2D electron density with and without backscattering coefficient are 3.927x1016 m-2 and 3.850x1016 m-2, respectively. The increment is because backscattered electrons and injected electrons superimposed and interfered with each other in the channel due to wave nature of electrons occurance in nanometer transistors. There are two current equations studied in this paper. The first one is based on flux-theory and the other one based on the product of electron concentration and electron velocity. The first method showed a current reduction from 2.548x103 μA/μm to 2.497x103 μA/μm. The second way also approximately showed reduction from 2.548x103 μA/μm to 2.497x103 μA/μm after minor modification in modeling. Both ways indicated that electrons are backscattered to the source by the potential barrier at the beginning of the channel and thereby reduced the number of electrons reaching the drain. In conclusion, backscattering is a physical phenomenon which can’t be ignored in describing electron transport in DG nano-MOSFETs.

Low-frequency noise in hBN/MoS2/hBN transistor at cryogenic temperatures toward low-noise cryo-CMOS device applications

As an application of cryo-CMOS technology for use in future quantum computing, we have explored low-frequency noise reduction in a two-dimensional (2D) system consisting of a molybdenum disulfide (MoS2) channel sandwiched by hexagonal boron nitride (hBN) layers. Due to the passivation effect of hBN layers, low-frequency noise in hBN/MoS2/hBN channel devices exhibited substantial reduction compared to the case of MoS2 channel directly on a silicon dioxide substrate and also silicon devices, suggesting that the clean interface of substrate and gate dielectric layers, as well as the protected surface of the MoS2 channel by hBN passivation from the damage by the fabrication process, contribute to the strong reduction in low-frequency noise. The results indicated that 2D materials are suitable for cryo-CMOS technology in terms of low-frequency noise since they will bring about mitigation of one of the most serious causes of quantum phase decoherence of qubits in future large-scale integrated quantum computers.

Optimization of Double-Gate Carbon Nanotube FET Characteristics for Short Channel Devices.

Transistors are the fundamental electronic component integrated into electronic devices' chips Carbon Nano Tube (CNT) based field. Effect Transistor (FET) is a promising component for next-generation transistor technologies; as it has high carrier mobility, device stability, and mechanical flexibility. Nevertheless, some shortcomings in the CNT FET's design prevent it from providing the best performance while preserving thermal stability. The structure and functionality of transistors with Double-Gate (DG) devices, which use carbon nanotubes as active channel regions, have been examined by the authors of this study. The DG CNT FET has been extensively simulated using an electronic device simulator with various device geometrics, including channel length, oxide thickness for its output, and transfer characteristics. In comparison to reported patents and published works, this demonstrates a significant improvement Conclusion: A new perspective on the DG CNT FET's device performance characteristics is provided by this research work, which can be scaled down to minimum channel length without Short Channel Effects (SCEs).

RSDFT-NEGF transport simulations in realistic nanoscale transistors

The paper presents a device simulator for computing transport characteristics from first principles. The developed computer program effectively performs large-scale parallel calculation of quasi-one-dimensional quantum transport in realistic nanoscale devices with thousands of atoms in the cross section area of the device channel. Our simulator is based on the real-space Kohn–Sham Hamiltonian in the density functional theory and improved numerical algorithms for reducing computational burden in non-equilibrium Green’s function (NEGF) method. Several computational improvements have been introduced in constructing a reduced quantum transport model from the original Kohn-Sham Hamiltonian and implementing the R-matrix computational scheme in the NEGF simulations.

Exciton annihilation in molecular aggregates suppressed through quantum interference.

Exciton-exciton annihilation (EEA), an important loss channel in optoelectronic devices and photosynthetic complexes, has conventionally been assumed to be an incoherent, diffusion-limited process. Here we challenge this assumption by experimentally demonstrating the ability to control EEA in molecular aggregates using the quantum phase relationships of excitons. We employed time-resolved photoluminescence microscopy to independently determine exciton diffusion constants and annihilation rates in two substituted perylene diimide aggregates featuring contrasting excitonic phase envelopes. Low-temperature EEA rates were found to differ by more than two orders of magnitude for the two compounds, despite comparable diffusion constants. Simulated rates based on a microscopic theory, in excellent agreement with experiments, rationalize this EEA behaviour based on quantum interference arising from the presence or absence of spatial phase oscillations of delocalized excitons. These results offer an approach for designing molecular materials using quantum interference where low annihilation can coexist with high exciton concentrations and mobilities.

Exploration of effects of gate underlap in HOI FinFETs at 10 nm gate length

With sub-22 nm technology nodes, the short channel effects (SCEs) arose in FinFETs, which hindered the further scaling of devices. The leakage currents became detrimental with scaling of the gate oxide thickness below 2 nm, hence the demand for control of leakage currents due to corner effects in the sidewalls of FinFETs. Research suggested use of gate underlap (GUL) architectures to suppress the leakage currents. The objective of this paper is to utilize a GUL structure in a 10 nm gate length Heterostructure-On-Insulator (HOI) FinFET, encompassing a three layered strained channel architecture to enrich the drive currents. Different structures with GUL lengths of 1 nm, 3 nm and 5 nm are designed to study the electrical characteristics besides the effects of leakage currents and other SCEs. A noteworthy decrease is observed in the leakage currents with increasing GUL lengths. However, it also leads to decrease of drive currents of the devices. A trade-off between the enhanced dimensions of source/drain along with an optimized GUL length proves beneficial in the strained silicon channel devices. The 10 nm HOI device employing a 3 nm GUL with height/width of source/drain at 8 nm provides drive currents and leakage currents at par with the 10 nm HOI device with no underlap. But with higher Ion/Ioff current ratio and lower SCEs, this device with 3 nm underlap decreases corner effects and is observed from the electron velocity and total current density contours leading to faster switching speeds and optimized device performance towards semiconductor industry.

Nuclear segmentation facilitates neutrophil migration.

Neutrophils are among the fastest-moving immune cells. Their speed is critical to their function as 'first responder' cells at sites of damage or infection, and it has been postulated that the unique segmented nucleus of neutrophils functions to assist their rapid migration. Here, we tested this hypothesis by imaging primary human neutrophils traversing narrow channels in custom-designed microfluidic devices. Individuals were given an intravenous low dose of endotoxin to elicit recruitment of neutrophils into the blood with a high diversity of nuclear phenotypes, ranging from hypo- to hyper-segmented. Both by cell sorting of neutrophils from the blood using markers that correlate with lobularity and by directly quantifying the migration of neutrophils with distinct lobe numbers, we found that neutrophils with one or two nuclear lobes were significantly slower to traverse narrower channels, compared to neutrophils with more than two nuclear lobes. Thus, our data show that nuclear segmentation in primary human neutrophils provides a speed advantage during migration through confined spaces.

Amplitude Measurements With SiPM and ASIC (Citiroc 1A) Front-End Electronics

The use of Application Specific Integrated Circuits (ASICs) in nuclear physics instrumentation is drastically increasing, thanks to the possibility of incorporating a large number of acquisition channels in compact devices. In this paper, we describe a SiPM-based application with CAEN Front-End Readout System [1] based on Citiroc 1A chip from Weeroc [2]. Besides the use of this chip for well known single photon spectra and event counting, this paper exploits the possibility to acquire energy spectra directly from scintillators, paired with SiPM, through peak-and-hold readout. In particular, good energy resolutions have been achieved even with slow scintillators, like LYSO, CsI(Tl), and BGO, which have 40 ns, 1000 ns, and 300 ns of light decay time, respectively. These values are of the same order of magnitude of the shaping time of the Citiroc 1A chip (maximum value of 87.5 ns) in the case of LYSO, and higher in the case of CsI(Tl) and BGO. Several measurements have been performed using multiple radioactive γ sources and the resulting energy spectra demonstrate a resolution compatible with that found in literature [4] [5] [6] [7], as well as with an alternative acquisition system based on a digitizer that implements an algorithm of Charge Integration in the FPGA [8].

Statistical Device Activity Detection for OFDM-Based Massive Grant-Free Access

Existing works on grant-free access, proposed to support massive machine-type communication (mMTC) for the Internet of things (IoT), mainly concentrate on narrow band systems under flat fading. In contrast, this paper investigates massive grant-free access in a wideband system under frequency-selective fading. First, we present an orthogonal frequency division multiplexing (OFDM)-based massive grant-free access scheme. Then, we propose two different but equivalent models for the received pilot signal. Specifically, one directly models the received signal for actual devices, whereas the other can be interpreted as a signal model for virtual devices. The two signal models are insightful and essential for designing various device activity detection and channel estimation methods for OFDM-based massive grant-free access. Next, we systematically investigate statistical device activity detection under frequency-selective Rayleigh fading based on the two signal models. In particular, in the case without prior knowledge of device activities, we model device activities as deterministic but unknown binary constants and propose three maximum likelihood (ML) estimation-based device activity detection methods with different detection accuracies and computation times. In the case with prior knowledge of device activities, we model device activities as realizations of Bernoulli random variables with a known joint distribution, which appropriately incorporates the prior knowledge, and propose three maximum a posterior probability (MAP) estimation-based device activity methods, which further enhance the accuracies of the corresponding ML estimation-based methods at the cost of increased computational complexities. The proposed methods can meet diverse practical needs for OFDM-based massive grant-free access.

Energy Constrained Sum-Rate Maximization in IRS-Assisted UAV Networks With Imperfect Channel Information

The focus of this work is maximizing the sum-rate of wireless unmanned aerial vehicle (UAV) networks with intelligent reflecting surfaces (IRS) in the presence of system practical limitations. More specifically, we consider that the phase compensation at the IRS is imperfect due to various factors such as device imperfections and channel estimation errors. Moreover, we consider that the IRS elements have limited switching frequency, which limits the possibility of being allocated to different UAVs over consecutive time slots when time-division multiple access (TDMA) is considered. To this end, we formulate an optimization problem where the objective is to maximize the network sum-rate subject to total energy and quality-of-service (QoS) constraints by optimizing the number of IRS elements and power allocated to each UAV. To solve the optimization problem, a low-complexity heuristic algorithm is proposed based on the quality of the estimated phase for each IRS element. The proposed approach is compared to benchmark techniques such as the uniform allocation process and genetic algorithm. The obtained results show that a significant sum-rate improvement of up to 45% can be gained using the proposed algorithm.

Coherent magnon-induced domain-wall motion in a magnetic insulator channel.

Advancing the development of spin-wave devices requires high-quality low-damping magnetic materials where magnon spin currents can efficiently propagate and effectively interact with local magnetic textures. Here we show that magnetic domain walls can modulate spin-wave transport in perpendicularly magnetized channels of Bi-doped yttrium iron garnet. Conversely, we demonstrate that the magnon spin current can drive domain-wall motion in the Bi-doped yttrium iron garnet channel device by means of magnon spin-transfer torque. The domain wall can be reliably moved over 15-20 µm distances at zero applied magnetic field by a magnon spin current excited by a radio-frequency pulse as short as 1 ns. The required energy for driving the domain-wall motion is orders of magnitude smaller than those reported for metallic systems. These results facilitate low-switching-energy magnonic devices and circuits where magnetic domains can be efficiently reconfigured by magnon spin currents flowing within magnetic channels.

Disaster Management of Flood and Retaintion Techniques

Abstract: The most frequent and destructive type of natural disaster, floods annually have an impact on the lives of tens of millions of people all over the world. Climate change and increased climate variability were predicted to result in more frequent and intense floods in the past. Growing demands for channels are being made in order to reduce severe rural flooding by effecting a significant amount of additional storm runoff. This investigation intends to assess how well a deep channel device proposed for Kolhapur’s historic centre will reduce flooding. In order to lessen the devastating effects of floods and regularly make the area more flood-proof, we will lower the flood force at the downstream aspect by providing a suitable channel of a specified sort of size.

Energy‐Efficient Operation Conditions of MoS2‐Based Memristors

Sufficient energy consumption for conventional information processing makes it necessary to look for new computational methods. One of the possible solutions to this problem is neuromorphic computations using memristive devices. Memristors based on molybdenum disulfide () are a promising way to provide a sizeable amount of hysteresis at low energy costs. Herein, different configurations of memristors as well as the mechanisms involved in hysteresis formation are shown. Bottom gated configuration is beneficial in terms of hysteresis area and energy efficiency. The impact of device channel dimensions on the hysteresis area and energy consumption is discussed. Different operation conditions with triangular, rectangular, sinusoidal, and sawtooth drain‐to‐source pulses are simulated, and rectangular pulses demonstrate the highest energy efficiency. The study shows the potential to realize low‐power neuromorphic systems using memristive devices.

Low-Cost Electroencephalographic Recording System Combined with a Millimeter-Sized Coil to Transcranially Stimulate the Mouse Brain In Vivo.

A low-cost electroencephalographic (EEG) recording system is proposed here to drive transcranial magnetic stimulation (TMS) of the mouse brain in vivo, utilizing a millimeter-sized coil. Using conventional screw electrodes combined with a custom-made, flexible, multielectrode array substrate, multi-site recording can be carried out from the mouse brain. In addition, we explain how a millimeter-sized coil is produced using low-cost equipment usually found in laboratories. Practical procedures for fabricating the flexible multielectrode array substrate and the surgical implantation technique for screw electrodes are also presented, which are necessary to produce low-noise EEG signals. Although the methodology is useful for recording from the brain of any small animal, the present report focuses on electrode implementation in an anesthetized mouse skull. Furthermore, this method can be easily extended to an awake small animal that is connected with tethered cables via a common adapter and fixed with a TMS device to the head during recording.The present version of the EEG-TMS system, which can include a maximum of 32 EEG channels (a device with 16 channels is presented as an example with fewer channels) and one TMS channel device, is described. Additionally, typical results obtained by the application of the EEG-TMS system to anesthetized mice are briefly reported.

Monolayer MoS2 synaptic devices synergistically modulated by Na+ ions and sulfur vacancies for neuromorphic computing and pain perception stimulation

Ion based synaptic devices (ISDs) are one of the excellent candidates for neuromorphic computing. However, most of ISDs utilized additional ion sources to supply ions for adjusting the conductance of the device channel, which might hinder the large-scale integration for fabricating hierarchical artificial neural network. Here a high-performance monolayer MoS2 ISD is demonstrated using Na+ ions doped in MoS2 lattice as ion sources. Benefited from the Na+ ions and S vacancy defects in the MoS2 lattice, the device not only exhibits various synaptic plasticity (long- and short-term plasticity) and typical biological features (pain-perceptual nociceptors and associative learning), but also has a low synaptic event response voltage (100 mV) and a low energy consumption (0.92 pJ) for a synaptic event. A dissociation-adsorption-migration-binding model is proposed to elaborate the resistance switching mechanism, which is corroborated by density functional theory calculations and characterizations. In addition, an artificial neural network (ANN) based on MoS2 ISDs is simulated for the recognition of the MNIST handwritten digits. The deviation of the recognition accuracy is less than 8% compared to the ideal floating-point numeric precision. These results provide a new strategy for fabricating high-performance ISDs for neuromorphic computing.

His bundle pacing: 10-years follow-up

Abstract Funding Acknowledgements Type of funding sources: None. Background His bundle pacing (HBP) ensures a physiologic ventricular activation and can prevent pacing-induced cardiomyopathy. Published experiences confirm good clinical results on short-term follow-up. Data on long-term follow-up are still lacking Objective analyze clinical and technical results of HBP in an unselected population during a very long-term follow-up. Methods We retrospectively analyzed 370 patients (mean age 75±8 years; 221 males) with standard indication for pacing implanted with HBP from 2003 to 2012. In all cases the HBP implant was performed by lumenless fixed screw 3830 Medtronic and deflectable sheath C304. In 52% cases selective-HBP was obtained while 48% was non selective-HBP. The indications for pacing were AV block in 51%, sinus node disease in 22%, atrial fibrillation with slow ventricular rate in 25%, heart failure in 2%. Ischemic cardiopathy was found in 84 patients (29%); hypertension in 317 patients (86%) and diabetes in 108 patients (29%). Pre-implant QRS duration was 119±30 ms and basal mean EF 57±11%. The Hisian lead was inserted in ventricular port of a CRT-P device in 162 (44%) patients, in the atrial port of a DR device in 183 (49%) patients, and in the only channel of a SR device in 25 (7%) patients. A back-up standard lead was implanted in right ventricular apex or septum in 203 (55%) patients. Results All patients were followed by ambulatory check once a year. 124 (34%) patients reached 10 years follow-up (mean 12.3 ±1.8 years). At the end of follow-up, the mean EF was 61±8% (P=NS) and the mean paced QRS duration 123 ± 27 (P=NS). 10 (8%) patients had heart failure hospitalizations. 26 (21%) died after a mean of 12.1 ±1.7 years. From a technical point of view, 99 (80%) patients showed a good performance of the HBP lead at the last follow-up while 25 (20%) patients experienced lead-related problems: 20 (16%) had issues related to HBP lead (2 cases of severe HBP malfunction required hospitalization due to syncope) and 5 (4%) had malfunction of the back-up lead. The mean longevity of the devices was 6.6 ±2.6 years and each patient had 1.5 ±0.8 replacements. It was required to add a back up catheter in 3.6% of patients. The remaining 205 patients completed a mean follow-up of 6.3±2.7 years while 41(11%) patients were lost at follow-up (died within the first month post-implant or checked in other centres). Conclusion HBP is safe and feasible in the clinical practice. The system maintains a good performance during a long-term follow-up and ensures a physiologic ventricular contraction thus allowing good clinical outcome. The EF and QRS duration remain in normal values.

Design Technology Co-Optimization Strategy for Ge Fraction in SiGe Channel of SGOI FinFET.

FinFET devices and Silicon-On-Insulator (SOI) devices are two mainstream technical routes after the planar MOSFET reached the limit for scaling. The SOI FinFET devices combine the benefits of FinFET and SOI devices, which can be further boosted by SiGe channels. In this work, we develop an optimizing strategy of the Ge fraction in SiGe Channels of SGOI FinFET devices. The simulation results of ring oscillator (RO) circuits and SRAM cells reveal that altering the Ge fraction can improve the performance and power of different circuits for different applications.

Impact of fin width on nano scale tri-gate FinFET including the quantum mechanical effect

An inversion charge-based threshold voltage model is proposed for 10 nm channel length Tri-gate (TG) FinFET. The variation threshold voltage has been studied with respect to fin width for different fin height and channel length The effect of width quantization has been explained with the help of the quantum mechanical effect (QME). A precise comparison of threshold voltage in terms of classical mechanics and quantum mechanics depicts the presence of width quantization in short channel device. The improvement of the short channel effects (SCEs), like subthreshold swing (SS), drain-induced barrier lowering (DIBL) and threshold voltage roll off have been studied. The impact of channel length to fin width ratio on DIBL and has been examined. The improvement of the SCEs at the same oxide thickness has been observed for high-k dielectric material. The potential and effect of hafnium oxide (HfO2) have been discussed and validated using technology computer-aided design (TCAD) simulation.