Next-generation Circuits Research Articles

Design and Evaluation of a New Nanoscale and Cost-Efficient Coplanar Digital Parity Generator Based on Quantum Dots

A parity generator as a combinational logic circuit in digital circuits can generate the parity bit in the transmitter. It is very applicable in digital networking and communications. Also, rather than diodes and transistors, quantum dots will be used in the next-generation circuits. Quantum-dot Cellular Automata (QCA) offers a new platform where binary data is represented by polarized cells that are defined by the electron configurations. Therefore, a coplanar 4-bit parity generator is suggested in this work. This new arrangement eliminates complicated crossovers and provides complete access to all input and output pins. An XOR gate is used to implement the suggested architecture. Simulation waveforms and performance data confirm the proposed circuits’ functioning and advantages. The suggested four-bit parity generator uses less overhead than its equivalents. We simulated and tested the suggested circuit with the assistance of the QCADesigner 2.0.3 simulator. The QCADesigner software findings demonstrate that the suggested design is simpler and less expensive than earlier designs. Compared to the present best design, the suggested four-bit parity generator reduces cell number and latency by 55.29% and 40%, respectively.

Wafer-Scale Demonstration of MBC-FET and C-FET Arrays Based on Two-Dimensional Semiconductors.

Two-dimentional semiconductors have shown potential applications in multi-bridge channel field-effect transistors (MBC-FETs) and complementary field-effect transistors (C-FETs) due to their atomic thickness, stackability, and excellent electrical properties. However, the exploration of MBC-FET and C-FET based on large-scale 2D semiconductors is still lacking. Here, based on a reliable vertical stacking of wafer-scale 2D semiconductors, large-scale MBC-FETs and C-FETs using n-type MoS2 and p-type MoTe2 are successfully fabricated. The drive current of an MBC-FET with two layers of MoS2 channel (20µm/10µm) is up to 60µA under 1V bias. Compared with the single-gate MoS2 FET, the carrier mobility of MBC-FET is 2.3 times higher and the sub-threshold swing is 70% smaller. Furthermore, NAND and NOR logic circuits are also constructed based on two vertically stacked MoS2 channels. Then, C-FET arrays are fabricated by 3D integrating n-type MoS2 FET and p-type MoTe2 FET, which exhibit a voltage gain of 7V/V when VDD = 4V. In addition, this C-FET device can directly convert light signals to an electrical digital signal within a single device. The demonstration of MBC-FET and C-FET based on large-scale 2D semiconductors will promote the application of 2D semiconductors in next-generation circuits.

ISSCC Special Event 2: Next-Generation Circuit Designer Workshop [Conference Reports

ISSCC Special Event 2: Next-Generation Circuit Designer Workshop [Conference Reports

Highly stretchable and durable fibrous strain sensor with growth ring-like spiral structure for wearable electronics

Wearable strain sensors promote various emerging intelligent fields. Compared with the planar strain sensors, fibrous strain sensors are highly desirable for practical applications because they are favour of conformably attaching onto uneven surfaces and integrating into regular fabrics. Herein, inspired by the growth ring of tree, a highly stretchable silver nanowire/polydimethylsiloxane based fibrous strain sensor with spiral structure was innovatively prepared by cost-efficient coating plus rolling up technique. This unique spiral structure endowed the fibrous strain sensor with wide sensing range of 100% strain, outstanding linearity, gauge factor of 3.0, negligible hysteresis, and excellent reliability. Thanks to these superior characteristics, our sensor can not only accurately detect human movements when being attached to joints directly or woven in a cotton glove but also control the brightness of bulb when being connected into a circuit, showing great potential for wearable sensing electronics and next-generation circuit control elements. This work paves a promising way for the development of high-performance fibrous strain sensor.

Vortex Domain Walls in Ferroelectrics.

Controlling the domain formation in ferroelectric materials at the nanoscale is a fertile ground to explore emergent phenomena and their technological prospects. For example, charged ferroelectric domain walls in BiFeO3 and ErMnO3 exhibit significantly enhanced conductivity which could serve as the foundation for next-generation circuits (Estévez and Laurson, Phys. Rev. B 2015, 91, 054407). Here, we describe a concept in which polar vortices perform the same role as a ferroelectric domain wall in classical domain structures with the key difference being that the polar vortices can accommodate charged (i.e., head-to-head and tail-to-tail) domains, for example, in ferroelectric PbTiO3/dielectric SrTiO3 superlattices. Such a vortex domain wall structure can be manipulated in a reversible fashion under an external applied field.

Atomic-Scale Studies of Overlapping Grain Boundaries between Parallel and Quasi-Parallel Grains in Low-Symmetry Monolayer ReS2

Summary Grain boundaries (GBs) are significant microstructures that dominate properties of polycrystalline two-dimensional (2D) materials. Low-symmetry rhenium disulfide monolayers provide an ideal platform to investigate diverse configurations of GBs and their orientation-dependent characteristics. Here, we utilize the preferential deposition of platinum-based nanoparticles on grain edges to rapidly locate nanoscale-wide overlapping GBs during microscopic-scale observation. Atomic-resolution investigations by aberration-corrected annular dark-field scanning transmission electron microscopy reveal diverse overlapping GBs constructed by parallel grains with transversal displacement. They prefer to align along several primary lattice directions with different interlayer atomic registries. Calculations show that the electronic band structures of overlapping GBs are strongly direction dependent, suggesting their potential in tunable electronic and photonic devices. Incommensurate overlapping GBs formed by quasi-parallel grains with ultrasmall twist angles are also observed. These results unveil the rich polymorphism of GBs and new opportunities to tailor properties of anisotropic 2D materials via GB engineering.

Intrinsic Ultrahigh Negative Poisson's Ratio in Two-Dimensional Ferroelectric ABP<sub>2</sub>X<sub>6</sub> Materials

Recently, ferroelectric materials have attracted considerable research attention. In particular, two dimensional (2D) ferroelectric materials have been considered as most crucial for nextgeneration circuit designs because of their application as novel electric memory devices. However, a 2D ferroelectric material is very rare. The ferroelectric materials with the form ABP2X6 (A = Ag, Cu; B = Bi, In; X = S, Se) are of interest because of their ferroelectric property maintained in their ultrathin structures. Within the ABP2X6 monolayer, the P—P bonds form the pillars that hold the top and bottom X planes, while the off-center A—B atoms between the X layers induce a spontaneous ferroelectric polarization. If the two off-center A—B sites are equally aligned, this would lead to the appearance of the paraelectric state. Such intriguing structures must impart novel mechanical properties to the materials. Until now, there has been no report on the mechanical properties of monolayer ABP2X6. Based on first-principles calculations, we studied the structural, electronic, mechanical as well as the electromechanical coupling properties of monolayer ABP2X6 (A = Ag, Cu; B = Bi, In; X = S, Se). We found that they are all semiconductors with wide bandgaps of 2.73, 2.17, 3.00, and 2.31 eV for CuInP2Se6, CuBiP2Se6, AgBiP2Se6, and AgBiP2Se6, respectively, which are calculated based on the Heyd-Scuseria-Ernzerhof (HSE) exchange correlation functional model. The conduction band minimum is mainly from p orbitals of X and B atoms, whereas the valence band maximum is due to the hybridization of the p orbital of X atoms and the d orbital of A atoms. Moreover, there are three short and three long A/B—X bonds due to the A—B offcenter displacement. Together with the d-p orbital hybridization, the main reason for the distorted ferroelectric structure in ABP2X6 monolayers is the Jahn-Teller effect. ABP2X6 monolayers are predicted to be a new class of auxetic materials with an out-of-plane negative Poisson’s ratio, i.e., the values of the negative Poisson’s ratio are in the order AgBiP2S6 (−0.805)

Nanopackaging for Component Assembly and Embedded Power in Flexible Electronics: Heterogeneous Component Integration for Flexible Systems

The trends to high-density, ultrathin, and low-cost electronic systems are currently changing the face of the mobile, security, health-care, and automotive industries. Providing a flexible platform extends the applicability of these next-generation circuits to smart displays, conformal sensors, Internet of Things (IoT) tags, remote health-monitoring systems, radar and millimeter (mm)-wave electronics, among others. As a result, the total market for f lexible, organic, and printed electronics is projected to grow from close to US$30 billion in 2017 to approximately US$75 billion in 2027 [1]. Major applications that drive the field of flexible and printed electronics are illustrated in Figure 1.

Exploring Two-Dimensional Materials toward the Next-Generation Circuits: From Monomer Design to Assembly Control.

Two-dimensional (2D) materials have attracted tremendous research interest since the breakthrough of graphene. Their unique optical, electronic, and mechanical properties hold great potential for harnessing them as key components in novel applications for electronics and optoelectronics. Their atomic thickness and exposed huge surface even make them highly designable and manipulable, leading to the extensive application potentials. What's more, after acquiring the qualification for being the candidate for next-generation devices, the assembly of 2D materials monomers into mass or ordered structure is also of great importance, which will determine their ultimate industrialization. By designing the monomers and regulating their assembling behavior, the exploration of 2D materials toward the next-generation circuits can be spectacularly achieved. In this review, we will first overview the emerging 2D materials and then offer a clear guideline of varied physical and chemical strategies for tuning their properties. Furthermore, assembly strategies of 2D materials will also be included. Finally, challenges and outlooks in this promising field are featured on the basis of its current progress.

High-brightness Cs focused ion beam from a cold-atomic-beam ion source

We present measurements of focal spot size and brightness in a focused ion beam system utilizing a laser-cooled atomic beam source of Cs ions. Spot sizes as small as (2.1 ± 0.2) nm (one standard deviation) and reduced brightness values as high as (2.4 ± 0.1) × 107 A m−2 Sr−1 eV−1 are observed with a 10 keV beam. This measured brightness is over 24 times higher than the highest brightness observed in a Ga liquid metal ion source. The behavior of brightness as a function of beam current and the dependence of effective source temperature on ionization energy are examined. The performance is seen to be consistent with earlier predictions. Demonstration of this source with very high brightness, producing a heavy ionic species such as Cs+, promises to allow significant improvements in resolution and throughput for such applications as next-generation circuit edit and nanoscale secondary ion mass spectrometry.

Centimeter-sized epitaxial h-BN films

We report the growth and transfer of centimeter-sized, epitaxial hexagonal boron nitride (h-BN) few-layer films using Ni(111) single-crystal substrates. The h-BN films were heteroepitaxially grown on 10 × 10 mm2 or 20 × 20 mm2 Ni(111) substrates using atmospheric pressure chemical vapor deposition with a single ammonia-borane precursor. The grown films were transferred to arbitrary substrates via an electrochemical delamination technique, and the remaining Ni(111) substrates were repeatedly re-used. A careful analysis of the growth parameters revealed that the crystallinity and area coverage of the h-BN films were mostly sensitive to the sublimation temperature of the ammonia-borane source. Moreover, various physical characterizations confirmed that the grown films exhibited the typical characteristics of hexagonal boron nitride layers over the entire area. Furthermore, the heteroepitaxial relationship between h-BN and Ni(111) and the overall crystallinity of the film were thoroughly investigated using a synchrotron radiation X-ray diffraction analysis including θ–2θ scans, grazing incident diffraction, and reciprocal space mapping. The crystallinity at the microscopic scale was further investigated using transmission electron microscopy (TEM)-based techniques, including selective area electron diffraction pattern mapping, electron back-scattered diffraction, and high-resolution TEM. Transparent and flexible ceramic films for electronic devices can now be made at centimetre scales by a low-cost technique. Hexagonal boron nitride (h-BN) crystals are attractive platforms for building next-generation circuits because their flat, graphite-like surfaces resist mechanical and chemical damage while offering excellent signal isolation. Gyu-Chul Yi from Seoul National University and colleagues have developed a way to improve large-scale manufacturing of these films using a reusable nickel template. Nickel has a surface structure that helps h-BN films grow with high crystallinity following chemical vapor deposition, but detaching the resulting ceramic layer has always proved troublesome. The Korean team solved this problem through an electrochemical delamination process that seamlessly separates h-BN films with dimensions up to 20 × 20 square millimetres using a stream of hydrogen bubbles. Centimeter-sized, epitaxial hexagonal boron nitride (h-BN) few-layer films were heteroepitaxially grown on Ni(111) single-crystal substrates using atmospheric pressure chemical vapor deposition with ammonia-borane single precursor. The grown films were transferred to arbitrary substrates via an electrochemical delamination technique, and the remaining Ni(111) substrates were repeatedly re-used. Over repeated growth and transfer after the initial annealing, no significant degradation of Ni(111) substrates was observed and the crystallinity of h-BN layers was reproduced reliably. The grown h-BN films showed typical physical characteristics of h-BN, with a high uniformity over a wide area. The large-area synthesis and transfer of atomically thin uniform epitaxial h-BN layers can be applied in various fields where high quality two-dimensional insulating layers are required.

Nanoplasmonic waveguides: towards applications in integrated nanophotonic circuits

The properties of propagating surface plasmon polaritons (SPPs) along one-dimensional metal structures have been investigated for more than 10 years and are now well understood. Because of the high confinement of electromagnetic energy, propagating SPPs have been considered to represent one of the best potential ways to construct next-generation circuits that use light to overcome the speed limit of electronics. Many basic plasmonic components have already been developed. In this review, researches on plasmonic waveguides are reviewed from the perspective of plasmonic circuits. Several circuit components are constructed to demonstrate the basic function of an optical digital circuit. In the end of this review, a prototype for an SPP-based nanochip is proposed, and the problems associated with building such plasmonic circuits are discussed. A plasmonic chip that can be practically applied is expected to become available in the near future. The prospects for creating sophisticated nanophotonic circuits by harnessing the opportunities provided by plasmonics are exciting. Yurui Fang and Mengtao Sun from the Beijing National Laboratory for Condensed Matter Physics review recent progress in the development of various components and devices for generating, manipulating and detecting surface plasmon polaritons — tightly confined waves that can be excited by light at the interface between a metal and a dielectric. Their small size offers opportunities for constructing photonic devices that are smaller than the wavelength of light, a major barrier to the miniaturization of optical integrated circuits. Fang and Sun describe how nanoscale waveguides, multiplexers, lasers, high-speed modulators, logic gates and detectors for surface plasmon polaritons are all coming to fruition. They also consider the future prospects of this technology.

Biomedically relevant circuit‐design strategies in mammalian synthetic biology

The development and progress in synthetic biology has been remarkable. Although still in its infancy, synthetic biology has achieved much during the past decade. Improvements in genetic circuit design have increased the potential for clinical applicability of synthetic biology research. What began as simple transcriptional gene switches has rapidly developed into a variety of complex regulatory circuits based on the transcriptional, translational and post-translational regulation. Instead of compounds with potential pharmacologic side effects, the inducer molecules now used are metabolites of the human body and even members of native cell signaling pathways. In this review, we address recent progress in mammalian synthetic biology circuit design and focus on how novel designs push synthetic biology toward clinical implementation. Groundbreaking research on the implementation of optogenetics and intercellular communications is addressed, as particularly optogenetics provides unprecedented opportunities for clinical application. Along with an increase in synthetic network complexity, multicellular systems are now being used to provide a platform for next-generation circuit design.

Circuit development using biological components: Principles, models and experimental feasibility

Today most VLSI circuits are built in silicon using CMOS transistors. Developments in design automation and process fabrication have resulted in the progressive increase of the number of transistors per chip and decrease in the size of the transistors. But transistor designers are fast approaching fundamental physical barriers to further size reduction. Thus engineers are looking at alternate technologies such as nano-devices and bio-circuits for next-generation circuits. In our research, we concentrate on the development of bio-circuits and their applications. Our eventual goal is the design and simulation of complete systems integrating bio-circuits and VLSI technology appropriately. Bio-circuits are circuits developed in vivo or in vitro, using DNA and proteins. A biological process such as glycolysis or bioluminescence can be viewed as a genetic regulatory circuit, a complex set of bio-chemical reactions regulating the behavior of genes, operons, DNA, RNA, and proteins. Similar to voltage in an electrical circuit, a genetic regulatory circuit produces an output protein in response to an input stimulus. We can engineer bio-circuits to meet design specifications, using genetic engineering. Our aim is to build a library of in vitro bio-circuits representing the Boolean functions. The bio-circuits from this library can be further cascaded to form larger circuits. In this paper, we review the feasibility of building bio-circuits. We discuss the construction of Boolean logic gates such as NOT, AND, and OR and their verification by simulation. We also address important aspects such as cascading of the bio-circuits and practical implementation. In addition, we describe an algorithm “Box” that can help to control bio-circuit characteristics such as gain and switching behavior. This approach is similar to design space exploration in traditional VLSI, but takes into account biological knowledge obtained through experiments. We also provide insight into the robustness of bio-circuits in the presence of noise. This paper is intended to pave the pathway for electrical engineers to start exploring the field of bio-circuits.

A 6-GHz integrated phase-locked loop using AlGaAs/GaAs heterojunction bipolar transistors

A fully integrated 6-GHz phase-locked-loop (PLL) fabricated using AlGaAs/GaAs heterojunction bipolar transistors (HBTs) is described. The PLL is intended for use in multigigabit-per-second clock recovery circuits for fiber-optic communication systems. The PLL circuit consists of a frequency quadrupling ring voltage-controlled oscillator (VCO), a balanced phase detector, and a lag-lead loop filter. The closed-loop bandwidth is approximately 150 MHz. The tracking range was measured to be greater than 750 MHz at zero steady-state phase error. The nonaided acquisition range is approximately 300 MHz. This circuit is the first monolithic HBT PLL and is the fastest yet reported using a digital output VCO. The minimum emitter area was 3 mu m*10 mu m with f/sub t/=22 GHz and f/sub max/=30 GHz for a bias current of 2 mA. The speed of the PLL can be doubled by using 1- mu m*10- mu m emitters in next-generation circuits. The chip occupies a die area of 2-mm*3-mm and dissipates 800 mW with a supply voltage of -8 V. >