Low dimensional materials are suitable candidates applying in next-generation high-performance electronic,optoelectronic,and energy storage devices because of their uniquely physical and chemical properties.In particu...Low dimensional materials are suitable candidates applying in next-generation high-performance electronic,optoelectronic,and energy storage devices because of their uniquely physical and chemical properties.In particular,one-dimensional(1D)atomic wires(AWs)exfoliating from 1D van der Waals(vdW)bulks are more promising in next generation nanometer(nm)even sub-nm device applications owing to their width of few-atoms scale and free dandling bonds states.Although several 1D AWs have been experimentally prepared,few 1D AW candidates could be practically applied in devices owing to lack of enough suitable 1D AWs.Herein,367 kinds of 1D AWs have been screened and the corresponding computational database including structures,electronic structures,magnetic states,and stabilities of these 1D AWs has been organized and established.Among these systems,unary and binary 1D AWs with relatively small exfoliation energy are thermodynamically stable and theoretically feasible to be exfoliated.More significantly,rich quantum states emerge,such as 1D semiconductors,1D metals,1D semimetals,and 1D magnetism.This database will offer an ideal platform to further explore exotic quantum states and exploit practical device applications using 1D materials.The database are openly available at http://www.dx.doi.org/10.11922/sciencedb.j00113.00004.展开更多
Niobium is sputtered onto a single crystalline silicon substrate in N2：Ar=4：1 gas mixture at the total pressure of 2 Pa. The temperature coefficient of resistance of the sample is about 0.5% at 30OK, and up to 7% at...Niobium is sputtered onto a single crystalline silicon substrate in N2：Ar=4：1 gas mixture at the total pressure of 2 Pa. The temperature coefficient of resistance of the sample is about 0.5% at 30OK, and up to 7% at 77K, indicating the possibility of using it to make room-temperature bolometers with performances better than those based on Pt, Bi, or Nb. For a 60-nm-thick sample, the rms surface roughness is 0.45nm over an area of 2 μm × 2 μm. Analyses based on x-ray diffraction and x-ray photoelectronic spectroscopy indicate that the samples are Nb5N6 thin films in which there is a combination of Nb^3＋ and Nb^5＋, or Nb^4＋.展开更多
In this paper the decrease in the Hurst exponent of human gait with aging and neurodegenerative diseases was observed by using an improved rescaled range （R/S） analysis method. It indicates that the long-range corre...In this paper the decrease in the Hurst exponent of human gait with aging and neurodegenerative diseases was observed by using an improved rescaled range （R/S） analysis method. It indicates that the long-range correlations of gait rhythm from young healthy people are stronger than those from the healthy elderly and the diseased. The result further implies that fractal dynamics in human gait will be altered due to weakening or impairment of neural control on locomotion resulting from aging and neurodegenerative diseases. Due to analysing short-term data sequences rather than long datasets required by most nonlinear methods, the algorithm has the characteristics of simplicity and sensitivity, most importantly, fast calculation as well as powerful anti-noise capacities. These findings have implications for modelling locomotor control and also for quantifying gait dynamics in varying physiologic and pathologic states.展开更多
In this paper, the authors present the transmission line (TL) realization of one-dimensional subwavelength resonator formed by a pair of conventional right-handed material (RHM) and left-handed material (LHM). In such...In this paper, the authors present the transmission line (TL) realization of one-dimensional subwavelength resonator formed by a pair of conventional right-handed material (RHM) and left-handed material (LHM). In such resonator, a novel reso- nant mode with the resonant frequency depending on the length ratio of the RH/LH TL sections occurs as a consequence of the full phase compensation due to the backward wave in the LH TL section. The theoretical circuit-model analyses are supported by simulation and experimental evidence on resonators with different RH/LH length ratios.展开更多
As a potential flexible substrate for flexible electronics, a polymer-sandwiched ultra-thin silicon platform is stud- ied. SU-8 photoresist coated on the silicon membrane improves its flexibility as shown by an ANSYS ...As a potential flexible substrate for flexible electronics, a polymer-sandwiched ultra-thin silicon platform is stud- ied. SU-8 photoresist coated on the silicon membrane improves its flexibility as shown by an ANSYS simulation. Using the plasma enhanced chemical vapor deposited Si02/Si3N4 composite film as an etching mask, a 4＂ silicon- （100） wafer is thinned to 26[tm without rupture in a 30wt.% KOH solution. The thinned wafer is coated on both sides with 20 pm of SU-8 photoresist and is cut into strips. Then the strips are bent by a caliper to measure its bending radius. A sector model of bending deformation is adopted to estimate the radius of curvature. The determined minimal bending radius of the polymer-sandwiched ultra-thin silicon layer is no more than 3.3mm. The fabrication process of this sandwich structure can be used as a post-fabrication process for high performance flexible electronics.展开更多
ZnO（002） films with different thicknesses ranging from 7 to 300 nm were grown on sapphire（006） substrates via metal-organic chemical vapor deposition （MOCVD）. The two-dimensional（2D） planar layer and the three...ZnO（002） films with different thicknesses ranging from 7 to 300 nm were grown on sapphire（006） substrates via metal-organic chemical vapor deposition （MOCVD）. The two-dimensional（2D） planar layer and the three-dimensional（3D） island layer were studied by using of X-ray diffraction（XRD） rocking curves and atomic force microscopy （AFM）. The room temperature photoluminescence （PL） spectra show a blue shift of the peak positions of the uhraviolet（UV） emission with increasing film thickness. The blue shift is remarkably high（393-380 nm） when an increase in film thickness（7-15 nm） is accompanied by the change of structure from a 2D planar layer to a 3D island layer. The PL spectra at 77 K also indicate that there are different transition mechanisms in the film thickness from a 2D planar layer to a 3D island layer near the 2D layer region.展开更多
We investigate the photoinduced effects on the electronic structure for half-metallic ferromagnet CrO2 （Tc 390 K）, in which the conducting electrons are totally polarized, by using the LSDA＋U method. A significant ...We investigate the photoinduced effects on the electronic structure for half-metallic ferromagnet CrO2 （Tc 390 K）, in which the conducting electrons are totally polarized, by using the LSDA＋U method. A significant change is found for the band structure and the density of states （DOS） for CrO2 under photo-excitation, especially for the Cr 3dt2g band： disappearance of the spin-split band, suggesting collapse of the half-metallic state. We ascribe the change of electronic structure under photo-excitation to the wider one-electron band W via the strong hybridization of the down-spin Cr 3d and O 2p states. Furthermore we discuss the magnetic properties under photo-excitation.展开更多
An epitsucial γ-Mg2SiO4 thin film can be a good buffer between the Si substrate and some oxide thin films. For high temperature superconducting multilayer structures, hopefully it can be taken as an insulating layer ...An epitsucial γ-Mg2SiO4 thin film can be a good buffer between the Si substrate and some oxide thin films. For high temperature superconducting multilayer structures, hopefully it can be taken as an insulating layer to replace the widely used MgO film. To explore such possibilities, we carry out systematic studies on the influences of pressure and substrate temperature on the epitaxy of γ-Mg2SiO4 thin films grown on Si （100） substrates using rf magnetron sputtering with an Mg target of purity of 99.95 percent. With the substrate temperature kept at 500℃ and the pressure changing from lO Pa to 15 Pa, in the XRD spectra the 7-Mg2SiO4 （400） peak grows drastically while the MgO （200） peak is suppressed. Keeping the pressure at 15Pa and increasing the temperature from 500℃ to 570℃ further can improve the film epitaxy, while working at 780℃ and 11Pa seems to give very good results. X-ray photoelectronic spectroscopy and φ scan are used to characterize the stoichiometry, crystallinity, and in-plane growth of the samples.展开更多
The band structures of two-monolayer Bi（110） films on black phosphorus substrates are studied using angleresolved photoemission spectroscopy. Within the band gap of bulk black phosphorus, the electronic states near ...The band structures of two-monolayer Bi（110） films on black phosphorus substrates are studied using angleresolved photoemission spectroscopy. Within the band gap of bulk black phosphorus, the electronic states near the Fermi level are dominated by the Bi（110） film. The band dispersions revealed by our data suggest that the orientation of the Bi（110） film is aligned with the black phosphorus substrate. The electronic structures of the Bi（110） film strongly deviate from the band calculations of the free-standing Bi（110） film, suggesting that the substrate can significantly affect the electronic states in the Bi（110） film. Our data show that there are no non-trivial electronic states in Bi（110） films grown on black phosphorus substrates.展开更多
We recently proposed a flexible quantum secure direct communication protocol [Chin. Phys. Lett. 23 （2006） 3152]. By analyzing its security in the perfect channel from the aspect of quantum information theory, we fin...We recently proposed a flexible quantum secure direct communication protocol [Chin. Phys. Lett. 23 （2006） 3152]. By analyzing its security in the perfect channel from the aspect of quantum information theory, we find that an eavesdropper is capable of stealing all the information without being detected. Two typical attacks are presented to illustrate this point. A solution to this loophole is also suggested and we show its powerfulness against the most general individual attack in the ideal case. We also discuss the security in the imperfect case when there is noise and loss.展开更多
Cu-based electrocatalysts have become the focus in the field of electrochemical CO_(2) reduction reaction(ECO_(2) RR)due to their ability to produce multicarbon products.However,the research on generating single carbo...Cu-based electrocatalysts have become the focus in the field of electrochemical CO_(2) reduction reaction(ECO_(2) RR)due to their ability to produce multicarbon products.However,the research on generating single carbon products with higher economic feasibility via ECO_(2) RR based on Cu-based electrocatalysts is rather rare,and the roles of the surface architecture and oxides of the electrocatalysts have not been explained exactly.In this work,a two-step method including thermal oxidation and electroreduction is proposed to introduce Cuþinto pure Cu foil to form Cu_(2)O/Cu electrocatalyst.By regulating the surface composition and morphology of the electrocatalyst in this way,the activity of ECO 2 RR to C_(1) products has been greatly improved.The Faradaic efficiency of carbon products of the Cu_(2)O/Cu electrode reaches 84%at?0.7 V vs.RHE with good selectivity for HCOOH and CO.The current density of Cu_(2)O/Cu electrode reaches-12.21 mA cm^(2) at-0.8 V vs.RHE,which is much higher than that of the Cu foil electrode(?0.09 mA cm?2).In-situ Raman characterization shows that Cuþin Cu_(2)O/Cu electrode could inhibit hydrogen generation and promote ECO_(2) RR by stabilizing the adsorption of CO_(2).展开更多
With the analysis of experiment and theory on GaN HEMT devices under DC sweep,an improved model for kink effect based on advanced SPICE model for high electron mobility transistors(ASM-HEMT)is pro⁃posed,considering th...With the analysis of experiment and theory on GaN HEMT devices under DC sweep,an improved model for kink effect based on advanced SPICE model for high electron mobility transistors(ASM-HEMT)is pro⁃posed,considering the relationship between the drain/gate-source voltage and kink effect.The improved model can not only accurately describe the trend of the drain-source current with the current collapse and kink effect,but also precisely fit different values of drain-source voltages at which the kink effect occurs under different gatesource voltages.Furthermore,it well characterizes the DC characteristics of GaN devices in the full operating range,with the fitting error less than 3%.To further verify the accuracy and convergence of the improved model,a load-pull system is built in ADS.The simulated result shows that although both the original ASM-HEMT and the improved model predict the output power for the maximum power matching of GaN devices well,the im⁃proved model predicts the power-added efficiency for the maximum efficiency matching more accurately,with 4%improved.展开更多
In this paper, we present the electromagnetic analysis of a rectangular cavity partially filled with a left-handed material slab. Our theoretical investigation shows that there exist novel resonant modes in the cavity...In this paper, we present the electromagnetic analysis of a rectangular cavity partially filled with a left-handed material slab. Our theoretical investigation shows that there exist novel resonant modes in the cavity, and such a cavity becomes a subwavelength cavity. The eigenvalue equation of the cavity is derived and the resonant frequencies of the novel modes are calculated by using numerical simulation. We also discuss the stability of the novel resonant modes and show the best condition under which a useful rectangular cavity of subwavelength dimensions with tolerable stability is obtained.展开更多
Multifunctional lead-free double perovskites demonstrate remarkable potential towards applications in various fields.Herein,an environmentally-friendly,low-cost,high-throughput Cs_(2)NaFeCl_(6) single crystal with exc...Multifunctional lead-free double perovskites demonstrate remarkable potential towards applications in various fields.Herein,an environmentally-friendly,low-cost,high-throughput Cs_(2)NaFeCl_(6) single crystal with exceedingly high thermal stability is designed and grown.It obtains a cubic lattice system in the temperature range of 80-500 K,accompanied by a completely reversible chromatic variation ranging from yellow to black.Importantly,the intriguing thermochromism is proved to own extremely high reproducibility(over 1000 cycles)without a hysteretic effect,originating from its structural flexibility that including(i)the noteworthy distortion/deformation of[NaCl_(6)]5−and[FeCl_(6)]3−octahedra;(ii)order-disorder arrangement transition of[NaCl_(6)]5−and[FeCl6]3−octahedra as the function of temperature.This study paves the way towards a new class of smart windows and camouflage coatings with an unprecedented colour range based on a Cs_(2)NaFeCl_(6) perovskite.展开更多
The complex refractive indices and the dielectric function of GaN for frequencies ranging from 0.25 to 1.22THz are obtained using THz time-domain spectroscopy. The real part of the dielectric function first decreases ...The complex refractive indices and the dielectric function of GaN for frequencies ranging from 0.25 to 1.22THz are obtained using THz time-domain spectroscopy. The real part of the dielectric function first decreases from 0.25 to 0.42THz and then oscillates from 0.42 to 1.22THz, whereas the imaginary part of the dielectric function is oscillating within the whole range of frequency. The simple Drude model is extended to take into account the effect of defects on the dielectric function. The extended model is in agreement with the experimental data.展开更多
The dispersion properties in the short wavelength region of total internal reflective photonic crystal fiber(TIRPCF) in Compton scattering have been studied by using the model of the equivalent twin waveguide soliton ...The dispersion properties in the short wavelength region of total internal reflective photonic crystal fiber(TIRPCF) in Compton scattering have been studied by using the model of the equivalent twin waveguide soliton coupling, dispersion management solitons and effective refractive index. It is shown that the positive dispersion of the cladding waveguide of TIRPCF and the negative dispersion of its core waveguide are quickly increased by the square of the collision non-elastic composition between the electron and photons, and they are lessened by the increase of the electron absorption photon number. Under the one-photon nonlinear Compton scattering, the method of the compensated probing laser diffraction by the phase hole induced by the stationary pumping laser in the cladding waveguide enables the average dispersion value of TIRPCF to be close to zero, and the zero dispersion point quickly shifts to the short wavelength region.展开更多
A novel framework for parallel subgraph isomorphism on GPUs is proposed, named GPUSI, which consists of GPU region exploration and GPU subgraph matching. The GPUSI iteratively enumerates subgraph instances and solves ...A novel framework for parallel subgraph isomorphism on GPUs is proposed, named GPUSI, which consists of GPU region exploration and GPU subgraph matching. The GPUSI iteratively enumerates subgraph instances and solves the subgraph isomorphism in a divide-and-conquer fashion. The framework completely relies on the graph traversal, and avoids the explicit join operation. Moreover, in order to improve its performance, a task-queue based method and the virtual-CSR graph structure are used to balance the workload among warps, and warp-centric programming model is used to balance the workload among threads in a warp. The prototype of GPUSI is implemented, and comprehensive experiments of various graph isomorphism operations are carried on diverse large graphs. The experiments clearly demonstrate that GPUSI has good scalability and can achieve speed-up of 1.4–2.6 compared to the state-of-the-art solutions.展开更多
A simple technique is reported for fabricating the mesa structure on Bi2Sr2CaCu2O8+δ single crystal. In the patterning process, metal masks are used instead of photolithography and argon ion milling is applied to for...A simple technique is reported for fabricating the mesa structure on Bi2Sr2CaCu2O8+δ single crystal. In the patterning process, metal masks are used instead of photolithography and argon ion milling is applied to form the small mesa on the Bi2Sr2CaCu2O8+δ crystal surface. Real four-probe transport measurements are made on the mesa structure and typical c-axis current-voltage (I - V) characteristics of the intrinsic Josephson effect have been observed. The superconducting gap parameter can be extracted from the multi-branch structure in the I - V characteristics. Additionally, from the strong hysteresis in the I - V characteristics, the capacitance CJ of the unit intrinsic Josephson junction has been estimated to be 2.3pF, which is in good agreement with that evaluated from the geometric parameters of the unit junction between the two copper oxide layers.展开更多
After considering Kerr nonlinear effect, group velocity dispersion of host and gain distribution of active particle in laser amplifying medium, a basic equation describing propagation of the coupling optical pulse und...After considering Kerr nonlinear effect, group velocity dispersion of host and gain distribution of active particle in laser amplifying medium, a basic equation describing propagation of the coupling optical pulse under the multi-photon nonlinear Compton scattering in the laser amplifying medium has been deduced. Besides, the profile and power spectrum of a picosecond-level super-Gaussian coupling pulse in the laser amplifying medium have been discussed when its central frequency coincides with the gain peak frequency of the laser amplifying medium.展开更多
Since its discovery in 2011,the emerging family of two-dimensional(2D)transition metal carbides,nitrides,and carbonitrides(denoted as MXenes)has shown tremendous promise in the field of energy storages,especially elec...Since its discovery in 2011,the emerging family of two-dimensional(2D)transition metal carbides,nitrides,and carbonitrides(denoted as MXenes)has shown tremendous promise in the field of energy storages,especially electrochemical capacitors(ECs).The intercalation of foreign species,including but not limited to proton,cations,organic ions,and solvents,is demonstrated as one of the dominant facts during the energy storage process of MXenes,through which interlayer spacing of MXenes can be reversibly tuned,followed with reversible redox reactions on the surface of MXenes.Such a mechanism provides MXenes extremely high capacitance up to 1500 F cm-3,in aqueous acidic electrolyte.In addition,because of the versatile terminations on their surface,the intercalation of ions into MXenes can simultaneously induce the reversible transformation of their electronic structure to trigger some other phenomenon,for example,electrochromic effect,which has great potential on electrochromic smart window—an extended application of ECs.Accordingly,regulating and facilitating the intercalation in MXenes is of great significance for MXene-based ECs.In this review,we summarize the recent progress on the intercalation in MXenes towards ECs,discussing on the intercalated species,working mechanisms,and methods to promote the intercalation.Furthermore,we prospect the future research directions of intercalation of MXenes in ECs,such as the combination of simulation and experiment on finding the best intercalation species,precisely controlling the interlayer spacing and beyond,to boost the electrochemical performance of MXene toward practical applications and multi-functional devices.展开更多
基金the National Key Research and Development Program of China(Grant No.2017YFE0129000)the National Natural Science Foundation of China(Grant Nos.51871121,11874223,and 11404172).
文摘Low dimensional materials are suitable candidates applying in next-generation high-performance electronic,optoelectronic,and energy storage devices because of their uniquely physical and chemical properties.In particular,one-dimensional(1D)atomic wires(AWs)exfoliating from 1D van der Waals(vdW)bulks are more promising in next generation nanometer(nm)even sub-nm device applications owing to their width of few-atoms scale and free dandling bonds states.Although several 1D AWs have been experimentally prepared,few 1D AW candidates could be practically applied in devices owing to lack of enough suitable 1D AWs.Herein,367 kinds of 1D AWs have been screened and the corresponding computational database including structures,electronic structures,magnetic states,and stabilities of these 1D AWs has been organized and established.Among these systems,unary and binary 1D AWs with relatively small exfoliation energy are thermodynamically stable and theoretically feasible to be exfoliated.More significantly,rich quantum states emerge,such as 1D semiconductors,1D metals,1D semimetals,and 1D magnetism.This database will offer an ideal platform to further explore exotic quantum states and exploit practical device applications using 1D materials.The database are openly available at http://www.dx.doi.org/10.11922/sciencedb.j00113.00004.
文摘Niobium is sputtered onto a single crystalline silicon substrate in N2：Ar=4：1 gas mixture at the total pressure of 2 Pa. The temperature coefficient of resistance of the sample is about 0.5% at 30OK, and up to 7% at 77K, indicating the possibility of using it to make room-temperature bolometers with performances better than those based on Pt, Bi, or Nb. For a 60-nm-thick sample, the rms surface roughness is 0.45nm over an area of 2 μm × 2 μm. Analyses based on x-ray diffraction and x-ray photoelectronic spectroscopy indicate that the samples are Nb5N6 thin films in which there is a combination of Nb^3＋ and Nb^5＋, or Nb^4＋.
基金Project supported by the National Natural Science Foundation of China(Grant No60501003)
文摘In this paper the decrease in the Hurst exponent of human gait with aging and neurodegenerative diseases was observed by using an improved rescaled range （R/S） analysis method. It indicates that the long-range correlations of gait rhythm from young healthy people are stronger than those from the healthy elderly and the diseased. The result further implies that fractal dynamics in human gait will be altered due to weakening or impairment of neural control on locomotion resulting from aging and neurodegenerative diseases. Due to analysing short-term data sequences rather than long datasets required by most nonlinear methods, the algorithm has the characteristics of simplicity and sensitivity, most importantly, fast calculation as well as powerful anti-noise capacities. These findings have implications for modelling locomotor control and also for quantifying gait dynamics in varying physiologic and pathologic states.
基金Project supported by the National Basic Research Program (973) of China (No. 2004CB719800) and the Specialized Research Fund for the Doctoral Program of Higher Education (No. 20030284024)
文摘In this paper, the authors present the transmission line (TL) realization of one-dimensional subwavelength resonator formed by a pair of conventional right-handed material (RHM) and left-handed material (LHM). In such resonator, a novel reso- nant mode with the resonant frequency depending on the length ratio of the RH/LH TL sections occurs as a consequence of the full phase compensation due to the backward wave in the LH TL section. The theoretical circuit-model analyses are supported by simulation and experimental evidence on resonators with different RH/LH length ratios.
基金Supported by the State Scholarship Fund of Chinathe Open Research Fund of Shanghai Key Laboratory of Multidimensional Information Processing of East China Normal University
文摘As a potential flexible substrate for flexible electronics, a polymer-sandwiched ultra-thin silicon platform is stud- ied. SU-8 photoresist coated on the silicon membrane improves its flexibility as shown by an ANSYS simulation. Using the plasma enhanced chemical vapor deposited Si02/Si3N4 composite film as an etching mask, a 4＂ silicon- （100） wafer is thinned to 26[tm without rupture in a 30wt.% KOH solution. The thinned wafer is coated on both sides with 20 pm of SU-8 photoresist and is cut into strips. Then the strips are bent by a caliper to measure its bending radius. A sector model of bending deformation is adopted to estimate the radius of curvature. The determined minimal bending radius of the polymer-sandwiched ultra-thin silicon layer is no more than 3.3mm. The fabrication process of this sandwich structure can be used as a post-fabrication process for high performance flexible electronics.
基金Supported by the National Natural Science Foundation of China(Nos. 20071013 and 20301007).
文摘ZnO（002） films with different thicknesses ranging from 7 to 300 nm were grown on sapphire（006） substrates via metal-organic chemical vapor deposition （MOCVD）. The two-dimensional（2D） planar layer and the three-dimensional（3D） island layer were studied by using of X-ray diffraction（XRD） rocking curves and atomic force microscopy （AFM）. The room temperature photoluminescence （PL） spectra show a blue shift of the peak positions of the uhraviolet（UV） emission with increasing film thickness. The blue shift is remarkably high（393-380 nm） when an increase in film thickness（7-15 nm） is accompanied by the change of structure from a 2D planar layer to a 3D island layer. The PL spectra at 77 K also indicate that there are different transition mechanisms in the film thickness from a 2D planar layer to a 3D island layer near the 2D layer region.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10574071 and 10374041, the Key Project of Chinese Ministry of Education under Grant No 107051, and the Program for New Century Excellent Talents in Chinese University under Grant No NECT-04-045.
文摘We investigate the photoinduced effects on the electronic structure for half-metallic ferromagnet CrO2 （Tc 390 K）, in which the conducting electrons are totally polarized, by using the LSDA＋U method. A significant change is found for the band structure and the density of states （DOS） for CrO2 under photo-excitation, especially for the Cr 3dt2g band： disappearance of the spin-split band, suggesting collapse of the half-metallic state. We ascribe the change of electronic structure under photo-excitation to the wider one-electron band W via the strong hybridization of the down-spin Cr 3d and O 2p states. Furthermore we discuss the magnetic properties under photo-excitation.
文摘An epitsucial γ-Mg2SiO4 thin film can be a good buffer between the Si substrate and some oxide thin films. For high temperature superconducting multilayer structures, hopefully it can be taken as an insulating layer to replace the widely used MgO film. To explore such possibilities, we carry out systematic studies on the influences of pressure and substrate temperature on the epitaxy of γ-Mg2SiO4 thin films grown on Si （100） substrates using rf magnetron sputtering with an Mg target of purity of 99.95 percent. With the substrate temperature kept at 500℃ and the pressure changing from lO Pa to 15 Pa, in the XRD spectra the 7-Mg2SiO4 （400） peak grows drastically while the MgO （200） peak is suppressed. Keeping the pressure at 15Pa and increasing the temperature from 500℃ to 570℃ further can improve the film epitaxy, while working at 780℃ and 11Pa seems to give very good results. X-ray photoelectronic spectroscopy and φ scan are used to characterize the stoichiometry, crystallinity, and in-plane growth of the samples.
基金Supported by National Key R&D Program of China under Grant Nos 2017YFA0402901,2016YFA0401004 and 2016YFB0901600the National Natural Science Foundation of China under Grant Nos 11534010,11404172,U1532136,U1632102,U1632272,11574201,11674296 and 11190022+3 种基金the National Basic Research Program of China under Grant No 2014CB921102the Key Research Program of the Chinese Academy of Sciences under Grant Nos QYZDY-SSW-SLH021 and XDPB01the Interdisciplinary Innovation Team of Chinese Academy of Sciencesthe Initiative Scientific Research Program of Shanghai Jiao Tong University
文摘The band structures of two-monolayer Bi（110） films on black phosphorus substrates are studied using angleresolved photoemission spectroscopy. Within the band gap of bulk black phosphorus, the electronic states near the Fermi level are dominated by the Bi（110） film. The band dispersions revealed by our data suggest that the orientation of the Bi（110） film is aligned with the black phosphorus substrate. The electronic structures of the Bi（110） film strongly deviate from the band calculations of the free-standing Bi（110） film, suggesting that the substrate can significantly affect the electronic states in the Bi（110） film. Our data show that there are no non-trivial electronic states in Bi（110） films grown on black phosphorus substrates.
文摘We recently proposed a flexible quantum secure direct communication protocol [Chin. Phys. Lett. 23 （2006） 3152]. By analyzing its security in the perfect channel from the aspect of quantum information theory, we find that an eavesdropper is capable of stealing all the information without being detected. Two typical attacks are presented to illustrate this point. A solution to this loophole is also suggested and we show its powerfulness against the most general individual attack in the ideal case. We also discuss the security in the imperfect case when there is noise and loss.
基金supported by National Natural Science Foundation of China(No.52071183).
文摘Cu-based electrocatalysts have become the focus in the field of electrochemical CO_(2) reduction reaction(ECO_(2) RR)due to their ability to produce multicarbon products.However,the research on generating single carbon products with higher economic feasibility via ECO_(2) RR based on Cu-based electrocatalysts is rather rare,and the roles of the surface architecture and oxides of the electrocatalysts have not been explained exactly.In this work,a two-step method including thermal oxidation and electroreduction is proposed to introduce Cuþinto pure Cu foil to form Cu_(2)O/Cu electrocatalyst.By regulating the surface composition and morphology of the electrocatalyst in this way,the activity of ECO 2 RR to C_(1) products has been greatly improved.The Faradaic efficiency of carbon products of the Cu_(2)O/Cu electrode reaches 84%at?0.7 V vs.RHE with good selectivity for HCOOH and CO.The current density of Cu_(2)O/Cu electrode reaches-12.21 mA cm^(2) at-0.8 V vs.RHE,which is much higher than that of the Cu foil electrode(?0.09 mA cm?2).In-situ Raman characterization shows that Cuþin Cu_(2)O/Cu electrode could inhibit hydrogen generation and promote ECO_(2) RR by stabilizing the adsorption of CO_(2).
基金Supported by the National Key R&D Program of China(2022YFF0707800,2022YFF0707801)Primary Research&Development Plan of Jiangsu Province(BE2022070,BE2022070-2)。
文摘With the analysis of experiment and theory on GaN HEMT devices under DC sweep,an improved model for kink effect based on advanced SPICE model for high electron mobility transistors(ASM-HEMT)is pro⁃posed,considering the relationship between the drain/gate-source voltage and kink effect.The improved model can not only accurately describe the trend of the drain-source current with the current collapse and kink effect,but also precisely fit different values of drain-source voltages at which the kink effect occurs under different gatesource voltages.Furthermore,it well characterizes the DC characteristics of GaN devices in the full operating range,with the fitting error less than 3%.To further verify the accuracy and convergence of the improved model,a load-pull system is built in ADS.The simulated result shows that although both the original ASM-HEMT and the improved model predict the output power for the maximum power matching of GaN devices well,the im⁃proved model predicts the power-added efficiency for the maximum efficiency matching more accurately,with 4%improved.
文摘In this paper, we present the electromagnetic analysis of a rectangular cavity partially filled with a left-handed material slab. Our theoretical investigation shows that there exist novel resonant modes in the cavity, and such a cavity becomes a subwavelength cavity. The eigenvalue equation of the cavity is derived and the resonant frequencies of the novel modes are calculated by using numerical simulation. We also discuss the stability of the novel resonant modes and show the best condition under which a useful rectangular cavity of subwavelength dimensions with tolerable stability is obtained.
基金The research was funded by the National Natural Science Foundation of China(No.51802120,51872126,22075103,51672111)Guangdong Basic and Applied Basic Research Foundation for Distinguished Young Scholar(No.2019B151502030)+7 种基金Natural Science Foundation of Guangdong Province(No.2018030310181)the Science and Technology Plan Project of Guangzhou(No.202002030159)Guangdong Basic and Applied Basic Research Foundation for Young Scholar(No.2020A1515111057)‘100 Talents Program of Hebei Province’(No.E2014100008)the Fundamental Research Funds for the Central Universities(No.21619406)X.Y.thanks for the Special Funds for the Cultivation of Guangdong College Students'Scientific and Technological Innovation("Climbing Program"Special Funds)(No.pdjh2019a0055)J.Fan also thanks for the project support for"Young Top talents"in the Pearl River Talent Project of Guangdong Province(2017GC010424)the Guangdong Provincial Innovation and Entrepreneurship Project(grant 2016ZT06D081).
文摘Multifunctional lead-free double perovskites demonstrate remarkable potential towards applications in various fields.Herein,an environmentally-friendly,low-cost,high-throughput Cs_(2)NaFeCl_(6) single crystal with exceedingly high thermal stability is designed and grown.It obtains a cubic lattice system in the temperature range of 80-500 K,accompanied by a completely reversible chromatic variation ranging from yellow to black.Importantly,the intriguing thermochromism is proved to own extremely high reproducibility(over 1000 cycles)without a hysteretic effect,originating from its structural flexibility that including(i)the noteworthy distortion/deformation of[NaCl_(6)]5−and[FeCl_(6)]3−octahedra;(ii)order-disorder arrangement transition of[NaCl_(6)]5−and[FeCl6]3−octahedra as the function of temperature.This study paves the way towards a new class of smart windows and camouflage coatings with an unprecedented colour range based on a Cs_(2)NaFeCl_(6) perovskite.
基金Supported by the National Basic Research Program of China under Grant No 2006CB6049, the National High-Tech Research and Development Program of China （863）, National Nature Science Foundation of China under Grant Nos 60721063, 60676057, 60731160628, 60776001 and 60820106003, the Natural Science Foundation of Jiangsu Province （BK2008019）.
文摘The complex refractive indices and the dielectric function of GaN for frequencies ranging from 0.25 to 1.22THz are obtained using THz time-domain spectroscopy. The real part of the dielectric function first decreases from 0.25 to 0.42THz and then oscillates from 0.42 to 1.22THz, whereas the imaginary part of the dielectric function is oscillating within the whole range of frequency. The simple Drude model is extended to take into account the effect of defects on the dielectric function. The extended model is in agreement with the experimental data.
文摘The dispersion properties in the short wavelength region of total internal reflective photonic crystal fiber(TIRPCF) in Compton scattering have been studied by using the model of the equivalent twin waveguide soliton coupling, dispersion management solitons and effective refractive index. It is shown that the positive dispersion of the cladding waveguide of TIRPCF and the negative dispersion of its core waveguide are quickly increased by the square of the collision non-elastic composition between the electron and photons, and they are lessened by the increase of the electron absorption photon number. Under the one-photon nonlinear Compton scattering, the method of the compensated probing laser diffraction by the phase hole induced by the stationary pumping laser in the cladding waveguide enables the average dispersion value of TIRPCF to be close to zero, and the zero dispersion point quickly shifts to the short wavelength region.
基金Projects(61272142,61103082,61003075,61170261,61103193)supported by the National Natural Science Foundation of ChinaProject supported by Funds for New Century Excellent Talents in University of ChinaProjects(2012AA01A301,2012AA010901)supported by the National High Technology Research and Development Program of China
文摘A novel framework for parallel subgraph isomorphism on GPUs is proposed, named GPUSI, which consists of GPU region exploration and GPU subgraph matching. The GPUSI iteratively enumerates subgraph instances and solves the subgraph isomorphism in a divide-and-conquer fashion. The framework completely relies on the graph traversal, and avoids the explicit join operation. Moreover, in order to improve its performance, a task-queue based method and the virtual-CSR graph structure are used to balance the workload among warps, and warp-centric programming model is used to balance the workload among threads in a warp. The prototype of GPUSI is implemented, and comprehensive experiments of various graph isomorphism operations are carried on diverse large graphs. The experiments clearly demonstrate that GPUSI has good scalability and can achieve speed-up of 1.4–2.6 compared to the state-of-the-art solutions.
基金the National Center for Research and Development on Superconductivity of Chinain part by the International Collaborative Research Project of Telecommunications Advancement Organization of Japan.
文摘A simple technique is reported for fabricating the mesa structure on Bi2Sr2CaCu2O8+δ single crystal. In the patterning process, metal masks are used instead of photolithography and argon ion milling is applied to form the small mesa on the Bi2Sr2CaCu2O8+δ crystal surface. Real four-probe transport measurements are made on the mesa structure and typical c-axis current-voltage (I - V) characteristics of the intrinsic Josephson effect have been observed. The superconducting gap parameter can be extracted from the multi-branch structure in the I - V characteristics. Additionally, from the strong hysteresis in the I - V characteristics, the capacitance CJ of the unit intrinsic Josephson junction has been estimated to be 2.3pF, which is in good agreement with that evaluated from the geometric parameters of the unit junction between the two copper oxide layers.
文摘After considering Kerr nonlinear effect, group velocity dispersion of host and gain distribution of active particle in laser amplifying medium, a basic equation describing propagation of the coupling optical pulse under the multi-photon nonlinear Compton scattering in the laser amplifying medium has been deduced. Besides, the profile and power spectrum of a picosecond-level super-Gaussian coupling pulse in the laser amplifying medium have been discussed when its central frequency coincides with the gain peak frequency of the laser amplifying medium.
基金supported by the start-up funding from University of Electronic Science and Technology of China
文摘Since its discovery in 2011,the emerging family of two-dimensional(2D)transition metal carbides,nitrides,and carbonitrides(denoted as MXenes)has shown tremendous promise in the field of energy storages,especially electrochemical capacitors(ECs).The intercalation of foreign species,including but not limited to proton,cations,organic ions,and solvents,is demonstrated as one of the dominant facts during the energy storage process of MXenes,through which interlayer spacing of MXenes can be reversibly tuned,followed with reversible redox reactions on the surface of MXenes.Such a mechanism provides MXenes extremely high capacitance up to 1500 F cm-3,in aqueous acidic electrolyte.In addition,because of the versatile terminations on their surface,the intercalation of ions into MXenes can simultaneously induce the reversible transformation of their electronic structure to trigger some other phenomenon,for example,electrochromic effect,which has great potential on electrochromic smart window—an extended application of ECs.Accordingly,regulating and facilitating the intercalation in MXenes is of great significance for MXene-based ECs.In this review,we summarize the recent progress on the intercalation in MXenes towards ECs,discussing on the intercalated species,working mechanisms,and methods to promote the intercalation.Furthermore,we prospect the future research directions of intercalation of MXenes in ECs,such as the combination of simulation and experiment on finding the best intercalation species,precisely controlling the interlayer spacing and beyond,to boost the electrochemical performance of MXene toward practical applications and multi-functional devices.
