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The rapid development of big-data analytics (BDA), internet of things (IoT) and artificial intelligent Technology (AI) demand outstanding electronic devices and systems with faster processing speed, lower power consumption, and smarter computer architecture. Memristor, as a promising Non-Volatile Memory (NVM) device, can effectively mimic biological synapse, and has been widely studied in recent years. The appearance and development of two-dimensional materials (2D material) accelerate and boost the progress of memristor systems owing to a bunch of the particularity of 2D material compared to conventional transition metal oxides (TMOs), therefore, 2D material-based memristors are called as new-generation intelligent memristors. In this review, the memristive (resistive switching) phenomena and the development of new-generation memristors are demonstrated involving graphene (GR), transition-metal dichalcogenides (TMDs) and hexagonal boron nitride (h-BN) based memristors. Moreover, the related progress of memristive mechanisms is remarked.

Compared with a conventional CMOS-based optoelectronic system, two-dimensional (2D) material-based nonvolatile optoelectronic memory has attracted increasing attention because of its ability to rapidly transform optoelectronic signals, as well as simultaneously store and output signals. However, existing two-dimensional optoelectronic memory cannot meet requirements in performance and cost and so on, and needs urgently to be explored. Here we developed a high-performance nonvolatile MoS2-based optoelectronic memory device based on a MoS2 bilayer grown by a Au catalyst. The device exhibits an excellent performance index of current on/off ratio ∼8 × 104 and retention time ∼2.2 × 104 s. Experimental observations and simulation calculations have revealed that the optoelectronic memory mechanism can be ascribed to defects including S vacancies and disorder of atoms in 2D MoS2 materials.

The local field enhancement in plasmonic nanostructures is vital for surface enhanced Raman scattering (SERS). However, it remains a challenge to achieve a large local field enhancement at an illumination wavelength in the green waveband. Here we report on an ultra-large local field enhancement effect of isolated thick triangular silver nanoplates (ITTSNPs) on a silicon substrate at an illumination wavelength in the green waveband. We show that when the thickness of the ITTSNP is larger than a critical thickness depending on the illumination wavelength, a large local field enhancement with an enhancement factor (EF) greater than 350 can be achieved at an illumination wavelength in the green waveband, which is due to the excitation of strong localized surface plasmon polaritons only at three top apexes of the ITTSNP. Furthermore, we experimentally demonstrate that at an excitation wavelength of 514.5 nm, the average SERS EF of the ITTSNPs can exceed 10 11 , and the sensitivity for the detection of Rhodamine 6 G molecules can reach 10 − 12 M .

Surface-enhanced Raman scattering (SERS) has received widespread attention in the rapid detection of trace substances. The super-hydrophobic surface of structures has a significant impact on improving SERS performance. Usually a low concentration of objective molecules is randomly distributed in a large area on a non-hydrophobic SERS substrate, resulting in the Raman signals of the molecules not being easily detected. As a solution, a super-hydrophobic surface can gather a large number of probe molecules around the plasmon hot spots to effectively improve Raman SERS detection sensitivity. In this work, a chloride super-hydrophobic surface is fabricated, for the first time, by a simple and low-cost method of combining surface hydrophobic structures with surface modification. The dispersed and uniform hierarchical Ag@BiOCl nanosheet (Ag@BiOCl NSs) substrate has a higher surface-to-volume ratio and rich nano-gap. Such a chip with a high static contact angle of 157.4° exhibits a Raman signal detection limit of R6G dyes up to 10−9 M and an enhancement factor up to 107. This SERS chip with a super-hydrophobic surface offers great potential in practical applications owing to its simple fabricating process, low cost, large area, and high sensitivity.

Indium tin oxide (ITO) plays an important role due to its high transparency and high conductivity in various optoelectronic thin-film devices. However, ITO has the drawback of mechanical fragility, limiting its development. Wrinkling has been considered a powerful tool for improving the flexibility and surface properties of thin films, but wrinkled ITO has not been reported so far. In this work, we fabricate uniform wrinkles on ITO and systematically study the properties of the wrinkled ITO in optics, electrics and mechanics. The wrinkled ITO shows a high optical transmittance and also a high haze value due to a remarkable wrinkle-induced enhancement of light scattering, which is beneficial for solar cells and light-emitting diodes. Our experimental results also indicate that wrinkles can effectively improve the mechanical bending performance of ITO without compromising the crystallization and electrical conductivity.

Nanoparticle self-assembly promises scalable fabrication of composite materials with unique properties, but symmetry control of assembled structures remains a challenge. By introducing a governing force in the assembly process, we develop a strategy to control assembly symmetry. As a demonstration, we realize the tetragonal superlattice of octagonal gold nanorods, breaking through the only hexagonal symmetry of the superlattice so far. Surprisingly, such sparse tetragonal superstructure exhibits much higher thermostability than its close-packed hexagonal counterpart. Multiscale modeling reveals that the governing force arises from hierarchical molecular and colloidal interactions. This force dominates the interactions involved in the assembly process and determines the superlattice symmetry, leading to the tetragonal superlattice that becomes energetically favorable over its hexagonal counterpart. This strategy might be instructive for designing assembly of various nanoparticles and may open up a new avenue for realizing diverse assembly structures with pre-engineered properties., Shape complementarity is the primary way to control the symmetry of nanoparticle assemblies. Here, the authors introduce a governing force that dominates symmetry control of nanorod superlattices, using it to obtain an unexpected and highly thermostable tetragonal lattice.

Correction for ‘High-performance optoelectronic memory based on bilayer MoS2 grown by Au catalyst’ by Fengyou Yang et al., J. Mater. Chem. C, 2020, 8, 2664–2668.

Two-dimensional materials (2DMs) are competitive candidates in replacing or supplementing conventional semiconductors owing to their atomically uniform thickness. However, current conventional micro/nanofabrication technologies realize hardly ultrashort channel and integration, especially for sub-10 nm. Meanwhile, experimental device performance associated with the scaling of dimension needs to be investigated, due to the short channel effects. Here, we show a novel and universal technological method to fabricate sub-10 nm gaps with sharp edges and steep sidewalls. The realization of sub-10 nm gaps derives from a corrosion crack along the cleavage plane of Bi2O3. By this method, ultrathin body field-effect transistors (FETs), consisting of 8.2 nm channel length, 6 nm high-k dielectric, and 0.7 nm monolayer MoS2, exhibit no obvious short channel effects. The corresponding current on/off ratio and subthreshold swing reaches to 106 and 140 mV/dec, respectively. Moreover, integrated circuits with sub-10 nm ch...

Complex surface structures have stimulated a great deal of interests due to many potential applications in surface devices. However, in the fabrication of complex surface micro-/nanostructures, there are always great challenges in precise design, or good controllability, or low cost, or high throughput. Here, we present a route for the accurate design and highly controllable fabrication of surface quasi-three-dimensional (quasi-3D) structures based on a thermal deformation of simple two-dimensional laser-induced patterns. A complex quasi-3D structure, coaxially nested convex–concave microlens array, as an example, demonstrates our capability of design and fabrication of surface elements with this method. Moreover, by using only one relief mask with the convex–concave microlens structure, we have gotten hundreds of target patterns at different imaging planes, offering a cost-effective solution for mass production in lithography and imprinting, and portending a paradigm in quasi-3D manufacturing., Complex surface micro- and nanostructures can be useful in many device applications, but are challenging in terms of controllability, low cost and high throughput. Here the authors have fabricated quasi 3D structures by the thermal deformation of simple two-dimensional laser-induced patterns.

A wrinkle-based thin-film device can be used to develop optoelectronic devices, photovoltaics, and strain sensors. Here, we propose a stable and ultrasensitive strain sensor based on two-dimensional (2D) semiconducting gallium selenide (GaSe) for the first time. The response of the electrical resistance to strain was demonstrated to be very sensitive for the GaSe-based strain sensor, and it reached a gauge factor of–4.3, which is better than that of graphene-based strain sensors. The results show us that strain engineering on a nanoscale can be used not only in strain sensors but also for a wide range of applications, such as flexible field-effect transistors, stretchable electrodes, and flexible solar cells.

Natural surface-enhanced Raman spectroscopy (SERS) chips based on plants or insects have gained increased attention due to their facile characteristics and low costs. However, such chips remain a major challenge for practical application because of poor reproducibility and stability as well as unavoidable damage to the surface structure during coating metal and uncontrolled dehydration. By using a simple wrinkling method, we develop a new route to fabricate a low-cost bionic SERS chip for practical detection. Inspired by the taro leaf, we fabricate a SERS chip with a super-hydrophobic and plasmonic micro/nano dual structure, and its structure parameters can be optimized. Compared with the natural taro-leaf SERS chip, our artificial chip exhibits Raman signals with an order of magnitude higher sensitivity (∼10−9 M) and enhancement factor (∼107) under the illumination of weak laser radiation, demonstrating that our SERS chip has great potential in biological detection. The excellent performances of our bionic SERS chip are attributed to a synergy of optimized micro-wrinkle and nano-nest, which is verified by experiment and simulation. We believe our bionic chip could be a promising candidate in practical application due to its merits such as simple fabricating process, optimizable structure, low cost, excellent homogeneity, high sensitivity, and stability.

Laser direct writing (LDW) as a significant maskless lithography technique has been widely applied in scientific research and industrial manufacture. However, low fabrication resolution restricts its application in nanofabrication due to optical diffraction limit. This work presents a simple and novel way to improve the LDW fabrication resolution by multiple-exposure method with a low energy laser beam. Experiments indicate that the method could increase the fabrication resolution by 33.3% for the same exposure depth, and is close to simulation results. It should be pointed out that principle of the method is universal, and may be instructive to improve the fabrication resolution of other maskless energy beam lithography techniques such as EBL and FIB.