查看更多>>摘要：Silver(Ag)paste is widely used in semiconductor metallization,especially in silicon solar cells.Ag powder is the material with the highest proportion in Ag paste.The morphology and structure of Ag powder are crucial which determine its characteristics,especially for the sintering activity.In this work,a simple method was developed to synthesize a type of microcrystalline spherical Ag particles(SP-A)with internal pores and the structural changes and sintering behavior were thoroughly studied by combining ultra-small-angle X-ray scattering(USAXS),small-angle X-ray scattering(SAXS),in-situ heating X-ray diffraction(XRD),focused ion beam(FIB),and thermal analysis measurement.Due to the unique internal pores,the grain size of SP-A is smaller,and the coefficient of thermal expansion(CTE)is higher than that of traditional solid Ag particles.As a result,the sintering activity of SP-A is excellent,which can form a denser sintered body and form silver nanoparticles at the Ag-Si interface to improve silver silicon contact.Polycrystalline silicon solar cell built with SP-A obtained a low series resistance(Rs)and a high photoelectric conversion efficiency(PCE)of 19.26％.These fill a gap in Ag particle structure research,which is significant for the development of high-performance electronic Ag particles and efficient semiconductor devices.
查看更多>>摘要：Electron energy dissipation is an important energy dissipation pathway that cannot be ignored in friction process.Two-dimensional zeolite imidazole frameworks(2D ZIFs)and fluorine doping strategies give 2D Zn-ZIF and 2D Co-ZIF unique electrical properties,making them ideal materials for studying electron energy dissipation mechanism.In this paper,based on the superlubricity modulation of 2D fluoridated ZIFs,the optimal tribological properties are obtained on the 2D F-Co-ZIF surface,with the friction coefficient as low as 0.0010.Electrical experiments,density functional theory(DFT)simulation,and fluorescence detection are used to explain the mechanism of fluorine doping regulation of tribological properties from the two stages,namely energy transfer and energy release.Specifically,the energy will transfer into the friction system through the generation of electron-hole pairs under an external excitation,and release by radiation and non-radiation energy dissipation channels.Fluorination reduces energy transfer by altering the electronic properties and band structures of ZIFs,and slows down the charge transfer by enhancing the shielding efficiency,thus slowing the non-radiative energy dissipation rate during the energy release stage.Our insights not only help us better understand the role of fluorine doping in improving tribological properties,but also provide a new way to further explore the electron energy dissipation pathway during friction.
查看更多>>摘要：Two-dimensional transition metal chalcogenides(2D-TMDs)have attracted much attention because of their unique layered structure and physical properties for transistor applications.Mechanically transferred metal contacts on these low-dimensional materials or their homogeneous and heterogeneous multilayers have generated huge interest to avoid deposition damages.In this paper,we show that there are large physical gaps at both the edge contact and surface contact between the transferred electrodes and the 2D materials.A method called laser shock induced superplastic deformation(LSISD)is proposed to tackle this issue and enhance the performance of the transistors.The enhancement mechanism was investigated by molecular dynamics(MD)simulations of the nanoforming process,atomic force microscopy(AFM),scanning electron microscopy(SEM),transmission electron microscopy(TEM)characterizations of the interfaces,and density functional theory(DFT)modeling.The force effect of laser shock can reduce the contact gap between metals and semiconductors.The electrical performances of the transistors before and after LSISD,along with MD simulations,are used to find the optimal process parameters.In addition,this paper applies the LSISD method to the short-channel MoS2/graphene vertical transistors to show potential improvement in interface contact and electrical properties.This paper demonstrates the first report on using mechanical force induced by laser shock to enhance metal-semiconductor interfaces and transistor performances.
查看更多>>摘要：Two-dimensional(2D)molybdenum disulfide(MoS2)holds great potential for various applications such as electronic devices,catalysis,lubrication,anti-corrosion and so on.Thermal evaporation is a versatile thin film deposition technique,however,the conventional thermal evaporation techniques face challenges in producing uniform thin films of MoS2 due to its high melting temperature of 1375 ℃.As a result,only thick and rough MoS2 films can be obtained using these methods.To address this issue,we have designed a vacuum thermal evaporation system specifically for large-scale preparation of MoS2 thin films.By using K2MoS4 as the precursor,we achieved reliable deposition of uniform polycrystalline MoS2 thin films with a size of 50 mm x 50 mm and controllable thickness ranging from 0.8 to 2.4 nm.This approach also allows for patterned deposition of MoS2 using shadow masks and sequential deposition of MoS2 and tungsten disulfide(WS2),similar to conventional thermal evaporation techniques.Moreover,we have demonstrated the potential applications of the obtained MoS2 thin films in field effect transistors(FETs),memristors and electrocatalysts for hydrogen evolution reaction(HER).
查看更多>>摘要：As a very promising epitaxy technology,the remote epitaxy has attracted extensive attention in recent years,in which graphene is the most used interlayer material.As an isomorphic of graphene,two-dimensional(2D)hexagonal boron nitride(h-BN),is another promising interlayer for the remote epitaxy.However,there is a current debate on the feasibility of using h-BN as interlayer in the remote epitaxy.Herein,we demonstrate that the potential field of sapphire can completely penetrate monolayer h-BN,and hence the remote epitaxy of ZrS2 layers can be realized on sapphire substrates through monolayer h-BN.The field of sapphire can only partially penetrate the bilayer h-BN and result in the mixing of remote epitaxy and van der Waals(vdWs)epitaxy.Due to the weak interfacial scattering and high crystalline quality of ZrS2 epilayer,the ZrS2 photodetector with monolayer h-BN shows the best performance,with an on/off ratio of more than 2 × 105 and a responsivity up to 379 mA·W-1.This work provides an efficient approach to prepare single-crystal transition metal dichalcogenides and their heterojunctions with h-BN,which have great potential in developing large-area 2D electronic devices.
查看更多>>摘要：The van der Waals heterostructures have evolved as novel materials for complementing the Si-based semiconductor technologies.Group-10 noble metal dichalcogenides(e.g.,PtS2,PtSe2,PdS2,and PdSe2)have been listed into two-dimensional(2D)materials toolkit to assemble van der Waals heterostructures.Among them,PdSe2 demonstrates advantages of high stability in air,high mobility,and wide tunable bandgap.However,the regulation of p-type doping of PdSe2 remains unsolved problem prior to fabricating p-n junction as a fundamental platform of semiconductor physics.Besides,a quantitative method for the controllable doping of PdSe2 is yet to be reported.In this study,the doping level of PdSe2 was correlated with the concentration of Lewis acids,for example,SnCl4,used for soaking.Considering the transfer characteristics,the threshold voltage(the gate voltage corresponding to the minimum drain current)increased after SnCl4 soaking treatment.PdSe2 transistors were soaked in SnCl4 solutions with five different concentrations.The threshold voltages from the as-obtained transfer curves were extracted for linear fitting to the threshold voltage versus doping concentration correlation equation.This study provides in-depth insights into the controllable p-type doping of PdSe2.It may also push forward the research of the regulation of conductivity behaviors of 2D materials.
查看更多>>摘要：Moire superlattices,arising from the controlled twisting of van der Waals homostructures at specific angles,have emerged as a promising platform for quantum emission applications.Concurrently,the manipulation of strain provides a versatile strategy to finely adjust electronic band structures,enhance exciton luminescence efficiency,and establish a robust foundation for two-dimensional quantum light sources.However,the intricate interplay between strain and moiré potential remains partially unexplored.Here,we introduce a meticulously designed fusion of strain engineering and the twisted 2L-WSe2/2L-WSe2 homobilayers,resulting in the precise localization of moiré excitons.Employing low-temperature photoluminescence spectroscopy,we unveil the emergence of highly localized moiré-enhanced emission,characterized by the presence of multiple distinct emission lines.Furthermore,our investigation demonstrates the effective regulation of moiré potential depths through strain engineering,with the potential depths of strained and unstrained regions differing by 91％.By combining both experimental and theoretical approaches,our study elucidates the complex relationship between strain and moiré potential,thereby opening avenues for generating strain-induced moiré exciton single-photon sources.
查看更多>>摘要：Two-dimensional(2D)tungsten selenide(WSe2)is promising candidate material for future electronic applications,owing to its potential for ultimate device scaling.For improving the electronic performance of WSe2-based field-effect transistors(FETs),the modification of surface properties is essential.In this study,the seamless structural phase transition in WSe2 lattice is achieved by soft oxygen plasma,regulating the electrical conductance of WSe2-based FETs.We found that during the soft oxygen plasma treatment with optimal processing time,the generated oxygen ions can substitute some selenium atoms and thus locally modify the bond length,inducing 2H → 1T phase transition in WSe2 with seamless interfaces.The mosaic structures have been proven to tailor the electronic structure and increase the hole carrier concentration inside WSe2,significantly increasing the channel conductance of WSe2 FETs.With the further increase of the oxygen plasma treatment time,the creation of more selenium vacancy defects leads to the electronic doping,resulting in the reduction of conductance.Benefiting from the hexagonal boron nitride(h-BN)encapsulation to interrupt the partial structural relaxation from 1T to 2H phase,our WSe2 FET exhibits high electronic stability with conductance of 6.8 × 10-4 S,which is about four orders of magnitude higher than 2H WSe2(5.8 × 10-8 S).This study could further broaden the WSe2 FETs in applications for functionalization and integration in electronics.
查看更多>>摘要：The appropriate catalysts can accelerate the reaction rate and effectively boost the efficient conversion of various molecules,which is of great importance in the study of chemistry,chemical industry,energy,materials and environmental science.Therefore,efficient,environmentally friendly,and easy to operate synthesis methods have been used to prepare various types of catalysts.Although previous studies have reported the synthesis and characterization of the aforementioned catalysts,more still remain in trial and error methods,without in-depth consideration and improvement of traditional synthesis methods.Here,we comprehensively summarize and compare the preparation methods of the trial-and-error synthesis strategy,structure-activity relationships and density functional theory(DFT)guided catalysts rational design for nanomaterials and atomically dispersed catalysts.We also discuss in detail the utilization of the nanomaterials and single atom catalysts for converting small molecules(H2O,O2,CO2,N2,etc.)into value-added products driven by electrocatalysis,photocatalysis,and thermocatalysis.Finally,the challenges and outlooks of mass preparation and production of efficient and green catalysts through conventional trial and error synthesis and DFT theory are featured in accordance with its current development.
查看更多>>摘要：In the green energy and carbon-neutral technology,electrochemical energy storage devices have received continuously increasing attention recently.However,due to the unavoidable volume expansion/shrinkage of key materials or irreversible mechanical damages during application,the stability of energy storage and delivery as well as the lifetime of these devices are severely shortened,leading to serious performance degradation or even safety issues.Therefore,the utilization of self-healable gels into electrochemical energy storage devices,such as electrodes,binders,and electrolytes,is proven as an effective method to realize long-term stable operation of these devices via the self-repairing of mechanical and electrochemical characteristics.Herein,this review first summarizes the feature and fabrication of different gels,paying special attention to hydrogels,organohydrogels,and ionogels.Then,basic concepts and figure of merit of self-healable gels are analyzed with a detailed discussion at the healing mechanisms,from reversible dynamic bonds to physical molecular diffusion,and to external healing trigger.Then we introduce all the important parts of electrochemical energy storage devices,which could be replaced by healable gels to enhance the durability,including electrodes,binders,and electrolytes.Finally,the critical challenges and future perspectives regarding the future development of healable gels based high-performance electrochemical energy storage devices or electronics are provided.
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