Highlights
A solvent-free thermoplastic forming processing of graphene materials is invented by polymer intercalation from graphene oxide precursor.
The correlation between interlayer spacing and ...thermoplastic forming capability of polymer-intercalated graphene oxide solid is uncovered.
The multi-scale forming of graphene materials from Gaussian curved shapes to surface relief patterns with size precision down to 360 nm is realized.
The processing capability is vital for the wide applications of materials to forge structures as-demand. Graphene-based macroscopic materials have shown excellent mechanical and functional properties. However, different from usual polymers and metals, graphene solids exhibit limited deformability and processibility for precise forming. Here, we present a precise thermoplastic forming of graphene materials by polymer intercalation from graphene oxide (GO) precursor. The intercalated polymer enables the thermoplasticity of GO solids by thermally activated motion of polymer chains. We detect a critical minimum containing of intercalated polymer that can expand the interlayer spacing exceeding 1.4 nm to activate thermoplasticity, which becomes the criteria for thermal plastic forming of GO solids. By thermoplastic forming, the flat GO-composite films are forged to Gaussian curved shapes and imprinted to have surface relief patterns with size precision down to 360 nm. The plastic-formed structures maintain the structural integration with outstanding electrical (3.07 × 10
5
S m
−1
) and thermal conductivity (745.65 W m
−1
K
−1
) after removal of polymers. The thermoplastic strategy greatly extends the forming capability of GO materials and other layered materials and promises versatile structural designs for more broad applications.
Graphical abstract
Highlights
Presenting the first investigation into the structurally bubbling-failure mechanism of graphitic film during cyclic liquid nitrogen shocks.
Proposing an innovative design about seamless ...heterointerface constructing a Cu-modified structure.
Inventing a new ultra-stable species of highly thermally conductive films to inspire new techniques for efficient and extreme thermal management.
Highly thermally conductive graphitic film (GF) materials have become a competitive solution for the thermal management of high-power electronic devices. However, their catastrophic structural failure under extreme alternating thermal/cold shock poses a significant challenge to reliability and safety. Here, we present the first investigation into the structural failure mechanism of GF during cyclic liquid nitrogen shocks (LNS), which reveals a bubbling process characterized by “permeation-diffusion-deformation” phenomenon. To overcome this long-standing structural weakness, a novel metal-nanoarmor strategy is proposed to construct a Cu-modified graphitic film (GF@Cu) with seamless heterointerface. This well-designed interface ensures superior structural stability for GF@Cu after hundreds of LNS cycles from 77 to 300 K. Moreover, GF@Cu maintains high thermal conductivity up to 1088 W m
−1
K
−1
with degradation of less than 5% even after 150 LNS cycles, superior to that of pure GF (50% degradation). Our work not only offers an opportunity to improve the robustness of graphitic films by the rational structural design but also facilitates the applications of thermally conductive carbon-based materials for future extreme thermal management in complex aerospace electronics.
Abstract With the rapid development of high‐power electronics in aerospace, communication, and energy storage systems, the huge heat flux poses an increasing threat to the safety of electronic ...devices. Compared with thin films of a few micro thicknesses, high‐quality graphene thick film (GTF) exceeding hundreds of microns thickness is a promising candidate to solve thermal management challenges owing to higher heat‐flux. However, traditional GTF usually has lower thermal conductivity and weak mechanical properties attributed to disordered sheet alignment and frail interfacial adhesion. Here, a seamless bonding assembly (SBA) strategy is proposed to attain GTF over record hundreds of microns with robust coalescence interfaces. For the GTF‐SBA with ≈250 µm thickness, the in‐plane and through‐plane thermal conductivities are 925.75 and 7.03 W m −1 K −1 , approximately two times and 12 times those of the GTF prepared by traditional adhesive assembly method, respectively. Furthermore, the GTF‐SBA demonstrates remarkable stability even after cycled harsh temperature shocks from 77 to 573 K, ensuring its environmental adaptability for long‐term service in extreme conditions. These findings provide valuable insights into the interfacial design of graphene bulk materials and highlight the potential applications of high‐performance graphene‐based materials for extreme thermal management demands.
Deep ultraviolet photodetectors play a critical role in applications such as ozone layer monitoring and missile alert systems. This work investigates the potential of graphene quantum dots to enhance ...deep ultraviolet light photodetection within the graphene/Si heterojunction. The addition of graphene quantum dots not only reduces the Schottky barrier between graphene and Si but also enhances the absorption ability of deep ultraviolet light by graphene and Si. As a result, the modified junction exhibited exceptional performance metrics, including a notable responsivity of 0.21 A/W, an impressive specific detectivity of <inline-formula> <tex-math notation="LaTeX">{1}.{13}\times {10} ^{{11}} </tex-math></inline-formula> Jones, substantial external quantum efficiency of 94.5 %, and swift response speed (23.7/47.4 ns). Elevating the reverse bias voltage increases electron kinetic energy, thereby inducing collision ionization effects in Si. Subsequent evaluations revealed a high responsivity value of 31.4 A/W and a good gain of 28, affirming the capability of the device to detect faint light signals. The successful utilization of the Gr QDs/Gr/Si heterojunction as a single-pixel imaging device underscored its prowess in imaging applications. This innovative hybrid approach opens avenues for large-scale fabrication and diverse applications in optoelectronic devices.
Heterojunction devices based on two-dimensional materials have been widely studied in the fields of electronics and optoelectronics. As the complexity of the chip system increases, the ability to ...realize multi-function in a single device is increasingly in demand. Here, we propose a multifunctional device based on graphene/silicon heterojunction, which can operate in photodetection mode or tunable rectifier mode. The heterojunction barrier is tunable by the external electric field. The photodetection range covers ultraviolet to visible, and the responsivity can reach 51 A/W and 495 A/W at 266 nm and 532 nm while keeping the off-state current at a low level of 10 −8 A. With the control of the external electric field, the device can also function as a tunable rectifier to achieve three states: positive-pass, off, and negative-pass, which can be applied in signal processing and logic circuit. The multifunctional integrated device has potential in future optoelectronic logic applications while reducing the cost and the device footprint.
p-type silicon (p-Si)/macro-assembled graphene nanofilm (nMAG)/n-type silicon (n-Si) heterojunction is utilized to fabricate near-infrared photodetector. Dual built-in electric fields were ...established in the same direction at the p-Si/nMAG and nMAG/n-Si heterojunctions, providing an enhanced electron-hole separation ability. The p-Si/nMAG/n-Si device has realized responsivities of 90 mA/W and 45 mA/W under 900 nm and 1064 nm illumination at room temperature and corresponding external quantum efficiency (EQE) of 11.8% and 5.2%, respectively, which is 30% and 45% higher than that of the single-junction nMAG/n-Si device. In this work, we applied two-dimensional (2D) carbon materials combined with monocrystalline silicon to explore complementary metal-oxide-semiconductor (CMOS) process-compatible device fabrication techniques, which paves the way to develop low-cost and large-scale near-infrared carbon-based photodetectors.
Abstract The demand for high‐performance X‐ray detectors leads to material innovation for efficient photoelectric conversion and carrier transfer. However, current X‐ray detectors are often ...susceptible to chemical and irradiation instability, complex fabrication processes, hazardous components, and difficult compatibility. Here, we investigate a two‐dimensional (2D) material with a relatively low atomic number, Ti 3 C 2 T x MXenes, and single crystal silicon for X‐ray detection and single‐pixel imaging (SPI). We fabricate a Ti 3 C 2 T x MXene/Si X‐ray detector demonstrating remarkable optoelectronic performance. This detector exhibits a sensitivity of 1.2 × 10 7 μC Gy air −1 cm −2 , a fast response speed with a rise time of 31 μs, and an incredibly low detection limit of 2.85 nGy air s −1 . These superior performances are attributed to the unique charge coupling behavior under X‐ray irradiation via intrinsic polaron formation. The device remains stable even after 50 continuous hours of high‐dose X‐ray irradiation. Our device fabrication process is compatible with silicon‐based semiconductor technology. Our work suggests new directions for eco‐friendly X‐ray detectors and low‐radiation imaging system. image
Van der Waals Integrated Silicon Broadband Imagers Xu, Yang; Tian, Feng; Bodepudi, Srikrishna C. ...
2023 IEEE Nanotechnology Materials and Devices Conference (NMDC),
2023-Oct.-22
Conference Proceeding
Van der Waals (vdWs) heterostructures with their extended cross-dimensional integration freedom, emerged as most appropriate choice for next-generation electronics and optoelectronics. In the post ...Moore era, the electronics industry is on the verge of shifting from covalent or ionic bond-dominated homo- and hetero-interfaces to vdWs integrated systems, hailed by clean interfaces free of dangling bonds and Fermi-level pinning while lodging rich device physics from confinement and gating effects. Hence, it is essential to develop devices exploiting cross-dimensional benefits, bringing the best of materials in different dimensions. One such strategy is to integrate two-dimensional (2D) materials with bulk semiconductors in the most widely used large-scale device schemes like charge-coupled devices (CCD) and complementary-metal-oxide-semiconductor (CMOS) using a flip-chip method. Taking this into consideration, we demonstrate 2D-silicon hybrid imagers with the benefits of both CCD and CMOS, showing potential for broadband, ultrafast photoresponse, viable for the period of Internet of Things (IoTs), artificial intelligence (AI), and compute-in-memory.
As traditional silicon-based optoelectronic devices are approaching the performance limit, there is an urgent need for materials that complement silicon while being compatible with the conventional ...semiconductor processing steps. Graphene has the advantages of a broad absorption spectrum, high mobility, and a strong field effect. Adapting graphene in conventional silicon-based optoelectronic devices can extend the device functionality to broader application areas while alleviating their fundamental limitations. Here, we discuss the broadband graphene-silicon integrated imagers, emphasizing the importance of graphene integration with silicon that delivers unique advantages in the performance of broadband photodetection and imaging.
The molecular mechanisms controlling the transition from meiotic arrest to meiotic resumption in mammalian oocytes have not been fully elucidated. Single-cell omics technology provides a new ...opportunity to decipher the early molecular events of oocyte growth in mammals. Here we focused on analyzing oocytes that were collected from antral follicles in different diameters of porcine pubertal ovaries, and used single-cell M&T-seq technology to analyze the nuclear DNA methylome and cytoplasmic transcriptome in parallel for 62 oocytes. 10× Genomics single-cell transcriptomic analyses were also performed to explore the bi-directional cell–cell communications within antral follicles. A new pipeline, methyConcerto, was developed to specifically and comprehensively characterize the methylation profile and allele-specific methylation events for a single-cell methylome. We characterized the gene expressions and DNA methylations of individual oocyte in porcine antral follicle, and both active and inactive gene’s bodies displayed high methylation levels, thereby enabled defining two distinct types of oocytes. Although the methylation levels of Type II were higher than that of Type I, Type II contained nearly two times more of cytoplasmic transcripts than Type I. Moreover, the imprinting methylation patterns of Type II were more dramatically divergent than Type I, and the gene expressions and DNA methylations of Type II were more similar with that of MII oocytes. The crosstalk between granulosa cells and Type II oocytes was active, and these observations revealed that Type II was more poised for maturation. We further confirmed Insulin Receptor Substrate-1 in insulin signaling pathway is a key regulator on maturation by in vitro maturation experiments. Our study provides new insights into the regulatory mechanisms between meiotic arrest and meiotic resumption in mammalian oocytes. We also provide a new analytical package for future single-cell methylomics study.
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