In-plane Mobility Research Articles

Effect of Strong Intermolecular Interaction in 2D Inorganic Molecular Crystals.

Strong intermolecular interactions in 2D organic molecular crystals arising from π-π stacking have been widely explored to achieve high thermal stability, high carrier mobility, and novel physical properties, which have already produced phenomenal progress. However, strong intermolecular interactions in 2D inorganic molecular crystals (2DIMCs) have rarely been investigated, severely limiting both the fundamental research in molecular physics and the potential applications of 2DIMCs for optoelectronics. Here, the effect of strong intermolecular interactions induced by unique short intermolecular Se-Se and P-Se contacts in 2D α-P4Se3 nanoflakes is reported. On the basis of theoretical calculations of the charge density distribution and an analysis of the thermal expansion and plastic-crystal transition, the physical picture of strong intermolecular interactions can be elucidated as a higher charge density between adjacent P4Se3 molecules, arising from an orderly and close packing of P4Se3 molecules. More importantly, encouraged by the strong intermolecular coupling, the in-plane mobility of α-P4Se3 nanoflakes is first calculated with a quantum nuclear tunneling model, and a competitive hole mobility of 0.4 cm2 V-1 s-1 is obtained. Our work sheds new light on the intermolecular interactions in 2D inorganic molecular crystals and is highly significant for promoting the development of molecular physics and optoelectronics.

Improvement of β-Ga2O3 Junction Field-Effect Transistors By Employing WSe2/β-Ga2O3 p-n Heterojunction Via Laser-Assisted Oxidation

Beta gallium oxide (β-Ga2O3) is a semiconductor material that has been receiving a lot of attention during the past years owing to its suitability for next-generation high-power devices. The attributes of β-Ga2O3 that make it attractive for use in high-power devices include ultra-wide bandgap energy of 4.9 eV, large breakdown field of ~8 MV/cm (estimated), and high Baliga’s and Johnson’s figures of merit of approximately 3214 and 2844, respectively. From the device fabrication point of view, β-Ga2O3 crystal having a monoclinic structure with an anisotropic unit cell facilitates the effortless fabrication of low-scale β-Ga2O3 devices through simple mechanical exfoliation. However, the nature of β-Ga2O3 that it is n-doped by its oxygen vacancies and its difficulties in p-doping limit the application of β-Ga2O3 in integrated structures such as the CMOS (complementary metal-oxide-semiconductor), where the semiconductor substrate is required to have both n- and p-doped areas. Various studies, with the aim of finding alternative solutions to this problem, are being conducted on the fabrication of p-n heterojunctions composed of n-type β-Ga2O3 and p-type or ambipolar semiconductor materials. Among them, transition metal dichalcogenides (TMDs) are studied for the p-n heterojunctions involving the n-type β-Ga2O3. TMDs have a crystal structure composed of layers, consisting of in-plane repeating units with two to three atoms, attached to one another by interplanar van der Waals interaction which gives rise to favorable electrical and structural characteristics, including high in-plane carrier mobility, atomic-scale thickness, and atomically clean surface allowing TMDs to form van der Waals heterostructures without strain from heteroepitaxial growth. In this work, tungsten diselenide (WSe2), which has a moderate bandgap of ~1.2 to 1.7 eV (bulk to monolayer, respectively), is utilized to form the p-n heterojunction with β-Ga2O3. WSe2 exhibits ambipolar transport characteristics in nature and shows excellent doping controllability through processes such as Ar plasma treatment, ultraviolet/ozone treatment, and laser-assisted oxidation. In this work, laser-assisted oxidation was utilized for the selective p-doping of WSe2 in the WSe2/β-Ga2O3 heterojunction area.In this work, β-Ga2O3 and WSe2 flakes were mechanically exfoliated from single crystal bulks with an adhesive tape, respectively. β-Ga2O3 flakes were transferred via dry transfer method onto Si/SiO2 substrates, followed by electron-beam lithography to define the β-Ga2O3 channels. Ti/Au (50/100 nm) source/drain electrodes were deposited by electron-beam evaporator. Rapid thermal annealing was performed in low vacuum (~10-2 Torr) at 500℃ for 60 s to form Ohmic contacts. Selected WSe2 flakes were transferred onto a specific position of the β-Ga2O3 channels by PDMS-film-assisted dry transfer method. Source/drain electrodes of the WSe2 channel were defined using electron-beam lithography, followed by Pt/Au (20/80 nm) electrode deposition with an electron-beam evaporator. Fabricated devices were thermally annealed in a high vacuum condition (~6×10-6 Torr) at 200℃ for 120 min to improve the contact. 325 nm laser with an intensity of 0.135 mW was utilized for the selective oxidation of WSe2 in the WSe2/β-Ga2O3 heterojunction.The fabricated device exhibited distinct rectifying behavior with an ideality factor of 1.16 and an on/off ratio of ~106, where the on-resistance decreased by approximately five orders of magnitude after WSe2 oxidation. β-Ga2O3 JFET with a WSe2 top gate showed outstanding characteristics with a subthreshold swing of 76.84 mV/dec and an on/off ratio of ~107. This work demonstrates low-scale, high-quality β-Ga2O3 JFETs with WSe2, paving the way to the potential applications of high power β-Ga2O3 device with high switching speed and small device footprint.

Highly efficient terahertz emission from layered ZrTe5 crystal with strong anisotropy and high in-plane carrier mobility

Intense, polarization controllable, and single-cycle terahertz pulses as light source are important tools to investigate physical and biological properties of materials. In this paper, we have detected efficient terahertz emission from layered transition-metal pentatelluride ZrTe5 excited by femtosecond laser pulse due to its strong anisotropy and high mobility of electrons. The physical mechanism of terahertz generation from this material is studied and the absolute predominance of diffusion current induced by photo-Dember effect is proved. In addition, we have achieved the modulation of terahertz polarization by adjusting the polarization states of the pump pulse. The generated elliptically polarized THz pulse is crucial for the investigation of vibration modes of chiral biological molecules, such as proteins and DNAs. Our findings indicate that strong and polarization-controllable THz emission can be generated by ZrTe5.

First-principles study of electron transport in ScN

We investigate the conduction-band structure and electron mobility in rocksalt ScN based on density functional theory. The first-principles band structure allows us to obtain band velocities and effective masses as a function of energy. Electron-phonon scattering is assessed by explicitly computing the $q$-dependent electron-phonon matrix elements, with the inclusion of the long-range electrostatic interaction. The influence of free-carrier screening on the electron transport is assessed using the random-phase approximation. We find a notable enhancement of electron mobility when the carrier concentration exceeds ${10}^{20}\phantom{\rule{4pt}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}$. We calculate the room-temperature electron mobility in ScN to be 587 ${\mathrm{cm}}^{2}/\mathrm{Vs}$ at low carrier concentrations. When the carrier concentration is increased, the electron mobility starts to decrease significantly around $n={10}^{19}\phantom{\rule{4pt}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}$ and drops to 240 ${\mathrm{cm}}^{2}/\mathrm{Vs}$ at $n={10}^{21}\phantom{\rule{4pt}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}$. We also explore the influence of strain in (111)- and (100)-oriented ScN films. For (111) films, we find that a 1.0% compressive epitaxial strain increases the in-plane mobility by 72 ${\mathrm{cm}}^{2}/\mathrm{Vs}$ and the out-of-plane mobility by 50 ${\mathrm{cm}}^{2}/\mathrm{Vs}$. For (100) films, a 1.0% compressive epitaxial strain increases the out-of-plane mobility by as much as 172 ${\mathrm{cm}}^{2}/\mathrm{Vs}$, but has a weak impact on the in-plane mobility. Our study sheds light on electron transport in ScN at different electron concentrations and shows how strain engineering could increase the electron mobility.

Slippery damper of an overlay for arresting and manipulating droplets on nonwetting surfaces

In diverse processes, such as fertilization, insecticides, and cooling, liquid delivery is compromised by the super-repellency of receiving surfaces, including super-hydro-/omni-phobic and superheated types, a consequence of intercalated air pockets or vapor cushions that promote droplet rebounds as floating mass-spring systems. By simply overlaying impacting droplets with a tiny amount of lubricant (less than 0.1 vol% of the droplet), their interfacial properties are modified in such a way that damper-roller support is attached to the mass-spring system. The overlayers suppress the out-of-plane rebounds by slowing the departing droplets through viscous dissipation and sustain the droplets’ in-plane mobility through self-lubrication, a preferential state for scenarios such as shedding of liquid in spray cooling and repositioning of droplets in printing. The footprint of our method can be made to be minimal, circumventing surface contamination and toxification. Our method enables multifunctional and dynamic control of droplets that impact different types of nonwetting surfaces.

Pulsed sputtering growth of heavily Si-doped GaN (201) for tunneling junction contacts on semipolar InGaN (201) LEDs

We report the in-plane anisotropic conductivity of heavily Si-doped GaN (201) prepared by pulsed sputtering deposition and its application to tunneling junction (TJ) contacts on InGaN (201) LEDs. Si-doped GaN (201) yielded a high electron mobility of 109 cm2 V−1 s−1 even at an electron concentration of 1.1 × 1020 cm−3. The average difference in the in-plane electron mobility along the [014] and [110] directions was small (approximately 9.7%) because of the low stacking fault density. The heavily Si-doped GaN (201) worked as a uniform current spreading layer and hole injection layer through the TJ on InGaN (201) LEDs.

Coplanar High Mobility and Interplanar Van Der Waals Heterojunction in Layered Two-Dimensional Bi₂O₂Se Nanosheets

In this letter, the electronic transport features of layered two-dimensional (2D) Bi <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Se semiconductor nanosheets are characterized along the in-plane and the out-of-plane directions, respectively. The modulation of double gate is manufactured on a 26.4 nm CVD-grown Bi <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Se-nanosheet MOSFET, thus executing the highest in-plane field-effect mobility of ~296 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> V <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> s <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> at room temperature. Furthermore, the rectification behavior of charge transport across the perpendicular interlayer of Bi <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Se nanosheet is distinctly scrutinized. Correspondingly, the existing of potential barrier between the [Bi <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ] <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2n+</sup> and [Se] <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2n-</sup> interlayers of Bi <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Se nanosheets is validated by the temperature-dependent current measurement and the Poole-Frenkel model. This work offers promising routes to implement high-efficient field-effect transports parallel to the in-plane direction, as well as tunable heterojunction transports across the perpendicular interlayer of 2D Bi <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Se nanosheets.

Impact of hydration on ion transport in Li2Sn2S5·xH2O

The layered material Li2Sn2S5 forms two hydrated solid phases under increasing humidity. Intercalated water hydrates the interlayer Li+ ions and screens coulombic interactions, leading to a high in-plane mobility of both Li+ and H2O.

Random copolymerization of polythiophene for simultaneous enhancement of in‐plane and out‐of‐plane charge transport for organic transistors and perovskite solar cells

High-performance conjugated polymers for electronic applications can be developed by modulating an appropriate chemical structure that optimizes their crystal characteristics and charge-transport behavior. Herein, we demonstrated the simultaneous enhancement of the in-plane and out-of-plane charge transport of polythiophenes by random polymerization. We synthesized a polythiophene polymer by varying the ratio of two different dialkyl-substituted bi-thiophene and triethylene glycol-substituted mono-thiophene units; this polymer exhibited weakened orientation preferences of polymer crystallite films, a denser packing, and a more homogeneous surface morphology in comparison with its homopolymer analogue. Furthermore, this optimized random polymer afforded an enhanced in-plane mobility of 7.72 cm2 V−1 second−1, measured by field-effect transistor, and out-of-plane mobility of 8.86 × 10−4 cm2 V−1 second−1, measured by space-charge-limited-current device. These are respectively 2.4 times and 10 times higher than the mobilities of the homopolymer (field-effect mobility = 3.25 cm2 V−1 second−1 and space-charge-limited-current mobility = 8.73 × 10−5 cm2 V−1 second−1). The enhanced charge transport in out-of-plane direction was also confirmed by fabricating perovskite solar cells using optimized polythiophene as a hole-transporting material, which exhibited a higher efficiency of nearly 16.2% than the device with homopolymer analogue (12.0%).

Conformational disorder of organic cations tunes the charge carrier mobility in two-dimensional organic-inorganic perovskites

The chemical nature of the organic cations governs the optoelectronic properties of two-dimensional organic-inorganic perovskites. But its mechanism is not fully understood. Here, we apply femtosecond broadband sum frequency generation vibrational spectroscopy to investigate the molecular conformation of spacer organic cations in two-dimensional organic-inorganic perovskite films and establish a correlation among the conformation of the organic cations, the charge carrier mobility, and broadband emission. Our study indicates that both the mobility and broadband emission show strong dependence on the molecular conformational order of organic cations. The gauche defect and local chain distortion of organic cations are the structural origin of the in-plane mobility reduction and broad emission in two-dimensional organic-inorganic perovskites. Both of the interlayer distance and the conformational order of the organic cations affect the out-of-plane mobility. This work provides molecular-level understanding of the conformation of organic cations in optimizing the optoelectronic properties of two-dimensional organic-inorganic perovskites.

Quantum Confinement and Thickness‐Dependent Electron Transport in Solution‐Processed In2O3 Transistors

AbstractThe dependence of charge carrier mobility on semiconductor channel thickness in field‐effect transistors is a universal phenomenon that has been studied extensively for various families of materials. Surprisingly, analogous studies involving metal oxide semiconductors are relatively scarce. Here, spray‐deposited In2O3 layers are employed as the model semiconductor system to study the impact of layer thickness on quantum confinement and electron transport along the transistor channel. The results reveal an exponential increase of the in‐plane electron mobility (µe) with increasing In2O3 thickness up to ≈10 nm, beyond which it plateaus at a maximum value of ≈35 cm2 V−1 s−1. Optical spectroscopy measurements performed on In2O3 layers reveal the emergence of quantum confinement for thickness &lt;10 nm, which coincides with the thickness that µe starts deteriorating. By combining two‐ and four‐probe field‐effect mobility measurements with high‐resolution atomic force microscopy, it is shown that the reduction in µe is attributed primarily to surface scattering. The study provides important guidelines for the design of next generation metal oxide thin‐film transistors.

Electronic Tunability and Mobility Anisotropy of Quasi-2D Perovskite Single Crystals with Varied Spacer Cations.

The organic-inorganic hybrid quasi-two-dimensional (quasi-2D) perovskites have attracted increasing attention for solar cell applications due to their improved moisture stability and excellent optoelectronic properties. To achieve a profound understanding and delicate control on the component of perovskite, it is indispensable to know how different spacer cations affect their intrinsic properties. Here, we synthesized a series of quasi-2D perovskite single crystals with different organic spacer cations and conducted a systematic investigation to correlate the optoelectronic behaviors to the spacer cations. We revealed the coupling effect between the π-electron (PEA+) and p orbital of I- from the inorganic framework, which changed the electronic configuration of resultant crystals leading to different band gap and carrier behavior. In particular, the anisotropic carrier mobility was probed quantitatively by space-charge limited current (SCLC) measurement, where PEA2MA2Pb3I10 exhibited the highest in-plane mobility due to the reduced exciton binding energy and the lowest out-of-plane mobility because of the widest organic barrier.

A novel two-dimensional sp-sp2-sp3 hybridized carbon nanostructure with a negative in-plane Poisson ratio and high electron mobility

A novel two-dimensional (2D) semiconducting carbon allotrope is proposed by inserting alkyne into tetrahexcarbon. This new carbon allotrope consists of tetra-rings and acetylenic linkages and is called TAL-carbon. To the best of our knowledge, this is the first 2D carbon allotrope composed of sp-sp2-sp3 hybridized carbon atoms. Due to its unique puckered structure, TAL-carbon is the fourth 2D carbon material with an intrinsic in-plane negative Poisson ratio (NPR) reported after graphene, penta-graphene, and tetrahexcarbon. Materials with NPR exhibit a wide range of potential applications in biomedicine, aerospace industries, and precision instruments. TAL-carbon has an indirect band gap of 1.614 eV. At room temperature, it exhibits high in-plane electron mobility of up to ~3.5 × 104 cm2V−1s−1, which is 30 times higher than monolayer black phosphorus and two orders of magnitude higher than monolayer MoS2. The phonon dispersion curves and in-plane elastic constants indicate that TAL-carbon is dynamically and mechanically stable. Its equibiaxial strain limit reaches 13.7%, similar to that of graphene. An ab initio molecular dynamics (AIMD) simulation demonstrates that TAL-carbon is thermally stable at 300 K and 1000 K. The results show that TAL-carbon is a promising 2D auxetic material for applications in nanomechanics and nanoelectronics.

Chemical Vapor Growth of Silicon Phosphide Nanostructures

ABSTRACTIn the search for chemically stable two-dimensional (2D) materials with high in-plane mobility, proper bandgap, and compatibility with vapor-based fabrication, van der Waals semiconductor SiP has become a potential candidate as a robust variation of black phosphorous. While bulk SiP crystals were synthesized in the 1970s, the vapor-based synthesis of SiP nanostructures or thin films is still absent. We here report the first chemical vapor growth of SiP nanostructures on SiO2/Si substrate. SiP islands with lateral size up to 20 μm and showing well-defined Raman signals were grown on SiO2/Si substrate or on SiP-containing concentric rings. The presence of SiP phase is confirmed by XRD. The formation of rings and islands is explained by a multiple coffee ring growth model where a dynamic fluctuation of droplet growth front induces the topography of concentric ring surfaces. This new growth method might shed light on the controlled growth of group IV-III high-mobility 2D semiconductors.

Control of grain orientation and its impact on carrier mobility in reactively sputtered Cu2O thin films

Grain orientation can be particularly important in devices such as thin film transistors (TFTs) where grain boundaries present a barrier to lateral carrier transport. This paper demonstrates that thin films of nanocrystalline cuprous oxide (Cu2O) can be grown with control of the grain orientation in the direction of either [111] or [100] perpendicular to the substrate surface using a high target utilization sputtering system. This allows a systematic study of the effect of grain orientation on the carrier mobility in Cu2O films. It is shown that the carrier mobility in as-deposited films is similar for both grain orientations while [100]-oriented thin films exhibit a higher carrier mobility for lateral conduction than films with a [111] orientation after annealing, which is discussed from the viewpoint of the Urbach energy, crystallinity and surface morphology. This experimental finding suggests that Cu2O thin films with a [100] surface grain orientation are favorable for device applications such as p-type TFTs where a high in-plane carrier mobility is desired.

Two-dimensional IV–VI materials with in-plane negative Poisson's ratio and anisotropic carrier mobility

Two-dimensional (2D) semiconductors with novel mechanical behaviors and electronic features are highly sought for a variety of potential applications.

Strain-Engineered Asymmetrical Superlattice Si/Si1–x Ge x Nano-ATT $\langle$ p++-n-n−-n++$\rangle$ Oscillator: Enhanced Photo-Sensitivity in Terahertz Domain

This paper proposes a strained Si-based single drift nano-mixed tunnel avalanche transit time (MITATT) oscillator capable of generating high RF power in the terahertz regime, inaccessible by conventional Si devices. The authors have developed a quantum modified classical drift-diffusion model to study the nanoscale properties of strained Si oscillator. The study reveals that 14.72-GW/m2 RF power could be generated from 0.715-THz strain-engineered Si oscillator. Such performance enhancement of the Si device is due to selective incorporation of trace amounts of Ge in the Si active region. This generates in-plane biaxial strain which in turn degrades the in-plane electron mobility, hence unsuitable for conventional MOSFETs. However, such strain remarkably enhances the out-of-plane mobility, and uniqueness of the current research is the utilization of in-plane strain to boost up the out-of-plane mobility depending on geometry and dimensions of the oscillator’s active region. The model incorporates parasitic series resistance and elevates junction temperature effects on terahertz properties of the device. Incorporation of the strained layer in the active region reduces the parasitic series resistance effect on high frequency properties of the oscillator. Validity of the developed model is established by comparing simulated data with the corresponding experimental observations. The authors have further studied photo irradiation effects on terahertz characteristics of the new class of devices. The structure-induced quantum confinement effect has made the Si-based active region to behave as a partially direct bandgap material, and therefore, a significant improvement is observed in optical sensitivity. To the best of the authors’ knowledge, this is the first report on strain-engineered asymmetrically doped Si/SiGe based avalanche photosensor in the high-frequency terahertz domain.

Pneumatic Soft Actuator with Anisotropic Soft and Rigid Restraints for Pure in-Plane Bending Motion

A variety of soft robots with prospective applications has been developed in recent years. As a key component of a soft robot, the soft actuator plays a critical role and hence must be designed carefully according to application requirements. The soft body may deform in undesired directions if no restraint is endued, due to the isotropy of the pure soft material. For some soft robots such as an inchworm-like biped climbing robot, the actuation direction must be constrained with the appropriate structure design of the soft actuator. This study proposes a pneumatic soft actuator (PSA) to achieve pure in-plane bending motion with anisotropic soft and rigid restraints. The in-plane bending pneumatic soft actuator (2D-PSA) is developed with a composite structure where a metal hinge belt is embedded into the soft material. The design method, material choice, and fabrication process are presented in detail in this paper. Tests are conducted to measure the actuating performance of 2D-PSA in terms of the relationship between the bending angle or force and the input air pressure. Dynamic response is also measured with a laser tracker. Furthermore, a comparative experiment is carried out between the presented 2D-PSA and a general PSA, with results verifying the effectiveness of the presented 2D-PSA. A robot consisting of two serially-connected 2D-PSAs and three pneumatic suckers, which can climb on a flat surface mimicking a snake’s locomotion, is developed as an application demo of the presented 2D-PSA. Its locomotion capability presents the in-plane performance and mobility of 2D-PSA.

A new Fourier series method and displacement function for in-plane vibration and power flow characteristics analysis of isotropic rectangular plates

The generation of in-plane vibration in plates is an important issue and frequently occurs due to the presence of excitations in the ship’s hull due to turbulent fluid flows, turbulent airflow excitation on aerospace structures, gear system subjected to axial excitation, assemblies housing piezoelectric crystals and sandwiched plates, and so on. The present analysis aims to establish a universal and numerically efficient method for determination of in-plane vibration characteristics of isotropic rectangular plates both for conventional and general boundary conditions. The new in-plane Fourier series and displacement function of the plate have been developed using beam displacement functions in x and y directions, respectively, under in-plane condition. A modified Fourier series assumption for the in-plane beam displacement has been utilised and further developed as plate displacement function. The computational efficiency of the present method is compared in terms of convergence of natural frequency parameter, speed of execution and manual convenience to reduce human errors with the frequently used Fourier series method by various researchers. Rayleigh–Ritz procedure has been applied to determine the in-plane natural frequencies. The mode shapes for few conventional and generally varying boundary conditions have been presented and analysed. The dynamic response has been obtained and analysed in terms of the in-plane mobility and power flow characteristics of the plate under varying boundary conditions. The validity of results obtained by the current method has shown excellent accuracy and faster convergence with the existing results. The present results can provide a benchmark to analyse the dynamic in-plane response of plate systems being used for built-up structures in real engineering applications.

Current-Driven Dynamics of Frustrated Skyrmions in a Synthetic Antiferromagnetic Bilayer

We report the current-driven dynamics of frustrated skyrmions in an antiferromagnetically exchange coupled bilayer system, where the bilayer skyrmion consists of two monolayer skyrmions with opposite skyrmion numbers $Q$. We show that the in-plane current-driven bilayer skyrmion moves in a straight path, while the out-of-plane current-driven bilayer skyrmion moves in a circular path. It is found that the in-plane current-driven mobility of a bilayer skyrmion is much better than the monolayer one at a large ratio of $\beta/\alpha$, where $\alpha$ and $\beta$ denote the damping parameter and non-adiabatic spin transfer torque strength, respectively. Besides, the out-of-plane current-driven mobility of a bilayer skyrmion is much better than the monolayer one when $\alpha$ is small. We also reveal that one bilayer skyrmion (consisting of monolayer skyrmions with $Q=\pm 2$) can be separated to two bilayer skyrmions (consisting of monolayer skyrmions with $Q=\pm 1$) driven by an out-of-plane current. Our results may be useful for designing skyrmionic devices based on frustrated multilayer magnets.