High quality Nb films were successfully prepared on both flexible polyimide(PI)and rigid Al2O3substrates and their transport properties were systematically studied at various applied currents,external magnetic fields,...High quality Nb films were successfully prepared on both flexible polyimide(PI)and rigid Al2O3substrates and their transport properties were systematically studied at various applied currents,external magnetic fields,and sample orientations.It is found that a curved Nb/PI film exhibits quite different superconducting transition and vortex dynamics compared to the flat Nb/Al2O3film.For the curved Nb/PI film,smooth superconducting transitions were obtained at low currents,while unexpected cascade structures were revealed in theρ(T)curves at high currents.We attribute this phenomenon to the gradient distribution of vortex density together with a variation of superconductivity along the curved film.In addition,reentrant superconductivity was induced in the curved Nb/PI thin film by properly choosing the measurement conditions.We attribute this effect to the vortex pinning from both in-plane vortices and out-of-plane vortices.This work reveals the complex transport properties of curved superconducting thin films,providing important insights for further theoretical investigations and practical developments of flexible superconductors.展开更多
In cases of high radiation emergencies,we propose a surface contamination monitor(SCM)that can quickly measure and pinpoint the contamination distribution in the affected population.Thick gaseous electron multiplier(T...In cases of high radiation emergencies,we propose a surface contamination monitor(SCM)that can quickly measure and pinpoint the contamination distribution in the affected population.Thick gaseous electron multiplier(THGEM)has several advantages,including fast response time and good spatial resolution.Based on new THGEMs,a two-dimensional imaging detector was developed for alpha detection,with a position resolution greater than 3 mm.The detector design and test results are described in this paper.Fast radiation imaging SCMs,with a 40mm×40 mm sensitive area,are currently under development.展开更多
We report the direct measurements of conductivity and mobility in millimeter-sized single-crystalline graphene on SiO2/Si via van der Pauw geometry by using a home-designed four-probe scanning tunneling microscope（4P...We report the direct measurements of conductivity and mobility in millimeter-sized single-crystalline graphene on SiO2/Si via van der Pauw geometry by using a home-designed four-probe scanning tunneling microscope（4P-STM）. The gate-tunable conductivity and mobility are extracted from standard van der Pauw resistance measurements where the four STM probes contact the four peripheries of hexagonal graphene flakes, respectively. The high homogeneity of transport properties of the single-crystalline graphene flake is confirmed by comparing the extracted conductivities and mobilities from three setups with different geometry factors. Our studies provide a reliable solution for directly evaluating the entire electrical properties of graphene in a non-invasive way and could be extended to characterizing other two-dimensional materials.展开更多
Some color centers in diamond can serve as quantum bits which can be manipulated with microwave pulses and read out with laser,even at room temperature.However,the photon collection efficiency of bulk diamond is great...Some color centers in diamond can serve as quantum bits which can be manipulated with microwave pulses and read out with laser,even at room temperature.However,the photon collection efficiency of bulk diamond is greatly reduced by refraction at the diamond/air interface.To address this issue,we fabricated arrays of diamond nanostructures,differing in both diameter and top end shape,with HSQ and Cr as the etching mask materials,aiming toward large scale fabrication of single-photon sources with enhanced collection efficiency made of nitrogen vacancy（NV） embedded diamond.With a mixture of O2 and CHF3 gas plasma,diamond pillars with diameters down to 45 nm were obtained.The top end shape evolution has been represented with a simple model.The tests of size dependent single-photon properties confirmed an improved single-photon collection efficiency enhancement,larger than tenfold,and a mild decrease of decoherence time with decreasing pillar diameter was observed as expected.These results provide useful information for future applications of nanostructured diamond as a single-photon source.展开更多
Silicene is a promising 2D Dirac material as a building block for van der Waals heterostructures （vdWHs）. Here we investigate the electronic properties of hexagonal boron nitride/silicene （BN/Si） vdWHs using first...Silicene is a promising 2D Dirac material as a building block for van der Waals heterostructures （vdWHs）. Here we investigate the electronic properties of hexagonal boron nitride/silicene （BN/Si） vdWHs using first-principles calculations. We calculate the energy band structures of BN/Si/BN heterostructures with different rotation angles and find that the electronic properties of silicene are retained and protected robustly by the BN layers. In BN/Si/BN/Si/BN heterostructure, we find that the band structure near the Fermi energy is sensitive to the stacking configurations of the silicene layers due to in- terlayer coupling. The coupling is reduced by increasing the number of BN layers between the silicene layers and becomes negligible in BN/Si/（BN）3/Si/BN. In （BN）n/Si superlattices, the band structure undergoes a conversion from Dirac lines to Dirac points by increasing the number of BN layers between the silicene layers. Calculations of silicene sandwiched by other 2D materials reveal that silicene sandwiched by low-carbon-doped boron nitride or HfO2 is semiconducting.展开更多
The neuromorphic systems for sound perception is under highly demanding for the future bioinspired electronics and humanoid robots.However,the sound perception based on volume,tone and timbre remains unknown.Herein,or...The neuromorphic systems for sound perception is under highly demanding for the future bioinspired electronics and humanoid robots.However,the sound perception based on volume,tone and timbre remains unknown.Herein,organic optoelectronic synapses(OOSs)are constructed for unprecedented sound recognition.The volume,tone and timbre of sound can be regulated appropriately by the input signal of voltages,frequencies and light intensities of OOSs,according to the amplitude,frequency,and waveform of the sound.The quantitative relation between recognition factor(ζ)and postsynaptic current(I=I_(light)−I_(dark))is established to achieve sound perception.Interestingly,the bell sound for University of Chinese Academy of Sciences is recognized with an accuracy of 99.8%.The mechanism studies reveal that the impedance of the interfacial layers play a critical role in the synaptic performances.This contribution presents unprecedented artificial synapses for sound perception at hardware levels.展开更多
By employing the asymmetric end-group engineering,an asymmetric nonfused-ring electron acceptor(NFREA)was designed and synthesized.Compared with the symmetric analogs(NoCA-17 and NoCA-18),NoCA-19 possesses broader lig...By employing the asymmetric end-group engineering,an asymmetric nonfused-ring electron acceptor(NFREA)was designed and synthesized.Compared with the symmetric analogs(NoCA-17 and NoCA-18),NoCA-19 possesses broader light absorption range,more coplanarπ-conjugated backbone,and appropriate crystallinity according to the experimental and theoretical results.The organic solar cells based on J52:NoCA-19 exhibited a power conversion efficiency as high as 12.26%,which is much higher than those of J52:NoCA-17(9.50%)and J52:NoCA-18(11.77%),mainly due to more efficient exciton dissociation,better and balanced charge mobility,suppressed recombination loss,shorter charge extraction time,longer charge carrier lifetimes,and more favorable blend film morphology.These findings demonstrate the great potential of asymmetric end-group engineering in exploring low-cost and high-performance NFREAs.展开更多
Topological photonics has received extensive attention from researchers because it provides brand new physical principles to manipulate light.Band topology is characterized using the Berry phase defined by Bloch state...Topological photonics has received extensive attention from researchers because it provides brand new physical principles to manipulate light.Band topology is characterized using the Berry phase defined by Bloch states.Until now,the scheme for experimentally probing the topological phase transition of band topology has always been relatively lacking in topological physics.Moreover,radiation topology can be aroused by the far-field polarization singularities of Bloch states,which is described by the Stokes phase.Although such two types of topologies are both related to Bloch states on the band structures,it is rather surprising that their development is almost independent.Here,in optical analogs of the quantum spin Hall effects(QSHEs)and Su-Schrieffer-Heeger model,we reveal the correlation between the phase transition of band topology and radiation topology and then demonstrate that the radiation topology can be employed to study the band topological transition.We experimentally demonstrate such an intriguing phenomenon in optical analogs of QSHEs.Our findings not only provide an insightful understanding of band topology and radiation topology,but also can serve as a route to manipulate light.展开更多
The electron microscope provides numerous insights into physics, from demonstrations of fundamental quantummechanical principles to the physics of imaging and materials. It reveals the atomic and electronic structure ...The electron microscope provides numerous insights into physics, from demonstrations of fundamental quantummechanical principles to the physics of imaging and materials. It reveals the atomic and electronic structure of key regionssuch as defects and interfaces. We can learn the underlying physics governing properties, and gain insight into how tosynthesize new materials with improved properties. Some recent advances and possible future directions are discussed.展开更多
Comprehensive Summary By employing thiazole and 4-chlorothiazole as the A′units,two A-D-A′-D-A type nonfused-ring electron acceptors(NFREAs)Tz-H and Tz-Cl were designed and synthesized.Replacing thiazole in Tz-H wit...Comprehensive Summary By employing thiazole and 4-chlorothiazole as the A′units,two A-D-A′-D-A type nonfused-ring electron acceptors(NFREAs)Tz-H and Tz-Cl were designed and synthesized.Replacing thiazole in Tz-H with 4-chlorothiazole can not only remarkably shorten the synthetic route through C—H direct arylation but also enhance molecular planarity with the simultaneous incorporation of S…N and S…Cl noncovalently conformational locks(NoCLs).The photovoltaic devices based on PM6:Tz-Cl exhibited a power conversion efficiency as high as 11.10%,much higher than that of PM6:Tz-H(6.41%),mainly due to more efficient exciton dissociation,better and more balanced carrier mobility,less charge recombination,and more favorable morphology.These findings demonstrate the great potential of NoCLs in achieving low-cost and high-performance NFREAs.展开更多
The rapid development of electronic devices such as organic field-effect transistors(OFETs)and solar cells makes the research and development of electronic transport materials imminent.The acceptor-acceptortype(Aà...The rapid development of electronic devices such as organic field-effect transistors(OFETs)and solar cells makes the research and development of electronic transport materials imminent.The acceptor-acceptortype(AàA-type)conjugated n-type polymer semiconductors have caught much attention due to the outstanding advantages on excellent electron-accepting capabilities,the precise adjustment of energy levels and the mass production at low fabrication cost.This article systematically reviews the polymerization methods of AàA-type polymers and the recent advancements applied in OFETs and polymer solar cells(PSCs).The analyses of the synthesis and the relationship between device performances and polymer molecular structures may provide a constructive guidance for the further development of highperformance n-type polymer materials.展开更多
Three-dimensional(3D)vertical architecture transistors represent an important technological pursuit,which have distinct advantages in device integration density,operation speed,and power consumption.However,the fabric...Three-dimensional(3D)vertical architecture transistors represent an important technological pursuit,which have distinct advantages in device integration density,operation speed,and power consumption.However,the fabrication processes of such 3D devices are complex,especially in the interconnection of electrodes.In this paper,we present a novel method which combines suspended electrodes and focused ion beam(FIB)technology to greatly simplify the electrodes interconnection in 3D devices.Based on this method,we fabricate 3D vertical core-double shell structure transistors with ZnO channel and Al_(2)O_(3) gate-oxide both grown by atomic layer deposition.Suspended top electrodes of vertical architecture could be directly connected to planar electrodes by FIB deposited Pt nanowires,which avoid cumbersome steps in the traditional 3D structure fabrication technology.Both single pillar and arrays devices show well behaved transfer characteristics with an Ion/Ioff current ratio greater than 106 and a low threshold voltage around 0 V.The ON-current of the 2×2 pillars vertical channel transistor was 1.2μA at the gate voltage of 3 V and drain voltage of 2 V,which can be also improved by increasing the number of pillars.Our method for fabricating vertical architecture transistors can be promising for device applications with high integration density and low power consumption.展开更多
The realization of active modulation of reflection phase based on metasurfaces is of great significance for flexible control of electromagnetic wavefront,which makes metasurfaces have practical application values in p...The realization of active modulation of reflection phase based on metasurfaces is of great significance for flexible control of electromagnetic wavefront,which makes metasurfaces have practical application values in polarization conversion,beam steering,metalens,etc.In this paper,a reflection phase tunable gap-surface plasmon(GSP)metasurface based on phase change materials Ge_(2)Sb_(2)Te_(5)(GST)is designed and experimentally demonstrated.By virtue of the characteristics of large permittivities difference before and after GST phase transition and the existence of stable intermediate states,the continuous modulation of near-infrared reflection phase larger than 200°has been realized.At the same time,through the reasonable design of the structure sizes,the reflection has been maintained at about 0.4 and basically does not change with the GST phase transition,which improved the working efficiency of the metasurface significantly.In addition,the coupled-mode theory(CMT)is introduced to make a full analysis of the modulation mechanism of the reflection phase,which proves that the phase transition of GST can induce the transition of metasurface working state from overcoupling mode to critical coupling mode.The improvement of the metasurface working efficiency has practical values for wavefront modulation.展开更多
M_(3)A_(2)X phases,named 321 phases,are an atypical series of MAX phases featuring in the MA-triangular-prism bilayers,with the A=As/P,exhibiting excellent elastic properties.This work systematically studies the therm...M_(3)A_(2)X phases,named 321 phases,are an atypical series of MAX phases featuring in the MA-triangular-prism bilayers,with the A=As/P,exhibiting excellent elastic properties.This work systematically studies the thermal expansion properties of 321 phases.We found their average linear thermal expansion coefficients(TECs),α_(L)=5-6μK^(–1),are the lowest among the reported values of MAX phases.The lowest average TEC was found in Nb_(3)As_(2)C(αa=4.46(4)μK^(–1),αc=5.09(4)μK–1,αL=5.09(4)μK–1).The average TEC and anisotropy factor(αc/αa)of Nb_(3)As_(2)C and Nb_(3)P_(2)C were lower than the ones of the corresponding 211 phases.The best isotropy performance was found in Nb_(3)P_(2)C (αc/αa=1.11).Moreover,our first-principles calculations demonstrate that the weaker chemical bonding between Nb-As/P than Nb-C induces thermal expansion in M_(3)A_(2)X phases.Furthermore,a relatively weaker anharmonic effect in 321 phases than in the 211 phases was revealed by the as-calculated average Grüneisen parameters,which account for the lower TECs in 321 phases.The low TECs and enhanced thermal isotropy make 321 phases outstanding among MAX phases,which could be sound candidates for varying-temperature structural-functional components.展开更多
Dimeric fused-ring electron acceptors(DFREAs)have attracted much attention due to the combined advantages of their monomeric and polymeric acceptors,including a well-defined molecular structure,excellent repeatability...Dimeric fused-ring electron acceptors(DFREAs)have attracted much attention due to the combined advantages of their monomeric and polymeric acceptors,including a well-defined molecular structure,excellent repeatability,and stable morphology.However,the additionally introduced single-bonds during dimerization may result in a twisted backbone of DFREAs,which is detrimental to intermolecular packing and charge transport.Herein,three DFREAs are designed and synthesized,in which DFREA conformations were systematically tuned via adjusting the intensities of intramolecular noncovalent interactions(INIs)to achieve high-performance organic solar cells(OSCs).Theoretical and experimental results show that the gradual introduction of S…F INIs can continuously improve molecular planarity and rigidity,resulting in reduced reorganization energies,ordered packing mode,and enhanced crystallization of DFREAs.Benefiting from the incorporation of fourfold S…F INIs,DYF-TF-based binary OSCs show a record high efficiency of 18.26%with an extremely low energy loss(0.493 eV)for DFREAbased OSCs.In addition,DYF-TF-based OSCs exhibited good long-term stability with a T_(80%)lifetime of 2681 h,and the power conversion efficiency of the DYF-TF-based ternary device is further enhanced to 18.73%.This contribution demonstrates the great potential of the INIs strategy in achieving excellent DFREAs materials.展开更多
Twin boundaries(TBs)in transition metal dichalcogenides(TMDs)constitute distinctive one dimensional electronic systems,exhibiting intriguing physical and chemical properties that have garnered significant attention in...Twin boundaries(TBs)in transition metal dichalcogenides(TMDs)constitute distinctive one dimensional electronic systems,exhibiting intriguing physical and chemical properties that have garnered significant attention in the fields of quantum physics and electrocatalysis.However,the controlled manipula-tion of TBs in terms of density and specific atomic configurations remains a fomidable challenge.In this study,we present a non-epitaxial growth approach that enables the controlled and large scale fabrication of homoge-neous catalytically active TBs in monolayer TMDs on arbitrary substrates.Notably,the density achieved using this strategy is six times higher than that observed in convention chemical vapor deposition(CVD)-grown sam-ples.Through rigorous experimental analysis and multigrain Wulff construc tion simulations,we elucidate theroleof regulating themetal source diffusion process,which serves as the key factor for inducing the self-oriented growth ofTMD grains and the formation of unified TBs.Furthermore,we demonstrate that this novel growth mode can be readily incorporated into the conventional CVD growth method by making a simple modification of the growth tempera-ture profle,thereby offering a universal approach for engineering of grain boundaries in two-dimensional materials.展开更多
Reducing the ever-growing level of CO_(2)in the atmosphere is critical for the sustainable development of human society in the context of global warming.Integration of the capture and upgrading of CO_(2)is,therefore,h...Reducing the ever-growing level of CO_(2)in the atmosphere is critical for the sustainable development of human society in the context of global warming.Integration of the capture and upgrading of CO_(2)is,therefore,highly desirable since each process step is costly,both energetically and economically.Here,we report a CO_(2)direct air capture(DAC)and fixation process that produces methane.Low concentrations of CO_(2)(∼400 ppm)in the air are captured by an aqueous solution of sodium hydroxide to form carbonate.The carbonate is subsequently hydrogenated to methane,which is easily separated from the reaction system,catalyzed by TiO2-supported Ru in the aqueous phase with a selectivity of 99.9%among gas-phase products.The concurrent regenerated hydroxide,in turn,increases the alkalinity of the aqueous solution for further CO_(2)capture,thereby enabling this one-ofits-kind continuous CO_(2)capture and methanation process.Engineering simulations demonstrate the energy feasibility of this CO_(2)DAC and methanation process,highlighting its promise for potential largescale applications.展开更多
Two-dimensional semiconductors(2DSCs)with appropriate band gaps and high mobilities are highly desired for future-generation electronic and optoelectronic applications.Here,using first-principles calculations,we repor...Two-dimensional semiconductors(2DSCs)with appropriate band gaps and high mobilities are highly desired for future-generation electronic and optoelectronic applications.Here,using first-principles calculations,we report a novel class of 2DSCs,group-11-chalcogenide monolayers(M_(2)X,M=Cu,Ag,Au;X=S,Se,Te),featuring with a broad range of energy band gaps and high carrier mobilities.Their energy band gaps extend from 0.49 to 3.76 eV at a hybrid density functional level,covering from ultraviolet-A,visible light to near-infrared region,which are crucial for broadband photoresponse.Significantly,the calculated room-temperature carrier mobilities of the M_(2)X monolayers are as high as thousands of cm^(2)·V^(-1)·s^(-1).Particularly,the carrier mobilities ofε-Au_(2)Se and e-Au2Te are up to 104 cm^(2)·V^(-1)·s^(-1),which is very attracitive for electronic devices.Benefitting from the broad range of energy band gaps and superior carrier mobilities,the group-11-chalcogenide M_(2)X monolayers are promising candidates for future-generation nanoelectronics and optoelectronics.展开更多
We use Z-contrast imaging and atomically resolved electron energy-loss spectroscopy on an aberration-corrected scanning transmission electron microscope to investigate the local electronic states of boron atoms at dif...We use Z-contrast imaging and atomically resolved electron energy-loss spectroscopy on an aberration-corrected scanning transmission electron microscope to investigate the local electronic states of boron atoms at different edge structures in monolayer and bilayer h-BN.We find that edges with bonding unsaturated sp2 boron atoms have a unique spectroscopic signature with a prominent pre-peak at - 190.2 eV in the B K-edge fine structure.First-principles calculations reveal that the observed pre-peak arises from excitations to the in-plane lowest-energy empty sp2 boron dangling bonds at the B-terminated edge.This spectroscopic signature can serve as a fingerprint to explore new edge structures in h-BN.展开更多
We report systematic in-plane magnetoresistance measurements on the electron-doped cuprate La2-x,.CexCuO4±δ thin films as a function of Ce doping and oxygen content in the magnetic field up to 14 T. A crossover ...We report systematic in-plane magnetoresistance measurements on the electron-doped cuprate La2-x,.CexCuO4±δ thin films as a function of Ce doping and oxygen content in the magnetic field up to 14 T. A crossover from negative to positive magnetoresistance occurs between the doping level x = 0.07 and 0.08. Above x = 0.08, the positive magnetoresistance effect appears, and is almost indiscernible at x = 0.15. By tuning the oxygen content, the as-grown samples show negative magnetoresistance effect, whereas the optimally annealed ones display positive magnetoresistance effect at the doping level x = 0.15. Intriguingly, a linear-field dependence of in-plane magnetoresistanee is observed at the underdoping level x = 0.06, the optimal doping level x = 0. i and slightly overdoping level x = 0.11. These anomalies of in-plane magnetoresistance may be related to the intrinsic inhomogeneity in the cuprates, which is discussed in the framework of network model.展开更多
基金Project supported by the National Key Basic Research Program of China(Grant Nos.2021YFA0718700,2018YFB0704102,2017YFA0303003,2017YFA0302902,2016YFA0300301,and 2021YFA0718802)the National Natural Science Foundation of China(Grant Nos.11927808,11834016,118115301,119611410,11961141008,61727805+5 种基金11961141002)the Key Research Program of Frontier Sciences,Chinese Academy of Sciences(CAS)(Grant Nos.QYZDB-SSW-SLH008 and QYZDY-SSW-SLH001)CAS Interdisciplinary Innovation Team,the Strategic Priority Research Program(B)of CAS(Grant Nos.XDB25000000and XDB33000000)the Beijing Natural Science Foundation(Grant No.Z190008)the Key-Area Research and Development Program of Guangdong Province,China(Grant No.2020B0101340002)the support from the China Postdoctoral Science Foundation(Grant No.2022M711497)。
文摘High quality Nb films were successfully prepared on both flexible polyimide(PI)and rigid Al2O3substrates and their transport properties were systematically studied at various applied currents,external magnetic fields,and sample orientations.It is found that a curved Nb/PI film exhibits quite different superconducting transition and vortex dynamics compared to the flat Nb/Al2O3film.For the curved Nb/PI film,smooth superconducting transitions were obtained at low currents,while unexpected cascade structures were revealed in theρ(T)curves at high currents.We attribute this phenomenon to the gradient distribution of vortex density together with a variation of superconductivity along the curved film.In addition,reentrant superconductivity was induced in the curved Nb/PI thin film by properly choosing the measurement conditions.We attribute this effect to the vortex pinning from both in-plane vortices and out-of-plane vortices.This work reveals the complex transport properties of curved superconducting thin films,providing important insights for further theoretical investigations and practical developments of flexible superconductors.
基金supported by the China Institute of Atomic Energy and University of Chinese Academy of SciencesNational Natural Science Foundation of China(Nos.11575193 and U1732266)+2 种基金Key Research Program of Frontier Sciences,CAS(No.QYZDB-SSWSLH039)the Youth Innovation Promotion Association of CAS(No.2016153)the Natural Science Key Foundation of Guangxi(No.2015GXNSFDA139002)
文摘In cases of high radiation emergencies,we propose a surface contamination monitor(SCM)that can quickly measure and pinpoint the contamination distribution in the affected population.Thick gaseous electron multiplier(THGEM)has several advantages,including fast response time and good spatial resolution.Based on new THGEMs,a two-dimensional imaging detector was developed for alpha detection,with a position resolution greater than 3 mm.The detector design and test results are described in this paper.Fast radiation imaging SCMs,with a 40mm×40 mm sensitive area,are currently under development.
基金supported by the Science Fund from the Ministry of Science and Technology of China(Grant No.2013CBA01600)the National Key Research&Development Project of China(Grant No.2016YFA0202300)+1 种基金the National Natural Science Foundation of China(Grant Nos.61474141,61674170,61335006,61390501,51325204,and 51210003)the Chinese Academy of Sciences(CAS) and Youth Innovation Promotion Association of CAS(Grant No.20150005)
文摘We report the direct measurements of conductivity and mobility in millimeter-sized single-crystalline graphene on SiO2/Si via van der Pauw geometry by using a home-designed four-probe scanning tunneling microscope（4P-STM）. The gate-tunable conductivity and mobility are extracted from standard van der Pauw resistance measurements where the four STM probes contact the four peripheries of hexagonal graphene flakes, respectively. The high homogeneity of transport properties of the single-crystalline graphene flake is confirmed by comparing the extracted conductivities and mobilities from three setups with different geometry factors. Our studies provide a reliable solution for directly evaluating the entire electrical properties of graphene in a non-invasive way and could be extended to characterizing other two-dimensional materials.
基金Project supported by the National Key Research and Development Plan of China(Grant No.2016YFA0200402)the National Natural Science Foundation of China(Grants Nos.11574369,11574368,91323304,11174362,and 51272278)the FP7 Marie Curie Action(project No.295208)sponsored by the European Commission
文摘Some color centers in diamond can serve as quantum bits which can be manipulated with microwave pulses and read out with laser,even at room temperature.However,the photon collection efficiency of bulk diamond is greatly reduced by refraction at the diamond/air interface.To address this issue,we fabricated arrays of diamond nanostructures,differing in both diameter and top end shape,with HSQ and Cr as the etching mask materials,aiming toward large scale fabrication of single-photon sources with enhanced collection efficiency made of nitrogen vacancy（NV） embedded diamond.With a mixture of O2 and CHF3 gas plasma,diamond pillars with diameters down to 45 nm were obtained.The top end shape evolution has been represented with a simple model.The tests of size dependent single-photon properties confirmed an improved single-photon collection efficiency enhancement,larger than tenfold,and a mild decrease of decoherence time with decreasing pillar diameter was observed as expected.These results provide useful information for future applications of nanostructured diamond as a single-photon source.
基金Project supported by the National Key Research and Development Program of China(Grant No.2016YFA0202300)the National Natural Science Foundation of China(Grant Nos.61390501 and 61471337)+2 种基金the National Basic Research Program of China(Grant No.2013CBA01600)the CAS Pioneer Hundred Talents Programthe Beijing Nova Program,China(Grant No.Z181100006218023)
文摘Silicene is a promising 2D Dirac material as a building block for van der Waals heterostructures （vdWHs）. Here we investigate the electronic properties of hexagonal boron nitride/silicene （BN/Si） vdWHs using first-principles calculations. We calculate the energy band structures of BN/Si/BN heterostructures with different rotation angles and find that the electronic properties of silicene are retained and protected robustly by the BN layers. In BN/Si/BN/Si/BN heterostructure, we find that the band structure near the Fermi energy is sensitive to the stacking configurations of the silicene layers due to in- terlayer coupling. The coupling is reduced by increasing the number of BN layers between the silicene layers and becomes negligible in BN/Si/（BN）3/Si/BN. In （BN）n/Si superlattices, the band structure undergoes a conversion from Dirac lines to Dirac points by increasing the number of BN layers between the silicene layers. Calculations of silicene sandwiched by other 2D materials reveal that silicene sandwiched by low-carbon-doped boron nitride or HfO2 is semiconducting.
基金supported by the NSFC(51925306 and 21774130)National Key R&D Program of China(2018FYA 0305800)+2 种基金Key Research Program of the Chinese Academy of Sciences(XDPB08-2)the Strategic Priority Research Program of Chinese Academy of Sciences(XDB28000000)University of Chinese Academy of Sciences.
文摘The neuromorphic systems for sound perception is under highly demanding for the future bioinspired electronics and humanoid robots.However,the sound perception based on volume,tone and timbre remains unknown.Herein,organic optoelectronic synapses(OOSs)are constructed for unprecedented sound recognition.The volume,tone and timbre of sound can be regulated appropriately by the input signal of voltages,frequencies and light intensities of OOSs,according to the amplitude,frequency,and waveform of the sound.The quantitative relation between recognition factor(ζ)and postsynaptic current(I=I_(light)−I_(dark))is established to achieve sound perception.Interestingly,the bell sound for University of Chinese Academy of Sciences is recognized with an accuracy of 99.8%.The mechanism studies reveal that the impedance of the interfacial layers play a critical role in the synaptic performances.This contribution presents unprecedented artificial synapses for sound perception at hardware levels.
基金the financial support fromtheNSFC(21975055,U2001222,52103352,52120105006,and 51925306)National Key R&D Program of China(2018FYA 0305800)+2 种基金Key Research Program of Chinese Academy of Sciences(XDPB08-2)the Youth Innovation Promotion Association of Chinese Academy of Sciences(2022165)the Fundamental Research Funds for the Central Universities.DFT results described in this article were obtained from the National Supercomputing Centre in Shenzhen(Shenzhen Cloud Computing Centre).
文摘By employing the asymmetric end-group engineering,an asymmetric nonfused-ring electron acceptor(NFREA)was designed and synthesized.Compared with the symmetric analogs(NoCA-17 and NoCA-18),NoCA-19 possesses broader light absorption range,more coplanarπ-conjugated backbone,and appropriate crystallinity according to the experimental and theoretical results.The organic solar cells based on J52:NoCA-19 exhibited a power conversion efficiency as high as 12.26%,which is much higher than those of J52:NoCA-17(9.50%)and J52:NoCA-18(11.77%),mainly due to more efficient exciton dissociation,better and balanced charge mobility,suppressed recombination loss,shorter charge extraction time,longer charge carrier lifetimes,and more favorable blend film morphology.These findings demonstrate the great potential of asymmetric end-group engineering in exploring low-cost and high-performance NFREAs.
基金National Key Research and Development Program of China(2021YFA1400700)National Natural Science Foundation of China(12321004,12234003).
文摘Topological photonics has received extensive attention from researchers because it provides brand new physical principles to manipulate light.Band topology is characterized using the Berry phase defined by Bloch states.Until now,the scheme for experimentally probing the topological phase transition of band topology has always been relatively lacking in topological physics.Moreover,radiation topology can be aroused by the far-field polarization singularities of Bloch states,which is described by the Stokes phase.Although such two types of topologies are both related to Bloch states on the band structures,it is rather surprising that their development is almost independent.Here,in optical analogs of the quantum spin Hall effects(QSHEs)and Su-Schrieffer-Heeger model,we reveal the correlation between the phase transition of band topology and radiation topology and then demonstrate that the radiation topology can be employed to study the band topological transition.We experimentally demonstrate such an intriguing phenomenon in optical analogs of QSHEs.Our findings not only provide an insightful understanding of band topology and radiation topology,but also can serve as a route to manipulate light.
文摘The electron microscope provides numerous insights into physics, from demonstrations of fundamental quantummechanical principles to the physics of imaging and materials. It reveals the atomic and electronic structure of key regionssuch as defects and interfaces. We can learn the underlying physics governing properties, and gain insight into how tosynthesize new materials with improved properties. Some recent advances and possible future directions are discussed.
基金the National Natural Science Foundation of China((52120105006,52103352,and 51925306)National Key R&D Program of China(2018FYA 0305800)+3 种基金Key Research Program of Chinese Academy of Sciences(XDPB08-2)the Strategic Priority Research Program of Chinese Academy of Sciences(XDB28000000)the Youth Innovation Promotion Association of Chinese Academy of Sciences(2022165)the Fundamental Research Funds for the Central Universities.DFT results described in this report were obtained from the National Supercomputing Center in Shenzhen(Shenzhen CloudComputing Center).
文摘Comprehensive Summary By employing thiazole and 4-chlorothiazole as the A′units,two A-D-A′-D-A type nonfused-ring electron acceptors(NFREAs)Tz-H and Tz-Cl were designed and synthesized.Replacing thiazole in Tz-H with 4-chlorothiazole can not only remarkably shorten the synthetic route through C—H direct arylation but also enhance molecular planarity with the simultaneous incorporation of S…N and S…Cl noncovalently conformational locks(NoCLs).The photovoltaic devices based on PM6:Tz-Cl exhibited a power conversion efficiency as high as 11.10%,much higher than that of PM6:Tz-H(6.41%),mainly due to more efficient exciton dissociation,better and more balanced carrier mobility,less charge recombination,and more favorable morphology.These findings demonstrate the great potential of NoCLs in achieving low-cost and high-performance NFREAs.
基金the financial support from the Natural Science Foundation of Beijing Municipality(2192059)the National Natural Science Foundation of China(21673059,21774130 and 51925306)+4 种基金the National Key R&D Program of China(2018FYA0305800)the Key Research Program of Frontier Sciences,CAS(QYZDB-SSW-JSC046)the Key Research Program of the Chinese Academy of Sciences(XDPB08-2)the Strategic Priority Research Program of Chinese Academy of Sciences(XDB28000000)the International Partnership Program of Chinese Academy of Sciences(211211KYSB20170014)。
文摘The rapid development of electronic devices such as organic field-effect transistors(OFETs)and solar cells makes the research and development of electronic transport materials imminent.The acceptor-acceptortype(AàA-type)conjugated n-type polymer semiconductors have caught much attention due to the outstanding advantages on excellent electron-accepting capabilities,the precise adjustment of energy levels and the mass production at low fabrication cost.This article systematically reviews the polymerization methods of AàA-type polymers and the recent advancements applied in OFETs and polymer solar cells(PSCs).The analyses of the synthesis and the relationship between device performances and polymer molecular structures may provide a constructive guidance for the further development of highperformance n-type polymer materials.
基金the National Key Research and Development Program of China(Grant Nos.2016YFA0200400 and 2016YFA0200800)the National Natural Science Foundation of China(Grant Nos.61888102,12074420,and 11674387)+1 种基金Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB33000000)Key Research Program of Frontier Sciences,Chinese Acdemy of Sciences(Grant No.QYZDJ-SSWSLH042).
文摘Three-dimensional(3D)vertical architecture transistors represent an important technological pursuit,which have distinct advantages in device integration density,operation speed,and power consumption.However,the fabrication processes of such 3D devices are complex,especially in the interconnection of electrodes.In this paper,we present a novel method which combines suspended electrodes and focused ion beam(FIB)technology to greatly simplify the electrodes interconnection in 3D devices.Based on this method,we fabricate 3D vertical core-double shell structure transistors with ZnO channel and Al_(2)O_(3) gate-oxide both grown by atomic layer deposition.Suspended top electrodes of vertical architecture could be directly connected to planar electrodes by FIB deposited Pt nanowires,which avoid cumbersome steps in the traditional 3D structure fabrication technology.Both single pillar and arrays devices show well behaved transfer characteristics with an Ion/Ioff current ratio greater than 106 and a low threshold voltage around 0 V.The ON-current of the 2×2 pillars vertical channel transistor was 1.2μA at the gate voltage of 3 V and drain voltage of 2 V,which can be also improved by increasing the number of pillars.Our method for fabricating vertical architecture transistors can be promising for device applications with high integration density and low power consumption.
基金the National Key Research and Development Program of China(Grant Nos.2016YFA0200400,2016YFA0200800,and 2016YFA0300601)the National Natural Science Foundation of China(Grant Nos.61888102,11674387,11974386,and 61905274)the Strategic Priority Research Program and Key Research Program of Frontier Sciences of Chinese Academy of Sciences(Grant Nos.XDB33000000,XDB28000000,and QYZDJ-SSW-SLH042).
文摘The realization of active modulation of reflection phase based on metasurfaces is of great significance for flexible control of electromagnetic wavefront,which makes metasurfaces have practical application values in polarization conversion,beam steering,metalens,etc.In this paper,a reflection phase tunable gap-surface plasmon(GSP)metasurface based on phase change materials Ge_(2)Sb_(2)Te_(5)(GST)is designed and experimentally demonstrated.By virtue of the characteristics of large permittivities difference before and after GST phase transition and the existence of stable intermediate states,the continuous modulation of near-infrared reflection phase larger than 200°has been realized.At the same time,through the reasonable design of the structure sizes,the reflection has been maintained at about 0.4 and basically does not change with the GST phase transition,which improved the working efficiency of the metasurface significantly.In addition,the coupled-mode theory(CMT)is introduced to make a full analysis of the modulation mechanism of the reflection phase,which proves that the phase transition of GST can induce the transition of metasurface working state from overcoupling mode to critical coupling mode.The improvement of the metasurface working efficiency has practical values for wavefront modulation.
基金financially supported by the National Science Foundation for Young Scientists of China(No.51902055)the Natural Science Foundation of Fujian Province(No.2021J011077)the Fuzhou Science and Technology Plan Project(No.2021-P-049).
文摘M_(3)A_(2)X phases,named 321 phases,are an atypical series of MAX phases featuring in the MA-triangular-prism bilayers,with the A=As/P,exhibiting excellent elastic properties.This work systematically studies the thermal expansion properties of 321 phases.We found their average linear thermal expansion coefficients(TECs),α_(L)=5-6μK^(–1),are the lowest among the reported values of MAX phases.The lowest average TEC was found in Nb_(3)As_(2)C(αa=4.46(4)μK^(–1),αc=5.09(4)μK–1,αL=5.09(4)μK–1).The average TEC and anisotropy factor(αc/αa)of Nb_(3)As_(2)C and Nb_(3)P_(2)C were lower than the ones of the corresponding 211 phases.The best isotropy performance was found in Nb_(3)P_(2)C (αc/αa=1.11).Moreover,our first-principles calculations demonstrate that the weaker chemical bonding between Nb-As/P than Nb-C induces thermal expansion in M_(3)A_(2)X phases.Furthermore,a relatively weaker anharmonic effect in 321 phases than in the 211 phases was revealed by the as-calculated average Grüneisen parameters,which account for the lower TECs in 321 phases.The low TECs and enhanced thermal isotropy make 321 phases outstanding among MAX phases,which could be sound candidates for varying-temperature structural-functional components.
基金support from the National Nature Science Foundation of China(grant nos.51925306,52103352,52120105006)National Key R&D Program of China(grant no.2018FYA 0305800)+3 种基金Key Research Program of Chinese Academy of Sciences(grant no.XDPB08-2)the Strategic Priority Research Program of Chinese Academy of Sciences(grant no.XDB28000000)the Youth Innovation Promotion Association of Chinese Academy of Sciences(grant no.2022165)the Fundamental Research Funds for the Central Universities.DFT results described in this article were obtained from the National Supercomputing Center in Shenzhen(Shenzhen Cloud Computing Center).
文摘Dimeric fused-ring electron acceptors(DFREAs)have attracted much attention due to the combined advantages of their monomeric and polymeric acceptors,including a well-defined molecular structure,excellent repeatability,and stable morphology.However,the additionally introduced single-bonds during dimerization may result in a twisted backbone of DFREAs,which is detrimental to intermolecular packing and charge transport.Herein,three DFREAs are designed and synthesized,in which DFREA conformations were systematically tuned via adjusting the intensities of intramolecular noncovalent interactions(INIs)to achieve high-performance organic solar cells(OSCs).Theoretical and experimental results show that the gradual introduction of S…F INIs can continuously improve molecular planarity and rigidity,resulting in reduced reorganization energies,ordered packing mode,and enhanced crystallization of DFREAs.Benefiting from the incorporation of fourfold S…F INIs,DYF-TF-based binary OSCs show a record high efficiency of 18.26%with an extremely low energy loss(0.493 eV)for DFREAbased OSCs.In addition,DYF-TF-based OSCs exhibited good long-term stability with a T_(80%)lifetime of 2681 h,and the power conversion efficiency of the DYF-TF-based ternary device is further enhanced to 18.73%.This contribution demonstrates the great potential of the INIs strategy in achieving excellent DFREAs materials.
基金National Key R&D Program of China(2018YFA0305800)Natural Science Foundation of China(51872285)+6 种基金Beijing Outstanding Young Scientist Program(BJJWZYJ H01201914430039)CAS Project for Young Scientists in Basic Research(YSBR-003)Fundamental Research Funds for the Central UniversitiesNational Key R&D Program of China(2019YFA0705400)Natural Science Foundation of China(1221101035,12225205,22073048)computations were in part performed at the High-performance Computational Center at NUAASingapore Ministry of Education AcRF Tier 2(MOE2019-T2-2-105 and MOE-MOET2EP101210006)and AcRF Tier 1(RG7/21).
文摘Twin boundaries(TBs)in transition metal dichalcogenides(TMDs)constitute distinctive one dimensional electronic systems,exhibiting intriguing physical and chemical properties that have garnered significant attention in the fields of quantum physics and electrocatalysis.However,the controlled manipula-tion of TBs in terms of density and specific atomic configurations remains a fomidable challenge.In this study,we present a non-epitaxial growth approach that enables the controlled and large scale fabrication of homoge-neous catalytically active TBs in monolayer TMDs on arbitrary substrates.Notably,the density achieved using this strategy is six times higher than that observed in convention chemical vapor deposition(CVD)-grown sam-ples.Through rigorous experimental analysis and multigrain Wulff construc tion simulations,we elucidate theroleof regulating themetal source diffusion process,which serves as the key factor for inducing the self-oriented growth ofTMD grains and the formation of unified TBs.Furthermore,we demonstrate that this novel growth mode can be readily incorporated into the conventional CVD growth method by making a simple modification of the growth tempera-ture profle,thereby offering a universal approach for engineering of grain boundaries in two-dimensional materials.
基金the Natural Science Foundation of China(grant nos.21725301,21932002,21821004,91645115,51872008,22172183,22172150,and 22222306)the National Key R&D Program of China(grant nos.2017YFB060220 and 2021YFA-1502804)+3 种基金the Beijing Outstanding Young Scientists Projects(grant nos.BJJWZYJH01201910005018 and BJJWZYJH01201914430039)the Strategic Priority Research Program of the Chinese Academy of Science(grant no.XDB0450102)the K.C.Wong Education Foundation(grant no.GJTD-2020-15)the Innovation Program for Quantum Science and Technology(grant no.2021ZD0303302).
文摘Reducing the ever-growing level of CO_(2)in the atmosphere is critical for the sustainable development of human society in the context of global warming.Integration of the capture and upgrading of CO_(2)is,therefore,highly desirable since each process step is costly,both energetically and economically.Here,we report a CO_(2)direct air capture(DAC)and fixation process that produces methane.Low concentrations of CO_(2)(∼400 ppm)in the air are captured by an aqueous solution of sodium hydroxide to form carbonate.The carbonate is subsequently hydrogenated to methane,which is easily separated from the reaction system,catalyzed by TiO2-supported Ru in the aqueous phase with a selectivity of 99.9%among gas-phase products.The concurrent regenerated hydroxide,in turn,increases the alkalinity of the aqueous solution for further CO_(2)capture,thereby enabling this one-ofits-kind continuous CO_(2)capture and methanation process.Engineering simulations demonstrate the energy feasibility of this CO_(2)DAC and methanation process,highlighting its promise for potential largescale applications.
基金supported by the National Natural Science Foundation of China(No.61888102)the National Key Research and Development Projects of China(No.2016YFA0202300)+1 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB30000000)the Fundamental Research Funds for the Central Universities.
文摘Two-dimensional semiconductors(2DSCs)with appropriate band gaps and high mobilities are highly desired for future-generation electronic and optoelectronic applications.Here,using first-principles calculations,we report a novel class of 2DSCs,group-11-chalcogenide monolayers(M_(2)X,M=Cu,Ag,Au;X=S,Se,Te),featuring with a broad range of energy band gaps and high carrier mobilities.Their energy band gaps extend from 0.49 to 3.76 eV at a hybrid density functional level,covering from ultraviolet-A,visible light to near-infrared region,which are crucial for broadband photoresponse.Significantly,the calculated room-temperature carrier mobilities of the M_(2)X monolayers are as high as thousands of cm^(2)·V^(-1)·s^(-1).Particularly,the carrier mobilities ofε-Au_(2)Se and e-Au2Te are up to 104 cm^(2)·V^(-1)·s^(-1),which is very attracitive for electronic devices.Benefitting from the broad range of energy band gaps and superior carrier mobilities,the group-11-chalcogenide M_(2)X monolayers are promising candidates for future-generation nanoelectronics and optoelectronics.
基金supported by the National Key R&D Program of China (No.2018 YFA0305800)the National Natural Science Foundation of China (Nos.51622211 and 51872284)+2 种基金the CAS Key Research Program of Frontier Sciences,the CAS Pioneer Hundred Talents Program,and Beijing Nova Program (No.Z181100006218023)supported by U.S.Department of Energy grant DE-FG02-09ER46554the McMinn Endowment.
文摘We use Z-contrast imaging and atomically resolved electron energy-loss spectroscopy on an aberration-corrected scanning transmission electron microscope to investigate the local electronic states of boron atoms at different edge structures in monolayer and bilayer h-BN.We find that edges with bonding unsaturated sp2 boron atoms have a unique spectroscopic signature with a prominent pre-peak at - 190.2 eV in the B K-edge fine structure.First-principles calculations reveal that the observed pre-peak arises from excitations to the in-plane lowest-energy empty sp2 boron dangling bonds at the B-terminated edge.This spectroscopic signature can serve as a fingerprint to explore new edge structures in h-BN.
基金supported by the National Key Basic Research Program of China (Grant Nos. 2015CB921000, and 2016YFA0300301)the National Natural Science Foundation of China (Grant Nos. 11674374, and 11474338)the Key Research Program of Frontier Sciences, Chinese Academy of Sciences (Grant No. QYZDB-SSW-SLH008)
文摘We report systematic in-plane magnetoresistance measurements on the electron-doped cuprate La2-x,.CexCuO4±δ thin films as a function of Ce doping and oxygen content in the magnetic field up to 14 T. A crossover from negative to positive magnetoresistance occurs between the doping level x = 0.07 and 0.08. Above x = 0.08, the positive magnetoresistance effect appears, and is almost indiscernible at x = 0.15. By tuning the oxygen content, the as-grown samples show negative magnetoresistance effect, whereas the optimally annealed ones display positive magnetoresistance effect at the doping level x = 0.15. Intriguingly, a linear-field dependence of in-plane magnetoresistanee is observed at the underdoping level x = 0.06, the optimal doping level x = 0. i and slightly overdoping level x = 0.11. These anomalies of in-plane magnetoresistance may be related to the intrinsic inhomogeneity in the cuprates, which is discussed in the framework of network model.
