Dry Lithography Patterning of Monolayer Flexible Field Effect Transistors by 2D Mica Stamping.

Organic field-effect transistors (OFETs) based on 2D monolayer organic semiconductors (OSC) have demonstrated promising potentials for various applications, such as light emitting diode (LED) display drivers, logic circuits, and wearable electrocardiography (ECG) sensors. To date, the fabrications of this class of highly crystallized 2D organic semiconductors (OSC) are dominated by solution shearing. As these organic active layers are only a few molecular layers thick, their compatibilities with conventional thermal evaporated top electrodes or sophisticated photolithography patterning are very limited, which also restricts their device density. Here, an electrode transfer stamp and a semiconductor patterning stamp are developed to fabricate OFETs with channel lengths down to 3 µm over a large area without using any chemicals or causing any damage to the active layer. 2D 2,9-didecyldinaphtho[2,3-b:2',3'-f]thieno[3,2-b]thiophene (C10 -DNTT) monolayer OFETs developed by this new approach shows decent performance properties with a low threshold voltage (VTH ) less than 0.5 V, intrinsic mobility higher than 10 cm2 V-1 s-1 and a subthreshold swing (SS) less than 100 mV dec-1 . The proposed patterning approach is completely comparable with ultraflexible parylene substrate less than 2 µm thick. By further reducing the channel length down to 2 µm and using the monolayer OFET in an AC/DC rectifying circuit, the measured cutoff frequency is up to 17.3 MHz with an input voltage of 4 V. The newly proposed electrode transfer and patterning stamps have addressed the long-lasting compatibility problem of depositing electrodes onto 2D organic monolayer and the semiconductor patterning. It opens a new path to reduce the fabrication cost and simplify the manufacturing process of high-density OFETs for more advanced electronic or biomedical applications.

Growth of Tellurium Nanobelts on h-BN for p-type Transistors with Ultrahigh Hole Mobility.

The lack of stable p-type van der Waals (vdW) semiconductors with high hole mobility severely impedes the step of low-dimensional materials entering the industrial circle. Although p-type black phosphorus (bP) and tellurium (Te) have shown promising hole mobilities, the instability under ambient conditions of bP and relatively low hole mobility of Te remain as daunting issues. Here we report the growth of high-quality Te nanobelts on atomically flat hexagonal boron nitride (h-BN) for high-performance p-type field-effect transistors (FETs). Importantly, the Te-based FET exhibits an ultrahigh hole mobility up to 1370 cm2 V-1 s-1 at room temperature, that may lay the foundation for the future high-performance p-type 2D FET and metal-oxide-semiconductor (p-MOS) inverter. The vdW h-BN dielectric substrate not only provides an ultra-flat surface without dangling bonds for growth of high-quality Te nanobelts, but also reduces the scattering centers at the interface between the channel material and the dielectric layer, thus resulting in the ultrahigh hole mobility .

Prediction of Lung Infection during Palliative Chemotherapy of Lung Cancer Based on Artificial Neural Network.

Lung infection seriously affects the effect of chemotherapy in patients with lung cancer and increases pain. The study is aimed at establishing the prediction model of infection in patients with lung cancer during chemotherapy by an artificial neural network (ANN). Based on the data of historical cases in our hospital, the variables were screened, and the prediction model was established. A logistic regression (LR) model was used to screen the data. The indexes with statistical significance were selected, and the LR model and back propagation neural network model were established. A total of 80 cases of advanced lung cancer patients with palliative chemotherapy were predicted, and the prediction performance of different model was evaluated by the receiver operating characteristic curve (ROC). It was found that age≧60 years, length of stay≧14 d, surgery history, combined chemotherapy, myelosuppression, diabetes, and hormone application were risk factors of infection in lung cancer patients during chemotherapy. The area under the ROC curve of the LR model for prediction lung infection was 0.729 ± 0.084, which was less than that of the ANN model (0.897 ± 0.045). The results concluded that the neural network model is better than the LR model in predicting lung infection of lung cancer patients during chemotherapy.

Self-powered bifunctional sensor based on tribotronic planar graphene transistors.

With the development of material science, micro-nano-fabrication and microelectronics, the higher level requirements are posed on the electronic skins (E-skin). The lower energy consumption and multiple functions are the imperative requirements to spurred scientists and mechanists to make joint efforts to meet. To achieve lower energy consumption, a promising energy-harvesting style of triboelectric nanogenerators (TENG) is incorporated into the field effect transistors (FETs) to play the important role for sensor. For bifunctional sensor, to harness the difficult for reflecting the magnitude of frequency, we resorted to synaptic transistors to achieve more intelligentization. Furthermore, with regards to the configuration of FET, we continued previous work: using the electrolyte gate dielectrics of FET-ion gel as the electrification layer to achieve high efficient, compact and extensively adoption for mechanosensation. The working principle of the GFET was based on the coupling effects of the FET and the TENG. This newly emerged self-powered sensor would offer a new platform for lower power consumption sensor for human-machine interface and intelligent robot.

Contact-electrification-activated artificial afferents at femtojoule energy.

Low power electronics endowed with artificial intelligence and biological afferent characters are beneficial to neuromorphic sensory network. Highly distributed synaptic sensory neurons are more readily driven by portable, distributed, and ubiquitous power sources. Here, we report a contact-electrification-activated artificial afferent at femtojoule energy. Upon the contact-electrification effect, the induced triboelectric signals activate the ion-gel-gated MoS2 postsynaptic transistor, endowing the artificial afferent with the adaptive capacity to carry out spatiotemporal recognition/sensation on external stimuli (e.g., displacements, pressures and touch patterns). The decay time of the synaptic device is in the range of sensory memory stage. The energy dissipation of the artificial afferents is significantly reduced to 11.9 fJ per spike. Furthermore, the artificial afferents are demonstrated to be capable of recognizing the spatiotemporal information of touch patterns. This work is of great significance for the construction of next-generation neuromorphic sensory network, self-powered biomimetic electronics and intelligent interactive equipment.

Bioinspired mechano-photonic artificial synapse based on graphene/MoS2 heterostructure.

Developing multifunctional and diversified artificial neural systems to integrate multimodal plasticity, memory, and supervised learning functions is an important task toward the emulation of neuromorphic computation. Here, we present a bioinspired mechano-photonic artificial synapse with synergistic mechanical and optical plasticity. The artificial synapse is composed of an optoelectronic transistor based on graphene/MoS2 heterostructure and an integrated triboelectric nanogenerator. By controlling the charge transfer/exchange in the heterostructure with triboelectric potential, the optoelectronic synaptic behaviors can be readily modulated, including postsynaptic photocurrents, persistent photoconductivity, and photosensitivity. The photonic synaptic plasticity is elaborately investigated under the synergistic effect of mechanical displacement and the light pulses embodying different spatiotemporal information. Furthermore, artificial neural networks are simulated to demonstrate the improved image recognition accuracy up to 92% assisted with mechanical plasticization. The mechano-photonic artificial synapse is highly promising for implementing mixed-modal interaction, emulating complex biological nervous system, and promoting the development of interactive artificial intelligence.

Atomic threshold-switching enabled MoS2 transistors towards ultralow-power electronics.

Power dissipation is a fundamental issue for future chip-based electronics. As promising channel materials, two-dimensional semiconductors show excellent capabilities of scaling dimensions and reducing off-state currents. However, field-effect transistors based on two-dimensional materials are still confronted with the fundamental thermionic limitation of the subthreshold swing of 60 mV decade-1 at room temperature. Here, we present an atomic threshold-switching field-effect transistor constructed by integrating a metal filamentary threshold switch with a two-dimensional MoS2 channel, and obtain abrupt steepness in the turn-on characteristics and 4.5 mV decade-1 subthreshold swing (over five decades). This is achieved by using the negative differential resistance effect from the threshold switch to induce an internal voltage amplification across the MoS2 channel. Notably, in such devices, the simultaneous achievement of efficient electrostatics, very small sub-thermionic subthreshold swings, and ultralow leakage currents, would be highly desirable for next-generation energy-efficient integrated circuits and ultralow-power applications.

Ion Gel Capacitively Coupled Tribotronic Gating for Multiparameter Distance Sensing.

Developing sophisticated device architectures is of great significance to go beyond Moore's law with versatility toward human-machine interaction and artificial intelligence. Tribotronics/tribo-iontronics offer a direct way to controlling the transport properties of semiconductor devices by mechanical actions, which fundamentally relies on how to enhance the tribotronic gating effect through device engineering. Here, we propose a universal method to enhance the tribotronic properties through electric double layer (EDL) capacitive coupling. By preparing an ion gel layer on top of tribotronic graphene transistor, we demonstrate a dual-mode field effect transistor (i.e., a tribotronic transistor with capacitively coupled ion gel and an ion-gel-gated graphene transistor with a second tribotronic gate). The resulted tribotronic gating performances are greatly improved by twice for the on-state current and four times for the on/off ratio (the first mode). It can also be utilized as a multiparameter distance sensor with drain current increased by ∼600 µA and threshold voltage shifted by ∼0.8 V under a mechanical displacement of 0.25 mm (the second mode). The proposed methodology of EDL capacitive coupling offers a facile and efficient way to designing more sophisticated tribotronic devices with superior performance and multifunctional sensations.

Flexible Photodetector Arrays Based on Patterned CH3 NH3 PbI3- x Clx Perovskite Film for Real-Time Photosensing and Imaging.

The quest for novel deformable image sensors with outstanding optoelectronic properties and large-scale integration becomes a great impetus to exploit more advanced flexible photodetector (PD) arrays. Here, 10 × 10 flexible PD arrays with a resolution of 63.5 dpi are demonstrated based on as-prepared perovskite arrays for photosensing and imaging. Large-scale growth controllable CH3 NH3 PbI3- x Clx arrays are synthesized on a poly(ethylene terephthalate) substrate by using a two-step sequential deposition method with the developed Al2 O3 -assisted hydrophilic-hydrophobic surface treatment process. The flexible PD arrays with high detectivity (9.4 × 1011 Jones), large on/off current ratio (up to 1.2 × 103 ), and broad spectral response exhibit excellent electrical stability under large bending angle (θ = 150°) and superior folding endurance after hundreds of bending cycles. In addition, the device can execute the functions of capturing a real-time light trajectory and detecting a multipoint light distribution, indicating that it has widespread potential in photosensing and imaging for optical communication, digital display, and artificial electronic skin applications.

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.

Static and Dynamic Piezopotential Modulation in Piezo-Electret Gated MoS2 Field-Effect Transistor.

The piezotronic effect links the mechanical stimuli with various semiconductor devices, promising for low-power-consuming electronic devices, sensitive sensors, and interactive control systems. The persistent requirement for external strains in piezotronic modulation may hinder its application in some circumstances (such as devices on rigid substrate or complicated synergistic piezoelectric modulation on multidevice). Here, we propose an efficient method to realize piezoelectric modulation of optical and electrical properties of MoS2 FET in both static and dynamic manner, expanding the application of piezotronics. Through capacitive coupling between piezo-electret and MoS2 FET, the remanent piezo-potential can efficiently tune the Fermi level of MoS2, programming the initial electrical property for subsequent fabrication of sophisticated devices. The external strain can induce enhanced piezo-potentials to further affect the energy band bending of MoS2 channel, giving rise to high-performance strain sensors (large gauge factor ∼4800, fast response time ∼0.15 s, and good durability >1000 s). The proposed static and dynamic piezopotential tuned MoS2 FET is easy to extend to devices based on other materials, which is highly desired in tunable sensory systems, active flexible electronics, and human-machine interface.

MoS2 Negative-Capacitance Field-Effect Transistors with Subthreshold Swing below the Physics Limit.

The Boltzmann distribution of electrons induced fundamental barrier prevents subthreshold swing (SS) from less than 60 mV dec-1 at room temperature, leading to high energy consumption of MOSFETs. Herein, it is demonstrated that an aggressive introduction of the negative capacitance (NC) effect of ferroelectrics can decisively break the fundamental limit governed by the "Boltzmann tyranny". Such MoS2 negative-capacitance field-effect transistors (NC-FETs) with self-aligned top-gated geometry demonstrated here pull down the SS value to 42.5 mV dec-1 , and simultaneously achieve superior performance of a transconductance of 45.5 µS µm and an on/off ratio of 4 × 106 with channel length less than 100 nm. Furthermore, the inserted HfO2 layer not only realizes a stable NC gate stack structure, but also prevents the ferroelectric P(VDF-TrFE) from fatigue with robust stability. Notably, the fabricated MoS2 NC-FETs are distinctly different from traditional MOSFETs. The on-state current increases as the temperature decreases even down to 20 K, and the SS values exhibit nonlinear dependence with temperature due to the implementation of the ferroelectric gate stack. The NC-FETs enable fundamental applications through overcoming the Boltzmann limit in nanoelectronics and open up an avenue to low-power transistors needed for many exciting long-endurance portable consumer products.

Ultrathin Piezotronic Transistors with 2 nm Channel Lengths.

Because silicon transistors are rapidly approaching their scaling limit due to short-channel effects, alternative technologies are urgently needed for next-generation electronics. Here, we demonstrate ultrathin ZnO piezotronic transistors with a ∼2 nm channel length using inner-crystal self-generated out-of-plane piezopotential as the gate voltage to control the carrier transport. This design removes the need for external gate electrodes that are challenging at nanometer scale. These ultrathin devices exhibit a strong piezotronic effect and excellent pressure-switching characteristics. By directly converting mechanical drives into electrical control signals, ultrathin piezotronic devices could be used as active nanodevices to construct the next generation of electromechanical devices for human-machine interfacing, energy harvesting, and self-powered nanosystems.

Tunable Tribotronic Dual-Gate Logic Devices Based on 2D MoS2 and Black Phosphorus.

With the Moore's law hitting the bottleneck of scaling-down in size (below 10 nm), personalized and multifunctional electronics with an integration of 2D materials and self-powering technology emerge as a new direction of scientific research. Here, a tunable tribotronic dual-gate logic device based on a MoS2 field-effect transistor (FET), a black phosphorus FET and a sliding mode triboelectric nanogenerator (TENG) is reported. The triboelectric potential produced from the TENG can efficiently drive the transistors and logic devices without applying gate voltages. High performance tribotronic transistors are achieved with on/off ratio exceeding 106 and cutoff current below 1 pA µm-1 . Tunable electrical behaviors of the logic device are also realized, including tunable gains (improved to ≈13.8) and power consumptions (≈1 nW). This work offers an active, low-power-consuming, and universal approach to modulate semiconductor devices and logic circuits based on 2D materials with TENG, which can be used in microelectromechanical systems, human-machine interfacing, data processing and transmission.

Enhancing Photoresponsivity of Self-Aligned MoS2 Field-Effect Transistors by Piezo-Phototronic Effect from GaN Nanowires.

We report high-performance self-aligned MoS2 field-effect transistors (FETs) with enhanced photoresponsivity by the piezo-phototronic effect. The FETs are fabricated based on monolayer MoS2 with a piezoelectric GaN nanowire (NW) as the local gate, and a self-aligned process is employed to define the source/drain electrodes. The fabrication method allows the preservation of the intrinsic property of MoS2 and suppresses the scattering center density in the MoS2/GaN interface, which results in high electrical and photoelectric performances. MoS2 FETs with channel lengths of ∼200 nm have been fabricated with a small subthreshold slope of 64 mV/dec. The photoresponsivity is 443.3 A·W(-1), with a fast response and recovery time of ∼5 ms under 550 nm light illumination. When strain is introduced into the GaN NW, the photoresponsivity is further enhanced to 734.5 A·W(-1) and maintains consistent response and recovery time, which is comparable with that of the mechanical exfoliation of MoS2 transistors. The approach presented here opens an avenue to high-performance top-gated piezo-enhanced MoS2 photodetectors.

p-Type MoS2 and n-Type ZnO Diode and Its Performance Enhancement by the Piezophototronic Effect.

A plasma-induced p-type MoS2 flake and n-type ZnO film diode, which exhibits an excellent rectification ratio, is demonstrated. Under 365 nm optical irradiation, this p-n diode shows a strong photoresponse with an external quantum efficiency of 52.7% and a response time of 66 ms. By increasing the pressure on the junction to 23 MPa, the photocurrent can be enhanced by a factor of four through the piezophototronic effect.