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We demonstrate a facile technique to scratch, manipulate, and solder exfoliated flakes of layered 2D materials using a microneedle probe attached to the precision xyz manipulators under an optical microscope. We show that the probe can be used to scratch the flakes into a designated shape with a precision at micrometer scales; move, rotate, roll-up, and exfoliate the flakes to help building various types of heterostructures; and form electric contacts by directly drawing/placing thin metal wires over the flake. All these can be done without lithography and etching steps that often take long processing time and involve harmful chemicals. Moreover, the setup can be easily integrated into any van der Waals assembly systems, such as those in a glove box for handling air/chemical-sensitive materials. The microneedle technique demonstrated in this study, therefore, enables quick fabrications of devices from diverse 2D materials for testing their properties at an early stage of research before conducting more advanced studies and helps to build different types of van der Waals heterostructures.

Abstract Ultrathin two‐dimensional transition‐metal dichalcogenides (TMDs) have been pursued extensively in recent years for interesting physics and application potentials. For the latter, it is essential to synthesize crystalline TMD monolayers at wafer‐scale. Here, we report growth of single‐crystalline MSe2 (M = Mo, W) monolayers at wafer‐scale by molecular‐beam epitaxy at low temperatures (200–400°C) on nominally flat Au(1 1 1) substrates. The epifilms have low intrinsic defect densities of low 1012 cm−2. The grown films have then been exfoliated and transferred onto SiO2/Si by a wet chemical process, on which some optical measurements are performed, revealing high spatial uniformity of the samples. We also establish that MSe2 grows on Au via the van der Waals epitaxy mechanism, where a continuous film extends across the whole surface, overhangs atomic‐layer steps on substrate. We identify that the growth of highly crystalline MSe2 is promoted by an enhanced interaction between Au substrate and MSe2 islands rather than by the guidance of surface steps on substrate. The latter only arrests MSe2 lateral growth if they are multilayer high. Key points MBE growth of wafer‐scale highly crystalline TMD monolayers at low‐temperature is achieved. Island‐substrate interaction is found to play a critical role in vdW epitaxy of single‐crystalline TMDs on on‐axis substates. The TMD monolayers are of high uniformity and low intrinsic defect density.

Abstract 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 .

Abstract 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.

Low power electronics endowed with artificial intelligence and biological afferent characters are beneficial to neuromorphic sensory network. Here, the authors report contact-electrification-activated artificial afferent at femtojoule energy, which is able to carry out spatiotemporal recognition on external stimuli.

Here, the authors demonstrate an atomic threshold-switching field-effect transistor constructed by integrating a metal filamentary switch with a two-dimensional MoS2 channel, and obtain abrupt steepness in the turn-on characteristics and 4.5 mV/dec subthreshold swing over five decades.