Tribotronic triggers and sequential logic circuits

In this paper,a floating-gate tribotronic transistor (FGTT) based on a mobile triboelectric layer and a traditional silicon-based field-effect transistor (FET) is proposed.In the FGTT,the triboelectric charges in the layer created by contact electrification can be used to modulate charge carrier transport in the transistor.Based on the FGTTs and FETs,a tribotronic negated AND (NAND) gate that achieves mechanical-electrical coupled inputs,logic operations,and electrical level outputs is fabricated.By further integrating tribotronic NAND gates with traditional digital circuits,several basic units such as the tribotronic S-R trigger,D trigger,and T trigger have been demonstrated.Additionally,tribotronic sequential logic circuits such as registers and counters have also been integrated to enable external contact triggered storage and computation.In contrast to the conventional sequential logic units controlled by electrical signals,contact-triggered tribotronic sequential logic circuits are able to realize direct interaction and integration with the external environment.This development can lead to their potential application in micro/nano-sensors,electTomechanical storage,interactive control,and intelligent instrumentation.     

Fully Bioabsorbable Natural‐Materials‐Based Triboelectric Nanogenerators

Implantable medical devices provide an effective therapeutic approach for neurological and cardiovascular diseases. With the development of transient electronics, a new power source with biocompatibility, controllability, and bioabsorbability becomes an urgent demand for medical sciences. Here, various fully bioabsorbable natural‐materials‐based triboelectric nanogenerators (BN‐TENGs), in vivo, are developed. The “triboelectric series” of five natural materials is first ranked, it provides a basic knowledge for materials selection and device design of the TENGs and other energy harvesters. Various triboelectric outputs of these natural materials are achieved by a single material and their pairwise combinations. The maximum voltage, current, and power density reach up to 55 V, 0.6 µA, and 21.6 mW m^?2, respectively. The modification of silk fibroin encapsulation film makes the operation time of the BN‐TENG tunable from days to weeks. After completing its function, the BN‐TENG can be fully degraded and resorbed in Sprague–Dawley rats, which avoids a second operation and other side effects. Using the proposed BN‐TENG as a voltage source, the beating rates of dysfunctional cardiomyocyte clusters are accelerated and the consistency of cell contraction is improved. This provides a new and valid solution to treat some heart diseases such as bradycardia and arrhythmia.     

Gate‐Controlled BP–WSe2 Heterojunction Diode for Logic Rectifiers and Logic Optoelectronics

p–n junctions play an important role in modern semiconductor electronics and optoelectronics, and field‐effect transistors are often used for logic circuits. Here, gate‐controlled logic rectifiers and logic optoelectronic devices based on stacked black phosphorus (BP) and tungsten diselenide (WSe₂) heterojunctions are reported. The gate‐tunable ambipolar charge carriers in BP and WSe₂ enable a flexible, dynamic, and wide modulation on the heterojunctions as isotype (p–p and n–n) and anisotype (p–n) diodes, which exhibit disparate rectifying and photovoltaic properties. Based on such characteristics, it is demonstrated that BP–WSe₂ heterojunction diodes can be developed for high‐performance logic rectifiers and logic optoelectronic devices. Logic optoelectronic devices can convert a light signal to an electric one by applied gate voltages. This work should be helpful to expand the applications of 2D crystals.     

Triboiontronic Transistor of MoS2

Electric double layers (EDLs) formed in electrolyte‐gated field‐effect transistors (FETs) induce an extremely large local electric field that gives a highly efficient charge carrier control in the semiconductor channel. To achieve highly efficient triboelectric potential gating on the FET and explore diversified applications of electric double layer FETs (EDL‐FETs), a triboiontronic transistor is proposed to bridge triboelectric potential modulation and ion‐controlled semiconductor devices. Utilizing the triboelectric potential instead of applying an external gate voltage, the triboiontronic MoS₂ transistor is efficiently operated owing to the formation of EDLs in the ion‐gel dielectric layer. The operation mechanism of the triboiontronic transistor is proposed, and high current on/off ratio over 10⁷, low threshold value (75 μm), and steep switching properties (20 µm dec^?1) are achieved. A triboiontronic logic inverter with desirable gain (8.3 V mm^?1), low power consumption, and high stability is also demonstrated. This work presents a low‐power‐consuming, active, and a general approach to efficiently modulate semiconductor devices through mechanical instructions, which has great potential in human–machine interaction, electronic skin, and intelligent wearable devices. The proposed triboiontronics utilize ion migration and arrangement triggered by mechanical stimuli to control electronic properties, which are ready to deliver new interdisciplinary research directions.     

Engineered and Laser‐Processed Chitosan Biopolymers for Sustainable and Biodegradable Triboelectric Power Generation

Recent advances achieved in triboelectric nanogenerators (TENG) focus on boosting power generation and conversion efficiency. Nevertheless, obstacles concerning economical and biocompatible utilization of TENGs continue to prevail. Being an abundant natural biopolymer from marine crustacean shells, chitosan enables exciting opportunities for low‐cost, biodegradable TENG applications in related fields. Here, the development of biodegradable and flexible TENGs based on chitosan is presented for the first time. The physical and chemical properties of the chitosan nanocomposites are systematically studied and engineered for optimized triboelectric power generation, transforming the otherwise wasted natural materials into functional energy devices. The feasibility of laser processing of constituent materials is further explored for the first time for engineering the TENG performance. The laser treatment of biopolymer films offers a potentially promising scheme for surface engineering in polymer‐based TENGs. The chitosan‐based TENGs present efficient energy conversion performance and tunable biodegradation rate. Such a new class of TENGs derived from natural biomaterials may pave the way toward the economically viable and ecologically friendly production of flexible TENGs for self‐powered nanosystems in biomedical and environmental applications.     

Large‐Area Direct Laser‐Shock Imprinting of a 3D Biomimic Hierarchical Metal Surface for Triboelectric Nanogenerators

Ongoing efforts in triboelectric nanogenerators (TENGs) focus on enhancing power generation, but obstacles concerning the economical and cost‐effective production of TENGs continue to prevail. Micro‐/nanostructure engineering of polymer surfaces has been dominantly utilized for boosting the contact triboelectrification, with deposited metal electrodes for collecting the scavenged energy. Nevertheless, this state‐of‐the‐art approach is limited by the vague potential for producing 3D hierarchical surface structures with conformable coverage of high‐quality metal. Laser‐shock imprinting (LSI) is emerging as a potentially scalable approach for directly surface patterning of a wide range of metals with 3D nanoscale structures by design, benefiting from the ultrahigh‐strain‐rate forming process. Here, a TENG device is demonstrated with LSI‐processed biomimetic hierarchically structured metal electrodes for efficient harvesting of water‐drop energy in the environment. Mimicking and transferring hierarchical microstructures from natural templates, such as leaves, into these water‐TENG devices is effective regarding repelling water drops from the device surface, since surface hydrophobicity from these biomicrostructures maximizes the TENG output. Among various leaves' microstructures, hierarchical microstructures from dried bamboo leaves are preferable regarding maximizing power output, which is attributed to their unique structures, containing both dense nanostructures and microscale features, compared with other types of leaves. Also, the triboelectric output is significantly improved by closely mimicking the hydrophobic nature of the leaves in the LSI‐processed metal surface after functionalizing it with low‐surface‐energy self‐assembled‐monolayers. The approach opens doors to new manufacturable TENG technologies for economically feasible and ecologically friendly production of functional devices with directly patterned 3D biomimic metallic surfaces in energy, electronics, and sensor applications.     

A Shape‐Adaptive Thin‐Film‐Based Approach for 50% High‐Efficiency Energy Generation Through Micro‐Grating Sliding Electrification

Effectively harvesting ambient mechanical energy is the key for realizing self‐powered and autonomous electronics, which addresses limitations of batteries and thus has tremendous applications in sensor networks, wireless devices, and wearable/implantable electronics, etc. Here, a thin‐film‐based micro‐grating triboelectric nanogenerator (MG‐TENG) is developed for high‐efficiency power generation through conversion of mechanical energy. The shape‐adaptive MG‐TENG relies on sliding electrification between complementary micro‐sized arrays of linear grating, which offers a unique and straightforward solution in harnessing energy from relative sliding motion between surfaces. Operating at a sliding velocity of 10 m/s, a MG‐TENG of 60 cm² in overall area, 0.2 cm³ in volume and 0.6 g in weight can deliver an average output power of 3 W (power density of 50 mW cm^?2 and 15 W cm^?3) at an overall conversion efficiency of ～50%, making it a sufficient power supply to regular electronics, such as light bulbs. The scalable and cost‐effective MG‐TENG is practically applicable in not only harvesting various mechanical motions but also possibly power generation at a large scale.     

2D MoS2 Neuromorphic Devices for Brain‐Like Computational Systems

Hardware implementation of artificial synapses/neurons with 2D solid‐state devices is of great significance for nanoscale brain‐like computational systems. Here, 2D MoS₂ synaptic/neuronal transistors are fabricated by using poly(vinyl alcohol) as the laterally coupled, proton‐conducting electrolytes. Fundamental synaptic functions, such as an excitatory postsynaptic current, paired‐pulse facilitation, and a dynamic filter for information transmission of biological synapse, are successfully emulated. Most importantly, with multiple input gates and one modulatory gate, spiking‐dependent logic operation/modulation, multiplicative neural coding, and neuronal gain modulation are also experimentally demonstrated. The results indicate that the intriguing 2D MoS₂ transistors are also very promising for the next‐generation of nanoscale neuromorphic device applications.     

Effects of Water and Different Solutes on Carbon‐Nanotube Low‐Voltage Field‐Effect Transistors

Semiconducting single‐walled carbon nanotubes (swCNTs) are a promising class of materials for emerging applications. In particular, they are demonstrated to possess excellent biosensing capabilities, and are poised to address existing challenges in sensor reliability, sensitivity, and selectivity. This work focuses on swCNT field‐effect transistors (FETs) employing rubbery double‐layer capacitive dielectric poly(vinylidene fluoride‐co‐hexafluoropropylene). These devices exhibit small device‐to‐device variation as well as high current output at low voltages (<0.5 V), making them compatible with most physiological liquids. Using this platform, the swCNT devices are directly exposed to aqueous solutions containing different solutes to characterize their effects on FET current–voltage (FET I–V) characteristics. Clear deviation from ideal characteristics is observed when swCNTs are directly contacted by water. Such changes are attributed to strong interactions between water molecules and sp²‐hybridized carbon structures. Selective response to Hg²⁺ is discussed along with reversible pH effect using two distinct device geometries. Additionally, the influence of aqueous ammonium/ammonia in direct contact with the swCNTs is investigated. Understanding the FET I–V characteristics of low‐voltage swCNT FETs may provide insights for future development of stable, reliable, and selective biosensor systems.     

WSe2 Homojunction Devices: Electrostatically Configurable as Diodes,MOSFETs, and Tunnel FETs for Reconfigurable Computing

In this paper, electrostatically configurable 2D tungsten diselenide (WSe₂) electronic devices are demonstrated. Utilizing a novel triple‐gate design, a WSe₂ device is able to operate as a tunneling field‐effect transistor (TFET), a metal–oxide–semiconductor field‐effect transistor (MOSFET) as well as a diode, by electrostatically tuning the channel doping to the desired profile. The implementation of scaled gate dielectric and gate electrode spacing enables higher band‐to‐band tunneling transmission with the best observed subthreshold swing (SS) among all reported homojunction TFETs on 2D materials. Self‐consistent full‐band atomistic quantum transport simulations quantitatively agree with electrical measurements of both the MOSFET and TFET and suggest that scaling gate oxide below 3 nm is necessary to achieve sub‐60 mV dec^?1 SS, while further improvement can be obtained by optimizing the spacers. Diode operation is also demonstrated with the best ideality factor of 1.5, owing to the enhanced electrostatic control compared to previous reports. This research sheds light on the potential of utilizing electrostatic doping scheme for low‐power electronics and opens a path toward novel designs of field programmable mixed analog/digital circuitry for reconfigurable computing.     

Anti‐Ambipolar Transport with Large Electrical Modulation in 2D Heterostructured Devices

Van der Waals materials and their heterostructures provide a versatile platform to explore new device architectures and functionalities beyond conventional semiconductors. Of particular interest is anti‐ambipolar behavior, which holds potentials for various digital electronic applications. However, most of the previously conducted studies are focused on hetero‐ or homo‐ p–n junctions, which suffer from a weak electrical modulation. Here, the anti‐ambipolar transport behavior and negative transconductance of MoTe₂ transistors are reported using a graphene/h‐BN floating‐gate structure to dynamically modulate the conduction polarity. Due to the asymmetric electrical field regulating effect on the recombination and diffusion currents, the anti‐ambipolar transport and negative transconductance feature can be systematically controlled. Consequently, the device shows an unprecedented peak resistance modulation factor (≈5 × 10³), and effective photoexcitation modulation with distinct threshold voltage shift and large photo on/off ratio (≈10⁴). Utilizing this large modulation effect, the voltage‐transfer characteristics of an inverter circuit variant are further studied and its applications in Schmitt triggers and multivalue output are further explored. These properties, in addition to their proven nonvolatile storage, suggest that such 2D heterostructured devices display promising perspectives toward future logic applications.     

Flexible Triboelectric Nanogenerator Based on High Surface Area TiO2 Nanotube Arrays

Triboelectric nanogenerators (TENGs) can harvest mechanical energy through coupling triboelectric effect and electrostatic induction. Typically, TENGs consist of organic materials, however on account of the potentially wide range of applications of TENGs as the self‐powered portable/wearable electronics, biomedical devices, and sensors; semiconductor metal oxide materials can be promising candidates to be incorporating in TENG structure. Here, flexible TENG based on self‐organized TiO₂ nanotube arrays (TNTAs) is fabricated via anodization method. The introduced flexible large area nanotubular electrode is employed as the moving electrode in contact with Kapton film in vertical contact separation mode of TENG. The fabricated TENG can deliver output voltage of 40 V with the current density of 1 μA cm^?2. To evaluate the role of nanostructured interface, its performance has been compared to the thin film flat compact TiO₂ electrode. The results of extracted charge measurements under short circuit condition indicate that larger triboelectric charge density formed in TNTA‐based electrode (about 110 nC per cycle of press and release) is in comparison to 15 nC in flat TiO₂ electrode. Due to the extensive range of applications of TiO₂, the introduced structure can potentially be applicable in various types of self‐powered systems such as photo‐detectors and environmental gas and bio‐sensors.

     

A Centimeter‐Scale Inorganic Nanoparticle Superlattice Monolayer with Non‐Close‐Packing and its High Performance in Memory Devices

Due to the near‐field coupling effect, non‐close‐packed nanoparticle (NP) assemblies with tunable interparticle distance (d) attract great attention and show huge potential applications in various functional devices, e.g., organic nano‐floating‐gate memory (NFGM) devices. Unfortunately, the fabrication of device‐scale non‐close‐packed 2D NPs material still remains a challenge, limiting its practical applications. Here, a facile yet robust “rapid liquid–liquid interface assembly” strategy is reported to generate a non‐close‐packed AuNP superlattice monolayer (SM) on a centimeter scale for high‐performance pentacene‐based NFGM. The d and hence the surface plasmon resonance spectra of SM can be tailored by adjusting the molecular weight of tethered polymers. Precise control over the d value allows the successful fabrication of photosensitive NFGM devices with highly tunable performances from short‐term memory to nonvolatile data storage. The best performing nonvolatile memory device shows remarkable 8‐level (3‐bit) storage and a memory ratio over 10⁵ even after 10 years compared with traditional devices with a AuNP amorphous monolayer. This work provides a new opportunity to obtain large area 2D NPs materials with non‐close‐packed structure, which is significantly meaningful to microelectronic, photovoltaics devices, and biochemical sensors.     

Novel Tunnel‐Contact‐Controlled IGZO Thin‐Film Transistors with High Tolerance to Geometrical Variability

Thin insulating layers are used to modulate a depletion region at the source of a thin‐film transistor. Bottom contact, staggered‐electrode indium gallium zinc oxide transistors with a 3 nm Al₂O₃ layer between the semiconductor and Ni source/drain contacts, show behaviors typical of source‐gated transistors (SGTs): low saturation voltage (V_{D_SAT} ≈ 3 V), change in V_{D_SAT} with a gate voltage of only 0.12 V V^?1, and flat saturated output characteristics (small dependence of drain current on drain voltage). The transistors show high tolerance to geometry: the saturated current changes only 0.15× for 2–50 µm channels and 2× for 9‐45 µm source‐gate overlaps. A higher than expected (5×) increase in drain current for a 30 K change in temperature, similar to Schottky‐contact SGTs, underlines a more complex device operation than previously theorized. Optimization for increasing intrinsic gain and reducing temperature effects is discussed. These devices complete the portfolio of contact‐controlled transistors, comprising devices with Schottky contacts, bulk barrier, or heterojunctions, and now, tunneling insulating layers. The findings should also apply to nanowire transistors, leading to new low‐power, robust design approaches as large‐scale fabrication techniques with sub‐nanometer control mature.     

Intelligent Sensing System Based on Hybrid Nanogenerator by Harvesting Multiple Clean Energy

The inexhaustible mechanical kinetic energy can be extracted from wind and flowing water. Besides, flowing water also possesses electrostatic energy owing to the triboelectric charges caused by contacting with surrounding media, such as air. Here, a rotating hybridized triboelectric nanogenerator (TENG) has been established, by comprising of a water‐TENG (W‐TENG), a disk‐TENG (D‐TENG), and an electromagnetic generator (EMG), which has been explored for simultaneously harvesting energies from flowing water and wind. The W‐TENG is fabricated by wheel blades, polyvinylidene fluoride (PVDF), superhydrophobic polytetrafluoroethylene (PTFE), and aluminum to harvest the electrostatic energy. Moreover, the flowing water and wind impact on the wheel blades also causes the rotation motion of D‐TENG and EMG, resulting in being converted into electricity. At the rotation speed of 200 rpm, the short circuit current of D‐TENG and EMG can reach 0.4 μA and 7 mA, respectively. The open circuit voltage of W‐TENG can be up to 10 V at a flowing water rate of 60 ml s^?1. Besides, the hybridized NG is demonstrated to harvest water and wind energy and to act as a power source to charge a lithium battery or capacitor, which can drive LEDs, PH monitoring system, and wireless temperature and humidity sensing system. All these results show the potentials of the hybridized NG for harvesting multiple types of energies from the environment and constructing different self‐powered systems.

     

Organic High Electron Mobility Transistors Realized by 2D Electron Gas

A key breakthrough in inorganic modern electronics is the energy‐band engineering that plays important role to improve device performance or develop novel functional devices. A typical application is high electron mobility transistors (HEMTs), which utilizes 2D electron gas (2DEG) as transport channel and exhibits very high electron mobility over traditional field‐effect transistors (FETs). Recently, organic electronics have made very rapid progress and the band transport model is demonstrated to be more suitable for explaining carrier behavior in high‐mobility crystalline organic materials. Therefore, there emerges a chance for applying energy‐band engineering in organic semiconductors to tailor their optoelectronic properties. Here, the idea of energy‐band engineering is introduced and a novel device configuration is constructed, i.e., using quantum well structures as active layers in organic FETs, to realize organic 2DEG. Under the control of gate voltage, electron carriers are accumulated and confined at quantized energy levels, and show efficient 2D transport. The electron mobility is up to 10 cm² V^?1 s^?1, and the operation mechanisms of organic HEMTs are also argued. Our results demonstrate the validity of tailoring optoelectronic properties of organic semiconductors by energy‐band engineering, offering a promising way for the step forward of organic electronics.     

Two‐Terminal Multibit Optical Memory via van der Waals Heterostructure

2D van der Waals (vdWs) heterostructures exhibit intriguing optoelectronic properties in photodetectors, solar cells, and light‐emitting diodes. In addition, these materials have the potential to be further extended to optical memories with promising broadband applications for image sensing, logic gates, and synaptic devices for neuromorphic computing. In particular, high programming voltage, high off‐power consumption, and circuital complexity in integration are primary concerns in the development of three‐terminal optical memory devices. This study describes a multilevel nonvolatile optical memory device with a two‐terminal floating‐gate field‐effect transistor with a MoS₂/hexagonal boron nitride/graphene heterostructure. The device exhibits an extremely low off‐current of ≈10^?14 A and high optical switching on/off current ratio of over ≈10⁶, allowing 18 distinct current levels corresponding to more than four‐bit information storage. Furthermore, it demonstrates an extended endurance of over ≈10⁴ program–erase cycles and a long retention time exceeding 3.6 × 10⁴ s with a low programming voltage of ?10 V. This device paves the way for miniaturization and high‐density integration of future optical memories with vdWs heterostructures.     

Highly Flexible Hybrid CMOS Inverter Based on Si Nanomembrane and Molybdenum Disulfide

2D semiconductor materials are being considered for next generation electronic device application such as thin‐film transistors and complementary metal–oxide–semiconductor (CMOS) circuit due to their unique structural and superior electronics properties. Various approaches have already been taken to fabricate 2D complementary logics circuits. However, those CMOS devices mostly demonstrated based on exfoliated 2D materials show the performance of a single device. In this work, the design and fabrication of a complementary inverter is experimentally reported, based on a chemical vapor deposition MoS₂ n‐type transistor and a Si nanomembrane p‐type transistor on the same substrate. The advantages offered by such CMOS configuration allow to fabricate large area wafer scale integration of high performance Si technology with transition‐metal dichalcogenide materials. The fabricated hetero‐CMOS inverters which are composed of two isolated transistors exhibit a novel high performance air‐stable voltage transfer characteristic with different supply voltages, with a maximum voltage gain of ≈16, and sub‐nano watt power consumption. Moreover, the logic gates have been integrated on a plastic substrate and displayed reliable electrical properties paving a realistic path for the fabrication of flexible/transparent CMOS circuits in 2D electronics.     

Tunable SnSe2/WSe2 Heterostructure Tunneling Field Effect Transistor

The burgeoning 2D semiconductors can maintain excellent device electrostatics with an ultranarrow channel length and can realize tunneling by electrostatic gating to avoid deprivation of band‐edge sharpness resulting from chemical doping, which make them perfect candidates for tunneling field effect transistors. Here this study presents SnSe₂/WSe₂ van der Waals heterostructures with SnSe₂ as the p‐layer and WSe₂ as the n‐layer. The energy band alignment changes from a staggered gap band offset (type‐II) to a broken gap (type‐III) when changing the negative back‐gate voltage to positive, resulting in the device operating as a rectifier diode (rectification ratio ~10⁴) or an n‐type tunneling field effect transistor, respectively. A steep average subthreshold swing of 80 mV dec^?1 for exceeding two decades of drain current with a minimum of 37 mV dec^?1 at room temperature is observed, and an evident trend toward negative differential resistance is also accomplished for the tunneling field effect transistor due to the high gate efficiency of 0.36 for single gate devices. The I _ON/I _OFF ratio of the transfer characteristics is >10⁶, accompanying a high ON current >10^?5 A. This work presents original phenomena of multilayer 2D van der Waals heterostructures which can be applied to low‐power consumption devices.     

Few‐Layer GeAs Field‐Effect Transistors and Infrared Photodetectors

The family of 2D semiconductors (2DSCs) has grown rapidly since the first isolation of graphene. The emergence of each 2DSC material brings considerable excitement for its unique electrical, optical, and mechanical properties, which are often highly distinct from their 3D counterparts. To date, studies of 2DSC are majorly focused on group IV (e.g., graphene, silicene), group V (e.g., phosphorene), or group VIB compounds (transition metal dichalcogenides, TMD), and have inspired considerable effort in searching for novel 2DSCs. Here, the first electrical characterization of group IV–V compounds is presented by investigating few‐layer GeAs field‐effect transistors. With back‐gate device geometry, p‐type behaviors are observed at room temperature. Importantly, the hole carrier mobility is found to approach 100 cm² V^?1 s^?1 with ON–OFF ratio over 10⁵, comparable well with state‐of‐the‐art TMD devices. With the unique crystal structure the few‐layer GeAs show highly anisotropic optical and electronic properties (anisotropic mobility ratio of 4.8). Furthermore, GeAs based transistor shows prominent and rapid photoresponse to 1.6 µm radiation with a photoresponsivity of 6 A W^?1 and a rise and fall time of ≈3 ms. This study of group IV–V 2DSC materials greatly expands the 2D family, and can enable new opportunities in functional electronics and optoelectronics based on 2DSCs.