Jiuxiang Dai

Our study explores the intrinsic toughening of monolayer amorphous carbon (MAC), a two-dimensional in-plane nanocomposite with a crystalline phase embedded into an amorphous matrix. MAC exhibits superior fracture energy with stable crack propagation owing to its unique internal structure, demonstrated through in situ SEM tensile testing and molecular dynamics simulations. These results unveil the toughening mechanisms and reveal the dependence of fracture energy on the amorphous-to-crystalline ratio, presenting a scalable toughening strategy for enhancing fracture resistance and expanding their practical applications.

A field-free, energy-efficient, nonvolatile spin–orbit torque system is demonstrated using chemical vapor deposition-grown Iron-doped monolayer molybdenum disulfide, a 2D dilute magnetic semiconductor with room-temperature stability, achieving a two-order-of-magnitude reduction in switching current above room temperature.

Abstract

The integration of 2D van der Waals (vdW) magnets with topological insulators or heavy metals holds great potential for realizing next-generation spintronic memory devices. However, achieving high-efficiency spin–orbit torque (SOT) switching of monolayer vdW magnets at room temperature poses a significant challenge, particularly without an external magnetic field. Here, it is shown field-free, deterministic, and nonvolatile SOT switching of perpendicular magnetization in the monolayer, diluted magnetic semiconductor (DMS), Fe-doped MoS₂ (Fe:MoS₂) at up to 380 K with a current density of ≈7 × 10⁴ A cm⁻². The in situ doping of Fe into monolayer MoS₂ via chemical vapor deposition and the geometry-induced strain in the crystal break the rotational switching symmetry in Fe:MoS₂, promoting field-free SOT switching by generating out-of-plane spins via spin-to-spin conversion. An apparent anomalous Hall effect (AHE) loop shift at a zero in-plane magnetic field verifies the existence of z spins in Fe:MoS₂, inducing an antidamping-like torque that facilitates field-free SOT switching. This field-free SOT application using a 2D ferromagnetic monolayer provides a new pathway for developing highly power-efficient spintronic memory devices.

Nature Materials, Published online: 14 February 2025; doi:10.1038/s41563-025-02117-w

A multi-layer wafer-scale 2D gate-all-around system with an atomically smooth interface fabricated via epitaxial monolithic 3D integration shows good performance and power efficiency, holding promise for the forthcoming ångström technology node.

Using surface-activated h-BN powders as precursors can realize the effective and green growth of high-quality h-BN film by chemical vapor deposition method. Combined with experimental results and molecular dynamics simulations, the activation mechanism of h-BN powders is revealed that unstable BO₃ and O-terminal edges on the surface of As-hBN will decompose to form B-H active species under H₂.

Abstract

Atomically thick hexagonal boron nitride (h-BN) films have gained increasing interest, such as nanoelectronics and protection coatings. Chemical vapor deposition (CVD) has been proven to be an efficient method for synthesizing h-BN thin films, but its precursors are still limited. Here, it is reported that a novel and easily available precursor, surface-activated h-BN (As-hBN), with NH₃/N₂ as an additional nitrogen source is used for CVD growth of monolayer h-BN films on the Cu foils. The as-grown h-BN films can significantly enhance the anti-oxidation ability of copper. Molecular dynamics simulations reveal that the reactivity of the As-hBN precursors is attributed to the decomposition of unstable BO₃ and O-terminal edges on the surface under H₂ atmosphere. This method provides a more reliable approach for fabricating h-BN films.

This study demonstrates novel magnetic tunnel junctions with low resistance-area product by integrating chemically vapor-deposited 2D Cr₃Te₄/WS₂ heterostructures with 2D Fe₃GeTe₂ magnets. Leveraging spin-orbit torque to manipulate spins in Fe₃GeTe₂, the authors fabricate an energy-efficient magnetic memory device. This breakthrough not only advances high-performance spintronics but also paves the way for next-generation low-power electronic devices.

Abstract

Spin-orbit torque (SOT) magnetic memory technology has garnered significant attention due to its ability to enable field-free switching of magnets with strong perpendicular magnetic anisotropy (PMA). However, concerns regarding power consumption of SOT-memory are persisting. Here, this work proposes a method to construct magnetic tunnel junction (MTJ) by transferring chemically vapor-deposited two-dimensional (2D) Cr₃Te₄/WS₂ van der Waals (vdW) heterostructures onto 2D Fe₃GeTe₂ (FGT) magnet. The robustness and tunability of 2D magnets allow MTJs to exhibit non-volatility, multiple output states, and impressive cycling durability. MTJs with thin WS₂ barriers (fewer than six layers) exhibit a linear tunneling effect, achieving a low resistance-area product (RA) of 15.5 kΩ·µm² using bilayer WS₂, which facilitats low-power operation. Furthermore, the different 2D magnets display a significant anti-parallel window of up to 8 kOe. SOT-memory based on the typical MTJ demonstrates a low write consumption of 0.3 mJ and read consumption of 9.7 nJ, marking a significant advancement in 2D vdW SOT-memory. This research has pointed out a new direction for constructing low power consumption SOT-memory with PMA field-free switching.

Super-resolution and magnified imaging of subdiffractional-sized inhomogeneities are performed in hBN-covered and encapsulated few-layer graphene (FLG), enabled by the hyperlensing effect. This hyperlensing effect is mediated by hBN's hyperbolic phonon polaritons that couple to the FLG's plasmon polaritons. The coupling is identified by determining the polariton dispersion in hBN-covered TLG to be stacking-dependent with scanning near-field optical microscopy.

Abstract

Encapsulating few-layer graphene (FLG) in hexagonal boron nitride (hBN) can cause nanoscale inhomogeneities in the FLG, including changes in stacking domains and topographic defects. Due to the diffraction limit, characterizing these inhomogeneities is challenging. Recently, the visualization of stacking domains in encapsulated four-layer graphene (4LG) has been demonstrated with phonon polariton (PhP)-assisted near-field imaging. However, the underlying coupling mechanism and ability to image subdiffractional-sized inhomogeneities remain unknown. Here, direct replicas and magnified images of subdiffractional-sized inhomogeneities in hBN-covered trilayer graphene (TLG) and encapsulated 4LG, enabled by the hyperlensing effect, are retrieved. This hyperlensing effect is mediated by hBN's hyperbolic PhP that couple to the FLG's plasmon polaritons. Using near-field microscopy, the coupling is identified by determining the polariton dispersion in hBN-covered TLG to be stacking-dependent. This work demonstrates super-resolution and magnified imaging of inhomogeneities, paving the way for the realization of homogeneous encapsulated FLG transport samples to study correlated physics.

Nature, Published online: 12 February 2025; doi:10.1038/s41586-024-08436-3

The altermagnetic order in CrSb films can be manipulated via crystal symmetry; the reconstructed altermagnetic order generates a room-temperature spontaneous anomalous Hall effect and designable switching modes as field-assisted and field-free modes.

A temperature sensor with In₂Se₃ ferroelectric-semiconductor field-effect transistor exhibits the record high thermal sensitivity of 696%/°C. Integration of ferroelectricity and semiconducting behavior of In₂Se₃ can give a highly sensitive thermal response. The flexible In₂Se₃ temperature sensor shows a hysteresis-free and stable real-time temperature sensing ability.

Abstract

In this study, a In₂Se₃ ferroelectric-semiconductor field-effect transistor is reported for highly sensitive temperature sensing. The high thermal sensitivity of 696%/°C can be achieved by integrating semiconducting behavior and ferroelectricity in In₂Se₃ thin film. By inducing a polarization up state in the ferroelectric-semiconductor by applying gate bias, the carriers within the In₂Se₃ semiconductor are depleted, suppressing channel formation. Under polarization up state, off-currents are very sensitive to temperature variation, following variable range hopping conduction. The drain currents are found to be in proportional to exp[T0T]14$\exp {{[ {\frac{{{{T}_0}}}{{\mathrm{T}}}} ]}^{\frac{1}{4}}}$ with T₀ of 1.27 × 10¹² K. To achieve variable range hopping transport, defective In₂Se₃ is deposited at low temperatures (240 °C) using spray pyrolysis. Fabricated In₂Se₃ temperature sensor on flexible polyimide substrate can detect a broad range of temperatures (RT to 200 °C) with high stability, exhibiting excellent temperature sensing performance. In addition, the very thin flexible temperature sensor array is demonstrated for large area spatial temperature sensing.

Nature Communications, Published online: 12 February 2025; doi:10.1038/s41467-025-56671-7

The authors report a wet-chemical selenization-based anisotropy optimization to control the orientation of the Ag2Se thin film, achieving a power factor of 30.8 μW cm−1 K−2 in the thin film and a normalized power density of 1.8 μW cm−2 K−2 in the device.

Nature Communications, Published online: 12 February 2025; doi:10.1038/s41467-025-56921-8

Researchers present the evidence and mechanism of distinct phase transformation pathways in MAX phases under ion irradiation, providing a new theory and predictive method for phase behavior based on composition, advancing understanding of materials in extreme conditions.

AgTiPS₆ atomic layers, the 2D in-plane anisotropic material with cross-stacked motifs, are discovered and added to the 2D material family. They feature a thick monolayer, strong stability, and inherent anisotropy. As an in-plane anisotropic 2D semiconductor, AgTiPS₆-based photodetectors demonstrate excellent photoresponse across a broad range from visible to mid-infrared, as well as high in-plane electrical (≈5.44) and optoelectrical (≈2.44) anisotropies.

Abstract

2D anisotropic materials, typically consisting of 1D distorted chains arranged in parallel or anti-parallel patterns, are gaining attention for their potential in anisotropic electronic and optoelectronic devices. 2D anisotropic materials with cross-stacked interconnected 1D chains will show improved anisotropy and stability. Nonetheless, to date, no 2D anisotropic materials featuring cross-stacked motifs have been experimentally realized. This work identifies AgTiPS₆ atomic layers, the 2D in-plane anisotropic material with cross-stacked structural motifs, as an n-type semiconductor with a 1.0 eV band gap. Significantly, the unique cross-stacked configuration of 2D AgTiPS₆ results in a significant in-plane anisotropy, with electrical and optoelectrical anisotropies measuring 5.44 and 2.44, respectively, as well as an axially orientation selectivity. Meanwhile, a broadband response from visible (Vis, 405 nm) to middle infrared (MIR, 10.6 µm) is achieved in the AgTiPS₆-based photodetector, with the photoresponse above the bandgap attributed to photothermoelectric effect. Furthermore, 2D AgTiPS₆ has demonstrated environmental stability exceeding 12 months and a laser damage threshold exceeding 10 W cm^{− 2}, attributed to its extra-thick monolayer (1.32 nm). This work introduces a novel in-plane anisotropic material, expanding the repertoire of 2D anisotropic materials and offering potential for the development of anisotropic electronic and optoelectronic devices.

The superconducting magnetization diode effect in stacking superconductors with ferromagnetic materials heterostructures, enabling robust magnetization readout through superconductivity with an ideally infinite on/off ratio, is demonstrated. Combining spin–orbit torque for current-driven magnetization switching, this work bridges superconductivity and spintronics, offering scalable, energy-efficient memory solutions with simplified design and improved performance.

Abstract

Stacking superconductors (SC) with ferromagnetic materials (FM) significantly impact superconductivity, enabling the emergence of spin-triplet states and topological superconductivity. The tuning of superconductivity in SC-FM heterostructure is also reflected in the recently discovered superconducting diode effect, characterized by nonreciprocal electric transport when time and inversion symmetries are broken. Notably, in SC-FM systems, a time reversal operation reverses both current and magnetization, leading to the conceptualization of superconducting magnetization diode effect (SMDE). In this variant, while the current direction remains fixed, the critical currents shall be different when reversing the magnetization. Here, the existence of SMDE in SC-FM heterostructures is demonstrated. SMDE uniquely maps magnetization states onto superconductivity by setting the read current between two critical currents for the positive and negative magnetization directions, respectively. Thus, the magnetization states can be read by measuring the superconductivity, while the writing process is accomplished by manipulating magnetization states through current-driven spin–orbit torque to switch the superconductivity. The proposed superconducting diode magnetoresistance in SC-FM heterostructures with an ideally infinite on/off ratio resolves the limitations of tunneling magnetoresistance in the magnetic tunneling junctions, thereby contributing to the advancement of superconducting spintronics.

In this work, a CVD method is reported to synthesize Bi₂WO₆ nanoflakes with an ultrathin structure. The ferroelectric phase transition temperature is ≈800 K. Both in-plane (IP) and out-of-plane (OOP) ferroelectricity are characterized by PFM measurements and confirmed through lateral and vertical devices. The emergence of OOP ferroelectricity is due to oxygen vacancy displacement between asymmetric sites, disrupting local symmetry and aligning dipole moments. This stable ultrathin ferroelectric Bi₂WO₆ expands the potential for ferroelectric materials and applications.

Abstract

Ferroelectricity in ultrathin 2D materials has garnered significant attention owing to its potential applications in nonvolatile memory, nanoelectronics, and optoelectronics. However, the exploration of ferroelectricity in materials possessing inherent centrosymmetric or mirror symmetry, particularly in the 2D domain, remains limited. In this study, the chemical vapor deposition (CVD) technique is utilized to synthesize ultrathin Bi₂WO₆ (BWO) nanoflakes, revealing robustly intercorrelated out-of-plane (OOP) and in-plane (IP) ferroelectric polarization. The measured ferroelectric phase transition temperature of ultrathin BWO nanoflake is ≈800 K. The emergence of OOP ferroelectricity in BWO nanoflake is ascribed to the displacement of oxygen vacancies between neighboring asymmetric sites, leading to the disruption of local structural mirror symmetry and the alignment of dipole moments. Moreover, the IP and OOP ferroelectric responses are modulated by distinct maximum bias voltages. This investigation offers novel insights into the advancement of 2D ferroelectrics with elevated Curie temperatures.

A bioinspired aqueous soft robot with a remarkable swimming speed, low power consumption, and capability to perform dexterous turning locomotion in confined environments is proposed. The robot utilizes the electro-hydraulic actuation principle and imitates the Ocyropsis-type rowing mode. In addition, polymer-based ionic gel is developed and applied to the robot as the electrode, achieving full transparency and high durability.

Abstract

Marine creatures achieve effective survival in unstructured ocean environments via fast swimming or transparent camouflage. Aqueous soft robots, capable of reproducing soft features of marine creatures, have the advantages of safe biological interaction, high environmental adaptation, and noise-free when compared with traditional rigid robots. Yet, there exists a persistent challenge to develop both fast and energy-efficient aqueous soft robots that can achieve better underwater operation or exploration. Enlightened by the morphology and swimming strategy of Ocyropsis — a jellyfish-like creature, Ocyropsis-inspired robots (i.e., Ocyrobots) that merge electro-hydraulic actuation and Ocyropsis-type rowing mechanisms to achieve high-performance underwater locomotion are developed. Ocyrobots demonstrate a record-high speed of 1.1 body length/s, which is approximately three times of previously reported fastest jellyfish-like robots while maintaining a low power consumption of 37 mW. Ocyrobots also exhibit an impressive turning speed of 34° s⁻¹, enabling dexterous locomotion and effective obstacle avoidance in confined underwater scenarios. Attributed to the self-developed highly reliable polymer-based ionic gel, Ocyrobots possess remarkable advantages of full transparency and high durability, which improves their lifetime and reduces potential disturbances to underwater ecosystems. The unprecedented biomimetic idea in this study is essential in enlightening the prototyping of future aqueous soft robotics.

An unexplored thulium (Tm) doping strategy is proposed to alter the formation energy of interstitial oxygen in p-type tin monoxide (SnO) with Hall mobility up to 284.0 ± 3.0 cm² V∙s⁻¹, in which a field-effect hole mobility of 12.8 cm² V∙s⁻¹ and an on/off ratio above 10⁴ are achieved. Benefiting from the enhanced reliability of Tm-doped SnO thin-film transistors (TFTs), complementary logic circuits such as inverters, NAND, and NOR gates are constructed. The inverters exhibit an ultrahigh gain, which is close to 800, surpassing most of existing counterparts. This work unfolds novel mechanism and highlights the effectiveness of the Tm doping strategy in developing Sn-based oxide complementary devices and circuits that meet the performance requirements of future TFTs technology.

Abstract

Developing high-performance p-type oxide semiconductors is a significant challenge in thin-film semiconductor technology due to their complex electronic structure and the presence of compensating intrinsic defects. To this aim, an unexplored thulium (Tm) doping strategy is proposed to alter the formation energy of interstitial oxygen in p-type tin monoxide (SnO) with Hall mobility up to 284.0 ± 3.0 cm² V∙s⁻¹, in which a field-effect hole mobility of 12.8 cm² V∙s⁻¹ and an on/off ratio above 10⁴ are achieved. Benefiting from the enhanced reliability of Tm-doped SnO thin-film transistors (TFTs), complementary logic circuits such as inverters, NAND, and NOR gates are constructed. The inverters exhibit an ultrahigh gain, which is close to 800, surpassing most of existing counterparts. This work unfolds novel mechanism and highlights the effectiveness of the Tm doping strategy in developing Sn-based oxide complementary devices and circuits that meet the performance requirements of future TFTs technology.

WSe₂ lateral p-n homojunctions controlled by dual floating gates on a SiO₂/Si substrate can form four different junctions by injecting charges into two floating gates through applying voltage pulses with different polarities. For p-n junction, a rectification ratio of ≈10⁵, an ideality factor of ≈1.56 and a maximum photovoltage responsivity of 6.67 × 10⁹ V W⁻¹ can be achieved.

Abstract

2D transition metal dichalcogenides (TMDs) materials with inherent flexibility, transparency, and sizable bandgap have gained significant attention as promising candidates for future semiconductor nanodevices. However, complementary doping in these 2D semiconductors remains a challenge because conventional ion implantation can lead to permanent damage to the atomically thin 2D channels. Here, programmable WSe₂ 2D lateral p-n homojunction controlled by dual floating gates on a SiO₂/Si substrate, achieving a rectification ratio of ≈10⁵ and three dynamically switchable current levels is demonstrated. By injecting charges into two floating gates by applying voltage pulses with different polarities, lateral p-n, n-p, n-n, p-p homojunction can be formed. The ideality factors for the p-n and n-p junctions are extracted as ≈1.56 and ≈1.57, respectively. The WSe₂ p-n homojunction shows a maximum photovoltage responsivity of 6.67 × 10⁹ V W⁻¹ under a weak light power of 0.09 nW. These results demonstrate outstanding electrical and optoelectronic properties in the programmable 2D lateral p-n junctions, establishing a solid foundation for the development of future non-volatile reconfigurable devices.

Nature Synthesis, Published online: 10 February 2025; doi:10.1038/s44160-025-00737-3

A space-confined chemical vapour transport strategy is reported for synthesizing multicomponent two-dimensional materials without phase separation and composition inhomogeneity. Twelve types of transition metal phosphorous chalcogenides and their high-entropy alloys (up to nine elements) are synthesized.

Nature Materials, Published online: 10 February 2025; doi:10.1038/s41563-025-02126-9

Synthesis of millimetre-sized hexagonal diamond has been demonstrated, facilitated by the formation of intermediate post-graphite phases and temperature gradients.