Current Device Technology Research Articles

Magnonic φ Josephson junctions and synchronized precession

There has been a growing interest in non-Hermitian physics. One of its main goals is to engineer dissipation and to explore ensuing functionality. In magnonics, the effect of dissipation due to local damping on magnon transport has been explored. However, the effects of nonlocal damping on the magnonic analog of the Josephson effect remain missing, despite that nonlocal damping is inevitable and has been playing a central role in magnonics. Here, we uncover theoretically that a surprisingly rich dynamics can emerge in magnetic junctions due to intrinsic nonlocal damping, using analytical and numerical methods. In particular, under microwave pumping, we show that coherent spin precession in the right and left insulating ferromagnet (FM) of the junction becomes synchronized by nonlocal damping and thereby a magnonic analog of the φ Josephson junction emerges, where φ stands here for the relative precession phase of right and left FM in the stationary limit. Remarkably, φ decreases monotonically from π to π/2 as the magnon-magnon interaction, arising from spin anisotropies, increases. Moreover, we also find a magnonic diode effect giving rise to rectification of magnon currents. Our predictions are readily testable with current device and measurement technologies at room temperatures. Published by the American Physical Society 2024

Ferromagnetic Order in 2D Layers of Transition Metal Dichlorides.

Magnetism in two dimensions is traditionally considered an exotic phase mediated by spin fluctuations, but far from collinearly ordered in the ground state. Recently, 2D magnetic states have been discovered in layered van der Waals compounds. Their robust and tunable magnetic state by material composition, combined with reduced dimensionality, foresee a strong potential as a key element in magnetic devices. Here, a class of 2D magnets based on metallic chlorides is presented. The magnetic order survives on top of a metallic substrate, even down to the monolayer limit, and can be switched from perpendicular to in-plane by substituting the metal ion from iron to nickel. Using functionalized STM tips as magnetic sensors, local exchange fields are identified, even in the absence of an external magnetic field. Since the compounds are processable by molecular beam epitaxy techniques, they provide a platform with large potential for incorporation into current devicetechnologies.

Rigicon ContiClassic and ContiReflex artificial urinary sphincter devices.

The modern AMS 800 artificial urinary sphincter (AUS) is often considered the standard of care for the treatment of moderate to severe stress urinary incontinence in male patients. Nonetheless, the AMS 800 device has several inherent limitations, and these factors can potentially impact its clinical utility and impede excellent clinical outcomes. The new Rigicon AUS devices such as ContiClassic and ContiReflex urinary sphincters are designed to overcome some of the existing issues pertaining to the AMS 800 device. The ContiClassic device is similar in terms of device design to the AMS 800 apart from the inclusion of a hydrophilic coating, has a greater range of cuff sizes with 0.25-cm diameter increments, and an Easy Clink Connectors which negates the need for an assembly tool. In contrast, The ContiReflex device differs from the ContiClassic model in that it features an extra stress relief balloon (SRB) to provide a safeguard on the urethral occlusive mechanism against any sudden increase in intra-abdominal pressure, and a larger pump system that is responsible to cycle fluid between the higher pressure two-balloon system and the sphincteric cuff. The following brief report evaluates the current device design and technology of the Rigicon ContiClassic and ContiReflex AUS devices.

Violation of the magnonic Wiedemann-Franz law in the strong nonlinear regime

The celebrated Wiedemann-Franz (WF) law which governs the relation between charge and heat transport traces back to the experimental discovery in 1853 by Wiedemann and Franz. Despite the fundamental difference of the quantum-statistical properties between fermions and bosons, the linear-in-$T$ behavior of the WF law at low temperatures has recently been found to be the universal property by the discovery of the WF law for magnon transport. However, the WF law is for the linear response, and whether or not the universal law is valid even in the nonlinear regime of Bose systems remains an open issue. Here we provide a solution to this fundamental challenge. We show that the ratio of the thermal to spin transport coefficient of magnons in topologically trivial insulating magnets exhibits a different behavior from the linear response and the universal law breaks down in the strong nonlinear regime. This finding is within experimental reach with current device and measurement technologies. Our discovery is the key ingredient in magnon-based spintronics, in the evaluation of the figure of merit for thermomagnetic conversion elements of spintronics devices.

Functional polymeric coatings: thiol-maleimide ‘click’ chemistry as a powerful surface functionalization tool

Functional polymeric coatings are instrumental in enabling many of the current device technologies to address challenges in disease diagnostics and their treatment. Thus, facile fabrication of readily functionalizable polymeric coatings is an actively pursued area of research. Over the past several years, our research group has established that the thiol-maleimide-based conjugation strategy provides a highly efficient avenue to obtain functionalizable polymeric coatings. In this feature article, we summarize in a chronological fashion, our efforts in the area of synthesis and application of maleimide-containing polymeric materials and coatings. Hopefully, this feature article provides the researchers with a quick overview of our contributions in the area, and the vast potential of maleimide-group containing polymeric materials to fabricate a variety of readily functionalizable soft interfaces for various biomedical applications.

Statistically inspired multi-shift Arnoldi projection for on-chip interconnects

Model order reduction of electronic devices and on-chip interconnects plays an important role in determining the performance of very large scale IC (Integrated Circuit) designs. The ever shrinking process technology continues to increase complexity of these systems with the current Intel device technology node standing at 10 nm. In the analysis of high-speed IC interconnects, the reduced model is often required to approximate the original system in the desired frequency range. In this paper, an efficient Statistically Inspired Multi-shift Arnoldi (SIMA) Method is proposed, which dynamically selects normally distributed shifts to determine the projection matrix. The SIMA is implemented by developing an iterative algorithm for approximation of large-scale systems as an eigenvalue problem using statistically generated interpolation points. The motivation of selecting these points weighted with the Gaussian kernel is derived from the fact that there exist many natural phenomenon, which follow normal distribution. Simulation results have shown better accuracy for the proposed method as compared to other existing model order reduction techniques.

Chlorine doping of MoSe2 flakes by ion implantation.

The efficient integration of transition metal dichalcogenides (TMDs) into the current electronic device technology requires mastering the techniques of effective tuning of their optoelectronic properties. Specifically, controllable doping is essential. For conventional bulk semiconductors, ion implantation is the most developed method offering stable and tunable doping. In this work, we demonstrate n-type doping in MoSe2 flakes realized by low-energy ion implantation of Cl+ ions followed by millisecond-range flash lamp annealing (FLA). We further show that FLA for 3 ms with a peak temperature of about 1000 °C is enough to recrystallize implanted MoSe2. The Cl distribution in few-layer-thick MoSe2 is measured by secondary ion mass spectrometry. An increase in the electron concentration with increasing Cl fluence is determined from the softening and red shift of the Raman-active A1g phonon mode due to the Fano effect. The electrical measurements confirm the n-type doping of Cl-implanted MoSe2. A comparison of the results of our density functional theory calculations and experimental temperature-dependent micro-Raman spectroscopy data indicates that Cl atoms are incorporated into the atomic network of MoSe2 as substitutional donor impurities.

Twistable dipolar aryl rings as electric field actuated conformational molecular switches.

The ability to control the chemical conformation of a system via external stimuli is a promising route for developing molecular switches. For eventual deployment as viable sub-nanoscale components that are compatible with current electronic device technology, conformational switching should be controllable by a local electric field (i.e. E-field gateable) and accompanied by a rapid and significant change in conductivity. In organic chemical systems the degree of π-conjugation is linked to the degree of electronic delocalisation, and thus largely determines the conductivity. Here, by means of accurate first principles calculations, we study the prototypical biphenyl based molecular system in which the dihedral angle between the two rings determines the degree of conjugation. In order to make this an E-field gateable system we create a net dipole by asymmetrically functionalising one ring with: (i) electron withdrawing (F, Br and CN), (ii) electron donating (NH2), and (iii) mixed (NH2/NO2) substituents. In this way, the application of an E-field interacts with the dipolar system to influence the dihedral angle, thus controlling the conjugation. For all considered substituents we consider a range of E-fields, and in each case extract conformational energy profiles. Using this data we obtain the minimum E-field required to induce a barrierless switching event for each system. We further extract the estimated switching speeds, the conformational probabilities at finite temperatures, and the effect of applied E-field on electronic structure. Consideration of these data allow us to assess which factors are most important in the design of efficient gateable electrical molecular switches.

Electro-thermal co-design of β -(AlxGa1-x)2O3/Ga2O3 modulation doped field effect transistors

Ultra-wide bandgap β-gallium oxide (Ga2O3) devices are of considerable interest with potential applications in both power electronics and radio frequency devices. However, current Ga2O3 device technologies are limited by the material's low intrinsic electron mobility and thermal conductivity. The former problem can be addressed by employing modulation-doped β-(AlxGa1−x)2O3/Ga2O3 heterostructures in the device architecture. In this work, (AlxGa1−x)2O3/Ga2O3 modulation-doped field effect transistors (MODFETs) have been investigated from a thermal perspective. Thermoreflectance thermal imaging was used to characterize the self-heating of the MODFETs. The (Al0.18Ga0.82)2O3 thermal conductivity (3.1–3.6 W/mK) was determined using a frequency domain thermoreflectance technique. Electro-thermal modeling was used to discern the effect of design parameters such as substrate orientation and channel length on the device self-heating behavior. Various thermal management schemes were evaluated using the electro-thermal device model. From an electro-thermal co-design perspective, the improvement in electrical performance followed by the mitigation of self-heating was also studied. For example, by employing a Ga2O3-on-SiC composite wafer, which was fabricated in this work, a 50% increase in power handling capability can be achieved as compared to a homoepitaxial device. Furthermore, flip-chip heterointegration and double-sided cooling approaches can lead to more than 2× improvement in the power handling capability. Using an augmented double-sided cooling design that includes nanocrystalline diamond passivation, a 5× improvement in the power handling capability can be accomplished, indicating the potential of the technology upon implementation of a suitable thermal management scheme.

Optomagnonic Barnett effect

Combining the technologies of quantum optics and magnonics, we find that the circularly polarized laser can dynamically realize the quasiequilibrium magnon Bose-Einstein condensates (BEC). The Zeeman coupling between the laser and spins generates the optical Barnett field, and its direction is controllable by switching the laser chirality. We show that the optical Barnett field develops the total magnetization in insulating ferrimagnets with reversing the local magnetization, which leads to the quasiequilibrium magnon BEC. This laser-induced magnon BEC transition through optical Barnett effect, dubbed the optomagnonic Barnett effect, provides an access to coherent magnons in the high frequency regime of the order of terahertz. We also propose a realistic experimental setup to observe the optomagnonic Barnett effect using current device and measurement technologies as well as the laser chirping. The optomagnonic Barnett effect is a key ingredient for the application to ultrafast spin transport.

Zero-field Optic Mode Beyond 20 GHz in a Synthetic Antiferromagnet

Antiferromagnets have considerable potential as spintronic materials. Their dynamic properties include resonant modes at frequencies higher than can be observed in conventional ferromagnetic materials. An alternative to single-phase antiferromagnets are synthetic antiferromagnets (SAFs), engineered structures of exchange-coupled ferromagnet/nonmagnet/ferromagnet trilayers. SAFs have significant advantages due to the wide-ranging tunability of their magnetic properties and inherent compatibility with current device technologies, such as those used for Spin-transfer-torque magnetic random-access memory production. Here we report the dynamic properties of fully compensated SAFs using broadband ferromagnetic resonance and demonstrate resonant optic modes in addition to the conventional acoustic (Kittel) mode. These optic modes possess the highest zero-field frequencies observed in SAFs to date with resonances of 18 and 21 GHz at the first and second peaks in antiferromagnetic Ruderman-Kittel-Kasuya-Yosida (RKKY) coupling, respectively. In contrast to previous SAF reports that focus only on the first RKKY antiferromagnetic coupling peak, we show that a higher optic mode frequency is obtained for the second antiferromagnetic coupling peak. We ascribe this to the smoother interfaces associated with a thicker nonmagnetic layer. This demonstrates the importance of interface quality to achieving high-frequency optic mode dynamics entering the subterahertz range.

Binarized Neural Network with Silicon Nanosheet Synaptic Transistors for Supervised Pattern Classification

In the biological neural network, the learning process is achieved through massively parallel synaptic connections between neurons that can be adjusted in an analog manner. Recent developments in emerging synaptic devices and their networks can emulate the functionality of a biological neural network, which will be the fundamental building block for a neuromorphic computing architecture. However, on-chip implementation of a large-scale artificial neural network is still very challenging due to unreliable analog weight modulation in current synaptic device technology. Here, we demonstrate a binarized neural network (BNN) based on a gate-all-around silicon nanosheet synaptic transistor, where reliable digital-type weight modulation can contribute to improve the sustainability of the entire network. BNN is applied to three proof-of-concept examples: (1) handwritten digit classification (MNIST dataset), (2) face image classification (Yale dataset), and (3) experimental 3 × 3 binary pattern classifications using an integrated synaptic transistor network (total 9 × 9 × 2 162 cells) through a supervised online training procedure. The results consolidate the feasibility of binarized neural networks and pave the way toward building a reliable and large-scale artificial neural network by using more advanced conventional digital device technologies.

Universal 13 -suppression of magnonic shot noise in diffusive insulating magnets

Extending a Boltzmann-Langevin theory to magnons, we show a universality of current-noise suppression in diffusive systems against the difference of quantum-statistical properties of bosons and fermions. To this end, starting from a quantum kinetic equation for magnons subjected to thermal gradient in dilute impurities, we derive a bosonic counterpart of the semiclassical Boltzmann-Langevin equation for electrons and evaluate a magnonic current-noise in the diffusive insulating magnet. We theoretically discover that compared with a Poissonian shot noise of magnons in an insulating ferromagnetic junction, the magnonic shot noise is suppressed in the diffusive insulating bulk magnet and noise-to-current ratio (Fano factor) at low temperatures exhibits a universal behavior, i.e., the same suppression $1/3$ as the one for electron transport in diffusive conductors, despite the difference of quantum-statistical properties. Finally, we show that our predictions are within experimental reach with current device and measurement technologies.

Current perspectives on mechanical circulatory support.

Summary Mechanical circulatory support gained a significant value in the armamentarium of heart failure therapy because of the increased awareness of the prevalence of heart failure and the tremendous advances in the field of mechanical circulatory support during the last decades. Current device technologies already complement a heart transplant as the gold standard of treatment for patients with end-stage heart failure refractory to conservative medical therapy. This article reviews important aspects of mechanical circulatory support therapy and focuses on currently debated issues.

Invited Commentary

The establishment of The Interagency Registry for Mechanically Assisted Circulatory Support (Intermacs) in 2005 was an important step forward for the community of medical providers who are involved in the field of mechanical circulatory support (MCS). For the first time, a large database was established to serve as a repository for all variables affecting patients receiving MCS. The mandate by the regulatory agencies (notably the Joint Commission) to require all programs performing device implantation to benchmark against Intermacs had the added benefit of incentivizing programs in the United States to make substantial internal investments to collect, track, and report their data accurately. On January 1, 2018, oversight and coordination of Intermacs moved to The Society of Thoracic Surgeons (STS) National Database. The incorporation of this database into the larger STS Council on Quality, Research, and Patient Safety will provide additional resources for detailed data collection, analysis, and scientific inquiry similar to the quality work that has emerged from the larger STS databases in cardiac, thoracic, and congenital surgery. In this issue of The Annals of Thoracic Surgery, Kormos and colleagues [1Kormos R.L. Cowger J. Pagani F.D. et al.The Society of Thoracic Surgeons Intermacs Database Annual Report: evolving indications, outcomes, and scientific partnerships.Ann Thorac Surg. 2019; 107: 341-354Abstract Full Text Full Text PDF PubMed Scopus (140) Google Scholar] have produced the annual report on the data from Intermacs. This report primarily focuses on documenting the outcomes of patients undergoing durable left ventricular assist device with the use of Food and Drug Administration-approved, continuous flow rotary pumps. One of the more interesting data points is the documentation of the shift from axial flow pumps to centrifugal flow pumps. This transition likely represents the natural history of pump implant choices that follow advances in technology with each new generation of devices. This report also continues to highlight the limitations of the current device technology; namely neurologic events, gastrointestinal bleeding, and infections. These remain the areas in need of the greatest improvement for caring for these patients and provide the benchmark by which each individual program should use in evaluating their outcomes. In addition, note that these data have traditionally been published in the Journal of Heart and Lung Transplantation that has a more generalized readership among transplant cardiologists, nursing professionals, pharmacists, and other disciplines. Thus, it is critical that we ensure that the publication of this data be widely accessible to the other members of the heart failure community and not restricted to the STS membership with a paid subscription. Similarly, with new leadership will come the daunting task of ensuring that these safeguarded data are easily accessible to other members in the discipline of MCS for research and analysis. With the STS now behind the database, we expect further scientific inquiries and scrutinized analyzes will continue to improve the outcomes for patients with end-stage heart failure for years to come. The Society of Thoracic Surgeons Intermacs Database Annual Report: Evolving Indications, Outcomes, and Scientific PartnershipsThe Annals of Thoracic SurgeryVol. 107Issue 2PreviewThe Interagency Registry for Mechanically Assisted Circulatory Support (Intermacs), a joint effort among the National Heart, Lung, and Blood Institute, the Food and Drug Administration, the Centers for Medicare and Medicaid Services, and others, was established in 2005 at the University of Alabama at Birmingham. The registry examined clinical outcomes and quality-of-life metrics of patients who received an Food and Drug Administration-approved durable mechanical circulatory support (MCS) device to treat advanced heart failure. Full-Text PDF

Impact of pacemaker longevity on expected device replacement rates: Results from computer simulations based on a multicenter registry (ESSENTIAL)

The rate of device replacement in pacemaker recipients has not been investigated in detail. Current pacemakers with automatic management of atrial and ventricular pacing output provide sufficient longevity to minimize replacement rate. We considered a cohort of 542 pacemaker patients (age 78 ± 9 years, 60% male, 71% de-novo implants) and combined 1-month projected device longevity with survival data and late complication rate in a 3-state Markov model tested in several Monte Carlo computer simulations. Predetermined subgroups were: age < or ≥ 70; gender; primary indication to cardiac pacing. At the 1-month follow-up the reported projected device longevity was 153 ± 45 months. With these values the proportion of patients expected to undergo a device replacement due to battery depletion was higher in patients aged <70 (49.9%, range 32.1%-61.9%) than in age ≥70 (24.5%, range 19.9%-28.8%); in women (39.9%, range 30.8%-48.1%) than in men (32.0%, range 24.7%-37.5%); in sinus node dysfunction (41.5%, range 30.2%-53.0%) than in atrio-ventricular block (33.5%, range 27.1-38.8%) or atrial fibrillation with bradycardia (27.9%, range 18.5%-37.0%). The expected replacement rate was inversely related to the assumed device longevity and depended on age class: a 50% increase in battery longevity implied a 5% reduction of replacement rates in patients aged ≥80. With current device technology 1/4 of pacemaker recipients aged ≥70 are expected to receive a second device in their life. Replacement rate depends on age, gender, and primary indication owing to differences in patients' survival expectancy. Additional improvements in device service time may modestly impact expected replacement rates especially in patients ≥80 years.

Nano-crystalline TiO2 thin film: Synthesis and investigation of its optical switching characteristics

Optical-switching property of nano-crystalline TiO2 thin films of thickness ~ 100 nm synthesized using sol-gel assisted spin coating method on ~ 0.14 mm thick Al substrate were investigated in this work. The structural analysis of TiO2 thin film show its polycrystalline nature with anatase phase. Surface analysis of the film via scanning electron microscopy and atomic force microscopy show rough TiO2 surface with nearly crack free surface. Current-voltage measurement carried out on this sample (Pt/TiO2/Al) in dark and under optical illumination show enhancement in dark current under optical illumination resulting from photo generation of charge carriers in TiO2 thin film. In addition to this, it also gives rise to optical-switching in the current from low to high and high to low as the illumination was ON and OFF. These results suggest that nano-crystalline TiO2 thin film based optical-switching devices have potential for integrating current device technology towards exciting photo-active device technology.

Evaluation of Core-Continuity-Constrained ROADMs for Flex-Grid/MCF Optical Networks

To effectively keep pace with the global IP traffic growth forecasted in the years to come, flex-grid over multi-core fiber (MCF) networks can bring superior spectrum utilization flexibility, as well as bandwidth scalability far beyond the non-linear Shannon's limit. In such a network scenario, however, full node switching re-configurability will require enormous node complexity, pushing the limits of current optical device technologies with prohibitive capital expenditures. Therefore, cost-effective node solutions will most probably be the key enablers of flex-grid/MCF networks, at least in the short- and mid-term future. In this context, this paper proposes a cost-effective reconfigurable optical add/drop multiplexer (ROADM) architecture for flex-grid/MCF networks, called CCC-ROADM, which reduces technological requirements (and associated costs) in exchange for demanding core continuity along the end-to-end communication. To assess the performance of the proposed CCC-ROADM in comparison with a fully flexible ROADM (i.e., a fully non-blocking ROADM, called FNB-ROADM in this work) in large-scale network scenarios, a novel lightweight heuristic to solve the route, modulation, core, and spectrum assignment problem in flex-grid/MCF networks is presented in this work, whose goodness is successfully validated against optimal ILP formulations previously proposed for the same goal. The obtained numerical results in a significant number of representative network topologies with different MCF configurations of 7, 12, and 19 cores show almost identical network performance in terms of maximum network throughput when deploying CCC-ROADMs versus FNB-ROADMs, while decreasing network capital expenditures to a large extent.

Toward Human-Scale Brain Computing Using 3D Wafer Scale Integration

The Von Neumann architecture, defined by strict and hierarchical separation of memory and processor, has been a hallmark of conventional computer design since the 1940s. It is becoming increasingly unsuitable for cognitive applications, which require massive parallel processing of highly interdependent data. Inspired by the brain, we propose a significantly different architecture characterized by a large number of highly interconnected simple processors intertwined with very large amounts of low-latency memory. We contend that this memory-centric architecture can be realized using 3D wafer scale integration for which the technology is nearing readiness, combined with current CMOS device technologies. The natural fault tolerance and lower power requirements of neuromorphic processing make 3D wafer stacking particularly attractive. In order to assess the performance of this architecture, we propose a specific embodiment of a neuronal system using 3D wafer scale integration; formulate a simple model of brain connectivity including short- and long-range connections; and estimate the memory, bandwidth, latency, and power requirements of the system using the connectivity model. We find that 3D wafer scale integration, combined with technologies nearing readiness, offers the potential for scaleup to a primate-scale brain, while further scaleup to a human-scale brain would require significant additional innovations.

Electrochemical behavior of high performance on-chip porous carbon films for micro-supercapacitors applications in organic electrolytes

Carbide derived carbons (CDCs) are promising materials for preparing integrated micro-supercapacitors, as on-chip CDC films are prepared via a process fully compatible with current silicon-based device technology. These films show good adherence on the substrate and high capacitance thanks to their unique nanoporous structure which can be fine-tuned by adjusting the synthesis parameters during chlorination of the metallic carbide precursor. The carbon porosity is mostly related to the synthesis temperature whereas the thickness of the films depends on the chlorination duration. Increasing the pore size allows the adsorption of large solvated ions from organic electrolytes and leads to higher energy densities. Here, we investigated the electrochemical behavior and performance of on-chip TiC-CDC in ionic liquid solvent mixtures of 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIBF4) diluted in either acetonitrile or propylene carbonate via cyclic voltammetry and electrochemical impedance spectroscopy. Thin CDC films exhibited typical capacitive signature and achieved 169 F cm−3 in both electrolytes; 65% of the capacitance was still delivered at 1 V s−1. While increasing the thickness of the films, EMI+ transport limitation was observed in more viscous PC-based electrolyte. Nevertheless, the energy density reached 90 μW h cm−2 in 2M EMIBF4/ACN, confirming the interest of these CDC films for micro-supercapacitors applications.