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To find a more efficient way to generate photocatalytic hydrogen, we developed the interfacial photocatalytic mode, in which the photocatalytic reaction can be transferred to a high-energy interfacial area. The new interfacial mode in this work is assembled with the help of carbonized mushrooms, which is an ideal water transporter as well as an excellent photothermal converter. The higher temperature from efficient light-to-heat conversion performance and thermal localization promote the efficiency of hydrogen evolution, and some effects peculiar to the interfacial mode can make the departure of hydrogen from the active sites of the photocatalyst smoother. As a result, the active sites can be exposed in a timely manner to allow the progress of the next cycle of the photocatalytic reaction to be smoother. The efficiency of interfacial photocatalytic hydrogen production can reach10 times that of the corresponding sample in the traditional bulk water mode. This work has allowed further exploration of the construction of the interfacial photocatalytic mode, provided a reliable experimental basis for the development of the interfacial mode, and illuminated a new path for the development of photocatalytic water splitting.

To fabricate high-quality catalysts with abundant active sites, a series of transition-metal-modified nitrogenous carbon catalysts (Ta-NOC, Nb-NOC, and Nb/Ta-NOC) was successfully fabricated via pyrolysis and ion exchange. Owing to the high conductivity and ion transport capacity of its unique nitrogen-carbon structure, and synergistic effect of dual-metal active sites on modulating electronic structure, Nb/Ta-NOC catalyst exhibited an excellent catalytic performance and a remarkable electrochemical stability in triiodide reduction reaction (IRR) and hydrogen evolution reaction (HER). Nb/Ta-NOC catalyst achieved an ideal conversion efficiency of 8.45% for IRR in solar cells, which was higher than that of Pt electrode (7.63%). Furthermore, Nb/Ta-NOC catalyst exhibited a small overpotential of 145 mV at a current density of 10 mA·cm-2 and a Tafel slope of 77 mV dec-1 for HER. This work provided a new approach for the rational design of the active-sites-rich electrocatalysts for energy conversion applications.

Developing electrocatalysts with excellent catalytic performance and superior durability for hydrogen evolution reaction (HER) remains a challenge. Herein, metal-nitrogen sites (M–Nx, M = Ni and Cu) are successfully implanted into zeolitic imidazolate zinc framework (ZIF-8)-derived nitrogen-doped porous carbon (ZIF/NC) to prepare Ni-ZIF/NC and Cu-ZIF/NC electrocatalysts for the HER. These M–Nx active sites significantly enhanced the electrocatalytic activities of Ni-ZIF/NC and Cu-ZIF/NC. Metal Ni acted as a catalyst for catalysis of Ni-ZIF/NC to form carbon nanotubes-like structures, which provided convenient ion transmission pathways. Owing to its special morphology and an increased number of defects, Ni-ZIF/NC displayed superior electrocatalytic activity in the HER compared to those of Cu-ZIF/NC and ZIF/NC. In an alkaline environment, Ni-ZIF/NC exhibited an overpotential at the current density of 10 mA cm−2 (η10) of 163.0 mV and Tafel slope of 85.0 mV dec−1, demonstrating an electrocatalytic property equivalent to that of Pt/C. In an acidic environment, Ni-ZIF/NC yielded a η10 of 177.4 mV and Tafel slope of 83.9 mV dec−1, which were comparable to those of 20 wt.% Pt/C. Moreover, Ni-ZIF/NC and Cu-ZIF/NC also exhibited superior stabilities in alkaline environments. This work offers a valuable strategy for controlling the morphology and implanting M–Nx active sites into carbon for designing novel catalysts for use in alternative new energy applications.

Development of low-cost and efficient photocatalytic materials with visible-light response is of urgent need for solving energy and environmental problems. Here, a metal-free two-dimensional (2D) π-conjugated hybrid g-C3N4 photocatalyst with tunable band structure was prepared by a novel one-pot bottom-up method based on a supersaturated precipitation process of urea and triethanolamine (TEOA) solution. The microstructure of the hybrid g-C3N4 is revealed to be a compound of periodic tri-s-triazine units grafted with N-doped graphene (GR) fragments. From experimental evidence and theoretical calculations, the two different π-conjugated fragments in the hybrid g-C3N4 material are proved to construct a 2D in-plane junction structure, thereby expanding the light absorption range and accelerating the interface charge transfer. The π-conjugated electron coupling in the 2D photocatalyst eliminates the grain boundary effect, and the coupled highest occupied molecular orbital (HOMO) effectively promotes the separation of photo-induced charge carriers. Compared with the g-C3N4 prepared by the conventional method, the visible-light H2 production activity of the optimized sample is enhanced by 253 %. This work provides a new strategy of constructing metal-free g-C3N4 hybrids for efficient photocatalytic water splitting.

In the research of photocatalysis, the effect of mass transfer has been seriously ignored, though its importance to photocatalytic performance has been already proved. In this work, self-propelled jet carbon micromotors, carbon bottle (CB), are combined with photocatalysts to enhance the photocatalytic performance, based on the infrared light utilization and active mass flow transfer, the so-called “on-the-fly” working mode. Compared with the traditional Janus motors, the environmentally friendly CB motors, which can be prepared through one-step hydrothermal route, has the advantages of simple synthesis, low price and not containing precious metal. The CB motor has excellent motion characteristics in pure water without additional chemicals as fuels. The photocatalytic activity of 10 wt% CB/g-C3N4 and 10 wt% CB/P25 are 2.1 and 2.3 times than that of pure g-C3N4 and P25, respectively. This work provides a new strategy for the development of photocatalytic technology by utilizing the self-propulsion of micromotors.

Energy and mass transfer in photocatalytic systems plays a significant role in photocatalytic water splitting, but relevant research has long been ignored. Here, an interfacial photocatalytic mode for photocatalytic hydrogen production is exploited to optimize the energy and mass flows and mainly includes a heat-insulating layer, a water-channel layer, and a photothermal photocatalytic layer. In this mode, the energy flow is optimized for efficient spreading, conversion, and utilization. A low-loss path (ultrathin water film) and an efficient heat localized zone are constructed, where light energy, especially infrared-light energy, can transfer to the target functional membrane surface with low loss and the thermal energy converted from light can be localized for further use. Meanwhile, the optimization of the mass flow is achieved by improving the desorption capacity of the products. The generated hydrogen bubbles can rapidly leave from the surface of the photocatalyst, along with the active sites being released timely. Consequently, the photocatalytic hydrogen production rate can be increased up to about 6.6 times that in a conventional photocatalytic mode. From the system design aspect, this work provides an efficient strategy to improve the performance of photocatalytic water splitting by optimizing the energy and mass flows.

The development of low-cost and high-active cocatalysts is one of the most significant links for photocatalytic water splitting. Herein, a novel strategy of electron delocalization modulation for transition metal sulfides has been developed by anion hybridization. P-modified CoS2 (CoS2∣P) nanocrystals were firstly fabricated via a gas-solid reaction and coupled with CdS nanorods to construct a composite catalyst for solar H2 evolution reaction (HER). The CdS/CoS2∣P catalyst shows an HER rate of 57.8 µmol·h−1, which is 18 times that of the bare CdS, 8 times that of the CdS/CoS2, and twice that of Pt/CdS. The reduced energy barrier and suppressed reverse reaction for HER on the catalyst have been predicted and explained by density functional theory (DFT) calculation. The underlying design strategy of novel cocatalysts by electron delocalization modulation may shed light on the rational development of other advanced catalysts for energy conversion.

Constructing cost-effective and robust counter electrodes (CEs) without noble metals remains a challenge for the commercialization of current dye-sensitized solar cells (DSSCs). In this study, we focus on the built-in zinc element into the zeolitic imidazolate framework (ZIF-8) to construct a composite of dual-phase zinc selenide (ZnSe) encapsulated by the size-reduced ZIF-derived Se/N-doped carbon (PS N-CSR) using a post-selenization procedure. Benefitting from the enhanced synergy and charge transfer between the small-sized doped carbon skeleton and well-dispersed dual-phase ZnSe active sites, the resultant PS N-CSR exhibited superior catalytic activity and durability to the triiodide reduction reaction (IRR). The devices that utilize PS N-CSR CE achieved a high power conversion efficiency of 8.48%, surpassing that of Pt (7.20%). It is expected that this work will provide an extensible pathway for designing efficient hybrid electrocatalysts with beneficial structures containing transition metal compounds based on ZIF analogs.

Graphitic carbon nitride (g-C3N4), as an organic polymer semiconductor, has been the focus of photocatalysts due to its physical and chemical stability, low cost and non-toxicity. However, pristine g-C3N4 also has many drawbacks, such as small specific surface area and easy recombination of photoexcited carriers, which hampered its practical application. In this work, we first propose a design idea of embedding stereo molecular scaffold into g-C3N4 framework with a facile copolymerization method for better exfoliating g-C3N4 to reach a better photocatalytic hydrogen evolution under ordinary pressure. The stereo molecular scaffold looses the interlayer stacking of bulk g-C3N4, benefitting the exfoliation of g-C3N4. The hydrogen evolution activity of stereo molecular scaffold doped g-C3N4 (AMCN-3-E) is about 7.54 times higher than that of the pristine MCN, which may due to the activated π → π* and n → π* electron transitions, creating more electron transition paths and accelerating the separation of photoexcited electrons and holes.

A simple combination of thermal etching and liquid-phase ultrasonic stripping was deployed to prepare high-performance graphite carbon nitride (g-C3N4) nanosheets. Also, graphene oxide with plentif...

Pomelo peel-derived bio-based carbon with controllable morphologies are successfully prepared by three different methods (microwave pyrolysis, two-step activation, hydrothermal carbonization combining chemical activation). The differences in specific surface area and pore size distribution caused by various morphology features remarkably affect the application potential of as-prepared bio-based carbon. Two-step activation carbonization is proven to be an effective and feasible method to synthesize small-size bio-based carbon with large specific surface area (1377.60 m2/g) and total pore volume (0.72 m3/g) as compared with other methods. The bio-based carbon prepared by two-step activation method as counter electrode catalyst in dye-sensitized solar cell (DSSC) obtains an excellent photovoltaic performance as compared with the Pt-based DSSC (6.94% vs. 6.71%). Furthermore, the as-prepared bio-based carbon is used as accelerant in anaerobic digestion (AD) systems and obtains the enhanced cumulative biogas production (525 mL/g VS) and chemical oxygen demand removal rate (70.95%) as compared with the control check group (296 mL/g VS, 29.55%). This work illustrates three promising methods to prepare bio-based carbon with controllable morphologies and superior surface area for realizing their multifunction resource utilizations in renewable energy fields.

Nitrogen-coordinated metal-modified carbon is regarded as a novel frontier electrocatalyst in energy conversion devices. However, the construction of intrinsic defects in a carbon matrix remains a great challenge. Herein, N-coordinated magnetic metal (Fe, Co) modified porous carbon dodecahedrons (Fe/Co-NPCD) with a large surface area, rich intrinsic defects, and evenly distributed metal-Nx species are successfully synthesized via the rational design of iron precursor and the bimetallic-organic frameworks. Because of a synergistic effect between N-coordinated dual magnetic metal active sites, the Fe/Co-NPCD exhibits exceptional electrocatalytic activity and electrochemical stability. A solar cell fabricates with the Fe/Co-NPCD yields an impressive power conversion efficiency of 8.35% in dye-sensitized solar cells, superior to that of mono-metal-doped carbon-based cells and conventional Pt-based cells. Furthermore, density functional theory calculations illustrate that Fe, Co, and N doping are in favor of improving the adsorption capacity of the catalyst for I3 - species by optimizing the magnetic momentum between the magnetic metal atoms, thereby upgrading its catalytic activity. This work develops a general strategy for synthesizing a high-performance defect-rich carbon-based catalyst, and offers valuable insight into the role of magnetic metals in catalysis, which can be used to guide the design of high-performance catalysts in the energy field.

A new kind of intermetallic compounds (IMC) were found around copper pillar in micron level bumps. To investigate the formation mechanism, three different sized Sn/Ni/Cu bumps (10 μm, 20 μm, 50 μm) were electroplated then reflowed at 230 °C for 100 s. After reflow process, a thin layer of IMC was formed around copper pillar, which is attributed to surface wetting behavior. After aging at 170 °C and 200 °C for different times, the growth mechanism of sidewall IMC was observed by scanning electron microscopy combined with electron backscatter diffraction (EBSD) technology. Surface diffusion was considered to be the main driving force for sidewall IMC growth for the activation energy of them was found to be much smaller than that in previous studies. The EBSD results showed a preferred orientation of sidewall Cu3Sn grains being perpendicular to copper periphery, which indicated direction of Cu atoms flux during Cu3Sn growth. Formation mechanism of this novel sidewall IMC was proposed based on surface wetting and surface diffusion. The findings contribute to the failure mechanism study in small size bumps and provide insights into the reliability of 3D electronic packaging.

Utilizing cocatalysts is an effective measure to enhance photocatalytic activities of photocatalysts. Nevertheless, noble-metal cocatalysts such as Pt and Au impose astounding costs on the application of photocatalytic technology. Herein, noble-metal-free MoS2 was used as a cocatalyst to improve the photocatalytic activity of visible-light-responsive TaON for the first time. This work indicates that MoS2/TaON presented higher activity than Pt/TaON while MoS2 costs much less than Pt. The photocatalytic degradation ratio of RhB over Ta1Mo1 (mass ratio of TaON:MoS2 = 1:1) was about 65% after 2 h visible light irradiation, which is about five times higher than that of pure TaON. Furthermore, MoS2/SiO2/TaON ternary photocatalysts were constructed to further improve the photocatalytic performance. When the mass ratio of Ta8Si1 (mass ratio of TaON:SiO2 = 8:1) to MoS2 was 1:1, the degradation ratio of RhB reached 75% after 2 h visible light irradiation. This work provides a facile method to construct high-efficient photocatalysts with the noble-metal-free cocatalyst MoS2, paving the way to realize the application of cheap and environment-friendly photocatalysis.

Developing highly-efficient multifunctional electrocatalysts for energy conversion devices is of great importance. A sequence of nano-sized bimetal (Al, Cr, Fe) niobium oxide nanoparticles anchored on aloe peel-derived porous carbon skeleton hybrids (AN/APPC, CN/APPC, and FN/APPC) are successfully prepared via co-precipitation avenue and used as electrocatalysts for photovoltaics and alkaline hydrogen evolution reaction. Benefiting from the synergies between nano-sized metal niobium oxides and highly conductive porous carbon skeleton, these robust polycomponent hybrid electrocatalysts exhibit superior catalytic performances for accelerating the triiodide reduction and hydrogen evolution reaction. The solar cell with AN/APPC electrocatalyst achieves an outstanding device efficiency of 7.31%, superior to that with Pt (6.84%), and the AN/APPC electrocatalyst exhibit an overpotential (131.6 mV) when the current density is 10 mA cm−2 and Tafel slope (54 mV dec−1) in 1 M KOH for hydrogen evolution reaction. The AN/APPC electrocatalysts illustrate remarkable electrochemical durability in both I3−/I− electrolyte and alkaline media. Furthermore, the catalytic mechanism was clarified both from the electronic structure and work function through first-principle density functional theory (DFT) calculations. This work opens a new avenue for electrocatalysis field via using nano-sized porous bio-carbon skeleton loaded with niobium-based binary metal.

Metal-dielectric hybrid bonding is a critical technique of inter-chip connections for 3D integration. In this work, a chip-level embedded hybrid bonding structure using Cu-Sn/BCB Bonding is proposed and realized. This embedded microbump structure with photosensitive BCB coated on the single side could be successfully developed without chemical mechanical polishing (CMP), while the cure temperature (250°C) of BCB is the same as that of Cu-Sn thermal compression bonding or solid-liquid interdiffusion (SLID). The deviation of misalignment could be reduced effectively due to the embedded bonding structure. Consecutive and void-free interface could be got at BCB-metal and BCB-Si boundary with optimized scale design of BCB patterns while the diameter/pitch of microbumps is 50μm/100μm, the thickness of bonding layer is approximately 10μm. Also, key factors of process for realizing good quality of bonding is discussed. The electrical test shows that interface of metal microbumps could be improved further. Besides, the die shear test shows good mechanical strength of this hybrid bonding structure as the shear strength of hybrid bonding area and pure BCB bonding area are over 13MPa and 19MPa, respectively.

： Developing high-performance and low-cost catalysts for replacing Pt-based catalysts is a significant challenge for solar cells and water splitting applications. In this work, a bifunctional hybrid catalyst of MnTa2O6@MPC (MPC: mesh-like bio-based porous carbon) was synthesized, using a co-precipitation approach. Benefiting from the high specific surface area (332.743 m2 g-1), integrating the merits of the electrical conductivity of MPC, the outstanding electrocatalytic ability of MnTa2O6, and the synergistic effect between MnTa2O6 and MPC, the catalytic activity of MnTa2O6@MPC was significantly enhanced. To boost the photovoltaic performance of dye-sensitized solar cells, a novel Cu2+/Cu+ redox mediator and dye (Y123, D35) were adopted for replacing the traditional I3-/I- redox mediator and N719 dye, respectively. The resulting advanced solar cell with the Cu2+/Cu+ redox mediator based on the MnTa2O6@MPC counter electrode catalyst exhibited a photovoltage of ~0.88 V, and cell efficiencies of 3.41% and 1.92% for the D35 and Y123 dye systems, respectively, which are respectively 16% and 8% higher than that of Pt. MnTa2O6@MPC also exhibited significant catalytic ability for hydrogen production, yielding a small overpotential of 141.9 mV at a current density of 10 mA cm-2 and a small Tafel slope of 105.0 mV dec-1 in an alkaline medium. This work provides promising guidance for designing bifunctional hybrid electrocatalysts for high-performance new energy devices.

The reliability of Sn-Ag-Cu (SAC) solder welded with Cu-organic solderability preservative (OSP) and NiAu- or NiPdAu-coated ball grid array (BGA) package pads has been investigated after isothermal aging. Moreover, the interfacial reaction and diffusion reaction are discussed. The intermetallic compound (IMC) layer was found to be too thick to withstand large stresses, leading to poor reliability of the solder joints on Cu-OSP pads. Additionally, for NiAu-coated pads, not only irregular Au-rich phases but also more diffused Ni without the barrier effect of Pd promoted formation of IMC in the solder balls, resulting in a potential mismatch with the initial solder. Compared with the NiAu-coated pad, the IMC layer that formed between the NiPdAu-coated pads and SAC105 solder was thinner, indicating an effective diffusion barrier effect of the Pd layer in the NiPdAu coating. Hence, SAC105 solder showed superior reliability on BGA package pads coated with NiPdAu.

Tin whiskers with different morphologies form on SnAg microbumps under long-term compressive stress. High resolution transmission electron microscopy results reveal that dislocations and stacking faults can be found inside tin whiskers and the neighboring grains, and the twin boundaries are irregular regions with twinning dislocations. The dislocations can slip from the adjacent grains into the tin whisker grains through the twin boundaries, resulting in whisker growth under compressive stress. The findings are of great significance to the study of tin whisker on isolated Sn-based solders and provide insights into the reliability of 3D electronic packaging.

The effects of Sn layer orientation on the evolution of Cu/Sn joint interfaces were investigated. Three Sn layers possessing (112), (321) and (420) orientations were electroplated on polycrystalline Cu substrates respectively. The orientations of Sn layer preserved during reflowing at 250 °C for 10 s. After aging at 150 °C for different time, the interfacial microstructures were observed from the cross-section and top-view. The alignment between the c-axis of Sn and Cu diffusion direction significantly sped up the Cu diffusion, leading to the thickest intermetallic compound layer formed in (112) joint. Two types of voids, namely, intracrystalline voids and grain islanding caused intercrystalline voids generated at Cu/Cu3Sn interfaces due to the different interdiffusion coefficients of Cu and Sn (112) oriented Sn/Cu joint produced many more voids than (321) joint, and no voids were detected in (420) joint. Therefore, to enhance the reliability of solder joints, using (420) oriented Sn as solder layer could be an efficient way.

An innovative controllable way has been proposed to mitigate tin whisker growth by inserting Ni nanocones prepared by electrodeposition. The results reveal that, after inserting Ni nanocones, tin whisker formation is mitigated effectively for 1.6 μm Sn coating but there is no inhibition effect for 4.5 μm Sn coating. The coatings are characterized by X-ray diffraction, scanning electron microscopy, energy dispersive spectrometer and electron backscatter diffraction (EBSD). The EBSD results show that Sn grain size without Ni nanocones increases significantly after indentation test compared with Sn grains with Ni nanocones. The inhibition effect of Ni nanocones on whisker growth can be ascribed to its specific structure which prevents dynamic recrystallization and produces horizontal grain boundaries of Sn grains. The structural inhibition method and mechanism proposed are of great importance to the research of tin whisker.

The elaborate design of electrode materials plays a critical role in developing high-performance supercapacitors. In the present work, a convenient avenue is adopted to adjust the supercapacitive behavior of carbon-based electrodes by incorporating transition metals (Co, Nb, Mo, and Fe) into Co/Zn-ZIF derived nitrogen-doped porous carbon (NDPC). The experiment results demonstrated that incorporating transition metal species tuned the microstructure, nanoporous textures, and hydrophilicities of as-prepared Co-NDPC and M/Co-NDPC (M = Nb, Mo, or Fe), which further tailored their supercapacitive performance. Owing to the higher surface area, abundant pores, and superior wettability of Nb/Co-NDPC sample, the corresponding electrode showed the highest specific capacitance of 293 F g−1 at 0.5 A g−1 with an outstanding capacitance retention of 82% at 20 A g−1. All the electrodes displayed remarkable stability over 15,000 charge–discharge cycles. The first-principle density functional theory (DFT) calculations revealed that the superior capacitive behaviors of Nb/Co-NDPC electrode could be attributed to the uneven electrostatic potential surface and robust K+ ion adsorption ability. This work provides an elaborate strategy for designing novel and high-performance electrode materials by adopting DFT calculations for supercapacitors.

Micron level Cu-pillar microbumps, which appear as the size of three-dimensional packaging shrinks down, have to introduce many unexpected reliability problems. The fast growth of intermetallic compounds (IMC) and voids tend to be a serious one. In this paper, the growth behaviors of IMC and voids were investigated in Sn–3.5Ag/Ni/Cu bumps, which were in the diameter ranging from 6 to 11 μm and fabricated under same reflow process. The consequence manifested that the growth rate of interfacial IMC increased from 0.448 to 0.578 μm/min as the bump diameter decreased from 11 to 6 μm and the acquired IMC could be divided into two layers: the (Cu, Ni)6Sn5 layer and Ni3Sn4 layer. As a result of the migration of Ni atoms, many voids were left in the interface between (Cu, Ni)6Sn5 and Ni3Sn4. In the edge of Cu pillar, side wall wetting reaction was detected, which was confirmed by the formation of voids and (Cu, Ni)6Sn5 phase. Further, as the bump diameter decreased, the side wall wetting reaction aggravated, which partly contributed to the acceleration of IMC growth.

Reduced graphene oxide (RGO) thin film was used to improve the performance of a low-temperature bonding process based on Cu microcones and Sn/Cu bumps (diameter: 25 μm), which has potential applications in high-density packaging. Under bonding conditions of a weight of 1500 g applied to each wafer for 10 min at a temperature of 120 °C, and incorporating a thin RGO layer, a compact bonding structure was obtained without interface voids. The RGO interlayer served as a barrier against interatomic diffusion of metals under zero applied pressure, and the formation of intermetallic compounds at the interface was thereby effectively reduced after bonding. Probable mechanisms for this bonding process are discussed. The investigation used standard 25 μm-diameter Sn/Cu bumps to simulate realistic industrial production.

Infrared light, more than 50% of the solar light energy, is long-termly ignored in the photocatalysis field due to its low photon energy. Herein, infrared-light-responsive photoinduced carriers driver is first constructed taking advantage of pyroelectric effect for enhancing photocatalytic hydrogen evolution. In order to give full play to its role, the photocatalytic reaction is localized on the surface and interface of the composite based on a new semi-immersion type heat collected photocatalytic microfiber system. The system is consisted of distinctive pyroelectric substrate poly(vinylidene fluoride-co-hexafluropropylene (PVDF-HFP), typical photothermal material carbon nanotube (CNT), and representative photocatalyst CdS. The transient photocurrent, electrochemical impedance spectroscopy, time-resolved photoluminescence and pyroelectric potential characterizations indicate that the infrared-light-responsive carriers driver significantly promotes the photogenerated charge separation, accelerates carrier migration, and prolongs carrier lifetime. The photocatalytic hydrogen evolution efficiency is remarkably improved more than five times with the highest average apparent quantum yield of 16.9%. It may open up new horizons to photocatalytic technology for the more efficient use of infrared light.

In multi-view three-dimensional reconstruction of objects, the accuracy of the image segmentation plays a key role in the accuracy of the model. The traditional Convolutional Neural Network segmentation method often leads to significant feature losses in the target’s edges. It also requires a lot of data for training. Therefore, this paper proposes an improved U-Net method for sequence image segmentation. To begin with, the U-Net structure is used as the basis to solve the problem of feature position information loss and to improve the precision of the edges of segmented objects. Next, multi-scale convolution modules are added on the basis of U-Net structure to increase the network depth and improve feature extraction capability. Then the batch normalization layer is added to solve the problem of vanishing gradient and to accelerate the speed of converged network. Finally, a heat-map channel is added in the input data to prevent errors of classification in similar areas. The experimental results showed that this method ranks higher than the classical U-Net on key indicators, Fl-score and IOU. It can effectively improve the segmentation accuracy, yielding results similar to those of manual segmentation.

Graphene is a promising candidate in analog electronics with projected operation frequency well into the terahertz range. In contrast to the intrinsic cutoff frequency (fT) of 427 GHz, the maximum oscillation frequency (fmax) of graphene device still remains at low level, which severely limits its application in radio frequency amplifiers. Here, we develop a novel transfer method for chemical vapor deposition graphene, which can prevent graphene from organic contamination during the fabrication process of the devices. Using a self-aligned gate deposition process, the graphene transistor with 60 nm gate length exhibits a record high fmax of 106 and 200 GHz before and after de-embedding, respectively. This work defines a unique pathway to large-scale fabrication of high-performance graphene transistors, and holds significant potential for future application of graphene-based devices in ultra high frequency circuits.

Selecting suitable barrier layer material is one of the crucial issues for solder microbump in advanced interconnect metallization. In this work, the inhibiting effect of two barriers, Co-W and Ni, on tin whisker growth in high temperature and humidity environment (55 °C/85% RH) were studied. Low-cost electrodeposition was conducted to prepare the 200 nm amorphous Co-W barrier layer on Cu substrate. Compared with the Ni barrier layer, the amorphous Co-W barrier layer can effectively reduce the formation of intermetallic compounds during the storage process, suppressing the growth of tin whiskers and oxidative corrosion. Based on experimental results and inner stress calculation, the mitigation mechanisms of tin whisker growth within the two barrier layers were proposed, respectively, which are of great importance to further understand the behavior of tin whisker mitigation.

A non-uniform copper oxide layer with several hundred nanometers thick was observed covering the surface of 10 μm-diameter Cu/SnAg microbump. Tin whiskers were also found to form on the weak spots of this copper oxide layer, where were localized stress relief centers. The HRTEM results reveal the existence of twin grain boundary between tin whisker and neighboring grain. Numerous dislocations at the twin boundary provide paths for the tin atoms to slip into tin whisker. It is the first time that the existence of copper oxide layer and the relationship between copper oxide layer and tin whiskers growth was studied and revealed in micron-level bumps. This present study has significant meaning for 3D electronic packaging as small size microbumps become increasingly prevalent and in which, surface diffusion becomes more important.

In this paper, the effect of reflow time on shear property of Sn-9Zn solder bumps was studied. The Sn-9Zn solder bumps were prepared by two step electroplating method. With the increase of reflow time, the shear strength decreased first and then increased. The change of shear strength was closely related to the formation of intermetallic compounds (IMCs). Scanning electron microscope (SEM) and Energy dispersive spectrometer (EDS) were used to analyze the composition and morphology of IMCs. The results indicated that IMCs were thickening with increasing reflow time and the morphology was flat, while IMCs thickness decreased and the morphology became fluctuant and unconsolidated when the reflow time extended to 20 min. The change trend of the shear strength was consistent with that of IMCs thickness. In addition, bumps fracture occurred inside the solders and dimples were observed on the fracture surface, which indicated that the solder bumps still had good ductility after reflow.

O 2 plasma treatment was performed on the JSR THB-430N negative UV photoresist to modify the surface wettability for micro-bumps electrodepositing. Wettability of photoresist was enhanced after O 2 plasma treatment. The samples were placed for different time at room temperature. Micro-FTIR indicated that the hydroxyl groups were introduced on the surface of photoresist after O 2 plasma surface treatment, meanwhile, the change of surface roughness and morphology was measured by atomic force microscopy. The results of contact angle between photoresist and test liquid showed that the wettability reduced with the increase of time after O 2 plasma treatment. The best wettability which had the minimum contact angle existed within a short period after O 2 plasma treatment. The combination of proper surface morphology and more hydroxyl groups are the reasons for photoresist to have better wettability. The mechanism of the aging effect on wettability was also discussed.

A novel low-temperature solid-state bonding method that Cu microcones coated with Ag and Ag buffer has been proposed. Thin Ag layer was used to prevent the oxidation of Cu microcones and Ag layer of several micrometers was used as a buffer layer between Cu microcones and Cu bumps. No brittle IMCs formed in the interfaces.

Defect engineering in heterostructured carbon-based electrode materials has evolved as an emerging strategy to boost the electrocatalytic activity. Herein, a facile single-step route is reported to synthesize novel N-coordinated bimetal doped graphitic carbon (Mn/Co-NGC). The formation of M(Mn, Co)-N-C in the catalyst (Mn/Co-NGC) significantly accelerated the triiodide reduction reaction (IRR) and hydrogen evolution reaction (HER). The electrocatalyst provided the synergistic effect of bimetal (Mn, Co)-N active-sites within graphitic-carbon framework, which promoted the conductivity and efficient charge transfer via multiple channels to enhance the IRR and HER. Therefore, as IRR electrocatalyst, Mn/Co-NGC equipped solar-cell attained a superior effi-ciency of 8.05% compared to Pt (6.82%). The electrocatalyst also exhibited an impressive potential towards HER, providing a low overpoential of 116 mV at 10 mA cm(-2) and Tafel slope of 58 mV dec(-1). Moreover, Mn/Co-NGC based solar-cell demonstrated superior stability with 99% efficiency retention (7.96% / 8.05%) after 50 redox-cycles for IRR, and a negligible change in overpotential after 1000 CV cycles. The intrinsic catalytic mechanism of electrocatalysts is studied by insighting their electronic structures, work functions, bonding, and ion-adsorption behaviors, using first-principle DFT-calculations. The current study leads towards designing highly efficient and cost-effective multifunctional electrocatalysts for advanced energy conversion technologies.