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The quantum anomalous Hall effect (QAHE) in a magnetic topological insulator system without the need of an external magnetic field becomes of great interest because of its dissipationless spin currents. The proximity effect via a magnetic adlayer is a promising strategy to bring magnetism into a topological insulator (TI) due to its boosted Curie temperature for a realistic application. In this work, a proximity-induced magnetism above 90 K in a TI, (Bi 0.25 Sb 0.75 ) 2 Te 3 , on a ferrimagnetic adlayer with perpendicular magnetic anisotropy, thulium-iron-garnet (TIG), was evidenced directly by using magnetic circular dichroism. A competition between exchange couplings with different sublattice-sites was further revealed element-specifically in a temperature-driven spin-reorientation of TI, bringing an issue on magnetic inhomogeneity at the interface, which might cause difficulties in obtaining QAHE in such a TI/TIG bilayer system. Our results prove directly the robust magnetism of TI above liquid nitrogen temperatures and also give a deep insight into the mechanism of interfacial coupling in the proximity effect for the bilayer of TI and magnetic oxide, which could be essential for the design of a system with QAHE.

Graphene transistors with a gate-controlled transition of neuromorphic functions between artificial neurons and synapses have attracted increasing attention because the atomic thickness could be easily modulated by different stimuli, which is very beneficial for synaptic applications. As a modulation method, a graphene electrolyte-gated transistor (EGT) has been proposed, in which the electrical conductance of the graphene channel is modulated by reversible electrochemical hydrogenation of graphene. However, only a sparse physically realized graphene-based synaptic H+-EGTs have been reported due to the difficulty of achieving a high concentration of protons at the electrolyte–graphene interface. Here, we have reported the H+-EGTs with a highly defective graphene channel and a gel electrolyte [H3PO4/poly(vinyl alcohol)], which is based on hydrogenation and dehydrogenation of highly defected-graphene, performing the similar functions as the common artificial synaptic transistors, with good retention (<1% attenuation per minute), analog tunability (>200 nonvolatile states), and precisely controllable resistance (∼0.4% step flipped per synaptic event). In addition, the cyclic voltammetry test was applied to confirm the hydrogenation and dehydrogenation of the graphene channel. It is expected that this principle can provide ideas for designing graphene-based artificial synapses enabling integrated functions of in-memory computing and in-memory sensing for the neuromorphic system. [ABSTRACT FROM AUTHOR]

Terahertz (THz) beam steering is of great significance for realizing high-speed communication, radar scanning, and information processing, but it is limited by the number of channels and strong crosstalk between different channels. In this work, we demonstrate a three-channel polarization multiplexed metasurface, enabling polarization-dependent and frequency-dependent multi-beam steering. The independent phase gradients are superimposed on a single-layer structure for three non-orthogonal polarization states, and we solved the supercell structure of the metasurface by Least Squares Approximation and Gradient Descent Algorithm to effectively suppress the crosstalk between non-orthogonal modes. The experimental results show that the deflection angles on different linear polarization states and frequencies can cover the angle range of 15°–50° in the broadband range of 0.3–0.5 THz, and the maximum crosstalk between channels is −27.84 dB at the center frequency of 0.4 THz. The proportion of beam energy correctly multiplexed by each channel reaches >80%. This non-orthogonal polarization multiplexing mechanism is of great value for THz metasurface multi-channel wavefront manipulation. [ABSTRACT FROM AUTHOR]

The grain boundary phase (GBP) has a significant influence on the magnetization behavior in nanocrystalline PrNd–Fe–B magnets. The current study demonstrates that reversible/irreversible magnetization behavior and the phenomenon of open recoil loops are related to both the nature of GBPs and the magnetization state by in situ observation. The optimization of GBPs nature (increase the volume fraction and improve the composition of GBPs) leads to the suppression of reversible magnetization behavior and the phenomenon of open recoil loops at low fields. Since the asymmetric magnetic domain structure appears only at low cycle fields, the openness phenomenon originates from the weak pinning grain boundaries (GBs). In addition, optimization of the GBPs also enhances pinning strength and uniformity, which contributes to the domain walls being pinned in the GBs at higher external fields. At this moment, the domain wall is dominated by irreversible magnetization behavior, and the openness phenomenon disappears. This proves that the coercivity mechanism is transformed from inhomogeneously weak pinning to homogeneously strong pinning with the optimization of GBPs. Consequently, the coercivity and squareness factor are significantly enhanced. This study sheds light on the understanding of the effects of GBP's nature on recoil loops and coercivity mechanism, and it also provides significant guidance for the development of advanced permanent magnets. [ABSTRACT FROM AUTHOR]

The Wiedemann–Franz (WF) law is a fundamental, empirical law that originally relates the electronic thermal conductivity (Λe) of a metal to its electrical resistivity (ρ) via the Lorenz number L = ρΛe/T, where T is the absolute temperature. Conventionally as ρ is measured or calculated, it has often been used to infer the Λe through the WF law at a wide range of pressure (P)–temperature (T) conditions. However, since the WF law was originally formulated based on a simple electron gas model with L being approximately the Sommerfeld value L0 = 2.44 × 10−8 W Ω K−2, its validity to transition metals involving correlated d-orbital electrons at a variety of P-T conditions has been questioned, not to mention to metallic alloys. Here, we report experimental measurements on the thermal conductivity and electrical resistivity of platinum (Pt), iron (Fe), as well as Fe0.85Si0.15 and FeS alloys at high pressures and room temperature. We demonstrate that the L of Pt and Fe both reasonably agree with L0 from ambient to ∼60 GPa, except for Fe around the pressures where a structural transition (∼12 GPa) and an electronic topological transition (∼30–40 GPa) occur. The L of Fe0.85Si0.15 and FeS alloys, however, both considerably deviate from L0, presumably due to significant inelastic scatterings between carriers and impurities. Our results suggest that using the WF law with ideal L0 to convert ρ of metallic alloys to Λe (and vice versa) at high pressures could lead to a large discrepancy from that obtained by direct measurements. [ABSTRACT FROM AUTHOR]

Freestanding semiconductor membranes hold significant potential for heterogeneous integration technology and flexible electronics. Remote epitaxy, which leverages electrostatic interactions between epilayers and substrates through two-dimensional (2D) materials such as graphene, offers a promising solution for fabricating freestanding single-crystal membranes. Although the thinness, uniformity, and cleanness of 2D materials need to be meticulously controlled to enable the remote epitaxy of high-quality thin films, attaining such ideal growth templates has been challenging thus far. In this study, we demonstrate a controlled graphitization method to form a pristine graphene buffer layer (GBL) directly on SiC substrates and utilize this GBL template for GaN remote epitaxy. The quasi-two-dimensional GBL layer obtained by the method is completely free of damage or contamination, facilitating strong epitaxial interaction between the GaN epilayer and the SiC substrate. Furthermore, we reveal that a two-step growth of GaN on this GBL template enables the formation of single-crystal GaN epilayers and their exfoliation. Thus, this study represents an important step toward developing high-quality, freestanding semiconductor membranes. [ABSTRACT FROM AUTHOR]

Experimental searches for axions or dark photons that couple to the standard model photon require photosensors with low noise, broadband sensitivity, and near zero backgrounds. Here, we introduce an experimental architecture, in which a small photon sensor, in our case a transition edge sensor (TES) with a photon energy resolution σ γ = 368.4 ± 0.4 meV, is colocated on the same substrate as a large high sensitivity athermal phonon sensor (APS) with a phonon energy resolution σ phonon = 701 ± 2 meV. We show that single 3.061 eV photons absorbed in the photon-sensing TES deposit ∼ 35% of their energy in the electronic system of the TES, while ∼ 26% of the photon energy leaks out of the photon-sensing TES during the downconversion process and becomes absorbed by the APS. Backgrounds, which we associate with the broadly observed "low energy excess" (LEE), are observed to be largely coupled to either the TES ("singles" LEE), or phonon system, ("shared" LEE). At high energies, these backgrounds can be efficiently discriminated from TES photon absorption events, while at low energies, their misidentification as photon events is well modeled. With significant sensitivity improvements to both the TES and APS, this coincidence technique could be used to suppress backgrounds in bosonic dark matter searches down to energies near the superconducting bandgap of the sensor. [ABSTRACT FROM AUTHOR]

The document discusses the importance of semiconductors in modern technology and the need for advanced chip manufacturing methods as chip features become smaller. It highlights the significance of investing in plasma research to develop highly advanced chips for future manufacturing plants. The special issue focuses on plasma sources for semiconductor applications, covering topics such as EUV light generation, plasma processing, and plasma etching. The research areas covered include enabling future EUV sources, improving chip plasma processing, developing diagnostics for moderate-pressure plasmas, and integrating physics-based machine learning models into plasma processing tools. The document emphasizes the importance of understanding energy transport from plasma, surface chemistry for etching and deposition, and the role of dusty plasmas in nanoparticle growth. [Extracted from the article]

Perovskite memristors have garnered significant interest for their potential simulating artificial synapses; however, the presence of the toxic lead-based perovskites has hindered advancements in this field. In this work, a nontoxic, thickness-controllable Cs3Cu2I5 perovskite functional layer is synthesized through a dual-source vapor deposition for the Ag/Cs3Cu2I5/ITO memristor. The co-evaporation method shows advantages of various element, controllable atomic ratio and thickness, free impurity, and continuously uniform film. This device demonstrates an operating voltage of 1.2 V, a low power consumption of 0.013 W, a retention time exceeding 104 s, and an endurance of over 400 cycles. The synaptic behavior is emulated using the memristor, focusing on phenomena such as short-term potentiation and depression, paired-pulse facilitation, and spike-time-dependent plasticity. The migration of Na+ and Cl− ions, which occurs between the synaptic cleft and the postsynaptic membrane in biological synapses, is analogously represented by the movement of Ag+ ions between functional layer and the bottom electrode of the memristor. This process is further analyzed using the Hodgkin–Huxley neuron model. The Cs3Cu2I5-based memristor shows considerable promise for applications in storage systems and artificial synapses. [ABSTRACT FROM AUTHOR]

As a power amplifier in nonlinear frequency conversion, semiconductor optical amplifiers around 1 μm can effectively realize the miniaturization of the light source system. In this paper, a low confinement factor anti-waveguide asymmetric super-large optical cavity semiconductor optical amplifier (AT-SLOC-SOA) with high saturation power is reported. We introduced a high-refractive-index mode filtration layer under the n-cladding layer, ensuring fundamental mode output in the epitaxial direction while reducing the optical confinement factor to 0.615% per quantum well. The SOA exhibits a fundamental mode in the epitaxial direction with an ultra-narrow vertical divergence angle of merely 13.8°, which can enhance the fiber coupling efficiency. At 20 °C and 3 A, the AT-SLOC-SOA showed a peak wavelength of 1017.15 nm and a −3 dB spectral bandwidth of 27.491 nm. The small-signal gain reaches a maximum of 22.3 dB, with a −3 dB saturated output power up to 26.4 dBm and a maximum output power as high as 30 dBm. The fabrication process utilizes conventional epitaxial growth and etching techniques to ensure low cost and high reliability while achieving high saturated output power. [ABSTRACT FROM AUTHOR]

An optical fiber biosensor based on tapered noncore fiber (NCF) and coupling effect between surface plasmon resonance (SPR) and localized surface plasmon resonance is proposed in this paper. The sensor consists of two multimode fibers and a tapered NCF spliced in the middle. The tapered fiber with a waist diameter of 40 μm is fabricated by flame-heated drawing technology, and then a layer of Au film of 50 nm thickness is deposited on the surface of the taper waist. Au nanoparticles (AuNPs) are immobilized on the surface of the Au film by using the rich functional groups of polydopamine (PDA). The sensitivity is improved by reducing the diameter of the NCF and the electric field coupling between the Au film and AuNPs. The refractive index sensitivity of the sensor is increased to 3558 nm/RIU in the detection range of 1.335–1.365, which is about 1.8 times higher than that of Au-NCF sensor without tapering and AuNPs. Goat anti-rabbit IgG was fixed on the sensor surface through the adhesion effect of PDA and used for the specificity detection of rabbit IgG. The sensitivity and limit of detection (LOD) of the proposed biosensor are 1.16 nm/(μg/ml) and 0.017 μg/ml, respectively. The proposed biosensor has low manufacturing cost and high biological sensitivity, which has potential applications in low concentration biomolecular detection and human health monitoring. [ABSTRACT FROM AUTHOR]

Spin-transfer torque magnetic random access memory (MRAM) devices have considerable potential for high-performance computing applications; however, progress in this field has been hindered by difficulties in etching the magnetic tunnel junction (MTJ). One notable issue is electrical shorting caused by the accumulation of etching by-products on MTJ surfaces. Attempts to resolve these issues led to the development of step-MTJs, in which etching does not proceed beyond the MgO barrier; however, the resulting devices suffer from poor scalability and unpredictable shunting paths due to asymmetric electrode structures. This paper outlines the fabrication of pillar-shaped MTJs via a four-step etching process involving reactive-ion etching, ion-beam etching, oxygen exposure, and ion-trimming. The respective steps can be cross-tuned to optimize the shape of the pillars, prevent sidewall redeposition, and remove undesired shunting paths in order to enhance MTJ performance. In experiments, the proposed pillar-MTJs outperformed step-MTJs in key metrics, including tunneling magnetoresistance, coercivity, and switching efficiency. The proposed pillar-MTJs also enable the fabrication of MRAM cells with smaller cell sizes than spin–orbit torque devices and require no external field differing from voltage-controlled magnetic anisotropy devices. [ABSTRACT FROM AUTHOR]

Active control of the transportation of liquid drops on a horizontal surface is achieved using surfaces with switchable wettability via remote stimuli. However, the mechanism how the dynamic wettability influences drop dynamics is rarely reported. In this paper, we demonstrate that a surface with switchable wettability induces depinning of the contact line through re-orientation of anisotropic molecules. We investigated the dynamics of contact lines and contact angles during the initiation of drop movement by the advancing and receding angles of the surface. We found that imbalance between advancing and receding angles with respect to the dynamic contact angle provides the force needed to overcome the energy barrier due to contact angle hysteresis on the surface. We discovered that the driving energy is accumulated with oscillations in contact angle until it breaks the pinning energy barrier. Understanding the role of dynamic contact angles in drop movement on switchable surfaces paves the way for designing effective fluid manipulation devices, such as water harvesters, biosensors, and oil–water separators. [ABSTRACT FROM AUTHOR]

Atomic layer deposition-derived FePt alloy catalysts exhibit superb hydrogen evolution reaction (HER) activity under tuning of their composition, where the electronic structure is modulated by the ligand effect. We demonstrate that HER activity can be correlated with the calculated d-band center via a linear relationship. [ABSTRACT FROM AUTHOR]

Reducing the reversal barrier of Al1−xScxN ferroelectric alloy is critical for improving the coercive voltage and power consumption of ferroelectric devices. Here, the synergistic effect of alloy composition and strain is introduced to optimize the ferroelectric properties of Al1−xScxN alloys. Because of the increased Al–N ionic bond character and the contribution of Sc-d orbitals, the spontaneous polarization, reversal barrier, and bandgap all reduce as the Sc concentration increases. Strain engineering improves the electron's electric dipole moment, resulting in a significant increase in spontaneous polarization (145.93 μC/cm2 for Al0.625Sc0.375N alloy). Meanwhile, the horizontal tension and vertical compression lower the reversal barrier of Al0.625Sc0.375N alloy to 95.45 meV/f.u., significantly lower than that of orthorhombic HfO2. Interestingly, the bandgap of Al1−xScxN alloy with low Sc concentration rises initially and then decreases as horizontal strain varies from compression to tension, whereas that of Al1−xScxN alloy with high Sc concentration monotonically decreases. The Al1−xScxN alloy exhibits the opposite tendency under vertical strain. These findings provide a thorough understanding of Al1−xScxN ferroelectric alloys and a guideline for designing high-performance Al1−xScxN ferroelectric alloys. [ABSTRACT FROM AUTHOR]

Effective manipulation of valley degrees of freedom can offer significant opportunities for both fundamental research and practical applications. In this work, based on the first-principles calculations, we, respectively, studied the modulation of the valley states of the two-dimensional (2D) ferrovalley material ScBr2 in its bilayers and multiferroic heterostructures. The sliding ferroelectricity is found in ScBr2 bilayers, and the ferroelectric polarization is coupled with valley polarization, which can enable the switching of layer-polarization anomalous Hall effect. The switching of magnetic ground states can also be achieved through layer sliding. On the other hand, the reversal of the ferroelectric polarization of Ga2S3 in the ScBr2/Ga2S3 heterojunction can induce a semiconductor to half-metal phase transition, thereby enabling control of the anomalous valley Hall effect for "on" and "off" states. Our work provides two effective ways to manipulate the valley states in 2D materials. [ABSTRACT FROM AUTHOR]

High-performance p-B-n infrared photodetectors based on In 0.53 Ga 0.47 As / Ga 0.51 As 0.49 Sb type-II superlattices with an Al 0.85 Ga 0.15 AsSb barrier on an InP substrate have been demonstrated. These photodetectors exhibit 50% and 100% cutoff wavelengths of ∼ 2.1 μm and ∼ 2.6 μm, respectively. At a bias voltage of −100 mV bias voltage, the device exhibits a peak responsivity of 0.618 A/W at 2.1 μm, corresponding to a quantum efficiency of 36.5%. The device exhibits a saturated dark current shot noise limited specific detectivity (D*) of 4.12 × 10 10 cm · Hz 1 / 2 / W (at a peak responsivity of 2.1 μm) under −100 mV applied bias at 300 K. [ABSTRACT FROM AUTHOR]

The optical excitation of nitrogen-vacancy (NV) color centers in diamonds mostly results in fluorescence emission. During this process, a portion of the incident energy is transferred to phonon vibration, which heats the diamond crystal. For single NV color centers, the heat generated by the optical cycle is negligible, while for an ensemble of NV defects, the generated heat accumulates rapidly and heats the diamond. The temperature rise is rapid due to the high thermal conductivity of the diamond. In addition to the ability to be heated by light, the NV defect's unique properties also allow for the precise measurement of temperature using optically detected magnetic resonance. Here, we experimentally demonstrate that microcrystalline diamond containing NV center ensembles can be used as a self-gauged microheater. We attached a microcrystal diamond to an optical fiber in an endoscope configuration, evaluated its performance as a self-gauged heater under varied biologically relevant environments, and discussed its potential applications. In addition to the aforementioned capabilities, the NV defect enables the precise measurement of local magnetic fields. This provides a unique multimodal sensor to probe temperature-controlled magnetic phenomena at microscopic scales. [ABSTRACT FROM AUTHOR]

The diketopyrrolopyrrole-based polymer (DPPT-TT) has been employed in organic power field effect transistors due to its exceptional off-state breakdown performance. The impact of organic semiconductor layer thickness on the breakdown performance has not been explored. In this study, we investigate the impact of DPPT-TT layer thickness on the breakdown voltage (BV) by fabricating organic field effect transistors (OFETs) with various DPPT-TT layer thicknesses. Our findings reveal that the devices' BV is a strong function of DPPT-TT layer thickness, and reducing the DPPT-TT layer thickness from 68 to 15 nm results in a decrease in BV from 291 to 86 V, attributed to the two-dimensional (2D) electric field crowding effect. An analytical model utilizing the 2D Poisson equation reveals an electric field at the DPPT-TT layer's surface. Thinner DPPT-TT layer exhibits larger electric field peak, leading to premature breakdown near the drain electrode. The relationship between breakdown electric field and DPPT-TT layer thickness was established by fitting the experimental data to the model, revealing an average BV error of only 8.8%. This phenomenon is validated to be ubiquitous in polymer based OFETs via DPPT-TT-based and P3HT-based devices. According to the proposed model, this 2D electric field crowding effect can be mitigated by adjusting the dielectric layer thickness (tD) and/or the dielectric material. [ABSTRACT FROM AUTHOR]

Increasing the efficiency of spin–orbit torque (SOT) is of great interest in applications for magnetic random access memory and logic devices due to decreased energy consumption. Here, we present that the SOT efficiency of Pt/Co/Ta films with perpendicular magnetic anisotropy can be improved by swift high-energy heavy Fe11+ ion irradiation, which is an effective method to alter crystallinity, interface roughness, and defects in ferromagnet/heavy metal heterostructures. Specifically, the Pt/Co/Ta films show an optimal SOT efficiency at ion fluence around 1.0 × 1013 ions/cm2 with the largest spin Hall angles reaching 0.59, which is the largest improvement of spin Hall angle by ion irradiation compared to previous studies using light ions. We demonstrate that the increase in SOT efficiency arises from structural changes in the Pt layer due to ion irradiation-induced damage effects at proper fluence, while the decrease in SOT efficiency is mainly attributed to the restoration of Pt crystallinity induced by beam-heating effects at high fluence. This work demonstrates that an appropriate ion irradiation process could improve the SOT efficiency and the spin Hall angle, thereby providing a way to develop future SOT-based spintronic devices. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) ferromagnetic and antiferromagnetic second-order topological insulators (SOTIs) coexisting with valley polarization have received increasing attention recently, while 2D valley-polarized ferrimagnetic (ferri-valley) SOTI has not been reported yet. In this work, we propose an effective six-band tight-binding model based on structural symmetry to confirm the possibility of coexistence of ferrimagnetism, second-order topological corner states, and valley polarization in 2D systems, and predict Mo2CSCl monolayer as the robust 2D ferri-valley SOTI with good structural stability, considerable Curie temperature estimated to be 100 K, and distinct valley polarization up to 109 meV under out-of-plane exchange field based on our model and first-principles calculations. Also, we find that the spin polarization direction of corner states combined with valley polarization can be controlled by switching the direction of the magnetization direction using an external magnetic field. These findings of the combination of intrinsic ferrimagnetism, second-order topological properties, and valley polarization in single 2D materials provide an ideal platform for practical applications in multifield-control spintronic devices. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) van der Waals (vdW) magnets are crucial for ultra-compact spintronics. However, so far, no vdW crystal has exhibited tunable above-room-temperature intrinsic ferromagnetism in the 2D ultrathin regime. Here, we report the tunable above-room-temperature intrinsic ferromagnetism in ultrathin vdW crystal Fe3+xGaTe2 (x = 0 and 0.3). By increasing the Fe content, the Curie temperature (TC) and room-temperature saturation magnetization of bulk Fe3+xGaTe2 crystals are enhanced from 354 to 376 K and 43.9 to 50.4 emu·g−1, respectively. Remarkably, the robust anomalous Hall effect in 3-nm Fe3.3GaTe2 indicates a record-high TC of 340 K and a large room-temperature perpendicular magnetic anisotropy energy of 6.6 × 105 J m−3, superior to other ultrathin vdW ferromagnets. First-principles calculations reveal the asymmetric density of states and an additional large spin exchange interaction in ultrathin Fe3+xGaTe2 responsible for robust intrinsic ferromagnetism and higher TC. This work opens a window for above-room-temperature ultrathin 2D magnets in vdW-integrated spintronics. [ABSTRACT FROM AUTHOR]

Silicon nitride (Si3N4) photonic integrated circuits are rapidly developing in recent decades. The low loss of Si3N4 attracts significant attention and facilitates a wide range of applications in integrated photonics. In this work, we demonstrate the foundry fabrication of a 300-nm-thick 8-in. wafer-scale Si3N4 platform, with a microresonator intrinsic quality factor of up to 15 × 10 6 , corresponding to an ultralow loss of 2.2 dB/m. Leveraging this platform, we develop a mature process design kit, achieving a single-mode waveguide propagation loss of less than 5 dB/m, an edge coupler loss of 1.3 dB, and an insertion loss of 0.07 dB for multimode interference couplers. Utilizing the processed Si3N4 chip, we realize a hybrid integrated tunable external cavity laser with a tuning range from 1534 to 1602 nm, a record-high side-mode suppression ratio of up to 76 dB, an optical power of 26 mW, and an intrinsic linewidth of down to 314 Hz. Our work lays a solid foundation for the further development of applications, including nonlinear optics, quantum optics, optical communications, and ranging. [ABSTRACT FROM AUTHOR]

In this Letter, we combine first-principles calculations with the non-adiabatic molecular dynamics (NAMD) method to investigate the photocatalytic and excited-state properties of blue phosphorene (BlueP). Doping with Group III A elements not only maintains an appropriate bandgap and band edge positions for photocatalytic water splitting but also converts the indirect bandgap of BlueP to a direct bandgap, significantly enhancing photon absorption efficiency. The dopants effectively improve optical absorption in the visible and ultraviolet light regions, potentially enabling a solar-to-hydrogen conversion efficiency of 22.3% in the photocatalytic water splitting process. In NAMD calculations, we consider the dynamics of the electron–hole pair recombination process between the valence band maximum and conduction band minimum. We demonstrate the regulatory impact of dopant elements, temperature, and non-adiabatic coupling strength on the exciton lifetime of doped BlueP through ab initio molecular dynamics and NAMD methods. This study reveals the relationship between the charge transfer mechanism and non-adiabatic coupling in low-dimensional materials, offering valuable insights into the excited-state properties of optoelectronic materials. Ultimately, our findings contribute to the development of tunable, long-lived exciton lifetimes and high carrier mobilities in doped BlueP, which hold significant potential for photocatalytic water splitting to generate hydrogen. [ABSTRACT FROM AUTHOR]

This work explores polyanionic phosphate-type α-Zn3(PO4)2 (ZP) as a negative electrode in lithium-ion batteries. It has a high theoretical capacity of 278 mA h g−1. The crystal structure of ZP is elucidated, and Patterson's electron density profiling is performed to understand the possible site of lithiation. To address the polaron-driven electrical insulation common to phosphates, we use superficial carbon coating (ZP/C). Furthermore, the electrochemical analysis of ZP and ZP/C is performed to validate the half-cell performance and Li+ kinetics. ZP/C delivers a high capacity of 260 mA h g−1 at 0.1 C. The positive effect of carbon coating is evident from a 100-fold increase in lithium diffusion coefficient from the galvanostatic intermittent titration technique. In addition, temperature-driven capacity performance is analyzed at −10, 25, and 50 °C. Temperature gradient charge–discharge is performed between −10 and −5 °C, where the discharge capacity increases from 70 to 100 mA h g−1 at 1 C rate, extending the application toward low-temperature non-carbonaceous energy storage solutions. [ABSTRACT FROM AUTHOR]

We report the observation of in-plane anisotropic magnetoresistance (AMR) and planar Hall effect in our recently discovered kagome antiferromagnetic off-stoichiometric single crystal of Mn3Ga. We found that the in-plane AMR is dominated by a sixfold symmetry at low temperature due to the kagome lattice magnetocrystalline anisotropy. However, an unusual fourfold symmetry is also revealed by the angular-dependent AMR measurements, which originates from the little distortion of the crystal accompanying the slight ferromagnetic transition. Moreover, we also found a clear planar Hall effect signal in off-stoichiometric single crystal of Mn3Ga, which may be related to the chiral anomaly, one of the signatures of the magnetic Weyl fermions. [ABSTRACT FROM AUTHOR]

In this work, the influence of the Fe and Fe/C co-doped buffer on the AlGaN/GaN HEMTs is systematically investigated and compared. Due to the pronounced Fe tail in the unintentionally doped layer of the Fe-doped buffer compared to the Fe/C co-doped buffer, and the utilization of a two-step C doping process in the Fe/C co-doped buffer, it results in effectively reducing leakage current and increasing breakdown voltage without sacrificing saturation current and peak transconductance. Meanwhile, the RF characteristics of the Fe/C co-doped buffer are also superior to the Fe-doped buffer. More importantly, Drain Transient Current measurements indicate that the current collapse in the Fe/C co-doped buffer is smaller than that in the Fe-doped buffer. Through simulation analysis, the reason was identified: In the near-channel region, the weaker Fe tail effect in Fe/C co-doped buffer leads to a lower acceptor trap ionization. When the concentration of C exceeds 1 × 1016 cm−3, the ionization of traps introduced by Fe is suppressed. Additionally, the two-step C impurity distribution in the Fe/C co-doped buffer design modulates the electric field and potential, reducing the effective range of the electric field and potential, thereby effectively reducing the trap effects. These results are highly meaningful for the design of high-power amplifier epitaxial structures. [ABSTRACT FROM AUTHOR]

This Letter pioneers an investigation into the influence of temperature on threshold voltage (VTH) instability under negative bias in ferroelectric charge trap gate stack (FEG) high electron mobility transistors. Based on the experimental stress condition, i.e., gate bias of −20 V and temperature (T) range from 30 to 150 °C, our findings reveal a unidirectional VTH shift with 30 °C < T < 90 °C, and transitioning to a bidirectional VTH shift at 90 °C ≤ T ≤ 150 °C. The observed VTH < 0 V can be ascribed to the emission of electrons from the trapping layer, prompted by the pre-poling of the ferroelectric (FE) layer and the presence of interface traps. In contrast, under high-temperature stress, where VTH > 0 V, it indicates the depletion of the two-dimensional electron gas electrons due to de-poling and saturation of the polarization in the reverse direction. Moreover, this phenomenon is consistent with extracted activation energies (Ea) of 0.55 ± 0.01 and 0.79 ± 0.01 eV. Additionally, the recovery characteristics validate the trapping/detrapping process. [ABSTRACT FROM AUTHOR]

Active control of heat transfer in nanostructured materials is crucial for the development of microelectronic devices. Thermal switch is a typical heat management device, which has attracted widespread attention. In this work, based on first-principles calculations, we propose a two-dimensional thermal switch based on the strain-induced ferroelectric phase transition in α-PbS. It is found that thermal conductivity can be significantly reduced by external strain and a room temperature two-dimensional thermal switch with a switch ratio of 3.7 can be constructed. The calculated phonon lifetime and scattering rate reveal that phonons around 2 THz frequency range predominantly contribute to the modulation in thermal conductivity when the strain is smaller than 2.0%. A detailed analysis on phonon dispersion indicates that these phonons are LO2 and TO3 branches. When the strain is larger than 2.0%, the decrease in phonon group velocity leads to the reduction in thermal conductivity. Our work elucidates the mechanisms for changes in the thermal conductivity of α-PbS under strain and provides a low-dimensional thermal switch, which is promising for future applications in microelectronic devices. [ABSTRACT FROM AUTHOR]

The growth of VO2 epitaxial films has been researched extensively for obtaining excellent phase-transition performance. However, previous methods typically necessitate high temperatures or post-annealing processes, which elevate both experimental complexity and cost. In this work, we prepared high-quality VO2 epitaxial films by reactive magnetron sputtering directly under a low growth temperature. Benefiting from the determination of the oxygen pressure ratio from the theoretical analysis of the sputtering process model, single-stoichiometric VO2 epitaxial films could be prepared under 450 °C with a resistance change of 103, and above 500 °C with a resistance change exceeding 104. The mechanism of achieving low-temperature growth of VO2 epitaxial films was analyzed utilizing Thornton's zone model; finally, the epitaxial characteristics of VO2 on the sapphire substrate were confirmed from in-plane and out-of-plane directions. This work presents a guideline for the low-temperature growth of VO2 epitaxial films with enhanced phase-transition performance, thereby reducing both the cost and the requirements associated with the epitaxial growth of VO2 films. [ABSTRACT FROM AUTHOR]

In this work, we designed and fabricated an acoustic metamaterial with unidirectional zero reflection. The metamaterial was developed based on the concept of a parity-time symmetric material using one-dimensional (1D) orifice-type unit cells as a loss material and cylindrical closed-end tubes as a gain material. Twenty such composite unit cells were connected in series to construct a one-dimensional loss–gain balanced metamaterial. The characteristics of reflection and transmission were studied at frequencies between 1100 and 1800 Hz, ensuring that the metamaterial met the conditions of a homogeneous medium. From the experiments, it was found that the designed loss–gain balanced metamaterial had nearly complete unidirectional zero reflection (r ≲ 1.6 %) at f = 1202 Hz; in addition, it was shown to exhibit bidirectional zero transmission (t ≃ 0) at f = 1501 Hz. [ABSTRACT FROM AUTHOR]

Energy level alignments are crucial for designing high-performance semiconductor devices. However, the reported energy levels, especially the lowest unoccupied energy levels (LUMOs), exhibit significant variability for a given molecular compound. This variability often leads to misunderstanding of device working mechanisms. In this study, single-carrier devices with organic/interlayer/organic structures are proposed to probe the energy level alignments at organic–organic heterojunctions. It is observed that carrier transport characteristics deviate significantly depending on charge scattering or trapping. Five organic molecules, including 1, 3, 5-tri(m-pyrid-3-ylphenyl)benzene (TmPyPB), 4, 4′-bis(arbazole-9-y1)biphenyl (CBP), 2, 2′, 2″-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi), bis[2-(2-hydroxyphenyl)-pyridine] beryllium (Bepp2), and tris(8-hydroxyquinolinato)aluminum (Alq3), are utilized to test the method. The deduced LUMO level order for these materials is found to deviate significantly from reported values. Furthermore, the effect of differences in the energy level arrangement on the performance of electroluminescent devices is investigated. This work suggests that determining LUMO energy alignments via single-carrier analysis is a valuable method for understanding device working mechanisms. [ABSTRACT FROM AUTHOR]