Logic Devices Research Articles

Symmetry breaking for current-induced magnetization switching

Electromagnetic phenomena, such as magnetization switching, are guided by parity and time-reversal symmetries. Magnetic field and magnetization are time-odd axial vectors. Therefore, the magnetic field can switch magnetization reversibly. In contrast, the electric field is a time-even polar vector that cannot directly switch magnetization. For magnetic recording, an electrical coil-generated local magnetic field is used to switch the magnetic bit. However, in order to integrate the magnetic functionality, e.g., nonvolatile magnetic memory with high speed and low energy consumption, into the chip, it is essential to implement the magnetization switching by an electrical current, where the current induces other axial vectors through spin-transfer torque or spin–orbit torque (SOT). As an energy-efficient tool of magnetization switching, current-induced SOT has been intensively studied for the past decade, which holds great promise in the next generation of magnetic memories and magnetic logic devices [A. Manchon et al., Rev. Mod. Phys. 91, 035004 (2019); X. Han et al., Appl. Phys. Lett. 118, 120502 (2021); C. Song et al., Prog. Mater. Sci. 118, 100761 (2021); Q. Shao et al., IEEE Trans. Magn. 57, 21076639 (2021); J. Ryu et al., Adv. Mater. 32, 1907148 (2020); Y. Cao et al., iScience 23, 101614 (2020)]. In this review, we will first give the basic principle of the symmetry considerations for current-induced magnetization switching. Then, different methods to break the mirror symmetry for deterministic SOT switching will be discussed, together with examples that contain recent progress. In the end, we will give a discussion on the challenges and perspectives of the symmetry designs for SOT, which aim to inspire future fundamental studies and device applications.

Experimental design for tri-state logic


 
 
 
 Tri-State Logic device effectively connects many devices into the same data line for data transfer. The Tri- State TTL inverter has three output states such as LOW, HIGH, and open or high-impedance (High-Z) states. The High-Z state either electrically isolates the devices from the data transmission line or connects them one at a time to the data transmission line. The measurement of the floating output (opened or disconnected) state is a challenging task. This issue can be resolved by introducing a potential divider into the output of the original Tri-State TTL inverter circuit and making it possible for a lab experiment
 
 
 

Tunable perfect absorber and multifunctional logic device based on graphene metamaterial

Both tunable perfect absorber and multifunctional logic device can be accomplished by a novel graphene metamaterial in this paper. The metamaterial utilizes gold as a substrate, covering with a graphene flake and a graphene double-strip-array on dielectric layers. First, the perfect absorption above 99.99% in the terahertz range is achieved depends on the coupling between the two graphene layers. In addition, the tunability is based on the correlation between the conductivity and the Fermi level of graphene. As the Fermi level changes, the absorption peak of the absorber will shift, thus the tunable perfect absorber is accomplished. On this basis, the input Boolean values of the logic function are defined by the Fermi levels of graphene. The output Booleans are distinguished by monitoring the reflections and comparing them with the thresholds. Finally, the multifunctional logic device have been successfully implemented in the terahertz domain. At different frequencies, the logic gates of OR, XNOR and NAND can be realized concurrently. And the NOT logic gate can be obtained synchronously at multiple frequencies. Furthermore, the operational frequencies of the aforementioned four logic functions can be tuned by varying the other Fermi level of graphene. The maximum extinction ratios of OR, XNOR, NAND, and NOT are 13.02 dB, 26.3 dB, 12.06 dB, and 26.3 dB, respectively. This multifunctional metamaterial has potential applications in terahertz optical communication due to its straightforward structure and multiple functions.

Layer-dependent Dzyaloshinskii–Moriya interaction and field-free topological magnetism in two-dimensional Janus MnSTe

Magnetic skyrmions, as topologically protected whirl-like solitons, have been the subject of growing interest in non-volatile spintronic memories and logic devices. Recently, much effort has been devoted to searching for skyrmion host materials in two-dimensional (2D) systems, where intrinsic inversion symmetry breaking and a large Dzyaloshinskii–Moriya interaction (DMI) are desirable to realize a field-free skyrmion state. Among these systems, 2D magnetic Janus materials have become important candidates for inducing a sizable DMI and chiral spin textures. Herein, we demonstrate that layer-dependent DMI and field-free magnetic skyrmions can exist in multilayer MnSTe. Moreover, strong interlayer exchange coupling and Bethe–Slater curve-like behaviors arising from the Mn–Mn double exchange mechanism are found in bilayer MnSTe. We also uncover that the distribution of DMIs in multilayer MnSTe can be understood as making a significant contribution to the intermediate DMI using the three-site Fert–Lévy model. Our results unveil great potential for designing skyrmion-based spintronic devices in multilayer 2D materials.

Novel approach for implementing ternary value logic devices showing negative differential transconductance characteristics by Fowler–Nordheim tunneling

Ternary value logic (TVL) devices are gaining attention owing to the limitations of binary devices in handling the increasing amount of information. However, the development of ternary devices has been hindered by the complex structures and use of materials lacking CMOS compatibility. This study presents a novel approach to develop ultra-simple TVL devices using thin-tunnel gate dielectrics of AlOx films and TiO2 channel layer. TVL devices are obtained by employing TiO2-based transistors with AlOx films as an oxide tunneling dielectric layer. The device exhibits typical transistor switching characteristics at low gate voltage (VG) and negative differential transconductance owing to Fowler−Nordheim tunneling current at high VG. The reversible implementation of three states, namely, ON, intermediate (INT), and OFF, with the same probability, is demonstrated with excellent reproducibility even after 200 cycles. A circuit is constructed to demonstrate the three output voltage states with respect to the input voltage by connecting the TVL device to a resistor. Additionally, the value and width of the plateau region of the INT output voltage state can be tuned by adjusting the variable resistance values. These highly simplistic TVL devices have the potential for application in low-power, highly integrated, and ultra-miniature electronic devices, thanks to their high level of CMOS compatibility.

Emergence of large spin-charge interconversion at an oxidized Cu/W interface

Spin-orbitronic devices can integrate memory and logic by exploiting spin-charge interconversion (SCI), which is optimized by design and materials selection. In these devices, such as the magnetoelectric spin-orbit (MESO) logic, interfaces are crucial elements as they can prohibit or promote spin flow in a device as well as possess spin-orbit coupling resulting in interfacial SCI. Here, we study the origin of SCI in a Py/Cu/W lateral spin valve and quantify its efficiency. An exhaustive characterization of the interface between Cu and W electrodes uncovers the presence of an oxidized layer (WO$_x$). We determine that the SCI occurs at the Cu/WO$_x$ interface with a temperature-independent interfacial spin-loss conductance of $G_{||} \approx$ 20 $\times$ 10$^{13} \Omega^{-1}m^{-2}$ and an interfacial spin-charge conductivity $\sigma_{SC}=-$1610 $\Omega^{-1}cm^{-1}$ at 10 K ($-$830 $\Omega^{-1}cm^{-1}$ at 300 K). This corresponds to an efficiency given by the inverse Edelstein length $\lambda_{IEE}=-$0.76 nm at 10 K ($-$0.4 nm at 300 K), which is remarkably larger than in metal/metal and metal/oxide interfaces and bulk heavy metals. The large SCI efficiency at such an oxidized interface is a promising candidate for the magnetic readout in MESO logic devices.

Controlled Growth of Semiconductor Alloy/Ferromagnetic Insulator (GeBi/Bi:Thulium Iron Garnet (TmIG)) Spin Heterojunction and Development of Quantum Logic Device

Replacing heavy metal and heavy metal alloy films with a semiconductor thin film, to form a semiconductor/ferromagnetic insulator spin heterojunction has always been an international research hotspot. This article reports on a Ge1–xBix/Bi:thulium iron garnet (TmIG) spin heterojunction. It was found that Ge1–xBix (x = 0.06–0.22) semiconductor alloy films and Bi3+-doped control Tm3–yBiyFe4.3Ga0.7O12 (Bi:TmIG, y = 0.2–1.0) films can enhance the spin–orbit coupling (SOC) strength, improving the abnormal spin Hall effect (ASHE) and the spin Hall magnetoresistance (RH) switch characteristics. As x varies from 0.06 to 0.22, it is noticed that the spin mixing conductance considerably increases. Because Bi ions have the ability to control the SOC strength, the 5–10 nm GeBi semiconductor thin film with the Bi-ion-doped Bi:TmIG film can realize a spin magnetic moment reversal and then drive the heterojunction magnetic moment switching effect, and the spin currents injected across this interface lead to deterministic magnetization reversal at an ultralow current density of 1.82 × 106 mA/cm2. This has significant practical applications in the design and implementation of spin quantum logic devices based on semiconductor processes, laying a material foundation for the development of quantum logic devices.

3D to 2D perspectives - Traditional and new doping and metrology challenges at the nanoscale

In this perspectives paper we will explore the doping state-of-the-art as it evolves for 3D to 2D structures and materials, and the following impact on the metrology methods needed to characterise them. Historically, silicon devices for logic complementary metal-oxide-semiconductor (MOS) are built in bulk monocrystalline substrates. In this context bulk silicon substrates are 3D, as there is not the electrostatic confinement associated with more technologically advanced device structures. The determination of technology figures-of-merit such as sheet resistance, impurity concentration and activation profiles versus depth, and reverse bias leakage current to track crystal quality post-doping process, have been the typical methods for evaluation. Since the emergence of FinFET, gate-all-around (GAA) for logic, and layered 2D materials such as transition-metal-dichalcogenides (TMDs) for MOS channel active areas, these figures-of-merit are more awkward to extract, or simply do not apply in the usual sense. Logic devices, like MOS transistors, depend on doping processes to lower access resistance and thus drive performance, traditionally relied on ion implantation to introduce impurities to the substrate, which is a physical bombardment that damages the target material. Gentler doping processes that rely on in-diffusion are an emerging category, and most recently the concept of terminating or functionalising the (near-) surface of the semiconductor is growing in popularity, at least in research labs. Likewise, methods to characterise these require evolution to adapt to the times, from the conventional high-throughput techniques to the more exploratory, albeit lower throughput, methods. Metrology relies upon high-sensitivity, large dynamic range of detection, spatial resolution, as well as time- and cost-efficient sample preparation and post-analysis data interpretation. Driven primarily by the continued development of novel, scaled-down, truly unique device architectures and the introduction of novel materials in the nano-fabrication technology, the portfolio of dopant characterisation methods is unremittingly enlarging its numbers. Herein, we focus our discussion onto dopant profiling for fin and nanowire FETs, and relate these to analysis of test vehicles such as arrays of fin structures with varying dimensions. Although reports detailing correlative use of the dopant characterisation methods are only a few, we present examples that provided unique new information, in absence of which the overall description of the dopant process is inconclusive and, in some cases, misleading.

Near IR Bandgap Semiconducting 2D Conjugated Metal-Organic Framework with Rhombic Lattice and High Mobility.

Two-dimensional conjugated metal-organic frameworks (2D c-MOFs) are emerging as a unique class of electronic materials. However, 2D c-MOFs with band gaps in the Vis-NIR and high charge carrier mobility are rare. Most of the reported conducting 2D c-MOFs are metallic (i.e. gapless), which largely limits their use in logic devices. Herein, we design a phenanthrotriphenylene-based, D2h -symmetric π-extended ligand (OHPTP), and synthesize the first rhombic 2D c-MOF single crystals (Cu2 (OHPTP)). The continuous rotation electron diffraction (cRED) analysis unveils the orthorhombic crystal structure at the atomic level with a unique slipped AA stacking. The Cu2 (OHPTP) is a p-type semiconductor with an indirect band gap of ≈0.50 eV and exhibits high electrical conductivity of 0.10 S cm-1 and high charge carrier mobility of ≈10.0 cm2 V-1 s-1 . Theoretical calculations underline the predominant role of the out-of-plane charge transport in this semiquinone-based 2D c-MOF.

Eine halbleitende 2D metallorganische Gerüstverbindung mit einer Bandlücke im nahen IR, rhombischem Gitter und hoher Ladungsträgermobilität

AbstractZweidimensionale konjugierte metallorganische Gerüstverbindungen (2D c‐MOFs) gehören zu einer einzigartigen Gruppe elektronischer Materialien. 2D c‐MOFs mit Bandlücken im sichtbaren oder nahen IR‐Bereich und hohen Ladungsträger‐mobilitäten sind jedoch rar. Die meisten literaturbekannten halbleitenden 2D c‐MOFs sind metallisch, was ihre Verwendung in logischen Bauelementen stark einschränkt. Im Folgenden konzipieren wir einen Phenanthrotriphenylen basierten, D2h‐symmetrischen, π‐konjugierten Liganden (OHPTP) und synthetisieren die ersten rhombischen 2D c‐MOF Einkristalle (Cu2(OHPTP)). Kontinuierliche Rotations‐Elektronendiffraktometrie (cRED) belegt die orthorhombische Kristallstruktur mit versschobene AA‐Schichtung auf atomarer Ebene. Cu2(OHPTP) ist ein p‐Typ Halbleiter mit einer indirekten Bandlücke von ≈0.50 eV, einer hohen elektrischen Leitfähigkeit von 0.10 S cm−1 und einer hohen Ladungsträgermobilität von ≈10.0 cm2 V−1 s−1. Theoretische Berechnungen unterstreichen die dominierende Rolle des Ladungstransports zwischen den Schichten in diesem Semichinon verknüpften 2D c‐MOF.

An unique DNA junction scaffold-based electrochemical sensing platform achieving multilevel signal responses for amplified multiplexed nucleic acid analysis and logic operation

Herein, a DNA junction scaffold structure was exploited as the only immobilization probe to construct a simple and multifunctional electrochemical sensing platform. The programmable operation of a catalytic DNA circuit reaction on it afforded the amplified and well-controllable signal responses for the individual and simultaneous analysis of two nucleic acid targets. Also, it could be flexibly harnessed for each target assay based on multilevel signal response behaviours including single-signal, dual-signal and ratiometric signal responses. Then, its application for the operation of two logic devices of “AND” and “OR” gates toward different target inputs was demonstrated. Interestingly, the “OR” gate could be in-situ evolved from the “AND” status by simply controlling signal output. The low detection limit could reach 10 fM whether for the simultaneous or individual analysis of two targets in buffer or serum. Current sensing platform by only a DNA junction scaffold probe features in facile biosensor fabrication and operation, sensitive and selective analysis of multiplexed targets, well-controllable and multilevel signal response behaviours, and expandable logic operation. It thus may open a promising avenue toward the development of advanced biosensors or logic devices applied for molecular diagnosis or information processing.

FerroX: A GPU-accelerated, 3D phase-field simulation framework for modeling ferroelectric devices

We present a massively parallel, 3D phase-field simulation framework for modeling ferroelectric materials based scalable logic devices. This code package, FerroX, self-consistently solves the time-dependent Ginzburg Landau (TDGL) equation for ferroelectric polarization, Poisson's equation for electric potential, and charge equation for carrier densities in semiconductor regions. The algorithm is implemented using the AMReX software framework [1], which provides effective scalability on manycore and GPU-based supercomputing architectures. We demonstrate the performance of the algorithm with excellent scaling results on NERSC multicore and GPU systems, with a significant (15×) speedup on the GPU using a node-by-node comparison. We further demonstrate the applicability of the code in simulations of ferroelectric domain-wall induced negative capacitance (NC) effect in Metal-Ferroelectric-Insulator-Metal (MFIM) and Metal-Ferroelectric-Insulator-Semiconductor-Metal (MFISM) devices. The charge (Q) v.s. voltage (V) responses for these 3D structures clearly indicate stabilized negative capacitance with multidomain formation, which is corroborated by amplification of the voltage at the interface between the ferroelectric and dielectric layers.

In-plane spin excitation of skyrmion bags

Skyrmion bags are spin structures with arbitrary topological charges, each of which is composed of a big skyrmion and several small skyrmions. In this work, by using an in-plane alternating current (AC) magnetic field, we investigate the spin-wave modes of skyrmion bags, which behave differently from the clockwise (CW) rotation mode and the counterclockwise (CCW) rotation mode of skyrmions because of their complex spin topological structures. The in-plane excitation power spectral density shows that each skyrmion bag possesses four resonance frequencies. By further studying the spin dynamics of a skyrmion bag at each resonance frequency, the four spin-wave modes, i.e., a CCW-CW mode, two CW-breathing modes with different resonance strengths, and an inner CCW mode, appear as a composition mode of outer skyrmion–inner skyrmions. Our results are helpful in understanding the in-plane spin excitation of skyrmion bags, which may contribute to the characterization and detection of skyrmion bags, as well as the applications in logic devices.

Proposal for a spin logic device based on magneto‐electric effect and spin Hall effect

AbstractBased on magneto‐electric (ME) effect and spin Hall effect (SHE), the authors propose a novel spin logic device named MESH‐SLD. In MESH‐SLD, the charge current is transmitted in the channel by employing inverse SHE, which solves the dissipation problem of spin current in the channel of all‐spin logic device (ASLD). By using a magnetization‐dynamics/spin‐transport hybrid model, the authors have investigated the influence of working voltage, channel lengths, and materials on the performance of the MESH‐SLD. And the simulation results show that the energy dissipation of the MESH‐SLD only increases approximately linearly with the increase of channel length, while the switching delay remains almost unchanged. In addition, with the increase of the spin Hall angle of the channel material, the energy dissipation and the minimum working voltage of the MESH‐SLD decrease significantly. Most importantly, compared with conventional ASLD, the proposed MESH‐SLD improve the switching delay and the energy dissipation by about 2.5 times and 851.8 times, respectively.

Enabling Logic Computation Between Ta/CoFeB/MgO Nanomagnets

Dipolar coupled magnets proved to have the potential to be capable of successfully performing digital computation in a highly parallel way. For that, nanomagnet-based computation requires precise control of the domain wall nucleation from a well-localized region of the magnet. Co/Pt and Co/Ni multilayer stacks were successfully used to demonstrate a variety of computing devices. However, Ta/CoFeB/MgO appears more promising thanks to the lower switching field required to achieve a full magnetization reversal, reduced thickness (less than 10 nm), and its compatibility with magnetic tunnel junctions. In this work, the switch of the information is achieved through the application of a magnetic field, which allows to scale more the nanomagnets with respect to current-driven magnetization reversal-based devices and to go towards 3D structures. We experimentally demonstrate that Ga <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> ions can be used to tune the energy landscape of the structured magnets to provide signal directionality and achieve a distinct logic computation. We prove that it is possible to define the artificial nucleation center in different structures with two irradiation steps and that this approach can enable logic computation in ultra-thin films by dipolar interaction. Moreover, different from previous studies, the results coming from the irradiation analysis are then used for real logic devices. We present the experimental demonstration of a set of fully working planar inverters, showing that it is possible to reach a coupling field between input and output, which is strong enough to reliably implement logic operations. Micromagnetic simulations are used to study the nucleation center’s effectiveness with respect to its position in the magnet and to support the experiments. Our results open the path to the development of more efficient nanomagnet-based logic circuits.

Proof-of-Concept Vacuum Microelectronic NOR Gate Fabricated Using Microelectromechanical Systems and Carbon Nanotube Field Emitters.

This paper demonstrates a fully integrated vacuum microelectronic NOR logic gate fabricated using microfabricated polysilicon panels oriented perpendicular to the device substrate with integrated carbon nanotube (CNT) field emission cathodes. The vacuum microelectronic NOR logic gate consists of two parallel vacuum tetrodes fabricated using the polysilicon Multi-User MEMS Processes (polyMUMPs). Each tetrode of the vacuum microelectronic NOR gate demonstrated transistor-like performance but with a low transconductance of 7.6 × 10-9 S as current saturation was not achieved due to a coupling effect between the anode voltage and cathode current. With both tetrodes working in parallel, the NOR logic capabilities were demonstrated. However, the device exhibited asymmetric performance due to differences in the CNT emitter performance in each tetrode. Because vacuum microelectronic devices are attractive for use in high radiation environments, to test the radiation survivability of this device platform, we demonstrated the function of a simplified diode device structure during exposure to gamma radiation at a rate of 45.6 rad(Si)/second. These devices represent a proof-of-concept for a platform that can be used to build intricate vacuum microelectronic logic devices for use in high-radiation environments.

Passive Gate-Tunable Kinetic Photovoltage along Semiconductor-Water Interfaces.

Moving boundaries of electrical double layer at solid-liquid interface enables unprecedented persistent energy conversion and provokes a kinetic photovoltaic effect by moving an illumination region along the semiconductor-water interface. Here, we report a transistor-inspired gate modulation of kinetic photovoltage by applying a bias at the semiconductor-water interface. The kinetic photovoltage of both p-type and n-type silicon samples can be facilely switched on/off, stemming from the electrical-field-modulated surface band bending. In contrast to the function of solid-state transistors relying on external sources, passive gate modulation of the kinetic photovoltage is achieved simply by introducing a counter electrode with materials of desired electrochemical potential. This architecture provides the ability to modulate the kinetic photovoltage over three orders of magnitude and opens up a new way for self-powered optoelectronic logic devices.

Passive Gate‐Tunable Kinetic Photovoltage along Semiconductor‐Water Interfaces

AbstractMoving boundaries of electric double layer at solid–liquid interface enables unprecedented persistent energy conversion and provokes a kinetic photovoltaic effect by moving an illumination region along the semiconductor‐water interface. Here, we report a transistor‐inspired gate modulation of kinetic photovoltage by applying a bias at the semiconductor‐water interface. The kinetic photovoltage of both p‐type and n‐type silicon samples can be facilely switched on/off, stemming from the electrical‐field‐modulated surface band bending. In contrast to the function of solid‐state transistors relying on external sources, passive gate modulation of the kinetic photovoltage is achieved simply by introducing a counter electrode with materials of desired electrochemical potential. This architecture provides the ability to modulate the kinetic photovoltage over three orders of magnitude and opens up a new way for self‐powered optoelectronic logic devices.

Experimental Realization of Topologically‐Protected All‐Optical Logic Gates Based on Silicon Photonic Crystal Slabs

AbstractAs the field of topological photonics has developed over the past 10 years, it has been proven that the combination of topology and photons is very beneficial to the design of robust optical devices against some disturbances. However, most of the work on robust optical logic devices stays at the theoretical level. There are very few topologically‐protected logic devices fabricated in experiments. Here, the experimental fabrication of a series of topologically‐protected all‐optical logic gates is reported. Seven topologically‐protected all‐optical logic gates (OR, XOR, NOT, XNOR, NAND, NOR, and AND) are fabricated on silicon photonic platforms, which show strong robustness even if some disorders exist. These robust logic devices are potentially applicable in future optical signal processing and computing applications.

Ferroelectricity of pristine Hf0.5Zr0.5O2 films fabricated by atomic layer deposition

Hafnium-based ferroelectric films, remaining their ferroelectricity down to nanoscale thickness, present a promising application for low-power logic devices and nonvolatile memories. It has been appealing for researchers to reduce the required temperature to obtain the ferroelectric phase in hafnium-based ferroelectric films for applications such as flexible and wearable electronics. This work demonstrates that a remanent polarization (P r) value of < 5 μC/cm2 can be obtained in as-deposited Hf0.5Zr0.5O2 (HZO) films that are fabricated by thermal atomic layer deposition (TALD) under low temperature of 250 °C. The ferroelectric orthorhombic phase (o-phase) in the as-deposited HZO films is detected by scanning transmission electron microscopy (STEM). This low fabrication temperature further extends the compatibility of ferroelectric HZO films to flexible electronics and avoids the cost imposed by following high-temperature annealing treatments.