Jing Zhang

Nature Electronics, Published online: 20 November 2023; doi:10.1038/s41928-023-01077-w

An effective gate voltage doping method can be used to create single-gate molybdenum ditelluride field-effect transistors that can be reconfigured between rectification, memory, logic and neuromorphic functions.

Metal–Organic Frameworks

In article number 2307369, Elena Bartolomé, José Giner Planas, and co-workers introduce a significant advancement in the synthesis of multi-metal multivariate rare earth materials, which were previously inaccessible. The current methodology is anticipated to pave the way towards the development of new multifunctional materials exhibiting tailor-made magnetic and optical properties for future applications.

A novel InAs_0.85P_0.15 homojunction detector with λ _c = 2.6 μm is achieved through lattice and bandgap engineering with well-designed InAs _y P_{1- y} metamorphic buffers. Such an InAsP metamorphic detector with excellent photodetection capabilities is expected to find applications in the implementation of large-format focal plane arrays for extended short-wavelength infrared imaging.

Abstract

Short-wavelength infrared (SWIR) photodetectors are of great interest owing to their unique advantages of SWIR imaging such as better penetration ability and improved sensitivity that allow high-resolution imaging. Commercially, extended In _x Ga_{1- x} As heterojunction detectors with cut-off wavelengths beyond λ _c = 1.7 µm are incorporated into SWIR imagers. However, their large dark current and limited cut-off wavelength tunability prevent their widespread use in SWIR imaging. Herein, a novel InAs_0.85P_0.15 homojunction detector with λ _c = 2.6 µm is achieved through lattice and bandgap engineering with well-designed InAs _y P_{1- y} metamorphic buffers. Compared to conventional In_0.83Ga_0.17As/InP detectors with a lattice mismatch of f = 2.0%, the InAs_0.85P_0.15 detector with f = 2.7% exhibits full strain relaxation and lower surface roughness (2.4 nm due to its superior crystallinity). Photocarrier generation in the InAsP detector is more efficiently supported by a smaller entropy for electron–hole pair formation. The lower trap density and longer carrier lifetime of the InAsP detector decrease the dark current, leading to high uniform detectivities of ≈1.0 × 10⁹ cm Hz^1/2 W⁻¹ over a wider voltage range at 300 K. Such an InAsP metamorphic detector with excellent photodetection capabilities is expected to find applications in the implementation of large-format focal plane arrays for extended SWIR imaging.

Nature Communications, Published online: 17 November 2023; doi:10.1038/s41467-023-42782-6

Antiferromagnetic topological materials have attracted attention recently due to their unique quantum properties and application potential. Here the authors establish an antiferromagnetic topological insulator in NdBi and demonstrate gapped and gapless surface states in two different magnetic domains.

Nature Electronics, Published online: 17 November 2023; doi:10.1038/s41928-023-01066-z

Dual-gate heterojunction transistors that are based on monolayer molybdenum disulfide and carbon nanotubes can provide tunable Gaussian and sigmoid functions for support vector machine computing.

Single-Walled Nanotubes

In article number 2306631, Yusuke Nakanishi, Yasumitsu Miyata, and co-workers engineer new single-walled nanotubes of transition metal dichalcogenides with different compositions and chiralities by templating off boron nitride nanotubes. They also realize ultrathin nanotubes grown inside the template, and successfully tailor compositions to create a family of new nanotubes.

Low-dimensional La-doped BaTiO₃ nanocrystals are prepared using supercritical CO₂ (SC CO₂). The generation of the self-trapped excitons is facilitated by doping La³⁺ ions and introducing CO₂ pressure, which effectively enhance the optical properties of BaTiO₃.

Abstract

Self-trapped excitons (STEs) typically give broadband photoluminescence emission with a large Stokes shift, which is important for the enhancement of the optical properties of materials. Here, low-dimensional La-doped BaTiO₃ nanocrystals with defects are prepared using supercritical CO₂ (SC CO₂). The generation of the STEs is facilitated by doping La³⁺ ions and introducing CO₂ pressure, which effectively enhance the luminescence intensity of BaTiO₃. This discovery shows that the La ion doping concentration can modulate the photoluminescence of BaTiO₃ nanocrystals under pressure. This work deepens the understanding of the influence of rare-earth-doped luminescent materials under pressure and provides insight to improve the capabilities of optical devices.

High concentration of Er³⁺/Yb³⁺ co-doped WS₂ monolayer is creatively prepared by in-situ chemical vapor deposition technique. The performances of the devices (photodetectors and field-effect transistors) are significantly enhanced after rare-earth (RE) co-doping, which can be attributed to the stronger light absorption and higher the transitions of electronic states, providing an excellent strategy for practical application in optoelectronics.

Abstract

Chemical doping is a significant means to modulate bandgap structures and optoelectronic properties of transition metal dichalcogenides (TMDCs). Herein, an Er³⁺/Yb³⁺ co-doped WS₂ monolayer with ultrahigh and tunable concentrations is successfully fabricated by in-situ chemical vapor deposition (CVD) technique. The morphologies, thicknesses, components, and structures of the samples are systemically characterized by optical microscope, atomic force microscopy, Raman, X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscope with energy dispersive spectrometer, and high-resolution transmission electron microscopy, respectively. Photoluminescent peaks are enhanced significantly with red shifts, and the absorption is broadened to near-infrared, implying a shrinked bandgap after RE co-doping, which is consistent to the calculation results by density functional theory (DFT). The Er³⁺/Yb³⁺ co-doped WS₂ device demonstrates high carrier mobility, photocurrent, photoresponsivity, external quantum efficiency, and specific detectivity, which are approximately two orders of magnitudes compared with those of the pristine WS₂ device. The values of photoresponsivity and specific detectivity approach 4.8 × 10⁴ A W⁻¹ and 5.5 × 10¹⁴ Jones, respectively, at 20 V bias and 1.77 mW cm⁻² luminescence, which may refresh the records as has been reported. The excellent performances of the WS₂ photodetector prove the effectiveness of Er³⁺/Yb³⁺ co-doping for practical application in optoelectronics.

The intercoupled ferroelectricity of 𝛼-In₂Se₃ is utilized to introduce non-volatile electrostatic doping in ambipolar WSe₂. The fabricated device presents stable p–n to n–p switching, superior rectification ≈10⁶, and low leakage current ≈10⁻¹² A. Furthermore, the switchable shortcircuit current is utilized to demonstrate self-powered, non-volatile memory based on photovoltaic reading.

Abstract

It is impossible to imagine modern electronic circuitry without a p–n junction—an essential building block for transistors, rectifiers, amplifiers, photovoltaics, etc. Conventional fabrication processes (ion implantation or chemical diffusion) result in an immutable potential configuration depriving reconfigurability. In contrast, the superior electrostatic tunability, dangling bonds- and reconstruction-free interfaces are some of the key features of 2D based heterostructures, making them promising candidates for cutting-edge optoelectronic and memory applications. Herein, the intercoupled 2D ferroelectricity of 𝛼-In₂Se₃ is utilized to introduce micron-scale, non-volatile electrostatic doping in ambipolar WSe₂, enabling reconfigurable p–n junction. The actuation mechanism is based on the strong polarization field along the edge topology of In₂Se₃. The fabricated device presents stable p–n to n–p switching, a superior rectification ratio of ≈10⁶, and a low leakage current of ≈10⁻¹² A. Furthermore, the switchable short-circuit current response is utilized to demonstrate a novel self-powered, non-volatile memory based on photovoltaic reading. The ferroelectric non-volatility coupled with the ability to control the device operation using optical and electrical signals paves the way for ultrathin energy-efficient, multi-level optoelectronic and in-memory logic devices.

Quasi-2D perovskites are gaining increasing attention for their broad commercial prospect in high-definition displays due to their superior optoelectronic properties. This review expounds on the crystal structure, formation mechanism, and multiple-quantum-well characteristics of quasi-2D perovskites, which are followed by a comprehensive summary of the mainstream phase regulation strategies for high-performance PeLEDs.

Abstract

As a promising family of semiconductor materials for high-quality displays, quasi-2D perovskites have gained a significant amount of attention in the field of light-emitting diodes for their superior optoelectronic properties compared with their 3D counterparts. The intrinsic multiple-quantum-well characteristics induced by reducing the crystal dimensionality enable perovskite emitters to possess high photoluminescence quantum yield and good film morphology. It is demonstrated that the n-value distribution of quasi-2D perovskites, where n refers to the number of inorganic MX₆ octahedron layers, has a strong impact on the electroluminescence efficiency and stability of perovskite light-emitting diodes (PeLEDs). In this review, the crystal structure of quasi-2D perovskites, the formation origin of different n-value distributions, and their optoelectronic characteristics are first introduced. Then, the mainstream strategies for regulating the phase distribution of layered perovskites are systematically reviewed to suggest their great significance in boosting the performances of PeLEDs. Lastly, the current deficiencies and potentially valuable research directions of phase distribution management for efficient and stable quasi-2D PeLEDs are provided.

The PU nanomesh is prepared using electrospinning, which expands due to capillary action after absorbing perspiration, altering the optical transmittance and leading to color changes. After building the dataset of wet nanomesh, the object detection algorithm YOLOv3 is used to classify the perspiration volume to achieve the target detection and an intelligent early warning.

Abstract

Perspiration is an important physiological process that maintains thermal homeostasis and water–salt balance. However, the collection and analysis of perspiration currently rely on microfluidic technology and colorimetric assays. The complexity and high cost of fabricating microfluidic channels and the insecurity of chemical reagents for color reactions should be optimized. In this work, a colorimetry electronic skin (e-skin) for intelligent perspiration monitoring has been realized. The colorimetry e-skin system consists of the polyurethane (PU) nanomesh and the object detection algorithm You Only Look Once version 3 (YOLOv3). Due to the 44% porosity of the PU nanomesh and capillary action, the low-cost PU nanomesh (<1 cent) can be used as the colorimetric indicator. The volume of the PU nanomesh expands to 362.37% as a result of perspiration being absorbed and changes the optical transmittance (up to 277.78%). A finite element model based on capillary action has been proposed to explain the change in optical transmittance. Finally, a database containing 735 images has been built, and the object detection algorithm YOLOv3 is used to analyze the perspiration absorbed by the PU nanomesh. The detection results can identify the perspiration volume with a high accuracy of 97%. These results show that this work has great potential in healthcare field.

A facile template-assisted approach is proposed for the synthesis of high-quality 2D perovskite grating films by temperature regulation. Subsequently, these synthesized grating films are utilized to fabricate photodetectors. The performance of devices based on grating films surpasses that of flat films, as evidenced by both simulation and experimental results. Furthermore, these grating film photodetectors exhibit sensitivity to UV-polarized light.

Abstract

2D perovskites have attracted tremendous attention due to their superior optoelectronic properties and potential applications in optoelectronic devices. Especially, the larger bandgap of 2D perovskite means that they are suitable for UV photodetection. However, the layered structure of 2D perovskites hinders the interlayer carrier transport, which limits the improvement of device performance. Therefore, nanoscale structures are normally used to enhance the light absorption ability, which is an effective strategy to improve the photocurrent in 2D perovskite-based photodetectors. Herein, a template-assisted low-temperature method is proposed to fabricate 2D perovskite ((C₆H₅C₂H₄NH₃)₂PbBr₄, (PEA)₂PbBr₄) grating single crystal films (GSCFs). The crystallinity of the (PEA)₂PbBr₄ GSCFs is significantly improved due to the slow evaporation of the precursor solution under low temperatures. Based on this high crystalline quality and extremely ordered microstructures, the metal–semiconductor–metal photodetectors are assembled. Finite-different time-domain (FDTD) simulation and experiment indicate that the GSCF-based photodetectors exhibit significantly improved performance in comparison with the plane devices. The optimized 2D perovskite photodetectors are sensitive to UV light and demonstrate a responsivity and detectivity of 28.6 mA W⁻¹ and 2.4 × 10¹¹ Jones, respectively. Interestingly, the photocurrent of this photodetector varies as the angle of the incident polarized light, resulting in a high polarization ratio of 1.12.

Graphene-based materials (GBM), transition metal dichalcogenide (TMDC), transition metal oxide (TMO), MXenes, and black phosphorus (BP) surge as new 2DnMat for cancer/infections treatment. 2DnMat + NIR kills cancer cells/bacteria through hyperthermia in vitro and in vivo. Magnetic hyperthermia therapy using magnetic 2DnMat causes cancer or bacteria death. 2DnMat can be conjugated with molecules via covalent or non-covalent interactions. Conjugation with drugs or polymers increase biocompatibility and therapeutic effect.

Abstract

Photothermal therapy (PTT) and magnetic hyperthermia therapy (MHT) using 2D nanomaterials (2DnMat) have recently emerged as promising alternative treatments for cancer and bacterial infections, both important global health challenges. The present review intends to provide not only a comprehensive overview, but also an integrative approach of the state-of-the-art knowledge on 2DnMat for PTT and MHT of cancer and infections. High surface area, high extinction coefficient in near-infra-red (NIR) region, responsiveness to external stimuli like magnetic fields, and the endless possibilities of surface functionalization, make 2DnMat ideal platforms for PTT and MHT. Most of these materials are biocompatible with mammalian cells, presenting some cytotoxicity against bacteria. However, each material must be comprehensively characterized physiochemically and biologically, since small variations can have significant biological impact. Highly efficient and selective in vitro and in vivo PTTs for the treatment of cancer and infections are reported, using a wide range of 2DnMat concentrations and incubation times. MHT is described to be more effective against bacterial infections than against cancer therapy. Despite the promising results attained, some challenges remain, such as improving 2DnMat conjugation with drugs, understanding their in vivo biodegradation, and refining the evaluation criteria to measure PTT or MHT effects.

High-promising violet phosphorus (VP) microfiber array-based artificial synapse devices are successfully developed to mimic the function of the optic nerve with dual responses to electrical and optical stimuli, which provides a promising approach for the design and manufacture of VP-based artificial synaptic devices.

Abstract

Memristor-based artificial synapses are regarded as the most promising candidate to develop brain-like neuromorphic network computers and overcome the bottleneck of Von–Neumann architecture. Violet phosphorus (VP) as a new allotrope of available phosphorus with outstanding electro-optical properties and stability has attracted more and more attention in the past several years. In this study, large-scale, high-yield VP microfiber vertical arrays have been successfully developed on a Sn-coated graphite paper and are used as the memristor functional layers to build reliable, low-power artificial synaptic devices. The VP devices can well mimic the major synaptic functions such as short-term memory (STM), long-term memory (LTM), paired-pulse facilitation (PPF), spike timing-dependent plasticity (STDP), and spike rate-dependent plasticity (SRDP) under both electrical and light stimulation conditions, even the dendritic synapse functions and simple logical operations. By virtue of the excellent performance, the VP artificial synapse devices can be conductive to building high-performance optic-neural synaptic devices simulating the human-like optic nerve system. On this basis, Pavlov's associative memory can be successfully implemented optically. This study provides a promising approach for the design and manufacture of VP-based artificial synaptic devices and outlines a direction with multifunctional neural devices.

Nature Communications, Published online: 15 November 2023; doi:10.1038/s41467-023-43032-5

Electrostrictors are materials that develop mechanical strain proportional to the square of the applied electric field. Here authors report. Zr-doped-Ceria as a new lead-free electrostrictive material with a similar electrostriction coefficient to the best electrostrictor material currently in use.

Nature, Published online: 15 November 2023; doi:10.1038/s41586-023-06633-0

Minimization of kinetic energy leads to ferromagnetic correlations between itinerant electrons in MoSe2/WS2 moiré lattices even in the absence of exchange interactions.

The overlooked process of partial melting is exploited to achieve continuous optical levels in a single film of the phase-change material Ge₂Sb₂Te₅. The stability of the optical switch is improved by introducing a multi-layer structure containing materials Ge₂Sb₂Te₅ and GeTe, with four discrete and reversible optical levels. The discussion is supported by nanosecond laser switching and multi-physics modeling.

Abstract

The optical properties of phase-change materials (PCMs) can be tuned to multiple levels by controlling the transition between their amorphous and crystalline phases. In multi-material PCM structures, the number of discrete reflectance levels can be increased according to the number of PCM layers. However, the effect of increasing the number of layers on quenching and reversibility has not been thoroughly studied. In this work, the phase-change physics and thermal conditions required for reversible switching of single and multi-material PCM switches are discussed based on thermo-optical phase-change models and laser switching experiments. By using nanosecond laser pulses, 16 different reflectance levels in Ge₂Sb₂Te₅ are demonstrated via amorphization. Furthermore, a multi-material switch based on Ge₂Sb₂Te₅ and GeTe with four discrete reflectance levels is experimentally proven with a reversible multi-level response. The results and design principles presented herein will impact active photonics applications that rely on dynamic multi-level operation, such as optical computing, beam steering, and next-generation display technologies.

Reducing the thickness of indium oxide, enabled by atomic layer deposition (ALD) process, can tune its material properties to achieve high performance devices beyond the capabilities of conventional oxide semiconductors. In this work, the history leading to the re-emergence of indium oxide, its fundamental material properties, growth techniques with a focus on ALD, and state-of-the-art indium oxide device research are reviewed.

Abstract

Amorphous oxide semiconductor transistors have been a mature technology in display panels for upward of a decade, and have recently been considered as promising back-end-of-line compatible channel materials for monolithic 3D applications. However, achieving high-mobility amorphous semiconductor materials with comparable performance to traditional crystalline semiconductors has been a long-standing problem. Recently it has been found that greatly reducing the thickness of indium oxide, enabled by an atomic layer deposition (ALD) process, can tune its material properties to achieve high mobility, high drive current, high on/off ratio, and enhancement-mode operation at the same time, beyond the capabilities of conventional oxide semiconductor materials. In this work, the history leading to the re-emergence of indium oxide, its fundamental material properties, growth techniques with a focus on ALD, state-of-the-art indium oxide device research, and the bias stability of the devices are reviewed.

Exoskeletons are generated to produce partial-coated bone marrow stem cells (BMSCs) as a novel biologic formulation with dual-sided characteristics. The exoskeleton side promotes cell viability and targeting, whereas the cell side retains the ability of cell adhesion and external secretion. With the synergism of increased survival, retention, and augmented paracrine secretion, the partial-coated BMSCs exhibit promising heart repair effects.

Abstract

The integration of abiotic materials with live cells has emerged as an exciting strategy for the control of cellular functions. Exoskeletons consisting ofmetal–organic frameworks are generated to produce partial-coated bone marrow stem cells (BMSCs) to overcome low cell survival leading to disappointing effects for cell-based cardiac therapy. Partially coated exoskeletons can promote the survival of suspended BMSCs by integrating the support of exoskeletons and unimpaired cellular properties. In addition, partial exoskeletons exhibit protective effects against detrimental environmental conditions, including reactive oxygen species, pH changes, and osmotic pressure. The partial-coated cells exhibit increased intercellular adhesion forces to aggregate and adhere, promoting cell survival and preventing cell escape during cell therapy. The exoskeletons interact with cell surface receptors integrin α5β1, leading to augmented biological functions with profitable gene expression alteration, such as Vegfa, Cxcl12, and Adm. The partial-coated BMSCs display enhanced cell retention in infarcted myocardium through non-invasive intravenous injections. The repair of myocardial infarction has been achieved with improved cardiac function, myocardial angiogenesis, proliferation, and inhibition of cell apoptosis. This discovery advances the elucidation of potential molecular and cellular mechanisms for cell-exoskeleton interactions and benefits the rational design and manufacture of next-generation nanobiohybrids.

Nature Electronics, Published online: 13 November 2023; doi:10.1038/s41928-023-01056-1

An effective-gate-voltage-programmed graded-doping method can be used to reconfigure a single-gate molybdenum ditelluride device to different states, including a polarity-switchable diode, memory, Boolean logic and artificial synapse.

Nature, Published online: 08 November 2023; doi:10.1038/s41586-023-06660-x

Following a micro-then-nano growth sequence to fabricate composites that are blends of block-copolymer-based supramolecules, small molecules and nanoparticles shows that high-performance barrier materials can be manufactured by means of entropy-driven assembly.

Nature Communications, Published online: 11 November 2023; doi:10.1038/s41467-023-43097-2

CuCrP2S6 is a potential candidate for realizing low-dimensional multiferroicity. Here, authors report direct observation of robust out-of-plane ferroelectricity in the two-dimensional van der Waals layered CuCrP2S6 at room temperature down to 2.6 nm and study its origin from an atomic perspective. (299 in total)

A series of twisted bilayer and tetralayer MoTe₂ with precisely controlled twist-angles ranging from 0° to 60° are prepared and characterized by polarization-dependent low-frequency Raman spectroscopy. The evolution of interlayer phonon modes and acoustic phonon modes activated by Moiré potentials against twist angles is analyzed in both twisted bilayer MoTe₂ and twisted tetralayer MoTe₂.

Abstract

A wide range of artificially twist-stacked van der Waals materials offer versatile building blocks for quantum optoelectronic devices. Among these, twisted bilayer MoTe₂ has excellent optical properties in the near-infrared range and can be integrated with silicon photonics. While recent studies mainly focus on the emission properties in twisted bilayer MoTe₂, a comprehensive investigation of how Moiré superlattice affects phonon modes in twisted thin-layer MoTe₂ remains unexplored. These phonon modes can serve as indicators of stacking configuration and interface uniformity. Here, a series of twisted bilayer and tetralayer MoTe₂ with precisely controlled twist angles ranging from 0° to 60° are prepared. Using polarization-dependent low-frequency Raman spectroscopy, the evolution of interlayer phonon modes at different twist angles is identified. Additionally, a range of acoustic phonon modes activated by Moiré potentials in both twisted bilayer MoTe₂ and twisted tetralayer MoTe₂ are observed and analyzed. The findings provide experimental evidence of the interlayer phonon coupling and Moiré phonons in MoTe₂, offering insights for the future development of near-infrared optoelectronic devices based on twisted thin-layer MoTe₂.

Untethered microgrippers can be manipulated on a microscopic scale and can reach hard-to-access regions in the body, holding great promise in precision medicine and personalized medicine. This review is focused on the shape-morphing mechanisms, actuation methods, design principles, and fabrication techniques of untethered microgrippers. Their representative biomedical applications are highlighted and future prospects are provided.

Abstract

Microgrippers, a branch of micro/nanorobots, refer to motile miniaturized machines that are of a size in the range of several to hundreds of micrometers. Compared with tethered grippers or other microscopic diagnostic and surgical equipment, untethered microgrippers play an indispensable role in biomedical applications because of their characteristics such as miniaturized size, dexterous shape tranformation, and  controllable motion, which enables the microgrippers to enter hard-to-reach regions to execute specific medical tasks for disease diagnosis and treatment. To date, numerous medical microgrippers are developed, and their potential in cell manipulation, targeted drug delivery, biopsy, and minimally invasive surgery  are explored. To achieve controlled locomotion and efficient target-oriented actions, the materials, size, microarchitecture, and morphology of microgrippers shall be deliberately designed. In this review, the authors summarizes the latest progress in untethered micrometer-scale grippers. The working mechanisms of shape-morphing and actuation methods for effective movement are first introduced. Then, the design principle and state-of-the-art fabrication techniques of microgrippers are discussed. Finally, their applications in the precise medicine are highlighted, followed by offering future perspectives for the development of untethered medical microgrippers.

Nature Communications, Published online: 08 November 2023; doi:10.1038/s41467-023-42996-8

A Weyl semimetal formally requires either broken time reversal symmetry or inversion symmetry. One class of Weyl semimetals-the crystal family of NdAlSi-exhibits both. Here, Li et al perform angle-resolved photoemission spectroscopy measurements on NdAlSi, and observe the formation of an additional Weyl fermion as the material becomes ferrimagnetic.

Nodal Superconductivity

Artistic representation of TaS₂, the first monolayer van der Waals material featuring nodal superconductivity in the ultra-clean limit. Experiments with scanning tunneling spectroscopy reveal the appearance of a nodal gap characteristic of strongly correlated superconductors, and the existence of many-body inelastic excitations at finite energies associated with hidden order fluctuations. More details can be found in article number 2305409 by Jose L. Lado, Peter Liljeroth, and co-workers.

1H/1T′ MoS₂ heterophase structure is synthesized via a facile chemical vapor deposition method. By precisely controlling the growth atmosphere, the semimetallic 1T′-MoS₂ nanoribbon can be grown on the top of the semiconducting 1H-MoS₂ nanosheet, forming a semiconductor/semimetal heterophase structure. The device fabricated with the 1H/1T′ MoS₂ heterophase structure displays a rectifying behavior, leading to enhanced performance for photodetection.

Abstract

2D heterostructures are emerging as alternatives to conventional semiconductors, such as silicon, germanium, and gallium nitride, for next-generation electronics and optoelectronics. However, the direct growth of 2D heterostructures, especially for those with metastable phases still remains challenging. To obtain 2D transition metal dichalcogenides (TMDs) with designed phases, it is highly desired to develop phase-controlled synthetic strategies. Here, a facile chemical vapor deposition method is reported to prepare vertical 1H/1T′ MoS₂ heterophase structures. By simply changing the growth atmosphere, semimetallic 1T′-MoS₂ can be in situ grown on the top of semiconducting 1H-MoS₂, forming vertical semiconductor/semimetal 1H/1T′ heterophase structures with a sharp interface. The integrated device based on the 1H/1T′ MoS₂ heterophase structure displays a typical rectifying behavior with a current rectifying ratio of ≈10³. Moreover, the 1H/1T′ MoS₂-based photodetector achieves a responsivity of 1.07 A W⁻¹ at 532 nm with an ultralow dark current of less than 10⁻¹¹ A. The aforementioned results indicate that 1H/1T′ MoS₂ heterophase structures can be a promising candidate for future rectifiers and photodetectors. Importantly, the approach may pave the way toward tailoring the phases of TMDs, which can help us utilize phase engineering strategies to promote the performance of electronic devices.

In this study, the spray pyrolysis technique, a novel approach for large-area manufacturing of 2D ferroelectric-semiconductor In₂Se₃, is proposed. It demonstrates excellent uniform growth with a 15 cm × 15 cm sized glass substrate. Excellent electrical characteristics such as a large memory window and high on/off current ratio exceeding 10⁷ are achieved with the fabricated In₂Se₃ ferroelectric-semiconductor field-effect transistor.

Abstract

In₂Se₃, 2D ferroelectric-semiconductor, is a promising candidate for next-generation memory device because of its outstanding electrical properties. However, the large-area manufacturing of In₂Se₃ is still a big challenge. In this work, spray pyrolysis technique is introduced for the growth of large-area In₂Se₃ thin film. A polycrystalline γ-In₂Se₃ layer can be grown on 15 cm × 15 cm glasss at the substrate temperature of 275 °C. The In₂Se₃ ferroelectric-semiconductor field effect transistor (FeS-FET) on glass substrate demonstrates a large hysteresis window of 40.3 V at the ±40 V of gate voltage sweep and excellent uniformity. The FeS-FET exhibits an electron field effect mobility of 0.97 cm² V⁻¹ s⁻¹ and an on/off current ratio of >10⁷ in the transfer curves. The memory behavior of the large-area, In₂Se₃ FeS-FETs for next-generation memory is demonstrated.

A resistless scanning probe-based nanolithography method is presented, which allows the controllable patterning of down to single atomic layers of MoTe₂. Through this, it is possible to demonstrate for the first time an anisotropic instability of 1T’-MoTe₂ to aqueous environments. It is furthermore used to fabricate a nanoribbon transistor out of a three atomic layer thick 2H-MoTe₂ nanosheet.

Abstract

An unconventional approach for the resistless nanopatterning 2H- and 1T’-MoTe₂ by means of scanning probe lithography is presented. A Fowler–Nordheim tunneling current of low energetic electrons (E = 30–60 eV) emitted from the tip of an atomic force microscopy (AFM) cantilever is utilized to induce a nanoscale oxidation on a MoTe₂ nanosheet surface under ambient conditions. Due to the water solubility of the generated oxide, a direct pattern transfer into the MoTe₂ surface can be achieved by a simple immersion of the sample in deionized water. The tip-grown oxide is characterized using Auger electron and Raman spectroscopy, revealing it consists of amorphous MoO₃/MoO _x as well as TeO₂/TeO _x . With the presented technology in combination with subsequent AFM imaging it is possible to demonstrate a strong anisotropic sensitivity of 1T’-/(T_d)-MoTe₂ to aqueous environments. Finally the discussed approach is used to structure a nanoribbon field effect transistor out of a few-layer 2H-MoTe₂ nanosheet.