Low-voltage 2D materials-based printed field-effect transistors for integrated digital and analog electronics on paper

Anomalous Phonon Behavior and Tunable Exciton Emissions: Insights into Pressure-Driven Dynamics in Silicon Phosphide

IV-V two-dimensional materials have emerged as key contenders for polarization-sensitive and angle-resolved devices, given their inherent anisotropic physical properties. While these materials exhibit intriguing high-pressure quasi-particle behavior and phase transition, the evolution of quasi-particles and their interactions under external pressure remain elusive. Here, employing a diamond anvil cell and spectroscopic measurements coupled with first-principles calculations, we unveil rarely observed pressure-induced phonon-phonon coupling in layered SiP flakes. This coupling manifests as an anomalous phonon hardening behavior for the A1 mode within a broad wavenumber phonon softening region. Furthermore, we demonstrate the effective tuning of exciton emissions in SiP flakes under pressure, revealing a remarkable 63% enhancement in the degree of polarization (DOP) within the pressure range of 0-3.5 GPa. These findings contribute to our understanding of high-pressure phonon evolution in SiP materials and offer a strategic approach to manipulate the anisotropic performance of in-plane anisotropic 2D materials.

Determination and investigation of defect domains in multi-shape monolayer tungsten disulfide

Single-layer tungsten disulfide (WS2) is among the most widely investigated two-dimensional materials. Synthesizing it over large areas would enable the exploitation of its appealing optical and electronic properties in industrial applications. However, defects of different nature, concentration and distribution profoundly affect the optical as well as the electronic properties of this crystal. Controlling the defect density distribution can be an effective way to tailor the local dielectric environment and therefore the electronic properties of the system. In this work we investigate the defects in single-layer WS2, grown in different shapes by liquid phase chemical vapor deposition, where the concentration of certain defect species can be controlled by the growth conditions. The properties of the material are surveyed by means of optical spectroscopy, photoelectron spectroscopy and Kelvin probe force microscopy. We determine the chemical nature of the defects and study their influence on the optical and electronic properties of WS2. This work contributes to the understanding of the microscopic nature of the intrinsic defects in WS2, helping the development of defect-based technologies which rely on the control and engineering of defects in dielectric 2D crystals.

Spray-lithography of hybrid graphene-perovskite paper-based photodetectors for sustainable electronics

Paper is an ideal substrate for the development of flexible and environmentally sustainable ubiquitous electronic systems. When combined with nanomaterial-based devices, it can be harnessed for various Internet-of-Things applications, ranging from wearable electronics to smart packaging. However, paper remains a challenging substrate for electronics due to its rough and porous nature. In addition, the absence of established fabrication methods is impeding its utilization in wearable applications. Unlike other paper-based electronics with added layers, in this study, we present a scalable spray-lithography on a commercial paper substrate. We present a non-vacuum spray-lithography of chemical vapor deposition (CVD) single-layer graphene (SLG), carbon nanotubes (CNTs) and perovskite quantum dots (QDs) on a paper substrate. This approach combines the advantages of two large-area techniques: CVD and spray-coating. The first technique allows for the growth of SLG, while the second enables the spray coating of a mask to pattern CVD SLG, electrodes (CNTs), and photoactive (QDs) layers. We harness the advantages of perovskite QDs in photodetection, leveraging their strong absorption coefficients. Integrating them with the graphene enhances the photoconductive gain mechanism, leading to high external responsivity. The presented device shows high external responsivity of ∼520 A W-1at 405 nm at <1 V bias due to the photoconductive gain mechanism. The prepared paper-based photodetectors (PDs) achieve an external responsivity of 520 A W-1under 405 nm illumination at <1 V operating voltage. To the best of our knowledge, our devices have the highest external responsivity among paper-based PDs. By fabricating arrays of PDs on a paper substrate in the air, this work highlights the potential of this scalable approach for enabling ubiquitous electronics on paper.

Wearable Sensors for Breath Monitoring Based on Water-Based Hexagonal Boron Nitride Inks Made with Supramolecular Functionalization

Wearable humidity sensors are attracting strong attention as they allow for real-time and continuous monitoring of important physiological information by enabling activity tracking as well as air quality assessment. Amongst 2Dimensional (2D) materials, graphene oxide (GO) is very attractive for humidity sensing due to its tuneable surface chemistry, high surface area, processability in water, and easy integration onto flexible substrates. However, strong hysteresis, low sensitivity, and cross-sensitivity issues limit the use of GO in practical applications, where continuous monitoring is preferred. Herein, a wearable and wireless impedance-based humidity sensor made with pyrene-functionalized hexagonal boron nitride (h-BN) nanosheets is demonstrated. The device shows enhanced sensitivity towards relative humidity (RH) (>1010 Ohms/%RH in the range from 5% to 100% RH), fast response (0.1 ms), no appreciable hysteresis, and no cross-sensitivity with temperature in the range of 25-60 °C. The h-BN-based sensor is able to monitor the whole breathing cycle process of exhaling and inhaling, hence enabling to record in real-time the subtlest changes of respiratory signals associated with different daily activities as well as various symptoms of flu, without requiring any direct contact with the individual.

The Roadmap of 2D Materials and Devices Toward Chips

Due to the constraints imposed by physical effects and performance degradation, silicon-based chip technology is facing certain limitations in sustaining the advancement of Moore's law. Two-dimensional (2D) materials have emerged as highly promising candidates for the post-Moore era, offering significant potential in domains such as integrated circuits and next-generation computing. Here, in this review, the progress of 2D semiconductors in process engineering and various electronic applications are summarized. A careful introduction of material synthesis, transistor engineering focused on device configuration, dielectric engineering, contact engineering, and material integration are given first. Then 2D transistors for certain electronic applications including digital and analog circuits, heterogeneous integration chips, and sensing circuits are discussed. Moreover, several promising applications (artificial intelligence chips and quantum chips) based on specific mechanism devices are introduced. Finally, the challenges for 2D materials encountered in achieving circuit-level or system-level applications are analyzed, and potential development pathways or roadmaps are further speculated and outlooked.

Contributions of Light to Novel Logic Concepts Using Optoelectronic Materials

Instead of the current method of transmitting voltage or current signals in electronic circuit operation, light offers an alternative to conventional logic, allowing for the implementation of new logic concepts through interaction with light. This manuscript examines the use of light in implementing new logic concepts as an alternative to traditional logic circuits and as a future technology. This article provides an overview of how to implement logic operations using light rather than voltage or current signals using optoelectronic materials such as 2D materials, metal-oxides, carbon structures, polymers, small molecules, and perovskites. This review covers the various technologies and applications of using light to dope devices, implement logic gates, control logic circuits, and generate light as an output signal. Recent research on logic and the use of light to implement new functions is summarized. This review also highlights the potential of optoelectronic logic for future technological advancements.

Nanomaterials Based Micro/Nanoelectromechanical System (MEMS and NEMS) Devices

The micro- and nanoelectromechanical system (MEMS and NEMS) devices based on two-dimensional (2D) materials reveal novel functionalities and higher sensitivity compared to their silicon-base counterparts. Unique properties of 2D materials boost the demand for 2D material-based nanoelectromechanical devices and sensing. During the last decades, using suspended 2D membranes integrated with MEMS and NEMS emerged high-performance sensitivities in mass and gas sensors, accelerometers, pressure sensors, and microphones. Actively sensing minute changes in the surrounding environment is provided by means of MEMS/NEMS sensors, such as sensing in passive modes of small changes in momentum, temperature, and strain. In this review, we discuss the materials preparation methods, electronic, optical, and mechanical properties of 2D materials used in NEMS and MEMS devices, fabrication routes besides device operation principles.

2D Materials in Flexible Electronics: Recent Advances and Future Prospectives

Flexible electronics have recently gained considerable attention due to their potential to provide new and innovative solutions to a wide range of challenges in various electronic fields. These electronics require specific material properties and performance because they need to be integrated into a variety of surfaces or folded and rolled for newly formatted electronics. Two-dimensional (2D) materials have emerged as promising candidates for flexible electronics due to their unique mechanical, electrical, and optical properties, as well as their compatibility with other materials, enabling the creation of various flexible electronic devices. This article provides a comprehensive review of the progress made in developing flexible electronic devices using 2D materials. In addition, it highlights the key aspects of materials, scalable material production, and device fabrication processes for flexible applications, along with important examples of demonstrations that achieved breakthroughs in various flexible and wearable electronic applications. Finally, we discuss the opportunities, current challenges, potential solutions, and future investigative directions about this field.

Two-Dimensional Van Der Waals Thin Film and Device

In the rapidly evolving field of thin-film electronics, the emergence of large-area flexible and wearable devices has been a significant milestone. Although organic semiconductor thin films, which can be manufactured through solution processing, have been identified, their utility is often undermined by their poor stability and low carrier mobility under ambient conditions. However, inorganic nanomaterials can be solution-processed and demonstrate outstanding intrinsic properties and structural stability. In particular, a series of two-dimensional (2D) nanosheet/nanoparticle materials have been shown to form stable colloids in their respective solvents. However, the integration of these 2D nanomaterials into continuous large-area thin with precise control of layer thickness and lattice orientation still remains a significant challenge. This review paper undertakes a detailed analysis of van der Waals thin films, derived from 2D materials, in the advancement of thin-film electronics and optoelectronic devices. The superior intrinsic properties and structural stability of inorganic nanomaterials are highlighted, which can be solution-processed and underscor the importance of solution-based processing, establishing it as a cornerstone strategy for scalable electronic and optoelectronic applications. A comprehensive exploration of the challenges and opportunities associated with the utilization of 2D materials for the next generation of thin-film electronics and optoelectronic devices is presented.

12-inch growth of uniform MoS2 monolayer for integrated circuit manufacture

Two-dimensional (2D) semiconductors, such as transition metal dichalcogenides, provide an opportunity for beyond-silicon exploration. However, the lab to fab transition of 2D semiconductors is still in its preliminary stages, and it has been challenging to meet manufacturing standards of stability and repeatability. Thus, there is a natural eagerness to grow wafer-level, high-quality films with industrially acceptable scale-cost-performance metrics. Here we report an improved chemical vapour deposition synthesis method in which the controlled release of precursors and substrates predeposited with amorphous Al2O3 ensure the uniform synthesis of monolayer MoS2 as large as 12 inches while also enabling fast and non-toxic growth to reduce manufacturing costs. Transistor arrays were fabricated to further confirm the high quality of the film and its integrated circuit application potential. This work achieves the co-optimization of scale-cost-performance metrics and lays the foundation for advancing the integration of 2D semiconductors in industry-standard pilot lines.

Reduced Defect Density in MOCVD-Grown MoS2 by Manipulating the Precursor Phase

Advancements in the synthesis of large-area, high-quality two-dimensional transition metal dichalcogenides such as MoS2 play a crucial role in the development of future electronic and optoelectronic devices. The presence of defects formed by sulfur vacancies in MoS2 results in low photoluminescence emission and imparts high n-type doping behavior, thus substantially affecting material quality. Herein, we report a new method in which single-phase (liquid) precursors are used for the metal-organic chemical vapor deposition (MOCVD) growth of a MoS2 film. Furthermore, we fabricated a high-performance photodetector (PD) and achieved improved photoresponsivity and faster photoresponse in the spectral range 405-637 nm compared to those of PDs fabricated by the conventional MOCVD method. In addition, the fabricated MoS2 thin film showed a threshold voltage shift in the positive gate bias direction owing to the reduced number of S vacancy defects in the MoS2 lattice. Thus, our method significantly improved the synthesis of monolayer MoS2 and can expand the application scope of high-quality, atomically thin materials in large-scale electronic and optoelectronic devices.

Low power flexible monolayer MoS2 integrated circuits

Monolayer molybdenum disulfide (ML-MoS₂) is an emergent two-dimensional (2D) semiconductor holding potential for flexible integrated circuits (ICs). The most important demands for the application of such ML-MoS₂ ICs are low power consumption and high performance. However, these are currently challenging to satisfy due to limitations in the material quality and device fabrication technology. In this work, we develop an ultra-thin high-κ dielectric/metal gate fabrication technique for the realization of thin film transistors based on high-quality wafer scale ML-MoS₂ on both rigid and flexible substrates. The rigid devices can be operated in the deep-subthreshold regime with low power consumption and show negligible hysteresis, sharp subthreshold slope, high current density, and ultra-low leakage currents. Moreover, we realize fully functional large-scale flexible ICs operating at voltages below 1 V. Our process could represent a key step towards using energy-efficient flexible ML-MoS₂ ICs in portable, wearable, and implantable electronics.

Flexible and Wearable Biosensors for Monitoring Health Conditions

Flexible and wearable biosensors have received tremendous attention over the past decade owing to their great potential applications in the field of health and medicine. Wearable biosensors serve as an ideal platform for real-time and continuous health monitoring, which exhibit unique properties such as self-powered, lightweight, low cost, high flexibility, detection convenience, and great conformability. This review introduces the recent research progress in wearable biosensors. First of all, the biological fluids often detected by wearable biosensors are proposed. Then, the existing micro-nanofabrication technologies and basic characteristics of wearable biosensors are summarized. Then, their application manners and information processing are also highlighted in the paper. Massive cutting-edge research examples are introduced such as wearable physiological pressure sensors, wearable sweat sensors, and wearable self-powered biosensors. As a significant content, the detection mechanism of these sensors was detailed with examples to help readers understand this area. Finally, the current challenges and future perspectives are proposed to push this research area forward and expand practical applications in the future.

Gate Dielectrics Integration for 2D Electronics: Challenges, Advances, and Outlook

2D semiconductors have emerged both as an ideal platform for fundamental studies and as promising channel materials in beyond-silicon field-effect-transistors due to their outstanding electrical properties and exceptional tunability via external field. However, the lack of proper dielectrics for 2D semiconductors has become a major roadblock for their further development toward practical applications. The prominent issues between conventional 3D dielectrics and 2D semiconductors arise from the integration and interface quality, where defect states and imperfections lead to dramatic deterioration of device performance. In this review article, the root causes of such issues are briefly analyzed and recent advances on some possible solutions, including various approaches of adapting conventional dielectrics to 2D semiconductors, and the development of novel dielectrics with van der Waals surface toward high-performance 2D electronics are summarized. Then, in the perspective, the requirements of ideal dielectrics for state-of-the-art 2D devices are outlined and an outlook for their future development is provided.

Van der Waals nanomesh electronics on arbitrary surfaces

Chemical bonds, including covalent and ionic bonds, endow semiconductors with stable electronic configurations but also impose constraints on their synthesis and lattice-mismatched heteroepitaxy. Here, the unique multi-scale van der Waals (vdWs) interactions are explored in one-dimensional tellurium (Te) systems to overcome these restrictions, enabled by the vdWs bonds between Te atomic chains and the spontaneous misfit relaxation at quasi-vdWs interfaces. Wafer-scale Te vdWs nanomeshes composed of self-welding Te nanowires are laterally vapor grown on arbitrary surfaces at a low temperature of 100 °C, bringing greater integration freedoms for enhanced device functionality and broad applicability. The prepared Te vdWs nanomeshes can be patterned at the microscale and exhibit high field-effect hole mobility of 145 cm²/Vs, ultrafast photoresponse below 3 μs in paper-based infrared photodetectors, as well as controllable electronic structure in mixed-dimensional heterojunctions. All these device metrics of Te vdWs nanomesh electronics are promising to meet emerging technological demands.

Local dielectric function of hBN-encapsulated WS2flakes grown by chemical vapor deposition

Hexagonal boron nitride (hBN), sometimes referred to as white graphene, receives growing interest in the scientific community, especially when combined into van der Waals (vdW) homo- and heterostacks, in which novel and interesting phenomena may arise. hBN is also commonly used in combination with two-dimensional (2D) semiconducting transition metal dichalcogenides (TMDCs). The realization of hBN-encapsulated TMDC homo- and heterostacks can indeed offer opportunities to investigate and compare TMDC excitonic properties in various stacking configurations. In this work, we investigate the optical response at the micrometric scale of mono- and homo-bilayer WS₂grown by chemical vapor deposition and encapsulated between two single layers of hBN. Imaging spectroscopic ellipsometry is exploited to extract the local dielectric functions across one single WS₂flake and detect the evolution of excitonic spectral features from monolayer to bilayer regions. Exciton energies undergo a redshift by passing from hBN-encapsulated single layer to homo-bilayer WS₂, as also confirmed by photoluminescence spectra. Our results can provide a reference for the study of the dielectric properties of more complex systems where hBN is combined with other 2D vdW materials into heterostructures and are stimulating towards the investigation of the optical response of other technologically-relevant heterostacks.

Recent advances in inkjet-printing technologies for flexible/wearable electronics

The rapid development of flexible/wearable electronics requires novel fabricating strategies. Among the state-of-the-art techniques, inkjet printing has aroused considerable interest due to the possibility of large-scale fabricating flexible electronic devices with good reliability, high time efficiency, a low manufacturing cost, and so on. In this review, based on the working principle, recent advances in the inkjet printing technology in the field of flexible/wearable electronics are summarized, including flexible supercapacitors, transistors, sensors, thermoelectric generators, wearable fabric, and for radio frequency identification. In addition, some current challenges and future opportunities in this area are also addressed. We hope this review article can give positive suggestions to the researchers in the area of flexible electronics.

Water-based 2-dimensional anatase TiO2 inks for printed diodes and transistors

2-Dimensional (2D) materials are attracting strong interest in printed electronics because of their unique properties and easy processability, enabling the fabrication of devices with low cost and mass scalable methods such as inkjet printing. For the fabrication of fully printed devices, it is of fundamental importance to develop a printable dielectric ink, providing good insulation and the ability to withstand large electric fields. Hexagonal boron nitride (h-BN) is typically used as a dielectric in printed devices. However, the h-BN film thickness is usually above 1 μm, hence limiting the use of h-BN in low-voltage applications. Furthermore, the h-BN ink is composed of nanosheets with broad lateral size and thickness distributions, due to the use of liquid-phase exfoliation (LPE). In this work, we investigate anatase TiO₂ nanosheets (TiO₂-NS), produced by a mass scalable bottom-up approach. We formulate the TiO₂-NS into a water-based and printable solvent and demonstrate the use of the material with sub-micron thickness in printed diodes and transistors, hence validating the strong potential of TiO₂-NS as a dielectric for printed electronics.

Electrical Contacts With 2D Materials: Current Developments and Future Prospects

Current electrical contact models are occasionally insufficient at the nanoscale owing to the wide variations in outcomes between 2D mono and multi-layered and bulk materials that result from their distinctive electrostatics and geometries. Contrarily, devices based on 2D semiconductors present a significant challenge due to the requirement for electrical contact with resistances close to the quantum limit. The next generation of low-power devices is already hindered by the lack of high-quality and low-contact-resistance contacts on 2D materials. The physics and materials science of electrical contact resistance in 2D materials-based nanoelectronics, interface configurations, charge injection mechanisms, and numerical modeling of electrical contacts, as well as the most pressing issues that need to be resolved in the field of research and development, will all be covered in this review.

Emerging Two-Dimensional Materials-Based Electrochemical Sensors for Human Health and Environment Applications

Two-dimensional materials (2DMs) have been vastly studied for various electrochemical sensors. Among these, the sensors that are directly related to human life and health are extremely important. Owing to their exclusive properties, 2DMs are vastly studied for electrochemical sensing. Here we have provided a selective overview of 2DMs-based electrochemical sensors that directly affect human life and health. We have explored graphene and its derivatives, transition metal dichalcogenide and MXenes-based electrochemical sensors for applications such as glucose detection in human blood, detection of nitrates and nitrites, and sensing of pesticides. We believe that the areas discussed here are extremely important and we have summarized the prominent reports on these significant areas together. We believe that our work will be able to provide guidelines for the evolution of electrochemical sensors in the future.

Printed Electronics Based on 2D Material Inks: Preparation, Properties, and Applications toward Memristors

Printed electronics, which fabricate electrical components and circuits on various substrates by leveraging functional inks and advanced printing technologies, have recently attracted tremendous attention due to their capability of large-scale, high-speed, and cost-effective manufacturing and also their great potential in flexible and wearable devices. To further achieve multifunctional, practical, and commercial applications, various printing technologies toward smarter pattern-design, higher resolution, greater production flexibility, and novel ink formulations toward multi-functionalities and high quality have been insensitively investigated. 2D materials, possessing atomically thin thickness, unique properties and excellent solution-processable ability, hold great potential for high-quality inks. Besides, the great variety of 2D materials ranging from metals, semiconductors to insulators offers great freedom to formulate versatile inks to construct various printed electronics. Here, a detailed review of the progress on 2D material inks formulation and its printed applications has been provided, specifically with an emphasis on emerging printed memristors. Finally, the challenges facing the field and prospects of 2D material inks and printed electronics are discussed.

Large-Scale Ultra-Robust MoS2 Patterns Directly Synthesized on Polymer Substrate for Flexible Sensing Electronics

Synthesis of large-area patterned MoS₂ is considered the principle base for realizing high-performance MoS₂ -based flexible electronic devices. Patterning and transferring MoS₂ films to target flexible substrates, however, require conventional multi-step photolithography patterning and transferring process, despite tremendous progress in the facilitation of practical applications. Herein, an approach to directly synthesize large-scale MoS₂ patterns that combines inkjet printing and thermal annealing is reported. An optimal precursor ink is prepared that can deposit arbitrary patterns on polyimide films. By introducing a gas atmosphere of argon/hydrogen (Ar/H₂ ), thermal treatment at 350 °C enables an in situ decomposition and crystallization in the patterned precursors and, consequently, results in the formation of MoS₂ . Without complicated processes, patterned MoS₂ is obtained directly on polymer substrate, exhibiting superior mechanical flexibility and durability (≈2% variation in resistance over 10,000 bending cycles), as well as excellent chemical stability, which is attributed to the generated continuous and thin microstructures, as well as their strong adhesion with the substrate. As a step further, this approach is employed to manufacture various flexible sensing devices that are insensitive to body motions and moisture, including temperature sensors and biopotential sensing systems for real-time, continuously monitoring skin temperature, electrocardiography, and electromyography signals.

Nanoscale structural and electronic properties of cellulose/graphene interfaces

The development of electronic devices based on the functionalization of (nano)cellulose platforms relies upon an atomistic understanding of the structural and electronic properties of a combined system, cellulose/functional element. In this work, we present a theoretical study of the nanocellulose/graphene interfaces (nCL/G) based on first-principles calculations. We find that the binding energies of both hydrophobic/G (nCL^phob/G) and hydrophilic/G (nCL^phil/G) interfaces are primarily dictated by the van der Waals interactions, and are comparable with those of their 2D interface counterparts. We verify that the energetic preference of nCL^phob/G has been reinforced by the inclusion of an aqueous medium via an implicit solvation model. Further structural characterization was carried out using a set of simulations of the carbon K-edge X-ray absorption spectra to identify and distinguish the key absorption features of the nCL^phob/G and nCL^phil/G interfaces. The electronic structure calculations reveal that the linear energy bands of graphene lie in the band gap of the nCL sheet, while depletion/accumulation charge density regions are observed. We show that external agents, i.e., electric field and mechanical strain, allow for tunability of the Dirac cone and charge density at the interface. The control/maintenance of the Dirac cone states in nCL/G is an important feature for the development of electronic devices based on cellulosic platforms.

Flexible high-performance microcapacitors enabled by all-printed two-dimensional nanosheets

Chemically exfoliated nanosheets have exhibited great potential for applications in various electronic devices. Solution-based processing strategies such as inkjet printing provide a low-cost, environmentally friendly, and scalable route for the fabrication of flexible devices based on functional inks of two-dimensional nanosheets. In this study, chemically exfoliated high-k perovskite nanosheets (i.e., Ca₂Nb₃O₁₀ and Ca₂NaNb₄O₁₃) are well dispersed in appropriate solvents to prepare printable inks, and then, a series of microcapacitors with Ag and graphene electrodes are printed. The resulting microcapacitors, Ag/Ca₂Nb₃O₁₀/Ag, graphene/Ca₂Nb₃O₁₀/graphene, and graphene/Ca₂NaNb₄O₁₃/graphene, demonstrate high capacitance densities of 20, 80, and 150 nF/cm² and high dielectric constants of 26, 110, and 200, respectively. Such dielectric enhancement in the microcapacitors with graphene electrodes is possibly attributed to the dielectric/graphene interface. In addition, these microcapacitors also exhibit good insulating performance with a moderate electrical breakdown strength of approximately 1 MV/cm, excellent flexibility, and thermal stability up to 200 ℃. This work demonstrates the potential of high-k perovskite nanosheets for additive manufacturing of flexible high-performance dielectric capacitors.

Stacked printed MoS2 and Ag electrodes using electrohydrodynamic jet printing for thin-film transistors

Transition metal dichalcogenide-based thin-film transistors (TFTs) have drawn intense research attention, but they suffer from high cost of materials and complex methods. Directly printed transistors have been in the limelight due to low cost and an environmentally friendly technique. An electrohydrodynamic (EHD) jet printing technique was employed to pattern both MoS₂ active layer and Ag source and drain (S/D) electrodes. Printed MoS₂ lines were patterned on a silicon wafer using a precursor solution and simple annealing, and the patterns were transferred on other SiO₂ substrates for TFT fabrication. On top of the patterned MoS₂, Ag paste was also patterned for S/D electrodes using EHD jet printing. The printed TFTs had a high on-off current ratio exceeding 10⁵, low subthreshold slope, and better hysteresis behavior after transferring MoS₂ patterns. This result could be important for practical TFT applications and could be extended to other 2D materials.

Etch and Print: Graphene-Based Diodes for Silicon Technology

The graphene-silicon junction is one of the simplest conceivable interfaces in graphene-integrated semiconductor technology that can lead to the development of future generation of electronic and optoelectronic devices. However, graphene's integration is currently expensive and time-consuming and shows several challenges in terms of large-scale device fabrication, effectively preventing the possibility of implementing this technology into industrial processes. Here, we show a simple and cost-effective fabrication technique, based on inkjet printing, for the realization of printed graphene-silicon rectifying devices. The printed graphene-silicon diodes show an ON/OFF ratio higher than 3 orders of magnitude and a significant photovoltaic effect, resulting in a fill factor of ∼40% and a photocurrent efficiency of ∼2%, making the devices suitable for both electronic and optoelectronic applications. Finally, we demonstrate large-area pixeled photodetectors and compatibility with back-end-of-line fabrication processes.

Nanopatterning Technologies of 2D Materials for Integrated Electronic and Optoelectronic Devices

With the reduction of feature size and increase of integration density, traditional 3D semiconductors are unable to meet the future requirements of chip integration. The current semiconductor fabrication technologies are approaching their physical limits based on Moore's law. 2D materials such as graphene, transitional metal dichalcogenides, etc., are of great promise for future memory, logic, and photonic devices due to their unique and excellent properties. To prompt 2D materials and devices from the laboratory research stage to the industrial integrated circuit-level, it is necessary to develop advanced nanopatterning methods to obtain high-quality, wafer-scale, and patterned 2D products. Herein, the recent development of nanopatterning technologies, particularly toward realizing large-scale practical application of 2D materials is reviewed. Based on the technological progress, the unique requirement and advances of the 2D integration process for logic, memory, and optoelectronic devices are further summarized. Finally, the opportunities and challenges of nanopatterning technologies of 2D materials for future integrated chip devices are prospected.

Interface Capture Effect Printing Atomic-Thick 2D Semiconductor Thin Films

2D semiconductor crystals offer the opportunity to further extend Moore's law to the atomic scale. For practical and low-cost electronic applications, directly printing devices on substrates is advantageous compared to conventional microfabrication techniques that utilize expensive photolithography, etching, and vacuum-metallization processes. However, the currently printed 2D transistors are plagued by unsatisfactory electrical performance, thick semiconductor layers, and low device density. Herein, a facile and scalable 2D semiconductor printing strategy is demonstrated utilizing the interface capture effect and hyperdispersed 2D nanosheet ink to fabricate high-quality and atomic-thick semiconductor thin-film arrays without additional surfactants. Printed robust thin-film transistors using 2D semiconductors (e.g., MoS₂ ) and 2D conductive electrodes (e.g., graphene) exhibit high electrical performance, including a carrier mobility of up to 6.7 cm² V^-1 s^-1 and an on/off ratio of 2 × 10⁶ at 25 °C. As a proof of concept, 2D transistors are printed with a density of ≈47 000 devices per square centimeter. In addition, this method can be applied to many other 2D materials, such as NbSe₂ , Bi₂ Se₃ , and black phosphorus, for printing diverse high-quality thin films. Thus, the strategy of printable 2D thin-film transistors provides a scalable pathway for the facile manufacturing of high-performance electronics at an affordable cost.

Defect-Free Metal Deposition on 2D Materials via Inkjet Printing Technology

2D materials have many outstanding properties that make them attractive for the fabrication of electronic devices, such as high conductivity, flexibility, and transparency. However, integrating 2D materials in commercial devices and circuits is challenging because their structure and properties can be damaged during the fabrication process. Recent studies have demonstrated that standard metal deposition techniques (like electron beam evaporation and sputtering) significantly damage the atomic structure of 2D materials. Here it is shown that the deposition of metal via inkjet printing technology does not produce any observable damage in the atomic structure of ultrathin 2D materials, and it can keep a sharp interface. These conclusions are supported by abundant data obtained via atomistic simulations, transmission electron microscopy, nanochemical metrology, and device characterization in a probe station. The results are important for the understanding of inkjet printing technology applied to 2D materials, and they could contribute to the better design and optimization of electronic devices and circuits.

Van der Waals-Interface-Dominated All-2D Electronics

The interface is the device. As the feature size rapidly shrinks, silicon-based electronic devices are facing multiple challenges of material performance decrease and interface quality degradation. Ultrathin 2D materials are considered as potential candidates in future electronics by their atomically flat surfaces and excellent immunity to short-channel effects. Moreover, due to naturally terminated surfaces and weak van der Waals (vdW) interactions between layers, 2D materials can be freely stacked without the lattice matching limit to form high-quality heterostructure interfaces with arbitrary components and twist angles. Controlled interlayer band alignment and optimized interfacial carrier behavior allow all-2D electronics based on 2D vdW interfaces to exhibit more comprehensive functionality and better performance. Especially, achieving the same computing capacity of multiple conventional devices with small footprint all-2D devices is considered to be the key development direction of future electronics. Herein, the unique properties of all-2D vdW interfaces and their construction methods are systematically reviewed and the main performance contributions of different vdW interfaces in 2D electronics are summarized, respectively. Finally, the recent progress and challenges for all-2D vdW electronics are discussed, and how to improve the compatibility of 2D material devices with silicon-based industrial technology is pointed out as a critical challenge.

Inkjet printing of two-dimensional van der Waals materials: a new route towards emerging electronic device applications

Two-dimensional (2D) van der Waals (vdW) materials are considered one of the most promising candidates to realize emerging electrical applications. Although until recently, much effort has been dedicated to demonstrating high-performance single 2D vdW devices, associated with rapid progress in 2D vdW materials, demands for their large-scale practical applications have noticeably increased from a manufacturing perspective. Drop-on-demand inkjet printing can be the most feasible solution by exploiting the advantages of layered 2D contacts and advanced 2D vdW ink formulations. This review presents recent achievements in inkjet-printed 2D vdW material-based device applications. A brief introduction to 2D vdW materials and inkjet printing principles, followed by various ink formulation methods, is first presented. Then, the state-of-the-art inkjet-printed 2D vdW device applications and their remaining technical issues are highlighted. Finally, prospects and challenges to be overcome to demonstrate fully inkjet-printed, high-performance 2D vdW devices are also discussed.

Liquid-Phase Exfoliation of Nonlayered Non-Van-Der-Waals Crystals into Nanoplatelets

For nearly 15 years, researchers have been using liquid-phase exfoliation (LPE) to produce 2D nanosheets from layered crystals. This has yielded multiple 2D materials in a solution-processable form whose utility has been demonstrated in multiple applications. It was believed that the exfoliation of such materials is enabled by the very large bonding anisotropy of layered materials where the strength of intralayer chemical bonds is very much larger than that of interlayer van der Waals bonds. However, over the last five years, a number of papers have raised questions about our understanding of exfoliation by describing the LPE of nonlayered materials. These results are extremely surprising because, as no van der Waals gap is present to provide an easily cleaved direction, the exfoliation of such compounds requires the breaking of only chemical bonds. Here the progress in this unexpected new research area is examined. The structure and properties of nanoplatelets produced by LPE of nonlayered materials are reviewed. A number of unexplained trends are found, not least the preponderance of isotropic materials that have been exfoliated to give high-aspect-ratio nanoplatelets. Finally, the applications potential of this new class of 2D materials are considered.

Printable inks and deformable electronic array devices

Deformable printed electronic array devices are expected to revolutionize next-generation electronics. However, although remarkable technological advances in printable inks and deformable electronic array devices have recently been achieved, technical challenges remain to commercialize these technologies. In this review article a brief introduction to printing methods highlighting significant research studies on ink formation for conductors, semiconductors, and insulators is provided, and the structural design and successful printing strategies of deformable electronic array devices are described. Successful device demonstrations are presented in the applications of passive- and active-matrix array devices. Finally, perspectives and technological challenges to be achieved are pointed out to print practically available deformable devices.

The Electronic Properties of g−ZnO Modulated by Organic Molecules Adsorption

Molecular doping is an excellent instrument to modify the electronic properties of two−dimensional materials. In our work, the structure and electronic properties of the adsorption systems of g−ZnO adsorbed by organic molecules (including Tetracyanoethylene (TCNE), Tetracyanoquinodimethane (TCNQ), and Tetrahydrofulvalene (TTF)) were investigated computationally using Density Functional Theory (DFT). The results showed that the TCNE and TCNQ, as electron receptors, doped the LUMO energy level above the valence band maximum (VBM) of the g−ZnO band structure, demonstrating effective p−type doping. The n−type doping of g−ZnO was obtained that the TTF molecules, as electron donors, doped the HOMO energy level below the conduction band minimum (CBM) of the band structure for g−ZnO. In addition, the TCNE, TCNQ, and TTF breathed additional holes or electrons into the monolayer g−ZnO, creating surface dipole moments between the g−ZnO and organic molecules, which caused work function to be adjustable, ranging from 3.871 eV to 5.260 eV. Our results prove that organic molecular doping was instrumental in improving the performance of g−ZnO−based nano−electronic devices, providing theoretical support for the fabrication of p−doping or n−doping nano−semiconductor components. The tunable range of field emission capability of g−ZnO−based electronic devices was also extended.

Tailoring the Electrical Characteristics of MoS2 FETs through Controllable Surface Charge Transfer Doping Using Selective Inkjet Printing

Surface charge transfer doping (SCTD) has been regarded as an effective approach to tailor the electrical characteristics of atomically thin transition metal dichalcogenides (TMDs) in a nondestructive manner due to their two-dimensional nature. However, the difficulty of achieving rationally controlled SCTD on TMDs via conventional doping methods, such as solution immersion and dopant vaporization, has impeded the realization of practical optoelectronic and electronic devices. Here, we demonstrate controllable SCTD of molybdenum disulfide (MoS₂) field-effect transistors using inkjet-printed benzyl viologen (BV) as an n-type dopant. By adjusting the BV concentration and the areal coverage of inkjet-printed BV dopants, controllable SCTD results in BV-doped MoS₂ FETs with elaborately tailored electrical performance. Specifically, the suggested solvent system creates well-defined droplets of BV ink having a volume of ∼2 pL, which allows the high spatial selectivity of SCTD onto the MoS₂ channels by depositing the BV dopant on demand. Our inkjet-printed SCTD method provides a feasible solution for achieving controllable doping to modulate the electrical and optical performances of TMD-based devices.

2D Molybdenum Sulfide-Based Materials for Photo-Excited Antibacterial Application

Bacterial infections have seriously threatened human health and the abuse of natural or artificial antibiotics leads to bacterial resistance, so development of a new generation of antibacterial agents and treatment methods is urgent. 2D molybdenum sulfide (MoS₂ ) has good biocompatibility, high specific surface area to facilitate surface modification and drug loading, adjustable energy bandgap, and high near-infrared photothermal conversion efficiency (PCE), so it is often used for antibacterial application through its photothermal or photodynamic effects. This review comprehensively summarizes and discusses the fabrication processes, structural characteristics, antibacterial performance, and the corresponding mechanisms of MoS₂ -based materials as well as their representative antibacterial applications. In addition, the outlooks on the remaining challenges that should be addressed in the field of MoS₂ are also proposed.

Optical Response of CVD-Grown ML-WS2 Flakes on an Ultra-Dense Au NP Plasmonic Array

The combination of metallic nanostructures with two-dimensional transition metal dichalcogenides is an efficient way to make the optical properties of the latter more appealing for opto-electronic applications. In this work, we investigate the optical properties of monolayer WS2 flakes grown by chemical vapour deposition and transferred onto a densely-packed array of plasmonic Au nanoparticles (NPs). The optical response was measured as a function of the thickness of a dielectric spacer intercalated between the two materials and of the system temperature, in the 75–350 K range. We show that a weak interaction is established between WS2 and Au NPs, leading to temperature- and spacer-thickness-dependent coupling between the localized surface plasmon resonance of Au NPs and the WS2 exciton. We suggest that the closely-packed morphology of the plasmonic array promotes a high confinement of the electromagnetic field in regions inaccessible by the WS2 deposited on top. This allows the achievement of direct contact between WS2 and Au while preserving a strong connotation of the properties of the two materials also in the hybrid system.

Low Power Consumption Gate-Tunable WSe2/SnSe2 Van Der Waals Tunnel Field-Effect Transistor

Two-dimensional (2D) transition-metal dichalcogenides (TMDCs) have attracted attention as promising next-generation electronic devices and sensors. In this study, we fabricated a novel nanoelectronic device based on a black-phosphorus-gated WSe2/SnSe2 van der Waals (vdW) tunnel field-effect transistor (TFET), where hexagonal boron nitride (h-BN) was used as the gate insulator. We performed morphological, electrical, and optoelectronic characterizations. The p-WSe2/n-SnSe2 heterostructure-based TFET exhibited p-type behavior with a good dependence on the gate voltage. The TFET device showed a trend toward negative differential resistance (NDR) originating from band-to-band tunneling, which can be tuned by applying a gate voltage. The optoelectronic performance of the TFET device was low, with a maximum photoresponsivity of 11 mA W−1, owing to the large device length. The results obtained herein promote the integration of black phosphorus into low-energy-consumption 2D vdW TFETs.

Van der Waals Epitaxy of Bi2 Te2 Se/Bi2 O2 Se Vertical Heterojunction for High Performance Photodetector

Bismuth oxyselenide (Bi₂ O₂ Se) has emerged as a promising candidate for electronic and optoelectronic applications due to its outstanding electron mobility and ambient stability. However, high dark current and relatively slow photoresponse that originate from high charge carrier concentration as well as bolometric effect in Bi₂ O₂ Se inhibit further improvement of Bi₂ O₂ Se based photodetectors. Here, a one-step van der Waals (vdW) epitaxy synthesis of Bi₂ Te₂ Se/Bi₂ O₂ Se vertical heterojunction with type-II band alignment and high-quality interface is demonstrated. The crystal quality and uniformity of the heterojunction are supported by Raman, transmission electron microscopy and energy dispersive spectroscopy results. A photodetector based on Bi₂ Te₂ Se/Bi₂ O₂ Se heterojunction demonstrates steady photoresponse over a large wavelength range (532-1456 nm), with a high specific responsivity of 2.21 × 10³ A W^-1 at 532 nm and fast response speed of 50 ms. Moreover, field effect regulation allows for further improvement of the photoresponse performance of the heterojunction field effect transistor device, where the responsivity can be increased to 3.34 × 10³ A W^-1 with a 60 V gate voltage. Overall, the one-step vdW epitaxy process is a promising and convenient route towards constructing high quality Bi₂ O₂ Se based heterojunction for improving its photodetection performance.

Unexpected Electron Transport Suppression in a Heterostructured Graphene-MoS2 Multiple Field-Effect Transistor Architecture

We demonstrate a graphene-MoS2 architecture integrating multiple field-effect transistors (FETs), and we independently probe and correlate the conducting properties of van der Waals coupled graphene-MoS2 contacts with those of the MoS2 channels. Devices are fabricated starting from high-quality single-crystal monolayers grown by chemical vapor deposition. The heterojunction was investigated by scanning Raman and photoluminescence spectroscopies. Moreover, transconductance curves of MoS2 are compared with the current-voltage characteristics of graphene contact stripes, revealing a significant suppression of transport on the n-side of the transconductance curve. On the basis of ab initio modeling, the effect is understood in terms of trapping by sulfur vacancies, which counterintuitively depends on the field effect, even though the graphene contact layer is positioned between the backgate and the MoS2 channel.

Mechanical sensors based on two-dimensional materials: Sensing mechanisms, structural designs and wearable applications

Compared with bulk materials, atomically thin two-dimensional (2D) crystals possess a range of unique mechanical properties, including relatively high in-plane stiffness and large bending flexibility. The atomic 2D building blocks can be reassembled into precisely designed heterogeneous composite structures of various geometries with customized mechanical sensing behaviors. Due to their small specific density, high flexibility, and environmental adaptability, mechanical sensors based on 2D materials can conform to soft and curved surfaces, thus providing suitable solutions for functional applications in future wearable devices. In this review, we summarize the latest developments in mechanical sensors based on 2D materials from the perspective of function-oriented applications. First, typical mechanical sensing mechanisms are introduced. Second, we attempt to establish a correspondence between typical structure designs and the performance/multi-functions of the devices. Afterward, several particularly promising areas for potential applications are discussed, following which we present perspectives on current challenges and future opportunities

Printed Zinc Paper Batteries

Paper electronics offer an environmentally sustainable option for flexible and wearable systems and perfectly fit the available printing technologies for high manufacturing efficiency. As the heart of energy-consuming devices, paper-based batteries are required to be compatible with printing processes with high fidelity. Herein, hydrogel reinforced cellulose paper (HCP) is designed to serve as the separator and solid electrolyte for paper batteries. The HCP can sustain higher strain than pristine papers and are biodegradable in natural environment within four weeks. Zinc-metal (Ni and Mn) batteries printed on the HCP present remarkable volumetric energy density of ≈26 mWh cm-3 , and also demonstrate the feature of cuttability and compatibility with flexible circuits and devices. As a result, self-powered electronic system could be constructed by integrating printed paper batteries with solar cells and light-emitting diodes. The result highlights the feasibility of hydrogel reinforced paper for ubiquitous flexible and eco-friendly electronics.

Ink Formulation and Printing Parameters for Inkjet Printing of Two Dimensional Materials: A Mini Review

Inkjet printing of two-dimensional (2D) material has been a center of interest for wearable electronics and has become a promising platform for next-generation technologies. Despite the enormous progress made in printed 2D materials, there are still challenges in finding the optimal printing conditions involving the ink formulation and printing parameters. Adequate ink formulation and printing parameters for target 2D materials rely on empirical studies and repeated trials. Therefore, it is essential to compile promising strategies for ink formulation and printing parameters. In this context, this review discusses the optimal ink formulations to prepare stable ink and steady ink jetting and then explores the critical printing parameters for fabricating printed 2D materials of a high quality. The summary and future prospects for inkjet-printed 2D materials are also addressed.

Paper-based field-effect transistor sensors

The present scenario in the world largely demands affordable, fast, recyclable, and flexible electronic devices for bio sensing. Varieties of paper-based devices such as microfluidics paper electrodes, paper diodes, and paper-based transistors etc. have been developed and validated. Most of the fabrication techniques published so far have focused on economic, environment-friendly straightforward methods to develop paper-based field-effect transistors (PFET) sensors, additionally, explored their applications. The synthetic-free, mechanically flexible, biocompatible, and signal amplification capability render PFET based sensors for wearable device makers. Modified organic/inorganic PFETs identify target analytes based on the electrical signal and endow them as perfect transducers. In the field of PFET bio sensing technology, numerous challenges are needed to be discussed to proceed forward in biomedical and other analytical applications. Realizing biologically or chemically modified PFET having an exceptional signal to noise ratio, specificity, with rapid detection ability is challenging. This review recapitulates the fabrication techniques, performances of various PFET sensors, and summarizes the report by concluding remarks including the limitations of the existing PFET based sensors and the future holds in regards to the sustainable nature of PFET.

Gold nanoparticle assisted synthesis of MoS2 monolayers by chemical vapor deposition

The use of metal nanoparticles is an established paradigm for the synthesis of semiconducting one-dimensional nanostructures. In this work we study their effect on the synthesis of two-dimensional semiconducting materials, by using gold nanoparticles for chemical vapor deposition growth of two-dimensional molybdenum disulfide (MoS₂). In comparison with the standard method, the employment of gold nanoparticles allows us to obtain large monolayer MoS₂ flakes, up to 20 μm in lateral size, even if they are affected by the localized overgrowth of MoS₂ bilayer and trilayer islands. Important modifications of the optical and electronic properties of MoS₂ triangular domains are reported, where the photoluminescence intensity of the A exciton is strongly quenched and a shift to a positive threshold voltage in back-gated field effect transistors is observed. These results indicate that the use of gold nanoparticles influences the flake growth and properties, indicating a method for possible localized synthesis of two-dimensional materials, improving the lateral size of monolayers and modifying their properties.

Fully Printed High-Performance n-Type Metal Oxide Thin-Film Transistors Utilizing Coffee-Ring Effect

Metal oxide thin-films transistors (TFTs) produced from solution-based printing techniques can lead to large-area electronics with low cost. However, the performance of current printed devices is inferior to those from vacuum-based methods due to poor film uniformity induced by the "coffee-ring" effect. Here, we report a novel approach to print high-performance indium tin oxide (ITO)-based TFTs and logic inverters by taking advantage of such notorious effect. ITO has high electrical conductivity and is generally used as an electrode material. However, by reducing the film thickness down to nanometers scale, the carrier concentration of ITO can be effectively reduced to enable new applications as active channels in transistors. The ultrathin (~10-nm-thick) ITO film in the center of the coffee-ring worked as semiconducting channels, while the thick ITO ridges (>18-nm-thick) served as the contact electrodes. The fully inkjet-printed ITO TFTs exhibited a high saturation mobility of 34.9 cm² V^-1 s^-1 and a low subthreshold swing of 105 mV dec^-1. In addition, the devices exhibited excellent electrical stability under positive bias illumination stress (PBIS, ΔV_th = 0.31 V) and negative bias illuminaiton stress (NBIS, ΔV_th = -0.29 V) after 10,000 s voltage bias tests. More remarkably, fully printed n-type metal-oxide-semiconductor (NMOS) inverter based on ITO TFTs exhibited an extremely high gain of 181 at a low-supply voltage of 3 V, promising for advanced electronics applications.

Local Optical Properties in CVD-Grown Monolayer WS2 Flakes

Excitons dominate the light absorption and re-emission spectra of monolayer transition-metal dichalcogenides (TMD). Microscopic investigations of the excitonic response in TMD almost invariably extract information from the radiative recombination step, which only constitutes one part of the picture. Here, by exploiting imaging spectroscopic ellipsometry (ISE), we investigate the spatial dependence of the dielectric function of chemical vapor deposition (CVD)-grown WS2 flakes with a microscopic lateral resolution, thus providing information about the spatially varying, exciton-induced light absorption in the monolayer WS2. Comparing the ISE results with imaging photoluminescence spectroscopy data, the presence of several correlated features was observed, along with the unexpected existence of a few uncorrelated characteristics. The latter demonstrates that the exciton-induced absorption and emission features are not always proportional at the microscopic scale. Microstructural modulations across the flakes, having a different influence on the absorption and re-emission of light, are deemed responsible for the effect.

Realization and training of an inverter-based printed neuromorphic computing system

Emerging applications in soft robotics, wearables, smart consumer products or IoT-devices benefit from soft materials, flexible substrates in conjunction with electronic functionality. Due to high production costs and conformity restrictions, rigid silicon technologies do not meet application requirements in these new domains. However, whenever signal processing becomes too comprehensive, silicon technology must be used for the high-performance computing unit. At the same time, designing everything in flexible or printed electronics using conventional digital logic is not feasible yet due to the limitations of printed technologies in terms of performance, power and integration density. We propose to rather use the strengths of neuromorphic computing architectures consisting in their homogeneous topologies, few building blocks and analog signal processing to be mapped to an inkjet-printed hardware architecture. It has remained a challenge to demonstrate non-linear elements besides weighted aggregation. We demonstrate in this work printed hardware building blocks such as inverter-based comprehensive weight representation and resistive crossbars as well as printed transistor-based activation functions. In addition, we present a learning algorithm developed to train the proposed printed NCS architecture based on specific requirements and constraints of the technology.

A Review of RFID Sensors, the New Frontier of Internet of Things

A review of technological solutions for RFID sensing and their current or envisioned applications is presented. The fundamentals of the wireless sensing technology are summarized in the first part of the work, and the benefits of adopting RFID sensors for replacing standard sensor-equipped Wi-Fi nodes are discussed. Emphasis is put on the absence of batteries and the lower cost of RFID sensors with respect to other sensor solutions available on the market. RFID sensors are critically compared by separating them into chipped and chipless configurations. Both categories are further analyzed with reference to their working mechanism (electronic, electromagnetic, and acoustic). RFID sensing through chip-equipped tags is now a mature technological solution, which is continuously increasing its presence on the market and in several applicative scenarios. On the other hand, chipless RFID sensing represents a relatively new concept, which could become a disruptive solution in the market, but further research in this field is necessary for customizing its employment in specific scenarios. The benefits and limitations of several tag configurations are shown and discussed. A summary of the most suitable applicative scenarios for RFID sensors are finally illustrated. Finally, a look at some sensing solutions available on the market are described and compared.

A wafer-scale synthesis of monolayer MoS2 and their field-effect transistors toward practical applications

Molybdenum disulfide (MoS2) has attracted considerable research interest as a promising candidate for downscaling integrated electronics due to the special two-dimensional structure and unique physicochemical properties. However, it is still challenging to achieve large-area MoS2 monolayers with desired material quality and electrical properties to fulfill the requirement for practical applications. Recently, a variety of investigations have focused on wafer-scale monolayer MoS2 synthesis with high-quality. The 2D MoS2 field-effect transistor (MoS2-FET) array with different configurations utilizes the high-quality MoS2 film as channels and exhibits favorable performance. In this review, we illustrated the latest research advances in wafer-scale monolayer MoS2 synthesis by different methods, including Au-assisted exfoliation, CVD, thin film sulfurization, MOCVD, ALD, VLS method, and the thermolysis of thiosalts. Then, an overview of MoS2-FET developments was provided based on large-area MoS2 film with different device configurations and performances. The different applications of MoS2-FET in logic circuits, basic memory devices, and integrated photodetectors were also summarized. Lastly, we considered the perspective and challenges based on wafer-scale monolayer MoS2 synthesis and MoS2-FET for developing practical applications in next-generation integrated electronics and flexible optoelectronics.