Logic Devices Research Articles

Light-Triggered Anti-ambipolar Transistor Based on an In-Plane Lateral Homojunction.

Currently, the construction of anti-ambipolar transistors (AATs) is primarily based on asymmetric heterostructures, which are challenging to fabricate. AATs used for photodetection are accompanied by dark currents that prove difficult to suppress, resulting in reduced sensitivity. This work presents light-triggered AATs based on an in-plane lateral WSe2 homojunction without van der Waals heterostructures. In this device, the WSe2 channel is partially electrically controlled by the back gate due to the screening effect of the bottom electrode, resulting in a homojunction that is dynamically modulated with gate voltage, exhibiting electrostatically reconfigurable and light-triggered anti-ambipolar behaviors. It exhibits high responsivity (188 A/W) and detectivity (8.94 × 1014 Jones) under 635 nm illumination with a low power density of 0.23 μW/cm2, promising a new approach to low-power, high-performance photodetectors. Moreover, the device demonstrates efficient self-driven photodetection. Furthermore, ternary inverters are realized using monolithic WSe2, simplifying the manufacturing of multivalued logic devices.

High-Performance 3D-Graphene/GaAs Photodetectors for Applications in Logic Devices and Imaging Sensing

High-Performance 3D-Graphene/GaAs Photodetectors for Applications in Logic Devices and Imaging Sensing

Controlling electron and hole concentration in MoS2 through scalable plasma processes

Conventional high-energy ion implant processes lack implant depth precision and minimally damaging properties needed to dope atomically thin two-dimensional (2D) semiconductors by ion modification without undesirable side effects. To overcome this limitation, controllable, reproducible, and robust doping methods must be developed for atomically thin semiconductors to enable commercially viable wafer-scale 2D material-based logic, memory, and optical devices. Ultralow energy ion implantation and plasma exposure are among the most promising approaches to realize high carrier concentrations in 2D semiconductors. Here, we develop two different plasma processes using commercially available semiconductor processing tools to achieve controllable electron and hole doping in 2H-MoS2. Doping concentrations are calculated from the measured Fermi level shift within the MoS2 electronic bandgap using x-ray photoelectron spectroscopy. We achieve electron doping up to 1.5 × 1019 cm−3 using a remote argon/hydrogen (H2) plasma process, which controllably generates sulfur vacancies. Hole doping up to 4.2 × 1017 cm−3 is realized using an inductively coupled helium/SF6 plasma, which substitutes fluorine into the MoS2 lattice at sulfur sites. The high doping concentrations reported here highlight the potential of scalable plasma processes for MoS2, which is crucial for enabling complementary circuits based on 2D semiconductors.

Multi-terminal logic transmission via orthogonal currents controlling magnetic skyrmion motion in a perpendicular ferromagnetic multilayer nanotrack

Magnetic skyrmions are topologically nontrivial whirling spin textures with great potential for next-generation magnetic logic and memory applications as spintronic information carriers. The abilities to precisely manipulate skyrmion generation and motion using electric current are considered to be important issues for developing the high-efficiency skyrmion-based devices. In this paper, a skyrmionic logic device structure is proposed to realize the generation of Néel-type skyrmions from the topologically trivial domains. Micromagnetic simulations are employed to investigate the controllable skyrmion motions manipulated by the orthogonal current excitations in a perpendicular ferromagnetic multilayer nanotrack. The transversal skyrmion motion induced by the skyrmion Hall effect is balanced through introducing a y-axial current. A three-terminals logic output is achieved by adjusting the strength of currents along x and y directions. The interlayer coupling effect for stabilizing skyrmion nucleation is finely tuned via a ferromagnetic pinning layer in absent of the external magnetic field. It is found that both the perpendicular magnetic anisotropy and the Dzyaloshinskii-Moriya interaction are critical for the formation of stabilized skyrmions. The controllable skyrmion motion and multi-terminal information transmission offer a novel path for designing skyrmion-based logic and memory devices.

Spintronic device in SWCNT-FET configuration based on chromium oxides thin films consisting of half-metallic ferromagnetic CrO2

Spintronic device architectures consisting of ferromagnetic chromium oxide electrodes in single-walled carbon nanotubes field effect transistor (SWCNT-FET) configuration have been fabricated to act as strategic building blocks for next generation super-compact high-speed nanoelectronic devices for logic and memory operations. Stable thin films of chromium oxides consisting of half-metallic ferromagnetic chromium-di-oxide (CrO2) were pulsed laser deposited (PLD) over lattice-matched rutile-type-tetragonal intermediate TiO2 thin layers over thermally oxidized Si substrates for engineering of the spintronic device structure. Focused ion beam (FIB) milling was applied to the ferromagnetic chromium oxide thin films for patterning of the source (S) and (D) electrodes. Typical electrical characteristics derived by lnρ vs. T−1/2 plots confirmed spin-dependent transport (SDT) as the dominant mechanism of electrical conduction upto temperatures of ∼280 K along with negative magnetoresistance (MR) of ∼30 % at 278 K. Electrical characteristics (output and transfer) of the spintronic device structure were drawn under application of magnetic field (H) in out-of-plane geometry at the temperatures of 5.6 K, 250 K & 300 K. Drain current (Id) is demonstrated to be controlled effectively as a function of gate bias (Vg) for different fixed Vd-biases at all the device operating temperatures. Change in %MR as a function of gate voltage (Vg) was acquired at T = 250 &T = 300 K that displayed higher %MR change under out-of-plane geometry of applied field of 0.75 T of the spintronic device operation.

Optically-reconfigurable integrated optical directed logic computing based on silicon photonics.

Optical directed logic, as a novel logical operation scheme, harmoniously combines the benefits of optical and electrical signals, surpassing traditional electrical and all-optical logic operations in terms of the flexibility and power consumption. Its potential in high-speed optical signal processing and electro-optical computing is immense. However, achieving tunability of the logic function normally relies on external electrical tuning or multiple laser sources, which often results in excessive power consumption and costs. In this work, by utilizing the polarization state of light within the optical directed logic, we demonstrate an optical directed logic device on a silicon-based platform. This single device can realize three different logic operations, which are XNOR, XOR and NAND, by simply changing the input light's polarization state, which comes at a minimal additional power consumption. Moreover, we also significantly enhance the device's response speed through a novel side-integrated metal thermal phase shifter, reducing the response time to 5 µs. Ultimately, we demonstrate logic operations at 60 kbps which maintains a leading standard among the currently reported thermally tuning optical-directed logic (ODL) devices, and successfully integrated polarization division multiplexing technique into ODL devices. This result provides a novel method to realize high-speed optical directed logic with high reconfigurability, which presents significant application prospects in the high-speed optical information processing field.

Engineering photoelectric conversion efficiency in two-dimensional ferroelectric C2PbI2Cl2/Sc2CO2 heterostructures

Properties of ferroelectric semiconductors have garnered significant research interest, particularly due to their non-volatile memory. Meanwhile, studies on the characteristics of two-dimensional (2D) ferroelectrics have appeared as a crucial topic in solar cells, i.e., bulk photovoltaic effects. In this work, we propose two heterostructures: Cs2PbI2Cl2/Sc2CO2-UP (CSUP) and Cs2PbI2Cl2/Sc2CO2-DOWN (CSDN) for solar cells, to examine their photoelectric properties by using first-principles. Our findings indicate that such two heterostructures may have both high exciton binding energies and strong optical absorption coefficients in the ultraviolet region, with the CSDN showing exceptional carrier mobility as well. Moreover, we explore their characteristics by means of modulations of electric fields and stresses. The results reveal that the transition of band alignment in the CSUP can be engineered from type-II to type-I under the control of the electric fields, which may significantly increase the power conversion efficiency in actual solar cells. Moreover, both may have good potential in the application of logic devices. All these outputs may imply that, by means of fine modulations on photoelectric properties, the Cs2PbI2Cl2/Sc2CO2 possess immense potential to become multifunctional devices in ultraviolet photodetectors, solar cells, and logic devices.

Surface crystallization effects on tellurium oxide thin films for low-power complementary logic circuit applications

Van-der-Waals-structured tellurium (IV) has demonstrated its potential as a promising building block for complementary logic device due to its superior electrical and optoelectronic features. Here, we demonstrated the novel approach for developing high-performance tellurium oxide (TeOX) thin film through TeOX formation and surface crystallization (SC). The crystalline structures and chemical bindings of the TeOX surfaces were carefully engineered by time- and temperature-dependent UV-ozone treatment and ALD-grown-Al2O3-assisted crystallization. The huge enhancement of device performance was achieved in the optimized SC-TeOX transistor, especially high on–off current ratio of 2.19 × 106, which can be ascribed to the synergistic effects of TeOX formation and SC process resulting in the enlarged bandgap, strong valence band edge localization, and the improved crystallinity. The performance enhancement mechanism was systematically studied by constructing SC-TeOX transistor with different TeOX region, where the TeOX creation in both Te channel and source/drain electrode regions dramatically improved performance owing to the decreased contact resistance and enhanced charge transport. Consequently, we achieved the high-performance low-power complementary logic circuits with SC-TeOX transistors, even reaching the maximum gain of 67.9 and low static power of 0.5 nW. Thus, this work demonstrates the great potentials of SC-TeOX transistor for developing advanced low-power complementary logic circuits.

Electrical detection of mobile skyrmions with 100% tunneling magnetoresistance in a racetrack-like device

Magnetic skyrmions are topological spin textures that are regarded as promising information carriers for next-generation spintronic memory and computing devices. For practical applications, their deterministic generation, manipulation, and efficient detection are the most critical aspects. Although the generation and manipulation of skyrmions have been extensively studied, efficient electrical detection of mobile skyrmions by using techniques that are compatible with modern magnetic memory technology, remains to be adequately addressed. Here, through integrating magnetic multilayers that host nanoscale skyrmions, together with the magnetic tunnel junctions (MTJ), we demonstrate the electrical detection of skyrmions by using the tunneling magnetoresistance (TMR) effect with a TMR ratio that reaches over 100% at room temperature. By building prototype three-terminal racetrack-like devices, we further show the electrical detection of mobile skyrmions by recording the time-dependent TMR ratios. Along with many recent developments, our results could advance the development of skyrmionic memory and logic devices.

Bias polarity dependent low-frequency noise in ultra-thin AlOx-based magnetic tunnel junctions

We exploit bias polarity dependent low-frequency noise (LFN) spectroscopy to investigate charge transport dynamics in ultra-thin AlOx-based magnetic tunnel junctions (MTJs) with bipolar resistive switching (RS). By measuring the noise characteristics across the entire bias voltage range of bipolar RS, we find that the voltage noise level exhibits an bias polarity dependence. This distinct feature is intimately correlated with reconfiguring of the inherently existing oxygen vacancies (VO..\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${V}_{O}^{..}$$\\end{document}) in as-grown MTJ devices during the SET and RESET switching processes. In addition, we observe two-level random telegraph noise (RTN) with a longer and shorter tunneling length in the high resistance state (HRS) and low resistance state (LRS) at a low bias voltage. The intrinsic voltage fluctuations of RTN arise from the dynamics of electron trapping/de-trapping processes at the VO..\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${V}_{O}^{..}$$\\end{document}-related trap sites. Notably, the RTN magnitude is similar in LRS but nonidentical in that of HRS for different bias polarity. These findings strongly suggest that the inherent VO..\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${V}_{O}^{..}$$\\end{document} are distributed near the top CoFe/AlOx interface in the HRS; in contrast, they are expanded to the middle region of the AlOx in the LRS. More importantly, we demonstrate that the location and distribution of the inherent VO..\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${V}_{O}^{..}$$\\end{document} can be electrically tuned, which plays an essential role in the charge transport dynamics in the ultra-thin AlOx-based MTJs and have significant implications for developing emergent memory and logic devices.

Low Gilbert damping and high perpendicular magnetic anisotropy in an Ir-coupled L10-FePd-based synthetic antiferromagnet

Thin ferromagnetic films possessing perpendicular magnetic anisotropy derived from the crystal lattice can deliver the requisite magnetocrystalline anisotropy density for thermally stable magnetic memory and logic devices at the single-digit-nm lateral size. Here, we demonstrate that an epitaxial synthetic antiferromagnet can be formed from L10 FePd, a candidate material with large magnetocrystalline anisotropy energy, through insertion of an ultrathin Ir spacer. Tuning of the Ir spacer thickness leads to synthetic antiferromagnetically coupled FePd layers, with an interlayer exchange field upwards of 0.6 T combined with a perpendicular magnetic anisotropy energy of 0.95 MJ/m3 and a low Gilbert damping of 0.01. Temperature-dependent ferromagnetic resonance measurements show that the Gilbert damping is mostly insensitive to temperature over a range of 20 K up to 300 K. In FePd|Ir|FePd trilayers with lower interlayer exchange coupling, optic and acoustic dynamic ferromagnetic resonance modes are explored as a function of temperature. The ability to engineer low damping and large interlayer exchange coupling in FePd|Ir|FePd synthetic antiferromagnets with high perpendicular magnetic anisotropy could prove useful for high performance spintronic devices.

Realization of 2D multiferroic with strong magnetoelectric coupling by intercalation: a first-principles high-throughput prediction

The discovery of novel two-dimensional (2D) multiferroic materials is attractive due to their potential for the realization of information storage and logic devices. Although many approaches have been explored to simultaneously introduce ferromagnetic (FM) and ferroelectric (FE) orders into a 2D material, the resulting systems are often plagued by weak magnetoelectric (ME) coupling or limited room-temperature stability. Here, we present a superlattice strategy to construct non-centrosymmetric AM2X4 multiferroic monolayers, i.e., intercalating transition metal ions (A) into the tetragonal-like vacancies of transition metal dichalcogenide bilayers (MX2). Starting from 960 intercalated AM2X4 compounds, our high-throughput calculations have identified 21 multiferroics with robust magnetic order, large FE polarization, low transition barrier, high FE/FM transition temperature, and strong ME coupling. According to the origin of magnetism, we have classified them into twelve type-a, seven type-b, and two type-c multiferroics, which exhibit different ME coupling behavior. During the switching of polarization, the reversal of skyrmions chirality, the transition of the magnetic ground state from FM to antiferromagnetic, and the changes in spin-polarized electron distribution were observed in type-a, type-b, and type-c 2D multiferroic materials, respectively. These results substantially expand the family of 2D ferroic materials and pave an avenue for designing and implementing nonvolatile logic and memory devices.

Bioinspired Liquid Metal Based Soft Humanoid Robots.

The pursuit of constructing humanoid robots to replicate the anatomical structures and capabilities of human beings has been a long-standing significant undertaking and especially garnered tremendous attention in recent years. However, despite the progress made over recent decades, humanoid robots have predominantly been confined to those rigid metallic structures, which however starkly contrast with the inherent flexibility observed in biological systems. To better innovate this area, the present work systematically explores the value and potential of liquid metals and their derivatives in facilitating a crucial transition towards soft humanoid robots. Through a comprehensive interpretation of bionics, an overview of liquid metals' multifaceted roles as essential components in constructing advanced humanoid robots-functioning as soft actuators, sensors, power sources, logical devices, circuit systems, and even transformable skeletal structures-is presented. It is conceived that the integration of these components with flexible structures, facilitated by the unique properties of liquid metals, can create unexpected versatile functionalities and behaviors to better fulfill human needs. Finally, a revolution in humanoid robots is envisioned, transitioning from metallic frameworks to hybrid soft-rigid structures resembling that of biological tissues. This study is expected to provide fundamental guidance for the coming research, thereby advancing the area.

Ferroelectric Domain Intrinsic Radiation Resistance of Lithium Niobate Ferroelectric Single−Crystal Film

The study of the properties of ferroelectric materials against irradiation has a long history. However, anti−irradiation research on the ferroelectric domain has not been carried out. In this paper, the irradiation of switched domain structure is innovatively proposed. The switched domain of 700 nm lithium niobate (LiNbO3, LN) thin film remains stable after gamma irradiation from 1 krad to 10 Mrad, which was prepared by piezoresponse force microscopy (PFM). In addition, the changing law of domain wall resistivity is explored through different sample voltages, and it is verified that the irradiated domain wall conductivity is still larger than the domain. This domain wall current (DWC) property can be applied to storage, logic, sensing, and other devices. Based on these, a ferroelectric domain irradiation resistance model is established, which explains the reason at an atomic level. The results open a possibility for exploiting ferroelectric materials as the foundation in the application of space and nuclear fields.

Full electrical manipulation of perpendicular exchange bias in ultrathin antiferromagnetic film with epitaxial strain

Achieving effective manipulation of perpendicular exchange bias effect remains an intricate endeavor, yet it stands a significance for the evolution of ultra-high capacity and energy-efficient magnetic memory and logic devices. A persistent impediment to its practical applications is the reliance on external magnetic fields during the current-induced switching of exchange bias in perpendicularly magnetized structures. This study elucidates the achievement of a full electrical manipulation of the perpendicular exchange bias in the multilayers with an ultrathin antiferromagnetic layer. Owing to the anisotropic epitaxial strain in the 2-nm-thick IrMn3 layer, the considerable exchange bias effect is clearly achieved at room temperature. Concomitantly, a specific global uncompensated magnetization manifests in the IrMn3 layer, facilitating the switching of the irreversible portion of the uncompensated magnetization. Consequently, the perpendicular exchange bias can be manipulated by only applying pulsed current, notably independent of the presence of any external magnetic fields.

Realization of logic operations via spin–orbit torque driven perpendicular magnetization switching in a heavy metal/ferrimagnet bilayer

Programmable and non-volatile spin-based logic devices have attracted significant interest for use in logic circuits. Realization of logic operations via spin–orbit torque (SOT) driven magnetization switching could be a crucial step in the direction of building logic-in-memory architectures. In this work, we demonstrate experimentally, the realization of four logic operations in a heavy metal/ferrimagnet bilayer structure via SOT switching. We also propose a general scheme for choosing input parameters to achieve programmable logic operations. The bulk and tunable perpendicular magnetic anisotropy and relatively lower saturation magnetization in ferrimagnets are found to make them more energy efficient in performing logic operations, as compared to conventional ferromagnets. Thus, ferrimagnets are promising candidates for use in logic-in-memory architectures, leading to the realization of user-friendly spin logic devices in the future.

Field-free switching of perpendicular magnetization in a noncollinear antiferromagnetic Mn3Sn/[Pt/Co]4 heterostructure

Spin-orbit torque (SOT) manipulation of perpendicular magnetization is essential for realizing spintronic storage and logic devices. When a charge current flows through a heavy metal/ferromagnetic layer structure, a spin current can be generated by the heavy metal and injects into the ferromagnetic layer with perpendicular magnetic anisotropy and switch its magnetization via the SOT. However, in order to realize the deterministic switching, an in-plane external magnetic field is needed to break the inversion symmetry, a technological requirement that hampers the practical application of SOT. Pt/Co multilayer is a good magnetic recording media and, thus, the all-electric manipulation of its perpendicular magnetic moments is of practical significance. The noncollinear spin structure in Mn3Sn allows an unconventional spin polarization direction, and the associated SOT can switch the magnetic moments in the absence of an external field. In this work, we demonstrate the field-free SOT switching of a heterostructure utilizing Mn3Sn and Pt/Co multilayer as the spin source and the ferromagnetic layer with perpendicular magnetization, respectively. Our results are important for advancing the development of spintronic devices based on noncollinear antiferromagnets.

Spin logic devices based on negative differential resistance-enhanced anomalous Hall effect

Spin logic devices based on negative differential resistance-enhanced anomalous Hall effect

Spin‐Orbit Torque Switching of Magnetization in Ultra‐Thick Ferromagnetic Layers

AbstractCurrent‐induced magnetization switching via spin‐orbit torque (SOT) holds great potential for applications in high‐speed and energy‐efficient magnetic memory and logic devices. In the extensively studied heavy metal/ferromagnet (HM/FM) SOT heterostructures, the thickness of the FM layer is typically restricted to a few nanometers or less due to the rapid spin dephasing, making it challenging to implement thermally stable memory cells with high density. In this study, it is demonstrated that this thickness constraint can be significantly alleviated by utilizing an oxide ferromagnet La0.67Sr0.33MnO3 (LSMO). Through electrical transport and magnetic optical measurements, it is found that the SOT can switch the magnetization in Pt/LSMO heterostructures even at an LSMO thickness of 35 nm, which is one order of magnitude larger than that for metallic FMs, such as CoFeB. Furthermore, based on the FM thickness dependence of the switching current and the domain switching type revealed by magnetic optical Kerr effect imaging (MOKE), a possible picture is proposed to describe the SOT switching in Pt/LSMO, which highlights the critical role of the domain wall propagation in the vertical direction. The work provides valuable insights into the behavior of SOT switching in ultra‐thick FM films, offering new possibilities for their practical applications.

Progress in Spin Logic Devices Based on Domain-Wall Motion.

Spintronics, utilizing both the charge and spin of electrons, benefits from the nonvolatility, low switching energy, and collective behavior of magnetization. These properties allow the development of magnetoresistive random access memories, with magnetic tunnel junctions (MTJs) playing a central role. Various spin logic concepts are also extensively explored. Among these, spin logic devices based on the motion of magnetic domain walls (DWs) enable the implementation of compact and energy-efficient logic circuits. In these devices, DW motion within a magnetic track enables spin information processing, while MTJs at the input and output serve as electrical writing and reading elements. DW logic holds promise for simplifying logic circuit complexity by performing multiple functions within a single device. Nevertheless, the demonstration of DW logic circuits with electrical writing and reading at the nanoscale is still needed to unveil their practical application potential. In this review, we discuss material advancements for high-speed DW motion, progress in DW logic devices, groundbreaking demonstrations of current-driven DW logic, and its potential for practical applications. Additionally, we discuss alternative approaches for current-free information propagation, along with challenges and prospects for the development of DW logic.