Bin Feng

The trend toward ultimate edge computing systems requires a paradigm shift from integrating individual components to intrinsic multifunctional devices. However, a primary challenge lies in engineering a single device capable of harvesting energy, sensing complex environmental information, and performing on-device computation without overcomplicated device configuration. Herein, we address the challenge by developing a single-step, facile, ultrafast laser-induced symmetry engineering (LISE) process to fabricate a self-powered, polarization-sensitive neuromorphic vision device in a single MoTe₂-based architecture. By engineering the localized phase transition, we achieve simultaneous symmetry engineering of both the energy band and crystal structures. This dual asymmetry allows for self-powered operation via a built-in photovoltaic effect and polarization sensitivity from the engineered crystal anisotropy. Leveraging the photovoltaic volatile memory, an engineered FeFET operating as a physical reservoir achieves fully self-powered and all-optical reservoir computing for underwater imaging. Computation can be actively modulated by the polarization state of incident light and preconditioned by gate voltage, revealing a powerful hardware-level method for tuning computation. The proposed LISE approach demonstrates the ultrafast laser as a powerful tool for the local manipulation of material-symmetry-related properties and facilitates the creation of high-performance multifunctional neuromorphic systems.

The emission efficiency of interlayer excitons (IEs) in twisted 2D heterostructures has long suffered from momentum mismatch, limiting their applications in ultracompact excitonic devices. Here, we report strong room-temperature emission of momentum-forbidden IE in 30°-twisted MoS₂/WS₂ heterobilayers. Utilizing a plasmonic nanocavity, the Purcell effect boosts the IE emission intensity in the cavity by over 2 orders of magnitude. We further study the interplay of this Purcell enhancement and phonon assistance in 30°- and 0°-twisted heterostructures. Temperature-dependent and time-resolved spectroscopy reveal that the IE enhancement in 30°-twisted cases involves competition between IEs and intralayer excitonic emission, which is remarkably distinct from the 0°-twisted cases. We propose a comprehensive exciton decay model capturing the features of the phonon-assisted momentum compensation and the Purcell enhancement of the IE emission, showing consistency with the experimental measurements. Our results enrich the understanding of the nanocavity-assisted light-matter interaction for momentum-indirect excitonic transitions.

An efficient quality evaluation method is crucial for the applications of high-quality microhole arrays drilled with ultrafast lasers. The vision-based feature extraction was used as a data acquisition method to evaluate the drilling quality in terms of the geometric quality of the hole shape. However, the morphological features such as the recast layer, microcracks, and debris on the surface are difficult to consider in the quality evaluation since simultaneous recognition of multiple features remains challenging. Herein, we successfully recognized and extracted multiple features by deep learning, thus achieving the quality evaluation of microhole arrays in terms of both geometrical and surface qualities. Microhole arrays of various sizes and surface quality are fabricated on copper, stainless steel, titanium, and glass using different processing parameters. Then, the images of the microhole arrays are prepared as the dataset to train the deep learning network by labeling the typical features of microholes. The well-trained deep learning network has efficient and powerful recognition ability. Typical features such as the hole profile, recast layer, microcracks, and debris can be recognized and extracted simultaneously; thereby the geometric and surface quality of the microhole are obtained. We also demonstrate the implementation of the method with a fast quality evaluation of an array of 2300 microholes based on a statistical approach. The methods presented here extend the quality evaluation of microhole arrays by considering both geometric and surface qualities and can also be applied to quality monitoring in other ultrafast laser micromachining.

Field-effect transistor (FET) devices with multi-gate coupled structures usually exhibit special electrical properties and are suitable for fabricating multifunctional devices. Among them, the 1D nanowire gate configuration has become a promising gate design to tailor 2D FET performances. However, due to possible short circuiting induced by nanowire contact and the high requirement for precision manipulation, the integration of multinanowires as gates in a single 2D electronic system remains a grand challenge. Herein, local laser--thinned multiple core-shell SiC@SiO2 nanowires are successfully integrated into MoS2 transistors as multi-gates for active control of extendable logic applications. Nanowire gates (NGs) locally enhance the carrier transportation, and the use of multiple NGs can achieve designed band structures to tune the performance of the device. For core-shell structures, a semiconducting core is used to introduce a gate bias, and the insulating shell provides protection against short circuiting between NGs, facilitating nanowire assembly. Furthermore, a global control gate is introduced to co-tune the overall electrical characteristics, while active control of logic devices and extendable inputs are achieved based on this model. This work proposes a novel nanowire multi-gate configuration, which provides possibilities for localized, precise control of band structures and the fabrication of highly integrated, multifunctional, and controllable nano-devices.

2D materials exhibit intriguing electrical and optical properties, making them promising candidates for next-generation nanoelectronic devices. However, the high contact resistance of 2D materials to electrode material often limits the ultimate performance and potential of 2D materials and devices. In this work, we demonstrate a localized femtosecond (fs) laser irradiation process to substantially minimize the resistance of MoS₂–metal contacts. A reduction of the contact resistance exceeding three orders of magnitude is achieved for mechanically exfoliated MoS₂, which remarkably improves the overall FET performance. The underlying mechanisms of resistance reduction are the removal of organic contamination induced by the transfer process, as well as the lowering of Schottky barrier resistance (R_SB) attributed to interface Fermi level pinning (FLP) by Au diffusion, and the lowering of interlayer resistance (R_int) due to interlayer coupling enhancement by Au intercalation under fs laser irradiation. By taking advantage of the improved MoS₂–metal contact behavior, a high-performance MoS₂ photodetector was developed with a photoresponsivity of 68.8 A W^–1 at quite a low V_ds of 0.5 V, which is ∼80 times higher than the pristine multilayer photodetector. This contamination-free, site-specific, and universal photonic fabrication technique provides an effective tool for the integration of complex 2D devices, and the mechanism of MoS₂–metal interface modification reveals a new pathway to engineer the 2D material–metal interface.

The realization of liquid metal‐based wearable systems will be a milestone toward high‐performance, integrated electronic skin. However, despite the revolutionary progress achieved in many other components of electronic skin, liquid metal‐based flexible sensors still suffer from poor sensitivity due to the insufficient resistance change of liquid metal to deformation. Herein, a nacre‐inspired architecture composed of a biphasic pattern (liquid metal with Cr/Cu underlayer) as “bricks” and strain‐sensitive Ag film as “mortar” is developed, which breaks the long‐standing sensitivity bottleneck of liquid metal‐based electronic skin. With 2 orders of magnitude of sensitivity amplification while maintaining wide (>85%) working range, for the first time, liquid metal‐based strain sensors rival the state‐of‐art counterparts. This liquid metal composite features spatially regulated cracking behavior. On the one hand, hard Cr cells locally modulate the strain distribution, which avoids premature cut‐through cracks and prolongs the defect propagation in the adjacent Ag film. On the other hand, the separated liquid metal cells prevent unfavorable continuous liquid‐metal paths and create crack‐free regions during strain. Demonstrated in diverse scenarios, the proposed design concept may spark more applications of ultrasensitive liquid metal‐based electronic skins, and reveals a pathway for sensor development via crack engineering.

Ag-Cu bimetallic nanoparticles, combining the advantages of both Ag and Cu, is a promising material for power electronic packaging. In this work, a supersaturated Ag-7.3wt%Cu alloy nanoparticles film was developed by using pulsed laser deposition (PLD). Unlike Cu nanoparticles, the supersaturated Ag-Cu alloy nanoparticles can conduct bonding in air without the assistant of reduction agent. The shear strength was >20 MPa when bonding temperature reached 300 °C, which was above the die share standard (MIL-STD-883K, 7.8 MPa) and compatible with the typical die attach process. The Cu separating behavior was accompanied by the bonding process at 250-400 °C, which was discussed systematically. Neck formation was delayed to about 250 °C due to hindering effect of the thin oxide shell of Ag-Cu alloy. The necking networks provide volume diffusion paths despite the growth of surface oxide, resulting in compact densification. The bondline under the SiC die consisted of porous Ag-Cu alloy matrix with dispersed secondary phase of Cu2O/CuO, which is supposed to have improved electrochemical migration resistance.