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Although many emerging new phenomena have been unraveled in two dimensional (2D) materials with long-range spin orderings, the usually low critical temperature in van der Waals (vdW) magnetic material has thus far hindered the related practical applications. Here, we show that ferromagnetism can hold above 300 K in a metallic phase of 1T-CrTe 2 down to the ultra-thin limit. It thus makes CrTe 2 so far the only known exfoliated ultra-thin vdW magnets with intrinsic long-range magnetic ordering above room temperature. An in-plane room-temperature negative anisotropic magnetoresistance (AMR) was obtained in ultra-thin CrTe 2 devices, with a sign change in the AMR at lower temperature, with −0.6% and +5% at 300 and 10 K, respectively. Our findings provide insights into magnetism in ultra-thin CrTe 2 , expanding the vdW crystals toolbox for future room-temperature spintronic applications.

Since its invention in the 1960s, one of the most significant evolutions of metal-oxide-semiconductor field effect transistors (MOS-FETs) would be the three dimensionalized version that makes the semiconducting channel vertically wrapped by conformal gate electrodes, also recognized as FinFET. During the past decades, the width of fin ( W fin ) in FinFETs has shrunk from about 150 nm to a few nanometers. However, W fin seems to have been levelling off in recent years, owing to the limitation of lithography precision. Here, we show that by adapting a template-growth method, different types of mono-layered two-dimensional crystals are isolated in a vertical manner. Based on this, FinFETs with one atomic layer fin are obtained, with on/off ratios reaching ~ 1 0 7 . Our findings push the FinFET to the sub 1 nm fin-width limit, and may shed light on the next generation nanoelectronics for higher integration and lower power consumption. FinFETs are an evolution of metal-oxide-semiconductor field effect transistors (MOSFETs) featuring a semiconducting channel vertically wrapped by conformal gate electrodes. Here, the authors use a two-dimensional semiconductor to push the FinFET width to sub-nm whilst achieving a 107 ON/OFF ratio.

Superconductor-ferromagnet interfaces in two-dimensional heterostructures present a unique opportunity to study the interplay between superconductivity and ferromagnetism. The realization of such nanoscale heterostructures in van der Waals (vdW) crystals remains largely unexplored due to the challenge of making atomically-sharp interfaces from their layered structures. Here, we build a vdW ferromagnetic Josephson junction (JJ) by inserting a few-layer ferromagnetic insulator Cr 2 Ge 2 Te 6 into two layers of superconductor NbSe 2 . The critical current and corresponding junction resistance exhibit a hysteretic and oscillatory behavior against in-plane magnetic fields, manifesting itself as a strong Josephson coupling state. Also, we observe a central minimum of critical current in some JJ devices as well as a nontrivial phase shift in SQUID structures, evidencing the coexistence of 0 and π phase in the junction region. Our study paves the way to exploring sensitive probes of weak magnetism and multifunctional building-blocks for phase-related superconducting circuits using vdW heterostructures. The superconductor-ferromagnet interface provides a unique opportunity to study the interplay between superconductivity and ferromagnetism. Here, the authors build a van der Waals ferromagnetic Josephson junction evidencing a strong 0 and π phase Josephson coupling.

Interfacial moiré superlattices in van der Waals vertical assemblies effectively reconstruct the crystal symmetry, leading to opportunities for investigating exotic quantum states. Notably, a two-dimensional nanosheet has top and bottom open surfaces, allowing the specific case of doubly aligned super-moiré lattice to serve as a toy model for studying the tunable lattice symmetry and the complexity of related electronic structures. Here, we show that by doubly aligning a graphene monolayer to both top and bottom encapsulating hexagonal boron nitride (h-BN), multiple conductivity minima are observed away from the main Dirac point, which are sensitively tunable with respect to the small twist angles. Moreover, our experimental evidences together with theoretical calculations suggest correlated insulating states at integer fillings of −5, −6, −7 electrons per moiré unit cell, possibly due to inter-valley coherence. Our results provide a way to construct intriguing correlations in 2D electronic systems in the weak interaction regime. The alignment of three 2D nanosheets leads to the formation of super-moiré atomic lattices, which can influence the electronic properties of van der Waals structures. Here, the authors report evidence of possible correlated insulating states in doubly-aligned hBN/graphene/hBN heterostructures, in a weak-interaction regime.

Anisotropy in crystals arises from different lattice periodicity along different crystallographic directions, and is usually more pronounced in two dimensional (2D) materials. Indeed, in the emerging 2D materials, electrical anisotropy has been one of the recent research focuses. However, key understandings of the in-plane anisotropic resistance in low-symmetry 2D materials, as well as demonstrations of model devices taking advantage of it, have proven difficult. Here, we show that, in few-layered semiconducting GaTe, electrical conductivity anisotropy between x and y directions of the 2D crystal can be gate tuned from several fold to over 10 3 . This effect is further demonstrated to yield an anisotropic non-volatile memory behavior in ultra-thin GaTe, when equipped with an architecture of van der Waals floating gate. Our findings of gate-tunable giant anisotropic resistance effect pave the way for potential applications in nanoelectronics such as multifunctional directional memories in the 2D limit. Some atomically thin crystals feature crystallographic anisotropy, but demonstrations of electrical anisotropy are scarce. Here, the authors show that the electrical conductivity of few-layered GaTe along the x and y directions can be widely gate tuned up to 10 3 , and demonstrate anisotropic non-volatile memory behavior.

The realization of graphene gapped states with large on/off ratios over wide doping ranges remains challenging. Here, we investigate heterostructures based on Bernal-stacked bilayer graphene (BLG) atop few-layered CrOCl, exhibiting an over-1-GΩ-resistance insulating state in a widely accessible gate voltage range. The insulating state could be switched into a metallic state with an on/off ratio up to 10 7 by applying an in-plane electric field, heating, or gating. We tentatively associate the observed behavior to the formation of a surface state in CrOCl under vertical electric fields, promoting electron–electron (e–e) interactions in BLG via long-range Coulomb coupling. Consequently, at the charge neutrality point, a crossover from single particle insulating behavior to an unconventional correlated insulator is enabled, below an onset temperature. We demonstrate the application of the insulating state for the realization of a logic inverter operating at low temperatures. Our findings pave the way for future engineering of quantum electronic states based on interfacial charge coupling. Here, the authors report evidence of unconventional correlated insulating states in bilayer graphene/CrOCl heterostructures over wide doping ranges and demonstrate their application for the realization of low-temperature logic inverters.

Transition metal phosphorous trichalcogenides (MPX3) have been extensively investigated as photodetectors due to their wide-bandgap semiconductor properties. However, the research involved in the photoresponses at low temperatures remain blank. Here, hexagonal boron nitride (hBN)-encapsulated NiPS3 field effect transistors were fabricated by using the dry-transfer technique, indicating strong stability under atmospheric environments. The NiPS3 devices with the thickness of 10.4 nm, showed broad photoresponses from near-infrared to ultraviolet radiation at the liquid nitrogen temperature, and the minimum of rise time can reach 30 ms under the wavelength of 405 nm. The mechanism of temperature-dependent photoresponses can be deduced by competition between Schottky barrier height and thermal fluctuation. Our findings provide insights into superior phototransistors in few-layered NiPS3 for ultrasensitive light detection.

Recently, gallium telluride (GaTe) has triggered much attention for its unique properties and offers excellent opportunities for nanoelectronics. Yet it is a challenge to bridge the semiconducting few-layered GaTe crystals with metallic electrodes for device applications. Here, we report a method on fabricating electrode contacts to few-layered GaTe field effect transistors (FETs) by controlled micro-alloying. The devices show linear I-V curves and on/off ratio of ∼10 4 on HfO 2 substrates. Kelvin probe force microscope (KPFM) and energy dispersion spectrum (EDS) are performed to characterize the electrode contacts, suggesting that the lowered Schottky barrier by the diffusion of Pd element into the GaTe conduction channel may play an important role. Our findings provide a strategy for the engineering of electrode contact for future device applications based on 2DLMs.

Transition metal phosphorous trichalcogenides (MPX[sub.3] ) have been extensively investigated as photodetectors due to their wide-bandgap semiconductor properties. However, the research involved in the photoresponses at low temperatures remain blank. Here, hexagonal boron nitride (hBN)-encapsulated NiPS[sub.3] field effect transistors were fabricated by using the dry-transfer technique, indicating strong stability under atmospheric environments. The NiPS[sub.3] devices with the thickness of 10.4 nm, showed broad photoresponses from near-infrared to ultraviolet radiation at the liquid nitrogen temperature, and the minimum of rise time can reach 30 ms under the wavelength of 405 nm. The mechanism of temperature-dependent photoresponses can be deduced by competition between Schottky barrier height and thermal fluctuation. Our findings provide insights into superior phototransistors in few-layered NiPS[sub.3] for ultrasensitive light detection.

Because of the discovery of carbon atomic flat land, emerging physical phenomena are reported using the platform of two-dimensional materials and their hetero-structures. Especially, quantum orderings, such as superconductivity, ferromagnetism, and ferroelectricity in the atomically thin limit are cutting edge topics, which are of broad interest in the scope of condensed matter physics. In this study, we will recall the recent developments on two-dimensional ferroic orderings from both experimental and theoretical points of view. The booming of ferroic orderings in van der Waals two-dimensional materials are believed to hold promises for the next generation spin- or dipole-related nanoelectronics, because they can be seamlessly interfaced into heterostructures, and in principle are in line with large scale low-cost growth, flexible wearable devices, as well as semiconducting electronics thanks to the existence of band gaps in many of them.