Layer Switching Research Articles

Oxidative-Reductive Near-Infrared Electrochromic Switching Enabled by Porous Vertically Stacked Multilayer Devices.

Here, we demonstrate for the first time the ability of a porous π-conjugated semiconducting polymer film to enable facile electrolyte penetration through vertically stacked redox-active polymer layers, thereby enabling electrochromic switching between p-type and/or n-type polymers. The polymers P1 and P2, with structures diketopyrrolopyrrole (DPP)-πbridge-3,4,-ethylenedioxythiophene (EDOT)-πbridge [πbridge = 2,5-thienyl for P1 and πbridge = 2,5-thiazolyl for P2] are selected as the p-type polymers and N2200 (a known naphthalenediimide-dithiophene semiconductor) as the n-type polymer. Single-layer porous and dense (control) polymer films are fabricated and extensively characterized using optical microscopy, atomic force microscopy, scanning electron microscopy, and grazing incidence wide-angle X-ray scattering. The semiconducting films are then incorporated into single and multilayer electrochromic devices (ECDs). It is found that when a p-type (P2) porous top layer is used in a multilayer ECD, it enables electrolyte penetration to the bottom layer, enabling oxidative electrochromic switching of the P1 bottom layer at low potentials (+0.4 V versus +1.2 V with dense P2). Importantly, when using a porous P1 as the top layer with an n-type N2200 bottom layer, dynamic oxidative-reductive electrochromic switching is also realized. These results offer a proof of concept for development of new types of multilayer electrochromic devices where precise control of the semiconductor film morphology and polymer electronic structure is essential.

Electric-field driven source of photocarriers for tunable electron spin polarization in InGaAs quantum dots

Electric-field control of spin polarization of electrons during injection into InGaAs quantum dots (QDs) was studied via circularly polarized time-resolved photoluminescence. Electric-field modulation of optical spin polarization in QDs will play a key role in future progress of semiconductor opto-spintronics. The tuning of band potentials by applying external electric fields can not only affect spin-injection efficiencies but also switch dominant spin-injection layers. In this study, we developed a QD-based electric-field-effect optical spin device with two different spin-injection layers, which consisted of a GaAs and GaAs/Al0.15Ga0.85As superlattice (SL) barriers. The bias-voltage modulation of the optical spin polarization in QDs was demonstrated by changing the spin polarization degree of electrons injected from these barriers into the QD via the electric-field switching of the spin-injection layers. This was achieved by exploiting the difference in spin relaxation properties between bulk GaAs and the SL. This proposed structure, which comprised of one luminescent layer and two spin-injection layers, is highly scalable because the modulation range of optical spin polarization can be enhanced by changing the combination of spin-injection layers, as well as the material used and its layer thickness.

Current shunting effects in Cd3As2: A closer look at the topological-ferromagnet interface

Topological materials, such as Cd3As2, are of great importance for next-generation computing systems where energy efficiency is paramount. For example, in spin–orbit torque magnetic access memory (SOT-MRAM), topological materials generate the spin–orbit torque necessary for magnetization switching of an adjacent magnetic layer. Current shunting at the ferromagnet–topological material interface can be detrimental for spin generation and overall SOT efficiency. Here, the current shunting effect is analyzed in permalloy- and gold-shunted Cd3As2 disk structures using angle-dependent magnetoresistance measurements. We observe Shubnikov–de Haas oscillations and weak antilocalization. Hakami–Larkin–Nagaoka and Tkachov–Hankiewicz models are used to evaluate the weak antilocalization. We confirm the effects of current shunting and discuss its detriment to the efficiency of spin-based devices.

Improving delivery efficiency using spots and energy layers reduction algorithms based on a large momentum acceptance beamline.

Intensity-modulated proton therapy (IMPT) is a well-known delivery method of proton therapy. Besides higher plan quality, reducing the delivery time is also essential to IMPT plans. It can enhance patient comfort, reduce treatment costs, and improve delivery efficiency. From the perspective of treatment efficacy, it contributes to mitigating the intra-fractional motions and improving the accuracy of radiotherapy, especially for moving tumors. However, there is a tradeoff problem between the plan quality and delivery time. We consider the potential of a large momentum acceptance (LMA) beamline and apply the spots and energy layers reduction method to reduce the delivery time. The delivery time for each field consists of the energy layer switching time, spot traveling time, and dose delivery time. The larger momentum spread and higher intensity beam offered by the LMA beamline contribute to reducing the total delivery time compared to the conventional beamline. In addition to the dose fidelity term, an L1 and logarithm items were added to the objective function to increase the sparsity of the low-weighted spots and energy layers. After that, the low-weighted spots and layers were iteratively excluded in the reduced plan, which reduced the energy layer switching time and spot traveling time. We used the standard, reduced, and LMA-reduced plans to validate the proposed method and tested it on prostate and nasopharyngeal cases. Then, we compared and evaluated the plan quality, treatment time, and plan robustness against delivery uncertainty. Compared with the standard plans, the number of spots in the LMA-reduced plans was on average reduced by 13 400 (95.6%) for prostate cases and by 48 300 (80.7%) for nasopharyngeal cases and the number of energy layers was on average reduced by 49 (61.3%) for prostate cases and by 97 (50.5%) for nasopharyngeal cases. And, the delivery time of the LMA-reduced plans was shortened from 34.5 to 8.6 s for prostate cases and from 163.8 to 53.6 s for nasopharyngeal cases. The LMA-reduced plans had comparable robustness to the spot monitor unit (MU) error compared with the standard plans, but the LMA-reduced plans became more sensitive to spot position uncertainty. The delivery efficiency can be significantly improved using the LMA beamline and spots and energy layers reduction strategies. The method is promising to improve the efficiency of motion mitigation strategies for treating moving tumors.

Aesthetic Possibilities of Building Thermal Control through Colored Envelopes

The possibilities of obtaining efficient building thermal control by means of colored envelopes while maintaining broad aesthetic options have been evaluated. The use of colored bilayers, where the inner layer presents strong solar absorbent or reflectance properties, while the outer layer provides visible coloration, represents a feasible way. A representative set of twenty bilayers spanning a broad color palette has been studied in two configurations, static and dynamic. The dynamic configuration allows for the switching of the inner layer between absorptive and reflective states. Simulations have been carried out in a total of nineteen locations around the world, representing the main habitable climates according to Köppen–Geiger climate classification. Comparative results between climate zones where this approach may have a significant impact have been obtained, and identification of feasible climate zones has been carried out. The use of the simpler static configuration is recommended for tropical climates, whereas the dynamic configuration could be effective in moderate climate locations (within arid or temperate climate classification). Possible savings for cold climates are negligible.

Manipulation of Magnetization Switching by Ultrafast Spin‐Polarized Hot‐Electron Transport in Synthetic Antiferromagnet

AbstractUncovering the physical mechanisms that govern ultrafast charge and spin dynamics is becoming indispensable both at the fundamental level and to develop future spin‐based electronics. Recently it has been shown that femtosecond pulsed‐laser excitation of magnetic thin films produces intense and ultrafast spin‐polarized hot electrons, thus attracting a lot of attention. While spin‐polarized hot electrons are known to play a pivotal role in the ultrafast laser‐induced demagnetization, their effect on magnetization switching remains an open issue. This study uncovers the effect of spin‐polarized hot electrons generated by laser excitation on magnetization switching in a Co/Pt based perpendicular magnetic anisotropy‐based synthetic antiferromagnet (p‐SAF) using the time‐resolved magneto‐optical Kerr effect. It has been found that, at low pump fluence, the equivalent magnetic field generated by the hot‐electron spin current plays a dominant role in assisting the magnetization switching of the lower layer in the antiferromagnetic configuration, while the strong thermal stability of the Ruderman Kittel Kasuya Yosida exchange interaction inhibits the further weakening of the switching field at high pump fluence. This study provides a viable way to control the magnetization switching of the antiferromagnetically exchange‐coupled systems for spintronic applications with ultrafast control of the information operation.

Fully electrical controllable spin-orbit torque based half-adder

A simple, reliable, and electrically controllable way to develop complementary spin–orbit logic devices is highly desired. In this work, controllable field-free spin–orbit torque (SOT) switching is demonstrated in the Pt/IrMn/Co/Ru/CoPt/CoO/MgO heterojunction at room temperature, which makes it an attractive building block for complementary spin logic. By applying current pulses along two orthogonal directions, both the in-plane exchange bias at the IrMn/Co interface and the perpendicular magnetization switching of the CoPt layer can be well controlled. Using this controllable SOT switching, multiple spin logic operations and a spin logic half-adder are obtained. These results indicate that controllable SOT switching could provide a potentially applicable way toward efficient spin logic and in-memory computing devices.

Plasmonic Slot Waveguide Propagation Analysis

Plasmonic slot waveguides provide extreme light confinement with the benefits of having naturally present electrodes for switching and high thermal conductivity of the metal layers to remove excess heat. Past works relied on numerical computation for these structures, which is time-consuming and lacks physical insight. Here, we present an analytical model of plasmonic slot waveguides to determine the modal properties based on single-mode matching to continuum. The model is accurate to within 3% of rigorous numerical simulations. The theory allows for rapid design and provides physical insight into mode propagation in plasmonic slot waveguides for information processing, optical manipulation, and sensing applications.

Development of integration mode proton imaging with a single CMOS detector for a small animal irradiation platform

A novel irradiation platform for preclinical proton therapy studies foresees proton imaging for accurate setup and treatment planning. Imaging at modern synchrocyclotron-based proton therapy centers with high instantaneous particle flux is possible with an integration mode setup. The aim of this work is to determine an object’s water-equivalent thickness (WET) with a commercially available large-area CMOS sensor. Image contrast is achieved by recording the proton energy deposition in detector pixels for several incoming beam energies (here, called probing energies) and applying a signal decomposition method that retrieves the water-equivalent thickness. A single planar 114 mm × 65 mm CMOS sensor (49.5 µm pixel pitch) was used for this study, aimed at small-animal imaging. In experimental campaigns, at two isochronous cyclotron-based facilities, probing energies suitable for small-animal-sized objects were produced once with built-in energy layer switching and the other time, using a custom degrader wheel. To assess water-equivalent thickness accuracy, a micro-CT calibration phantom with 10 inserts of tissue-mimicking materials was imaged at three phantom-to-detector distances: 3 mm, 13 mm, and 33 mm. For 3 mm and 13 mm phantom-to-detector distance, the average water-equivalent thickness error compared to the ground truth was about 1% and the spatial resolution was 0.16(3) mm and 0.47(2) mm, respectively. For the largest separation distance of 33 mm air gap, proton scattering had considerable impact and the water-equivalent thickness relative error increased to 30%, and the spatial resolution was larger than 1.75 mm. We conclude that a pixelated CMOS detector with dedicated post-processing methods can enable fast proton radiographic imaging in a simple and compact setup for small-animal-sized objects with high water-equivalent thickness accuracy and spatial resolution for reasonable phantom-to-detector distances.

The influence of interface effects on the switching behavior in ultra-scaled MRAM cells

The development of advanced magnetic tunnel junctions with a single-digit nanometer footprint can be achieved using an elongated multilayered ferromagnetic free layer structure. In this work, we demonstrate the switching of a composite free layer consisting of two ferromagnets separated by an MgO layer and an additional capping MgO layer to boost perpendicular anisotropy. This serially connected MTJs form a multi-state memory cell. Because of the ability to store data in more than one bit (0 or 1), the memory density can be increased, making the memory more efficient and cost-effective. A proper design of the free layer and its interface-induced perpendicular anisotropy helps to achieve reliable switching.

TURBO: A novel beam delivery system enabling rapid depth scanning for charged particle therapy

Charged particle therapy (CPT) is a well-established modality of cancer treatment and is increasing in worldwide presence due to improved accelerator technology and modern techniques. The beam delivery system (BDS) determines the overall timing and beam shaping capabilities, but is restricted by the energy variation speed: energy layer switching time (ELST). Existing treatment beamlines have a ±1% momentum acceptance range, needing time to change the magnetic fields as the beam is delivered in layers at various depths across the tumour volume. Minimising the ELST can enable the delivery of faster, more effective and advanced treatments but requires an improved BDS. A possibility for this could be achieved with a design using Fixed Field Alternating Gradient (FFA) optics, enabling a large energy acceptance to rapidly transport beams of varying energies. A scaled-down, novel system – Technology for Ultra Rapid Beam Operation (TURBO) – is being developed at the University of Melbourne, to explore the potential of rapid depth scanning. Initial simulation studies, beam and field measurements, project plans and clinical considerations are discussed.

Physical Transient Photoresistive Variable Memory Based on Graphene Quantum Dots.

Biomaterials have attracted attention as a major material for biodegradable and transient electronic devices. In this work, biocompatible gelatin-doped graphene quantum dot films are reported as active layer switching memories with good electrical properties and physical transient properties. Such nonvolatile memory devices have write-once-read-many electrical properties and a concentrated distribution of low-resistance and high-resistance states. It provides a solution for the current obstacle of resistive memory storage and computing integration. Based on the sensitivity of the device to ultraviolet light, the "OR gate" logic operation is completed. Furthermore, the active layer can be dissolved in deionized water within 15 min, and the gelatin substrate-based device can be destroyed immediately in water, indicating the potential biodegradation and physical transient properties of our fabricated device. Biocompatible memory devices are environmentally friendly, sustainable for safe storage, and low-cost, making them ideal for storage applications.

Machine-Specific Delivery Sequence Model of Compact Superconducting Synchrocyclotron Proton Therapy Systems – A Multi-Institutional Investigation

<h3>Purpose/Objective(s)</h3> Proton pencil beam scanning delivery sequence varies among institutions due to the vendor, machine type, and configuration. However, having a reliable model of delivery time and sequence is critical to maximizing throughput when proton beam time is limited. In this study, we used an experimental approach to build a precise beam delivery time (BDT) and sequence prediction model for a new compact superconducting synchrocyclotron proton system (PTC#1) and compare it with a different institution using an older version of the same system (PTC#2). We investigated treatment efficiency and the interplay effect for the treatment of mobile tumors. <h3>Materials/Methods</h3> The machine delivery log files from PTC#1 were retrospectively analyzed to model beam delivery parameters. We compared the PTC#1 delivery sequence with PTC#2's published machine-specific model using the same type of proton system. A total of twenty clinical beams from head neck, lung, breast, and esophagus treatment sites were used for model comparison. Also, we used a single clinical treatment day to compare treatment efficiency. The interplay effect is evaluated and compared based on these two different delivery sequence models. A digital thoracic 4DCT phantom image set with a rigid target in the right lung was used for the study. Different delivery techniques such as standard delivery (N_vol=1) and volumetric repainting delivery (N_vol=2-5) were simulated. <h3>Results</h3> The results showed PTC#1 has a much faster spot scanning speed than PTC#2 thanks to a new generation of scanning magnets. The spot switching time (SSWT) is 0s within 11.3mm in x-direction and 8 mm in y-direction. Compared to PTC#2, the average SSWT reduces by 94.37%±3.82% (50.76s±35.10s) in PTC#1. PTC#1 also demonstrated improved burst switching transmission efficiency, which reduced burst switching time (BST) by 39.84%±3.64% (6.00s±2.21s) on average. The energy layer switching time (ELST) dominates the PTC#1 delivery time instead of SSWT for PTC#2 (Table). The total BDT was reduced by 54.61%±12.12% (53.45s±34.47s) on average. Based on the single day patient mix, it was estimated that 67 min irradiation time could be saved by upgrading the scanning magnets in PTC#2 (10% daily patient treatment throughput improvement). The results also indicated the interplay effect would be reduced as volumetric repainting number increased. The system in PTC#2 had better target coverage and homogeneity than PTC#1 for=1-3. Their target coverage converges at=5. <h3>Conclusion</h3> A precise machine-specific delivery sequence model is highly recommended in the interplay effect evaluation and clinical decision. It provided the first quantitative analysis of the impact of the new scanning magnets regarding the improvement in the treatment delivery efficiency.

Effects of self-torque in rare earth-transition metal alloy on the magnetization switching by spin-orbit torque

We investigated the spin–orbit torque (SOT) switching of the single CoTb layer with or without the heavy metals (Pt and W) in different thickness to identify the self-torque effects generated in the CoTb layer. The generation of self-torque heavily depends on the thickness of CoTb. The SOT switching was not observed for a single CoTb layer with 3 nm in thickness, suggesting self-torque may be quite weak in a very thin film. A deterministic SOT switching can be obtained for a single 9 nm CoTb layer. The amplitude of the self-torque generated in CoTb is comparable to the Co/Pt case with the same switching polarity as the Co/Pt one. When 3 nm CoTb was deposited on Pt or W underlayer, the Jc is smaller in W/CoTb than that of Pt/CoTb, which can be attributable to a high spin hall angle of W and negligible self-torque of CoTb. On the other hand, when the CoTb is increased to 9 nm, the Jc of W/CoTb is significantly increased and becomes higher than that of Pt/CoTb. The enhanced Jc of W/CoTb may result from the opposite sign of spin orbit torque generated in W and CoTb. Since the self-torque generated in 9 nm CoTb becomes substantial, the competition of spin orbit torque between W and CoTb occurs, leading to a high Jc. Our findings may shed light to utilize self-torque induced in rare earth-transition metal alloy for new design of SOT devices.

Simulation of 5G Mobile Core Network using SDN &amp; MPLS

In particular, in order to have the best possible understanding of the effects that program-able networking has, carry out a low cost analysis of both the (software define network) system and the (multiple protocol layer switching)&nbsp; system. This will give you the possible understanding of the effects that program-able networking has on the economics of a network in comparison to traditional networking, which is also known as MPLS technology. This is done so that a better understanding of the effects that program-able networking, also known as software-defined networking (SDN), technology has on the economics of a network can be gained. Conducting a quantitative investigation using an activity-based methodology to compute the (capital expenditure) and (operation expenditure) costs associated with a network was the first step in achieving this objective. This investigation was carried out.&nbsp; Second, in order to compare the aforementioned architectures in terms of their financial performances, we used the USC Scalability metric in addition to the Cost-to-Service metric. Both of these metrics were used. These models include (centralized control plane), (distributed control plane), and (hierarchical control plane). This was done in order to obtain the possible understanding of the different SDN plane systems that are currently in use. The separation of control plane and data plane that is achieved through the implementation of software-defined networking (SDN) makes it possible to program networks. Because of this separation, network operators and administrators are now in a position to make better use of the network's resources and have an easier time provisioning those resources when compared to the situation before the separation took place.

Energy layer optimization via energy matrix regularization for proton spot-scanning arc therapy.

Spot-scanning arc therapy (SPArc) is an emerging proton modality that can potentially offer a combination of advantages in plan quality and delivery efficiency, compared with traditional IMPT of a few beam angles. Unlike IMPT, frequent low-to-high energy layer switching (so called switch-up (SU)) can degrade delivery efficiency for SPArc. However, it is a tradeoff between the minimization of SU times and the optimization of plan quality. This work will consider the energy layer optimization (ELO) problem for SPArc and develop a new ELO method via energy matrix (EM) regularization to improve plan quality and delivery efficiency. The major innovation of EM method for ELO is to design an EM that encourages desirable energy-layer map with minimal SU during SPArc, and then incorporate this EM into the SPArc treatment planning to simultaneously minimize the number of SU and optimize plan quality. The EM method is solved by the fast iterative shrinkage-thresholding algorithm and validated in comparison with a state-of-the-art method, so-called energy sequencing (ES). EM is validated and compared with ES using representative clinical cases. In terms of delivery efficiency, EM had fewer SU than ES with an average of 35% reduction of SU. In terms of plan quality, compared with ES, EM had smaller optimization objective values and better target dose conformality, and generally lower dose to organs-at-risk and lower integral dose to body. In terms of computational efficiency, EM was substantially more efficient than ES by at least 10-fold. We have developed a new ELO method for SPArc using EM regularization and shown that this new method EM can improve both delivery efficiency and plan quality, with substantially reduced computational time, compared with ES.

Reconfigurable InP waveguide components using the Sb2S3 phase change material

Reconfigurable waveguide components are promising building blocks for photonic neural networks and as an optical analogue to field-programmable gate arrays. By changing the effective index of the waveguide, reconfigurable waveguide components can achieve on-chip light routing and modulation. In this paper, we design and demonstrate an Sb2S3-reconfigurable InP membrane Mach–Zehnder interferometer (MZI) on a silicon substrate. Sb2S3, which has tunable refractive index and low absorption in the near-infrared spectrum, was patterned on the InP waveguide MZIs to make an optical switch in the telecoms conventional-band. By laser induced crystallisation of the Sb2S3, it was possible to control interference in the MZI and achieve 18 dB on/off switching at 1540 nm. Laser reamorphisation and reversible switching of the Sb2S3 layer resulted in damage to the waveguide structure. However, simulations show that transition metal di-chalcogenide two-dimensional crystal layers can act as efficient thermal barriers that prevent thermal damage to the waveguide during laser amorphisation. Therefore, combining Sb2S3 with InP waveguides seems to be a feasible approach to achieve low-loss reprogrammable waveguide components for on-chip photonics routing and neural networks.

Switching function parameter variation analysis of a quasi-sliding mode controlled induction motor drive

Sliding mode control is a nonlinear, robust control that is having better load disturbance rejection capability, less parameter sensitivity and fast dynamic response. Conventional sliding mode control introduces high chattering that can degrade the induction motor (IM) drive system responses. Hence, a quasi-sliding mode controller (Q-SMC) using a hyperbolic tangent function coupled with equivalent control is designed for robust speed control of vector-controlled IM drive in this work. This work focuses on the effect of variation of the switching function parameters of the Q-SMC on the performance of the drive. Extensive simulations are performed using MATLAB/Simulink software, and the switching function parameters are adjusted across a wide range and its impact on motor performance is studied qualitatively and quantitatively, with accompanying graphical results and various transient parameters. It is observed that a Q-SMC controller with a larger boundary layer width has less overshoot, less steady-state error, and a lower current THD. It is also observed that even though a high gain Q-SMC controller responds quickly, the percentage overshoot for high gain systems is likewise large. Hence, if the boundary layer width and switching gain parameters are optimized, a Q-SMC speed controller is a promising choice for a high-performance IM drive.

Design of static and dynamic ridge filters for FLASH-IMPT: A simulation study.

This paper focused on the design and optimization of ridge filter-based intensity-modulated proton therapy (IMPT), and its potential applications for FLASH. Differing from the standard pencil beam scanning (PBS) mode, no energy/layer switching is required and total treatment time can be shortened. Unique dose-influence matrices were generated as a proton beam traverses through slabs of different thicknesses (i.e., modulation by different layers). To establish the references for comparison, conventional IMPT plans (single field) were created using a large-scale nonlinear solver. The spot weights from the reference IMPT plans were used as inputs for optimizing the design of ridge filters. Two designs were evaluated: model A (static) and model B (dynamic). The ridge filter designs were first verified (by GEANT4 simulation) in a water phantom and then in an H&N case. A direct comparison was made between the GEANT4 simulation results of two models and their respective references, with regard to plan quality, dose-averaged dose rate, and total treatment time. In both the water phantom and the H&N case, two models are able to modulate dose distributions with high conformity, showing no significant difference relative to the reference plans. Dose rate-volume histograms suggest that in order to achieve a dose rate of 40Gy/s over 90% PTV, the beam intensity needs to be 2.5×1011 protons/s for both models. For a fraction dose of 10Gy, the total treatment time (including both irradiation time and dead time) can be shortened by a factor of 4.9 (model A) and 6.5 (model B), relative to the reference plans. Two proposed designs (both static and dynamic) can be used for PBS-IMPT requiring no layer switching. They are promising candidates for FLASH-IMPT capable of reducing treatment time and achieving high dose rates while maintaining dose conformity simultaneously.

Simultaneous emulation of synaptic and intrinsic plasticity using a memristive synapse

Neuromorphic computing targets the hardware embodiment of neural network, and device implementation of individual neuron and synapse has attracted considerable attention. The emulation of synaptic plasticity has shown promising results after the advent of memristors. However, neuronal intrinsic plasticity, which involves in learning process through interactions with synaptic plasticity, has been rarely demonstrated. Synaptic and intrinsic plasticity occur concomitantly in learning process, suggesting the need of the simultaneous implementation. Here, we report a neurosynaptic device that mimics synaptic and intrinsic plasticity concomitantly in a single cell. Threshold switch and phase change memory are merged in threshold switch-phase change memory device. Neuronal intrinsic plasticity is demonstrated based on bottom threshold switch layer, which resembles the modulation of firing frequency in biological neuron. Synaptic plasticity is also introduced through the nonvolatile switching of top phase change layer. Intrinsic and synaptic plasticity are simultaneously emulated in a single cell to establish the positive feedback between them. A positive feedback learning loop which mimics the retraining process in biological system is implemented in threshold switch-phase change memory array for accelerated training.