Large Device Research Articles

Recursive Green’s functions optimized for atomistic modelling of large superlattice-based devices

Recursive Green’s functions optimized for atomistic modelling of large superlattice-based devices

Evidence for the utility of quantum computing before fault tolerance

Quantum computing promises to offer substantial speed-ups over its classical counterpart for certain problems. However, the greatest impediment to realizing its full potential is noise that is inherent to these systems. The widely accepted solution to this challenge is the implementation of fault-tolerant quantum circuits, which is out of reach for current processors. Here we report experiments on a noisy 127-qubit processor and demonstrate the measurement of accurate expectation values for circuit volumes at a scale beyond brute-force classical computation. We argue that this represents evidence for the utility of quantum computing in a pre-fault-tolerant era. These experimental results are enabled by advances in the coherence and calibration of a superconducting processor at this scale and the ability to characterize1 and controllably manipulate noise across such a large device. We establish the accuracy of the measured expectation values by comparing them with the output of exactly verifiable circuits. In the regime of strong entanglement, the quantum computer provides correct results for which leading classical approximations such as pure-state-based 1D (matrix product states, MPS) and 2D (isometric tensor network states, isoTNS) tensor network methods2,3 break down. These experiments demonstrate a foundational tool for the realization of near-term quantum applications4,5.

Beyond the smart city: a communications-led agenda for twentyfirst century cities

Abstract Digital media technologies, from networked sensors to large video screens and mobile devices, have become pervasive urban infrastructure in the twentyfirst century. The dominant framework for understanding the integration of digital technology into urban space has been smart city discourse. In this article, I will argue that this framework, as it has so far been articulated, is inadequate to maximizing the social potential of digital urban infrastructure. Digital urban infrastructure not only changes how cities look, but how they function as social settings. I will propose the ‘communicative city’ as an alternative framework for thinking about digitally mediated cities. The communicative city offers an opportunity to consider networked urban space as a test case in which key problematics of contemporary globalized media are materially instantiated. It is the frontier zone at which everyday experiences of embodied media and new forms of communicative agency collide with powerful logics of tracing and tracking, and the widespread deployment of new forms of automation and machine learning as techniques of urban governance.

Free-standing ultra-thin film with semi-embedded metal nanofiber web for high-performance flexible transparent electrodes

We develop a novel manufacturing process for freestanding conductive nanofiber web films in which metal nanofibers are semi-embedded in polydimethylsiloxane (PDMS) to realize high-performance flexible transparent electrode films. This concept utilizes a sacrificial layer to induce a very thin, free-standing film, and the semi-embedded structure maintains the nanofiber web structure. The excellent adhesion properties of PDMS as well as improved mechanical strength mean that it can be applied to large area devices. In this study, we demonstrate that our approach has improved mechanical strength and excellent conductivity through transparency/conductivity analysis and bending, cycle, and taping tests.

Large active-area superconducting microwire detector array with single-photon sensitivity in the near-infrared

Superconducting nanowire single photon detectors (SNSPDs) are the highest-performing technology for time-resolved single-photon counting from the UV to the near-infrared. The recent discovery of single-photon sensitivity in micrometer-scale superconducting wires is a promising pathway to explore for large active area devices with application to dark matter searches and fundamental physics experiments. We present 8-pixel 1 mm2 superconducting microwire single photon detectors (SMSPDs) with 1 μm-wide wires fabricated from WSi and MoSi films of various stoichiometries using electron-beam and optical lithography. Devices made from all materials and fabrication techniques show saturated internal detection efficiency at 1064 nm in at least one pixel, and the best performing device made from silicon-rich WSi shows single-photon sensitivity in all eight pixels and saturated internal detection efficiency in 6/8 pixels. This detector is the largest reported active-area SMSPD or SNSPD with near-IR sensitivity, and it extends the SMSPD to an array format. By further optimizing the photolithography techniques presented in this work, a viable pathway exists to realize larger devices with cm2-scale active area and beyond.

Non-volatile electrically programmable integrated photonics with a 5-bit operation

Scalable programmable photonic integrated circuits (PICs) can potentially transform the current state of classical and quantum optical information processing. However, traditional means of programming, including thermo-optic, free carrier dispersion, and Pockels effect result in either large device footprints or high static energy consumptions, significantly limiting their scalability. While chalcogenide-based non-volatile phase-change materials (PCMs) could mitigate these problems thanks to their strong index modulation and zero static power consumption, they often suffer from large absorptive loss, low cyclability, and lack of multilevel operation. Here, we report a wide-bandgap PCM antimony sulfide (Sb2S3)-clad silicon photonic platform simultaneously achieving low loss (<1.0 dB), high extinction ratio (>10 dB), high cyclability (>1600 switching events), and 5-bit operation. These Sb2S3-based devices are programmed via on-chip silicon PIN diode heaters within sub-ms timescale, with a programming energy density of sim 10,{fJ}/n{m}^{3}. Remarkably, Sb2S3 is programmed into fine intermediate states by applying multiple identical pulses, providing controllable multilevel operations. Through dynamic pulse control, we achieve 5-bit (32 levels) operations, rendering 0.50 ± 0.16 dB per step. Using this multilevel behavior, we further trim random phase error in a balanced Mach-Zehnder interferometer.

Fast Twist Angle Mapping of Bilayer Graphene Using Spectroscopic Ellipsometric Contrast Microscopy.

Twisted bilayer graphene provides an ideal solid-state model to explore correlated material properties and opportunities for a variety of optoelectronic applications, but reliable, fast characterization of the twist angle remains a challenge. Here we introduce spectroscopic ellipsometric contrast microscopy (SECM) as a tool for mapping twist angle disorder in optically resonant twisted bilayer graphene. We optimize the ellipsometric angles to enhance the image contrast based on measured and calculated reflection coefficients of incident light. The optical resonances associated with van Hove singularities correlate well to Raman and angle-resolved photoelectron emission spectroscopy, confirming the accuracy of SECM. The results highlight the advantages of SECM, which proves to be a fast, nondestructive method for characterization of twisted bilayer graphene over large areas, unlocking process, material, and device screening and cross-correlative measurement potential for bilayer and multilayer materials.

Design of a Ventilated Façade Integrating a Luminescent Solar Concentrator Photovoltaic Panel

The increasing trend towards decarbonization requires the reduction of the environmental impact of the building sector that currently accounts for approximately 40% of the total CO2 emissions of European countries. Even though Luminescent Solar Concentrator (LSC) panels could be a very promising technology to be installed in urban environments, there is still little implementation of LSC panels in building façades. Here, the realization of a Ventilated Façade (VF) integrating an LSC device as an external pane is presented and a preliminary numerical and experimental investigation is used to evaluate the interaction between the different structure components. Thanks to the realization of a dedicated mock-up finite element method, models are calibrated and validated against experimental measurements, showing a good correspondence between simulated and measured data. Moreover, the electrical characterization of the LSC panel confirms that large area devices can be used as an external skin of VF, reporting a photovoltaic efficiency of 0.5%. The system’s thermal and optical properties (estimated thanks to the software COMSOL Multiphysics) encourage the continuation of the research by considering different technologies for the VF internal skin, by scaling up the case study, and by running the simulation of an entire building considering winter and summer energy demands.

Effect of drift layer doping and NiO parameters in achieving 8.9 kV breakdown in 100 μm diameter and 4 kV/4 A in 1 mm diameter NiO/β-Ga2O3 rectifiers

The effect of doping in the drift layer and the thickness and extent of extension beyond the cathode contact of a NiO bilayer in vertical NiO/β-Ga2O3 rectifiers is reported. Decreasing the drift layer doping from 8 × 1015 to 6.7 × 1015 cm−3 produced an increase in reverse breakdown voltage (VB) from 7.7 to 8.9 kV, the highest reported to date for small diameter devices (100 μm). Increasing the bottom NiO layer from 10 to 20 nm did not affect the forward current–voltage characteristics but did reduce reverse leakage current for wider guard rings and reduced the reverse recovery switching time. The NiO extension beyond the cathode metal to form guard rings had only a slight effect (∼5%) in reverse breakdown voltage. The use of NiO to form a pn heterojunction made a huge improvement in VB compared to conventional Schottky rectifiers, where the breakdown voltage was ∼1 kV. The on-state resistance (RON) was increased from 7.1 m Ω cm2 in Schottky rectifiers fabricated on the same wafer to 7.9 m Ω cm2 in heterojunctions. The maximum power figure of merit (VB)2/RON was 10.2 GW cm−2 for the 100 μm NiO/Ga2O3 devices. We also fabricated large area (1 mm2) devices on the same wafer, achieving VB of 4 kV and 4.1 A forward current. The figure-of-merit was 9 GW cm−2 for these devices. These parameters are the highest reported for large area Ga2O3 rectifiers. Both the small area and large area devices have performance exceeding the unipolar power device performance of both SiC and GaN.

Moderate temperature deposition of RF magnetron sputtered SnO2-based electron transporting layer for triple cation perovskite solar cells

The perovskite solar cells (PSCs) are still facing the two main challenges of stability and scalability to meet the requirements for their potential commercialization. Therefore, developing a uniform, efficient, high quality and cost-effective electron transport layer (ETL) thin film to achieve a stable PSC is one of the key factors to address these main issues. Magnetron sputtering deposition has been widely used for its high quality thin film deposition as well as its ability to deposit films uniformly on large area at the industrial scale. In this work, we report on the composition, structural, chemical state, and electronic properties of moderate temperature radio frequency (RF) sputtered SnO2. Ar and O2 are employed as plasma-sputtering and reactive gases, respectively. We demonstrate the possibility to grow a high quality and stable SnO2 thin films with high transport properties by reactive RF magnetron sputtering. Our findings show that PSC devices based on the sputtered SnO2 ETL have reached a power conversion efficiency up to 17.10% and an average operational lifetime over 200 h. These uniform sputtered SnO2 thin films with improved characteristics are promising for large photovoltaic modules and advanced optoelectronic devices.

BIO27: Automated PDMS Engraving and Assembly of a Prototype Microfluidic Artificial Lung

Purpose: The ability to cost-effectively produce high-surface area microfluidic devices would bring many small-scale technologies from the realm of research to clinical and commercial applications. In particular microfluidic artificial lungs (µALs) promise improved gas exchange efficiency through micron-scale feature sizes. However, most µALs have only a single layer which limits their rated flows. Efforts to scale up these devices, such as by stacking multiple flat µALs have been labor intensive and resulted in bulky devices. Here, we present an automated roll-to-roll (R2R) manufacturing system and a cylindrical multi-layer µAL. Methods: The R2R system (Fig 1A) begins with a roll of biocompatible silicone rubber (Silpuran 2030). A heavily-modified CO2 laser engraver (Omtech K40 with custom vacuum engraving bed, N2 purge, and custom motherboard) creates patterns in the silicone sheet (Fig 1B). The sheet is then plasma-activated using two CeraPlas F-series cold-plasma wands to bond the PDMS to itself in an irreversible bond. Finally, it is rerolled into a processed device around a 30 mm PDMS core. This entire process from unrolling to rerolling is performed simultaneously and synchronously, allowing the creation of very large area microfluidic devices. Further, it is automated (Arduino Mega 1680), eliminating human error over this repetitive process. Results: Using our automated manufacturing system, we fabricated a 27-layer cylindrical prototype µAL, consisting of 1) an 8-layer base, 2) 11 layers of alternating blood and gas channels, and 3) an 8-layer protective cover. Laser-engraved fluidic channels were triangular, 60 µm deep and 180 µm wide (Fig 1B). If unrolled, the microfluidic part of this system would stretch 1.1 m, and the total length would stretch 2.7 m. This was placed into a custom 3D printed housing which routes blood and gas to their respective microfluidic channels (Fig 2A,B; filled with dyed water for visualization). Empirical pressure drop data were gathered for flows from 1 mL/min to 10 mL/min, which were similar to theoretical values (Fig 3). While the R2R manufacturing system successfully created the prototype 27-layer µAL, the device exhibited some internal fluid pooling and layer-to-layer leaks during fluidic testing. Both issues are believed to be caused by inadequate localized layer-to-layer adhesion. We plan to remedy these issues in the coming months. Conclusion: This roll-to-roll manufacturing system is designed to manufacture the first large surface-area microfluidic devices that are impractical to manufacture by conventional means. This can be employed for large-scale membrane gas exchange such as human-scale µALs.Figure 1. (A) An automated roll to roll manufacturing system for silicone. The path of the silicone is shown in green. The silicone comes on a protective PET backing, which is removed and highlighted in cyan. (B) Confocal scan of engraved Silpuran 2030. Channels were 60 µm deep, and 180 µm wide.Figure 2. (A) Finished device, with custom housing (B) Device with colored water being routed through. Red arrows depict blood connections, and blue arrows depict gas connections. Two of the blood outlets filled with blue dye, and there is a dark blue region indicating imperfect layer-to-layer bonding resulting in leaking.Figure 3. Experimental vs theoretical pressure drop across the μAL (water)

Silicon Carbide Power Devices: Progress and Future Outlook

Silicon Carbide (SiC) power devices have become commercialized and are being adopted for many applications after 40 years of effort to produce large diameter wafers and high performance device structures. This paper provides a historical perspective of the key breakthroughs that were needed to make progress towards this goal. The JBS rectifier concept was a critical innovation required to make SiC power Schottky rectifiers viable. The Baliga-Pair or Cascode concept was an intermediate step to realize a practical SiC power switch in the 1990s. An essential unique innovation created in the 1990s was the shielded planar SiC power MOSFET structure that is now commonly used for commercial products. Shielded trench-gate SiC power MOSFETs were also proposed in the 1990s which led to commercial products in the last 5 years. Although achieving a low specific on-resistance in SiC power MOSFETs was essential at the inception of the technology, its penetration into power electronics applications is now driven by performance metrics for high frequency circuits. Device structural enhancements to improve the high frequency figures-of-merit are described that have led to major strides in performance. This includes the JBSFET concept where a JBS diode is integrated into the MOSFET structure to suppress current flow through the body diode; the SG and BG MOSFET structures which reduce the gate-drain charge; and the OCTFET structure where the gate-drain overlap area is reduced. Future developments in SiC power devices include increasing the blocking voltage rating to expand the applications spectrum. In addition, a SiC monolithic bi-directional switch has been demonstrated to allow implementation of matrix converters; and a SiC monolithic reverse blocking switch has been demonstrated to allow deployment of current source inverters.

Ion beam analysis of W irradiated with deuterium-based plasma discharges at PF-1000U

Plasma focus devices generate discharges with dense hot plasma (HP) flows and fast ion streams (FIS) with energies up to several MeV, enabling their use to test materials for nuclear fusion applications. Tungsten plates were exposed to deuterium and to mixed deuterium-helium plasmas at distinct power flux densities at the large PF-1000U device. Elemental modifications as the induced deuterium retention and co-deposition of impurities at the target surfaces were studied by scanning electron microscopy and, particularly, by ion beam analysis (IBA). The results evidence that typically, deuterium retention is enhanced during the first discharges and may decreases afterwards due to surface erosion. Additionally, by adding helium to the working gas to generate the plasmas, deuterium retention increase. Similar results may be achieved by decreasing incident flux densities. The experiment highlights the role of the use of IBA to quantify elemental modifications imposed by irradiation of materials in plasma focus facilities.

An energy-efficient and reliable data gathering infrastructure using the internet of things and smart grids

Introduction: The Internet of Things (IoT) and Smart Grids (SGs) growth results from the advancement of computer hardware and ubiquitous computation for energy-efficient and reliable data gathering. Background: The limitations of the present cloud computing framework in energy systems remain unresolved, such as fully recognizing the requisites of high data usage with low latency which is discussed for a cloud computing scheme in IoT-based smart power stations. Problem Statement: IoT growth results from the advancement of computer hardware and ubiquitous computation. Among the various IoT solutions, SGs stand out because they combine several embedded smart techniques to increase the security and dependability of electricity grids. Methodology: A Particle Swarm Optimization based energy efficient integration of Smart Grid (PSO-SG) is designed using IoT. Modern technology establishes a novel hardware and software architecture and integrates cloud services into the cloud-based electricity network. Findings: As a result, a sizable amount of data produced by the electricity network will be examined, handled, and saved at the network. IoT-based power systems will enable the interconnection and administration of large endpoint devices, offer real-time evaluation and treatment of vast data, and promote the modernization of the power grid with the help of the cloud computing model.

A Porous Perovskite Nanofiber with Reinforced Aerophobicity for High-Performance Anion Exchange Membrane Water Splitting.

Perovskite oxides stand out as emerging oxygen evolution reaction (OER) catalysts on account of their effective electrocatalytic performance and low costs. Nevertheless, perovskite oxides suffer from severe bubble overpotential and inhibited electrochemical performance in large current densities due to their small specific surface areas and structural compactness. Herein, the study highlights the electrospun nickel-substituted La0.5 Sr0.5 FeO3-δ (LSF) porous perovskite nanofibers, that is, La0.5 Sr0.5 Fe1-x Nix O3-δ (denoted as ES-LSFN-x, x=0, 0.1, 0.3, and 0.5), as high-performance OER electrocatalysts. The most effective La0.5 Sr0.5 Fe0.5 Ni0.5 O3-δ (ES-LSFN-0.5) nanofibers suggest a larger specific surface area, higher porosity, and faster mass transfer than the counterpart sample prepared by conventional sol-gel method (SG-LSFN-0.5), showing notably increased geometric and intrinsic activities. The bubble visualization results demonstrate that the enriched and nano-sized porosity of ES-LSFN-0.5 enables reinforced aerophobicity and rapid detachment of oxygen bubbles, thereby reducing the bubble overpotential and enhancing the electrochemical performance. As a result, the ES-LSFN-0.5-based anion exchange membrane water electrolysis delivers a superior stability of 100h while the SG-LSFN-0.5 counterpart degrades rapidly within 20h under a current density of 100mAcm-2 . The results highlight the advantage of porous electrocatalysts in optimizing the performance of large current density water electrolysis devices by reducing the bubble overpotential.

P112 CLINICAL OUTCOMES OF LEFT ATRIAL APPENDAGE OCCLUSION WITH CONSCIOUS SEDATION WITHOUT ANESTHESIOLOGIST ON SITE: RESULTS FROM A MULTICENTER RETROSPECTIVE STUDY

Abstract Background Left atrial appendage (LAA) occlusion is an important therapeutic option to prevent cardioembolic stroke in patients with atrial fibrillation (AF) with contraindications for oral anticoagulation (OAC). It is usually performed with transesophageal echocardiography (TOE) under general anesthesia (GA). In this retrospective study we present a multicenter experience of LAA occlusion performed with conscious sedation (CS) without anesthesiologist on site. Methods We collected all the LAA occlusion procedures performed from October 2018 to May 2022. All the included patients underwent the procedure for OAC intolerance mainly due to bleeding with irreversible causes. All the procedures were performed with Watchman or Amulet LAA occluders under TOE and fluoroscopy guidance by two expert interventional cardiologists without anesthesiologist on site. CS was performed with a combination of midazolam and fentanyl. Results One hundred and fifteen patients (age 76.4 ± 7.6 year) with non–valvular AF (median CHA2DS2Vasc 4.4 ± 1.4) were included in the study. CS was performed using midazolam (mean dose 5.9 ± 2.1 mg), adding fentanyl (mean dose 52.8 ± 19.6 mcg) in case of poor tolerance of the procedure despite midazolam. Acute procedural success rate was of 99.2%. One patient suffered a cardiac tamponade, urgent necessity of cardiac surgery and died 5 days after procedure. Two patients (2.6%) had anemia with need for transfusion after interventions. A patient (0.8%) suffered from oropharynx hematoma due to TOE. One case (0,8%) of vascular access site pseudoaneurysm occurred. One case (0.8%) of device thrombosis at 3 months TOE follow–up was reported. One procedure (0.8%) result in large leak device (³5 mm), confirmed at TOE follow–up performed at 3 months follow–up. No thromboembolic complications were reported. One hundred and fourteen (99.2%) patients stopped dual antiplatelet therapy within 12 months. In a follow–up of 10 ± 9 months one case of stroke (0.8%) and one case (0.8%) of transient ischemic attack (TIA) occurred. Conclusion LAA occlusion performed under CS and without the presence of anesthesiologist in cath–lab appear to be safe and effective. It can be an attractive alternative to (GA) because of lower medical staff needed and organizational effort required. In our retrospective study the success rate and the incidence of adverse events appear to be comparable with those of previous studies on the topic of LAA occlusion

FluTO: Graded multi-scale topology optimization of large contact area fluid-flow devices using neural networks

FluTO: Graded multi-scale topology optimization of large contact area fluid-flow devices using neural networks

Facultative male investment in prolonged mate-guarding in a butterfly

Abstract Sexual conflict over mating may induce male mate-guarding prolonged in time in the absence of males, via devices such as mating plugs, widespread in insects. In most Lepidoptera, internal plugs are common, while in some butterfly families large external devices, called sphragides, evolved independently. Lack of, or incomplete sphragis in a few individuals were reported in sphragis-bearing species. Previous studies focused on typifying species-specific devices in a few specimens of many species. In contrast, we investigated alternative mate-guarding devices in detail of a sphragis-bearing butterfly. We conducted a six-year observational field study in a Clouded Apollo Parnassius mnemosyne population. Inspecting 492 females, we identified 3 different devices, filament, stopple and shield (i.e., sphragis) increasing in size and structure complexity, implying differential male investment and effectiveness in securing paternity. Shield dimensions, colour and all devices’ shapes varied considerably. Shields were far more frequent than other devices. Some devices were lost, and a few were video-recorded when removed by males, showing the role of different parts of male external genitalia. We discuss potential causes of device variation and the role of removal attempts, and assess potential costs and benefits for both sexes.

Processing and characterization of large area InP nanowire photovoltaic devices

III−V nanowire (NW) photovoltaic devices promise high efficiencies at reduced materials usage. However, research has so far focused on small devices, mostly ≤1 mm2. In this study, the upscaling potential of axial junction InP NW photovoltaic devices is investigated. Device processing was carried out on a full 2″ wafer, with device sizes up to 1 cm2, which is a significant increase from the mm-scale III−V NW photovoltaic devices published previously. The short-circuit current density of the largest 1 cm2 devices, in which 460 million NWs are contacted in parallel, is on par with smaller devices. This enables a record power generation of 6.0 mW under AM1.5 G illumination, more than one order of magnitude higher than previous III−V NW photovoltaic devices. On the other hand, the fill factor of the larger devices is lower in comparison with smaller devices, which affects the device efficiency. By use of electroluminescence mapping, resistive losses in the indium tin oxide (ITO) front contact are found to limit the fill factor of the large devices. We use combined light-beam induced current (LBIC) and photoluminescence (PL) mapping as a powerful characterization tool for NW photovoltaic devices. From the LBIC and PL maps, local defects can be identified on the fully processed devices.

Accelerating the variational quantum eigensolver using parallelism

Quantum computers are getting larger and larger, but device fidelities may not be able to keep up with the increase in qubit numbers. One way to make use of a large device that has a limited gate depth is to run many small circuits simultaneously. In this paper we detail our investigations into running circuits in parallel on the Rigetti Aspen-M-1 device. We run two-qubit circuits in parallel to solve a simple instance of the Hubbard model using the variational quantum eigensolver (VQE). We present results for running up to 33 circuits in parallel (66 qubits), showing that with the use of error mitigation techniques it is possible to make use of, and gain a real-time speedup from, parallelisation on current quantum hardware. We obtain a speedup by 18× for exploring the VQE energy landscape, and by more than 8× for running VQE optimisation.