Jiuxiang Dai

Author(s): Cheng Tan, Ji-Hai Liao, Guolin Zheng, Meri Algarni, Jia-Yi Lin, Xiang Ma, Edwin L. H. Mayes, Matthew R. Field, Sultan Albarakati, Majid Panahandeh-Fard, Saleh Alzahrani, Guopeng Wang, Yuanjun Yang, Dimitrie Culcer, James Partridge, Mingliang Tian, Bin Xiang, Yu-Jun Zhao, and Lan Wang

A ferromagnetism to antiferromagnetism phase transition in a van der Waals magnet at room temperature uses CrTe nanoflakes that may lead to improved spintronic devices.

[Phys. Rev. Lett. 131, 166703] Published Tue Oct 17, 2023

In summary, an frequency modulation-based uncooled long wave infrared (LWIR) detector is demonstrated using a cavity-coupled phase change material. The measured detectivity of the proposed detector is higher than commercially-available uncooled LWIR detectors with a faster response time. There is also great potential for the presented detection scheme with the implementation of other phase change materials with unique light responses.

Abstract

Detection of long wave infrared (LWIR) light at room temperature is a long-standing challenge due to the low energy of photons. A low-cost, high-performance LWIR detector or camera that operates under such conditions is pursued for decades. Currently, all available detectors operate based on amplitude modulation (AM) and are limited in performance by AM noises, including Johnson noise, shot noise, and background fluctuation noise. To address this challenge, a frequency modulation (FM)-based detection technique is introduced, which offers inherent robustness against different types of AM noises. The FM-based approach yields an outstanding room temperature noise equivalent power (NEP), response time, and detectivity (D*). This result promises a novel uncooled LWIR detection scheme that is highly sensitive, low-cost, and can be easily integrated with electronic readout circuitry, without the need for complex hybridization.

Here, oxide–metal–oxide (OMO) structures with ultra-thin Au layers as anodes in Stretchable OLEDs (SOLEDs) are introduced. V₂O₅ and MoO₃ seed layers in OMO inhibits non-uniform growth, with V₂O₅ providing better surface energy. This leads to superior current efficiency and mechanical robustness in V₂O₅-based SOLEDs. Enhanced surface energy at the bottom layer plays a crucial role in ensuring SOLEDs' mechanical stretchability and efficiency.

Abstract

The challenges for stretchable organic light-emitting diodes (SOLEDs) have led research into advanced manufacturing processes. Several electrodes have been researched to replace conventional indium tin oxide in SOLEDs due to its brittleness, indium scarcity in earth, and poor deformation capabilities. Oxide–metal–oxide (OMO) electrodes are promising alternatives for flexible/stretchable electronics owing their excellent charge injection and optical transparencies, including mechanical compliance. In this study, two oxides (i.e., MoO₃ and V₂O₅) with different surface energies in an OMO structure to effectively inhibit the island growth of the ultra-thin Au (5 nm) metal is incorporated. The morphology and interfacial coordinate covalent bonds between the seed layer and ultra-thin Au film are extensively studied. The improved ultra-thin Au growth in OMO structure together with figure-of-merit have been employed as the anode for a phosphorescent SOLED structure. The SOLEDs with OMO electrode under V₂O₅ as bottom oxide remain stable after peeling-off and sustain a >50% uniaxial strain with a negligible reduction in luminance and current efficiencies. The surface energy and interface of the bottom oxide in the OMO structure are crucial for thin metals to attain superior optical, structural, electronic, and mechanical stability in SOLEDs.

A non-volatile III-V-on-silicon photonic phase shifter based on a HfO₂ memristor with sub-pJ switching energy (≈400 fJ) is reported, representing over an order of magnitude improvement in energy efficiency compared to the state-of-the-art. The non-volatile phase shifter can be switched reversibly using a single 100 ns pulse and exhibits excellent endurance over 800 cycles.

Abstract

Silicon photonics has evolved from lab research to commercial products in the past decade as it plays an increasingly crucial role in data communication for next-generation data centers and high-performance computing. Recently, programmable silicon photonics has also found new applications in quantum and classical information processing. A key component of programmable silicon photonic integrated circuits (PICs) is the phase shifter, traditionally realized via thermo-optic or free-carrier effects that are weak, volatile, and power hungry. A non-volatile phase shifter can circumvent these limitations by requiring zero power to maintain the switched phases. Previously non-volatile phase modulation is achieved via phase-change or ferroelectric materials, but the switching energy remains high (pico to nano joules) and the speed is slow (micro to milliseconds). Here, a non-volatile III-V-on-silicon photonic phase shifter based on a HfO₂ memristor with sub-pJ switching energy (≈400 fJ), representing over an order of magnitude improvement in energy efficiency compared to the state of the art, is reported. The non-volatile phase shifter can be switched reversibly using a single 100 ns pulse and exhibits excellent endurance over 800 cycles. This technology can enable future energy-efficient programmable PICs for data centers, optical neural networks, and quantum information processing.

Abstract

Small-scale robots, ranging in size from micrometers to centimeters, have gained significant attention in the biomedical field. However, conventional small-scale robots made of rigid materials encounter challenges in adapting themselves to the soft tissues and complicated environments of human body. Compared to the rigid counterpart, small-scale hydrogel-based robots hold great promises due to their tissue-like low modulus, outstanding biocompatibility and accessible stimuli-responsive capabilities. These attributes offer small-scale hydrogel-based robots with multimodal locomotion and reinforced functions, further enhancing the adaptability in manipulation and tasks execution for various biomedical applications. In this review, we present recent advances in small-scale hydrogel-based robots. We first summarize the design principles of small-scale hydrogel-based robots including materials, fabrication techniques and manipulation strategies, then highlighting their upgraded functions and adaptive biomedical applications. Finally, we discuss existing challenges and future perspectives for small-scale hydrogel-based robots.

An unprecedented amorphous silicon carbide (a-SiC) thin film exhibits the highest ultimate tensile strength recorded for any nanostructured amorphous material, surpassing 10 GPa. This study showcases the fabrication of high-aspect-ratio a-SiC strings with quality factors exceeding 10⁸, revealing significant potential for diverse high-performance applications, from nanomechanical sensors to space exploration, and offering newfound prospects for employing amorphous materials where strength and stability are crucial.

Abstract

For decades, mechanical resonators with high sensitivity have been realized using thin-film materials under high tensile loads. Although there are remarkable strides in achieving low-dissipation mechanical sensors by utilizing high tensile stress, the performance of even the best strategy is limited by the tensile fracture strength of the resonator materials. In this study, a wafer-scale amorphous thin film is uncovered, which has the highest ultimate tensile strength ever measured for a nanostructured amorphous material. This silicon carbide (SiC) material exhibits an ultimate tensile strength of over 10 GPa, reaching the regime reserved for strong crystalline materials and approaching levels experimentally shown in graphene nanoribbons. Amorphous SiC strings with high aspect ratios are fabricated, with mechanical modes exceeding quality factors 10⁸ at room temperature, the highest value achieves among SiC resonators. These performances are demonstrated faithfully after characterizing the mechanical properties of the thin film using the resonance behaviors of free-standing resonators. This robust thin-film material has significant potential for applications in nanomechanical sensors, solar cells, biological applications, space exploration, and other areas requiring strength and stability in dynamic environments. The findings of this study open up new possibilities for the use of amorphous thin-film materials in high-performance applications.

In light of recent advancements in gallium-based liquid metal droplets (LMDs)-based electronics, this review outlines their unique properties, various preparation methods, and recent applications. Furthermore, existing challenges and future directions are discussed in this promising field.

Abstract

Liquid metals, particularly non-toxic gallium-based alloys, have emerged as promising materials for future soft electronics due to their unique properties, including fluidity, excellent electrical and thermal conductivities, and surface reactivity. They demonstrate adaptability, responsivity, and self-healing abilities, offering a platform for innovative electronic devices. Embodied in a droplet form factor, gallium-based liquid metal droplets (LMDs) combine the traits of liquid metals with the advantages of miniaturized structures, including high surface tension, high surface area, high mobility, and surface functionalization. This review discusses the inherent properties of LMDs, which have driven substantial research interest across various fields, such as sensors, robotics, electronic circuits, energy harvesters, drug delivery, and microfluidics systems, among others. Effective fabrication and processing techniques are detailed for LMDs, illustrating their role in applications previously challenging with conventional materials, such as reconfigurable, self-healing, and transient electronics. Existing challenges and future directions in this growing field are discussed. This extensive review seeks to further the understanding of LMDs and their potential, offering a roadmap for their journey from a niche interest to a key material in various electronic devices.

This review explores thin-film transistor integrated circuits (TFT ICs), highlighting their potential for enhancing healthcare, edge computing, and Internet of Things (IoT) applications. It discusses the development of various channel materials, from conventional silicon-based types to amorphous oxide semiconductors and emerging low-dimensional alternatives, and addresses manufacturing challenges and future directions in this field.

Abstract

High-performance thin-film transistors (TFTs) integrated circuits (ICs) have become increasingly necessary to meet the emerging demands such as healthcare, edge computing, and the Internet of Things, etc. This article aims to point out the potential development trends and bottlenecks of TFT ICs, enhancing their performance in terms of electronic performance, stability, consistency, CMOS design, and manufacturing capability. Basic device structures and overall metrics of TFT ICs are explored, as well as their superiority compared to silicon-based ultrathin chips. Hydrogenated amorphous silicon, low-temperature polycrystalline silicon, and amorphous oxide semiconductors are widely used in displays due to their ability to be deposited on large areas at low processing temperatures and low cost, and are validated in many prototypes for TFT ICs. Their conduction mechanisms, process flows, performance evaluation, and recent advances are comprehensively viewed. In addition, the potential of emerging low-dimensional materials as next-generation channel materials is discussed, along with their limitations and progress in this field. Finally, the major challenges in manufacturing high-performance TFT ICs and future perspectives are summarized.

Nature Communications, Published online: 13 October 2023; doi:10.1038/s41467-023-42214-5

The soft fluidic robots designed so far are lacking intelligent self-protection and present poor fluidic power source. Here, the authors report soft fluidic robots that integrate soft electrohydrodynamic pumps, healing electrofluids, actuators and E-skins endowing them with self-sensing, self-judgment, and self-heating behaviours for rapid self-healing.

Abstract

Image sensors with an in-sensor computing architecture have shown great potential in meeting the energy-efficient requirements of emergent data-intensive applications, where images are processed within the photodiode arrays. It demands the composed photodiodes are reconfigurable, which are usually achieved by ambipolar two-dimensional (2D) semiconductors. To improve the ambipolar charges injection, here we report a top-gated field-effect transistor (FET) design that is of bottom van der Waals contact via transferring ambipolar 2D WSe₂ onto Pd/Cr source/drain electrodes. The devices exhibit nearly negligible effective barrier heights for both holes and electrons based on thermionic emission mode, and show an almost balanced on/off ratio in the p-branch and n-branch. By replacing the top gate with two aligned semi-gates, the devices can effectively function as reconfigurable photodiodes. They can be switched between PIN and NIP configurations via controlling the two semi-gates, exhibiting good linearity in terms of short-circuit current (I_SC) and incident light power density. The photodiode arrays are also demonstrated for in-sensor optoelectronic convolutional image processing, showing significant potential for in-sensor computing image processors.

In this study, a new method is presented for synthesizing hexagonal boron nitride (h-BN) on a Cu substrate using magnetron sputtering and heat annealing in a vacuum environment. The structure and thickness of h-BN films can be controlled by appropriately adjusting the radio-frequency power, temperature, and synthesis time in the combination of sputtering and annealing processes.

Hexagonal boron nitride (h-BN) is an extensively investigated 2D material with exceptional quantum effects, which renders it promising for use in next-generation nanoelectronic devices. However, the synthesis of single- or few-layer h-BN nanosheets with large-area single-crystal structures is extremely challenging. In this article, a new method is presented for synthesizing h-BN on a Cu substrate via magnetron sputtering and heat annealing. Three samples with different radio-frequency (RF) power levels are prepared to evaluate the effect of RF power on h-BN nanosheet synthesis. Under a higher RF power, the B-to-N bonding ratio is closer to 1:1 and further reduces the full width at half maximum of X-Ray photoelectron spectroscopy B1s and N1s narrow spectra. Heating at 1000 °C reveals white domains with 60° facets, which may correspond to the hexagonal honeycomb lattice structure of h-BN. Cross-sectional observations show that a layered structure comprising 10–20 layers forms along the Cu interface. The elemental composition ratio and bonding states reveal the presence of equal amounts of N and B as well as a single peak derived from the B–N bond. Meanwhile, the E _2g mode of h-BN's six-membered ring structure is indicated at 1364.6 cm⁻¹, thus demonstrating the successful synthesis of an h-BN film.

Nature Reviews Materials, Published online: 12 October 2023; doi:10.1038/s41578-023-00596-4

Owing to their suitable and tunable optoelectronic properties, regulation-compliant InP-based colloidal quantum dots have attracted considerable academic and industrial interest for visible and near-infrared photonics. This Review covers the fundamentals, the design, the fabrication and the many applications of this class of materials, highlighting current challenges and future prospects.

Abstract

Two-dimensional (2D) materials hold great potential for the development of next-generation integrated circuits (ICs) at the atomic limit. However, it is still very challenging to build high performance devices. One of the main factors that limit the incorporation of 2D materials into IC technology is their relatively low carrier mobility. Thus, the engineering strategies that focus on optimizing performance continue to emerge. Herein, using a spatiotemporal resolved pump-probe setup, the carrier transport performance and relaxation process of few-layer and bulk MoSe₂ under pressure were investigated nondestructively and simultaneously. Our results show that pressure can tune the transport performance effectively. In particular, under pressure regulation, the carrier mobility of the bulk MoSe₂ increases by ∼ 4 times; meanwhile, the carrier lifetimes of the samples become shorter. Although the processes almost return to their initial state after the pressure release, it is still surprising to see that the carrier mobilities of few-layer and bulk MoSe₂ are still ∼ 1.5 and 2 times enhanced, and carrier lifetimes are still shorter than the initial state. Combined with the Raman spectra under pressure, we consider that it is caused by the enhanced layer coupling and lattice compression. The combination of enhanced mobility and shortened lifetime in MoSe₂ under pressure holds great potential for optoelectronic applications under the deep ocean and deep earth.

Nature Communications, Published online: 12 October 2023; doi:10.1038/s41467-023-41779-5

2D semiconductors have been proposed as a potential option to replace or complement silicon electronics at the nanoscale. Here, the authors discuss the recent progress and remaining challenges that need to be addressed by the academic and industrial research communities towards the commercialization of 2D transistors.

Nature Communications, Published online: 12 October 2023; doi:10.1038/s41467-023-42270-x

The growth of monolayer hexagonal boron nitride (hBN) on insulating substrates could promote high-end applications of 2D (opto-)electronic devices, but remains difficult to achieve. Here, the authors report a stamp-like growth-transfer technique to produce inch-sized single-crystal hBN and graphene monolayers on various insulating substrates.