We have experimentally achieved the all-optical trapping of a ^(40)Ca^(+)ion.An optical dipole trap was established using a high-power,far-detuned,tightly focused laser with a wavelength of 532 nm.The single ^(40)Ca^(...We have experimentally achieved the all-optical trapping of a ^(40)Ca^(+)ion.An optical dipole trap was established using a high-power,far-detuned,tightly focused laser with a wavelength of 532 nm.The single ^(40)Ca^(+)ion was trapped without any RF fields and demonstrated a long lifetime of over 3 s.In this experiment,we implemented several measures to improve the optical trapping probability,including focusing the dipole beam waist near the diffraction limit,precisely compensating for stray electric fields,and mitigating electron shelving in metastable states.The optical trapping of a ^(40)Ca^(+)ion eliminates the influence of micromotion induced by RF fields,potentially paving the way for development of all-optical trapping ion optical clocks.展开更多
Future applications of portable40Ca^(+)optical clocks require reliable magnetic field stabilization to improve frequency stability, which can be achieved by implementing an active and passive magnetic field noise supp...Future applications of portable40Ca^(+)optical clocks require reliable magnetic field stabilization to improve frequency stability, which can be achieved by implementing an active and passive magnetic field noise suppression system. On the one hand, we have optimized the magnetic shielding performance of the portable optical clock by reducing its apertures and optimizing its geometry;on the other hand, we have introduced an active magnetic field noise suppression system to further suppress the magnetic field noise experienced by the ions. These efforts reduced the ambient magnetic field noise by about 10000 times, significantly reduced the linewidth of the clock transition spectrum, improved the stability of the portable40Ca+optical clock, and created the conditions for using portable optical clocks in non-laboratory magnetic field environments. This active magnetic field suppression scheme has the advantages of simple installation and wide applicability.展开更多
A liquid-nitrogen cryogenic40Ca^(+)optical clock is presented that is designed to greatly reduce the blackbody radiation(BBR) shift. The ion trap, the electrodes and the in-vacuum BBR shield are installed under the li...A liquid-nitrogen cryogenic40Ca^(+)optical clock is presented that is designed to greatly reduce the blackbody radiation(BBR) shift. The ion trap, the electrodes and the in-vacuum BBR shield are installed under the liquid-nitrogen container,keeping the ions in a cryogenic environment at liquid-nitrogen temperature. Compared with the first design in our previous work, many improvements have been made to increase the performance. The liquid-nitrogen maintenance time has been increased by about three times by increasing the volume of the liquid-nitrogen container;the trap position recovery time after refilling the liquid-nitrogen container has been decreased more than three times by using a better fixation scheme in the liquid-nitrogen container;and the magnetic field noise felt by the ions has been decreased more than three times by a better design of the magnetic shielding system. These optimizations make the scheme for reducing the BBR shift uncertainty of liquid-nitrogen-cooled optical clocks more mature and stable, and develop a stable lock with a narrower linewidth spectrum,which would be very beneficial for further reducing the overall systematic uncertainty of optical clocks.展开更多
Temperature-dependent photoluminescence characteristics of organic-inorganic halide perovskite CH3NH3Pb I3-xClx films prepared using a two-step method on ZnO/FTO substrates were investigated. Surface morphology and ab...Temperature-dependent photoluminescence characteristics of organic-inorganic halide perovskite CH3NH3Pb I3-xClx films prepared using a two-step method on ZnO/FTO substrates were investigated. Surface morphology and absorption characteristics of the films were also studied. Scanning electron microscopy revealed large crystals and substrate coverage. The orthorhombic-to-tetragonal phase transition temperature was-140 K. The films' exciton binding energy was 77.6 ± 10.9 meV and the energy of optical phonons was 38.8 ± 2.5 meV. These results suggest that perovskite CH3NH3Pb I(3-x)Clx films have excellent optoelectronic characteristics which further suggests their potential usage in perovskitebased optoelectronic devices.展开更多
Assessment of the relationship between Pseudoxenodon and Dipsadinae has been hampered by lack of adequate samples. In this paper, we conducted phylogenetic analyses using two mitochondrial genes (12S and 16S rRNA) a...Assessment of the relationship between Pseudoxenodon and Dipsadinae has been hampered by lack of adequate samples. In this paper, we conducted phylogenetic analyses using two mitochondrial genes (12S and 16S rRNA) and one nuclear gene (c-mos) from thirteen specimens representing two species of Pseudoxenodon, together with 84 sequences of caenophidians and an outgroup sequence of Boa constrictor. Our study suggests that the Southeast Asian genus, Pseudoxenodon forms a robust genetic subclade within South American xenodontines, indicating that at least one lineage within this genus entered or returned to the Old World (OW) from the New World (NW) across the Beringian Land Bridge during the early Tertiary and the warm mid-Miocene. It also reveals the high intraspecific genomic variation within the populations of Pseudoxenodon macrops, indicating that species diversity of Pseudoxenodon in China is likely underestimated.展开更多
Progress of the ^40Ca^+ion optical clock based on the 4^2S1/2-3d ^2D5/2 electric quadrupole transition is reported.By setting the drive frequency to the“magic”frequencyΩ0,the frequency uncertainty caused by the scal...Progress of the ^40Ca^+ion optical clock based on the 4^2S1/2-3d ^2D5/2 electric quadrupole transition is reported.By setting the drive frequency to the“magic”frequencyΩ0,the frequency uncertainty caused by the scalar Stark shift and second-order Doppler shift induced by micromotion is reduced to the 10^-19 level.By precisely measuring the differential static scalar polarizability∆α0,the uncertainty due to the blackbody radiation(BBR)shift(coefficient)is reduced to the 10^-19 level.With the help of a second-order integrating servo algorithm,the uncertainty due to the servo error is reduced to the 10^-18 level.The total fractional uncertainty of the ^40Ca^+ion optical clock is then improved to 2.2×10^-17,whereas this value is mainly restricted by the uncertainty of the BBR shift due to temperature fluctuations.The state preparation is introduced together with improvements in the pulse sequence,and furthermore,a better signal to noise ratio(SNR)and less dead time are achieved.The clock stability of a single clock is improved to 4.8×10^-15√τ(in seconds).展开更多
Directed Self-Assembly(DSA)of block copolymers(BCPs)is a promising technique for sub-10 nm nanofabrication,which is highly compatible with conventional lithography.DSA relies on the microphase separation of block copo...Directed Self-Assembly(DSA)of block copolymers(BCPs)is a promising technique for sub-10 nm nanofabrication,which is highly compatible with conventional lithography.DSA relies on the microphase separation of block copolymers to form nanostructures of different morphologies.The pitch size of the obtained nanostructure depends largely on the intrinsic properties of BCPs and is usually fixed when BCPs are produced.One effective way of tuning the pitch size of BCPs is by blending BCPs of different molecular weight.In this paper,we have demonstrated the pitch tuning capability by blending the triblock poly(2-vinyl pyridine-bpolystyrene-b-poly 2-vinyl)pyridine(P2VP-b-PS-b-P2VP)with another triblock P2VP-b-PS-b-P2VP or diblock copolymer(PS-b-P2VP)at various volume ratios by solvent annealing.The nanopatterns of blended BCPs after sequential infiltration synthesis(SIS)and plasma etching process,were characterized by scanning electron microscopy.It’s observed that the blended BCPs can form highly ordered lamellar nanostructures of different pitch sizes at different blending ratios.The method of blending BCPs of varying molecular weights greatly extends the functionality of existing BCPs,with the capability of fine-tuning nanopatterning pitch at nanometer resolution.展开更多
Background It is necessary to determine the optimal treatment for melanoma as the incidence of melanoma is increasing every year.In this study,we conducted a metaanalysis to compare the effectiveness of available trea...Background It is necessary to determine the optimal treatment for melanoma as the incidence of melanoma is increasing every year.In this study,we conducted a metaanalysis to compare the effectiveness of available treatments for melanoma.Methods The index keywords“melanoma”and“treatment”were used to search the PubMed,Cochrane Library,Web of Science,and Embase databases,and the articles were limited to randomized controlled trials.The search was filtered for articles published until February 2020,and articles were independently extracted by two reviewers.Network metaanalysis(Stata®14.0 software network package,StataCorp LLC,TX,USA)was used to compare the effectiveness of the mentioned treatments of melanoma.Results A total of 616 articles were screened of which 6 were selected for meta-analysis,involving 5 treatment measures and 2047 patients(those who were not followed up on were excluded).The treatment strategies reported for melanoma included tumor necrosis factor(L19-TNFα)and interleukin-2(L19IL2)in combination with dacarbazine(L19IL2+DTIC),DTIC,programmed cell death-1 plus cytotoxic T cell antigen-4(PD-1+CTLA-4),PD-1,and CTLA-4.Conclusion Among L19IL2+DTIC,DTIC,PD-1+CTLA-4,PD-1,and CTLA-4,CTLA-4 is found to be the best treatment method for melanoma.Our study findings provide a reference for the clinical treatment of melanoma and can clarify the direction for setting up controlled clinical trials.展开更多
Mutation of the MAPK7 gene was related to human scoliosis.Mapk7 regulated the development of limb bones and skulls in mice.However,the role of MAPK7 in vertebral development is still unclear.In this study,we construct...Mutation of the MAPK7 gene was related to human scoliosis.Mapk7 regulated the development of limb bones and skulls in mice.However,the role of MAPK7 in vertebral development is still unclear.In this study,we constructed Col2a1-cre;Mapk7 f/f transgenic mouse model to delete Mapk7 in cartilage,which displayed kyphosis and osteopenia.Mechanistically,Mapk7 loss decreased MEF2C expression and thus activated PTEN to oppose PI3K/AKT signaling in vertebral growth plate chondrocytes,which impaired chondrocyte hypertrophy and attenuated vertebral ossification.In vivo,systemic pharmacological activation of AKT rescued impaired chondrocyte hypertrophy and alleviated mouse vertebral defects caused by Mapk7 deficiency.Our study firstly clarified the mechanism by which MAPK7 was involved in vertebral development,which might contribute to understanding the pathology of spinal deformity and provide a basis for the treatment of developmental disorders of the spine.展开更多
SrZrS_(3)is a promising chalcogenide perovskite with unique advantages including high abundance of consisting elements,high chemical stability,strong light absorption above its direct band gap,excellent carrier transp...SrZrS_(3)is a promising chalcogenide perovskite with unique advantages including high abundance of consisting elements,high chemical stability,strong light absorption above its direct band gap,excellent carrier transport ability.While unfortunately,due to the lack of breakthroughs in its thin film synthesis technique,its optoelectronic properties are not fully investigated,not to mention the device applications.In this work,large-area and uniform SrZrS_(3)thin film(5 cm×5 cm)was prepared by facile sputtering method,followed by a post-annealing treatment at a high temperature of 1000℃for 2–12 h under CS_(2)atmosphere.All SrZrS_(3)samples prepared adopt distorted orthorhombic structure with pnma space group and have high crystallinity.In addition,the band gap of SrZrS_(3)thin film is measured to be 2.29 eV,higher than that of the powder form(2.06 eV).Importantly,the light absorption coefficient of SrZrS_(3)thin film reaches over 105 cm^(−1),the carrier mobility is as high as 106 cm^(2)/(V∙s).The above advantages allow us to use the SrZrS_(3)thin film as photoactive layer for photodetector applications.Finally,a symmetrically structured photoconductive detector was fabricated,performing a high responsivity of 8 A/W(405 nm light excitation).These inspiring results promise the glorious application potential of SrZrS_(3)thin film in photodetectors,solar cells,other optoelectronic devices.展开更多
Strain modulation is crucial for heteroepitaxy such as GaN on foreign substrates.Here,the epitaxy of strain-relaxed GaN films on graphene/SiC substrates by metal-organic chemical vapor deposition is demonstrated.Graph...Strain modulation is crucial for heteroepitaxy such as GaN on foreign substrates.Here,the epitaxy of strain-relaxed GaN films on graphene/SiC substrates by metal-organic chemical vapor deposition is demonstrated.Graphene was directly prepared on SiC substrates by thermal decomposition.Its pre-treatment with nitrogen-plasma can introduce C–N dangling bonds,which provides nucleation sites for subsequent epitaxial growth.The scanning transmission electron microscopy measurements confirm that part of graphene surface was etched by nitrogen-plasma.We study the growth behavior on different areas of graphene surface after pre-treatment,and propose a growth model to explain the epitaxial growth mechanism of GaN films on graphene.Significantly,graphene is found to be effective to reduce the biaxial stress in GaN films and the strain relaxation improves indium-atom incorporation in InGaN/GaN multiple quantum wells(MQWs)active region,which results in the obvious red-shift of light-emitting wavelength of InGaN/GaN MQWs.This work opens up a new way for the fabrication of GaN-based long wavelength light-emitting diodes.展开更多
It is presented in this paper that the new design and its analysis of finite difference domain decomposition algorithms for the two-dimensional heat equation, and the numerical results have shown the stability and acc...It is presented in this paper that the new design and its analysis of finite difference domain decomposition algorithms for the two-dimensional heat equation, and the numerical results have shown the stability and accuracy of the algorithms, where SauFyev asymmetric schemes have been used at the interface points. The Algorithm II in this paper has further extended those developed by Dawson and the others, Zhang and Shen.展开更多
By using the concept of multigraphs, the difference graphs of a class of alternating block Crank-Nicolson methods are defined and described, which extends the results on difference graphs of parallel computing for the...By using the concept of multigraphs, the difference graphs of a class of alternating block Crank-Nicolson methods are defined and described, which extends the results on difference graphs of parallel computing for the finite difference method.展开更多
基金supported by the National Basic Research R&D Program of China(Grant Nos.2022YFB3904001 and 2018YFA0307500)the National Natural Science Foundation of China(Grant Nos.12022414 and 11934014)+1 种基金the Natural Science Foundation of Hubei Province(Grant No.2022CFA013)the CAS Project for Young Scientists in Basic Research(Grant Nos.YSBR-085 and YSBR-055)。
文摘We have experimentally achieved the all-optical trapping of a ^(40)Ca^(+)ion.An optical dipole trap was established using a high-power,far-detuned,tightly focused laser with a wavelength of 532 nm.The single ^(40)Ca^(+)ion was trapped without any RF fields and demonstrated a long lifetime of over 3 s.In this experiment,we implemented several measures to improve the optical trapping probability,including focusing the dipole beam waist near the diffraction limit,precisely compensating for stray electric fields,and mitigating electron shelving in metastable states.The optical trapping of a ^(40)Ca^(+)ion eliminates the influence of micromotion induced by RF fields,potentially paving the way for development of all-optical trapping ion optical clocks.
基金supported by the National Key R&D Program of China (Grant Nos.2022YFB3904001, 2022YFB3904004, and 2018YFA0307500)the National Natural Science Foundation of China (Grant Nos. 12022414 and 12121004)+3 种基金the CAS Youth Innovation Promotion Association (Grant Nos. Y201963 and Y2022099)the Natural Science Foundation of Hubei Province (Grant No. 2022CFA013)the CAS Project for Young Scientists in Basic Research (Grant No. YSBR-055)the Interdisciplinary Cultivation Project of the Innovation Academy for Precision Measurement of Science and Technology (Grant No. S21S2201)。
文摘Future applications of portable40Ca^(+)optical clocks require reliable magnetic field stabilization to improve frequency stability, which can be achieved by implementing an active and passive magnetic field noise suppression system. On the one hand, we have optimized the magnetic shielding performance of the portable optical clock by reducing its apertures and optimizing its geometry;on the other hand, we have introduced an active magnetic field noise suppression system to further suppress the magnetic field noise experienced by the ions. These efforts reduced the ambient magnetic field noise by about 10000 times, significantly reduced the linewidth of the clock transition spectrum, improved the stability of the portable40Ca+optical clock, and created the conditions for using portable optical clocks in non-laboratory magnetic field environments. This active magnetic field suppression scheme has the advantages of simple installation and wide applicability.
基金supported by the National Key R&D Program of China (Grant Nos. 2022YFB3904001 and 2018YFA0307500)the National Natural Science Foundation of China (Grant Nos. 12121004 and 12022414)+4 种基金Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDB21030100)CAS Project for Young Scientists in Basic Research (Grant No. YSBR055)CAS Youth Innovation Promotion Association (Grant Nos. Y201963 and Y2022099)the Natural Science Foundation of Hubei Province (Grant No. 2022CFA013)the Interdisciplinary Cultivation Project of the Innovation Academy for Precision Measurement of Science and Technology (Grant No. S21S2201)。
文摘A liquid-nitrogen cryogenic40Ca^(+)optical clock is presented that is designed to greatly reduce the blackbody radiation(BBR) shift. The ion trap, the electrodes and the in-vacuum BBR shield are installed under the liquid-nitrogen container,keeping the ions in a cryogenic environment at liquid-nitrogen temperature. Compared with the first design in our previous work, many improvements have been made to increase the performance. The liquid-nitrogen maintenance time has been increased by about three times by increasing the volume of the liquid-nitrogen container;the trap position recovery time after refilling the liquid-nitrogen container has been decreased more than three times by using a better fixation scheme in the liquid-nitrogen container;and the magnetic field noise felt by the ions has been decreased more than three times by a better design of the magnetic shielding system. These optimizations make the scheme for reducing the BBR shift uncertainty of liquid-nitrogen-cooled optical clocks more mature and stable, and develop a stable lock with a narrower linewidth spectrum,which would be very beneficial for further reducing the overall systematic uncertainty of optical clocks.
基金supported by the International Science and Technology Cooperation Program of Science and Technology Bureau of Changchun City,China(Grant No.12ZX68)
文摘Temperature-dependent photoluminescence characteristics of organic-inorganic halide perovskite CH3NH3Pb I3-xClx films prepared using a two-step method on ZnO/FTO substrates were investigated. Surface morphology and absorption characteristics of the films were also studied. Scanning electron microscopy revealed large crystals and substrate coverage. The orthorhombic-to-tetragonal phase transition temperature was-140 K. The films' exciton binding energy was 77.6 ± 10.9 meV and the energy of optical phonons was 38.8 ± 2.5 meV. These results suggest that perovskite CH3NH3Pb I(3-x)Clx films have excellent optoelectronic characteristics which further suggests their potential usage in perovskitebased optoelectronic devices.
基金funded by the National Natural Science Foundation of China(30870290,31071891,31060280)the Students Science Research Program of Huangshan University(2010xdkj019)
文摘Assessment of the relationship between Pseudoxenodon and Dipsadinae has been hampered by lack of adequate samples. In this paper, we conducted phylogenetic analyses using two mitochondrial genes (12S and 16S rRNA) and one nuclear gene (c-mos) from thirteen specimens representing two species of Pseudoxenodon, together with 84 sequences of caenophidians and an outgroup sequence of Boa constrictor. Our study suggests that the Southeast Asian genus, Pseudoxenodon forms a robust genetic subclade within South American xenodontines, indicating that at least one lineage within this genus entered or returned to the Old World (OW) from the New World (NW) across the Beringian Land Bridge during the early Tertiary and the warm mid-Miocene. It also reveals the high intraspecific genomic variation within the populations of Pseudoxenodon macrops, indicating that species diversity of Pseudoxenodon in China is likely underestimated.
基金Project supported by the National Key Research and Development Program of China(Grant Nos.2017YFA0304401,2018YFA0307500,2017YFA0304404,and 2017YFF0212003)the National Natural Science Foundation of China(Grant Nos.11622434,11774388,11634013,11934014,and 91736310)+2 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB21030100)the CAS Youth Innovation Promotion Association(Grant Nos.Y201963 and 2018364)the Science Fund for Distinguished Young Scholars of Hubei Province,China(Grant No.2017CFA040).
文摘Progress of the ^40Ca^+ion optical clock based on the 4^2S1/2-3d ^2D5/2 electric quadrupole transition is reported.By setting the drive frequency to the“magic”frequencyΩ0,the frequency uncertainty caused by the scalar Stark shift and second-order Doppler shift induced by micromotion is reduced to the 10^-19 level.By precisely measuring the differential static scalar polarizability∆α0,the uncertainty due to the blackbody radiation(BBR)shift(coefficient)is reduced to the 10^-19 level.With the help of a second-order integrating servo algorithm,the uncertainty due to the servo error is reduced to the 10^-18 level.The total fractional uncertainty of the ^40Ca^+ion optical clock is then improved to 2.2×10^-17,whereas this value is mainly restricted by the uncertainty of the BBR shift due to temperature fluctuations.The state preparation is introduced together with improvements in the pulse sequence,and furthermore,a better signal to noise ratio(SNR)and less dead time are achieved.The clock stability of a single clock is improved to 4.8×10^-15√τ(in seconds).
基金This work was supported by the Awards No.SXH1232030,IDH1232054 and KBH1232189 from the Shanghai Municipal Science and Technology CommissionThis work is partially supported by the National Natural Science Foundation of China(General program).Y.C would like to thank the Shanghai super postdoc award for supporting this workThe authors declare no competing financial interest.
文摘Directed Self-Assembly(DSA)of block copolymers(BCPs)is a promising technique for sub-10 nm nanofabrication,which is highly compatible with conventional lithography.DSA relies on the microphase separation of block copolymers to form nanostructures of different morphologies.The pitch size of the obtained nanostructure depends largely on the intrinsic properties of BCPs and is usually fixed when BCPs are produced.One effective way of tuning the pitch size of BCPs is by blending BCPs of different molecular weight.In this paper,we have demonstrated the pitch tuning capability by blending the triblock poly(2-vinyl pyridine-bpolystyrene-b-poly 2-vinyl)pyridine(P2VP-b-PS-b-P2VP)with another triblock P2VP-b-PS-b-P2VP or diblock copolymer(PS-b-P2VP)at various volume ratios by solvent annealing.The nanopatterns of blended BCPs after sequential infiltration synthesis(SIS)and plasma etching process,were characterized by scanning electron microscopy.It’s observed that the blended BCPs can form highly ordered lamellar nanostructures of different pitch sizes at different blending ratios.The method of blending BCPs of varying molecular weights greatly extends the functionality of existing BCPs,with the capability of fine-tuning nanopatterning pitch at nanometer resolution.
文摘Background It is necessary to determine the optimal treatment for melanoma as the incidence of melanoma is increasing every year.In this study,we conducted a metaanalysis to compare the effectiveness of available treatments for melanoma.Methods The index keywords“melanoma”and“treatment”were used to search the PubMed,Cochrane Library,Web of Science,and Embase databases,and the articles were limited to randomized controlled trials.The search was filtered for articles published until February 2020,and articles were independently extracted by two reviewers.Network metaanalysis(Stata®14.0 software network package,StataCorp LLC,TX,USA)was used to compare the effectiveness of the mentioned treatments of melanoma.Results A total of 616 articles were screened of which 6 were selected for meta-analysis,involving 5 treatment measures and 2047 patients(those who were not followed up on were excluded).The treatment strategies reported for melanoma included tumor necrosis factor(L19-TNFα)and interleukin-2(L19IL2)in combination with dacarbazine(L19IL2+DTIC),DTIC,programmed cell death-1 plus cytotoxic T cell antigen-4(PD-1+CTLA-4),PD-1,and CTLA-4.Conclusion Among L19IL2+DTIC,DTIC,PD-1+CTLA-4,PD-1,and CTLA-4,CTLA-4 is found to be the best treatment method for melanoma.Our study findings provide a reference for the clinical treatment of melanoma and can clarify the direction for setting up controlled clinical trials.
基金supported by the National Natural Science Foundation of China(No.92068105,82172376,82072385).
文摘Mutation of the MAPK7 gene was related to human scoliosis.Mapk7 regulated the development of limb bones and skulls in mice.However,the role of MAPK7 in vertebral development is still unclear.In this study,we constructed Col2a1-cre;Mapk7 f/f transgenic mouse model to delete Mapk7 in cartilage,which displayed kyphosis and osteopenia.Mechanistically,Mapk7 loss decreased MEF2C expression and thus activated PTEN to oppose PI3K/AKT signaling in vertebral growth plate chondrocytes,which impaired chondrocyte hypertrophy and attenuated vertebral ossification.In vivo,systemic pharmacological activation of AKT rescued impaired chondrocyte hypertrophy and alleviated mouse vertebral defects caused by Mapk7 deficiency.Our study firstly clarified the mechanism by which MAPK7 was involved in vertebral development,which might contribute to understanding the pathology of spinal deformity and provide a basis for the treatment of developmental disorders of the spine.
基金the National Natural Science Foundation of China(Nos.62104215 and 12074347)China Postdoctoral Science Foundation(Nos.2020M672257 and 2020TQ0286)+1 种基金Natural Science Foundation of Henan Province of China(No.202300410439)Department of Science and Technology of Henan Province of China(No.202102210214).
文摘SrZrS_(3)is a promising chalcogenide perovskite with unique advantages including high abundance of consisting elements,high chemical stability,strong light absorption above its direct band gap,excellent carrier transport ability.While unfortunately,due to the lack of breakthroughs in its thin film synthesis technique,its optoelectronic properties are not fully investigated,not to mention the device applications.In this work,large-area and uniform SrZrS_(3)thin film(5 cm×5 cm)was prepared by facile sputtering method,followed by a post-annealing treatment at a high temperature of 1000℃for 2–12 h under CS_(2)atmosphere.All SrZrS_(3)samples prepared adopt distorted orthorhombic structure with pnma space group and have high crystallinity.In addition,the band gap of SrZrS_(3)thin film is measured to be 2.29 eV,higher than that of the powder form(2.06 eV).Importantly,the light absorption coefficient of SrZrS_(3)thin film reaches over 105 cm^(−1),the carrier mobility is as high as 106 cm^(2)/(V∙s).The above advantages allow us to use the SrZrS_(3)thin film as photoactive layer for photodetector applications.Finally,a symmetrically structured photoconductive detector was fabricated,performing a high responsivity of 8 A/W(405 nm light excitation).These inspiring results promise the glorious application potential of SrZrS_(3)thin film in photodetectors,solar cells,other optoelectronic devices.
基金supported by the National Key Research and Development Program(No.2018YFB0406703)the National Natural Science Foundation of China(Nos.61734001 and 62074069)+1 种基金the Science and Technology Developing Project of Jilin Province(No.20200801013GH)the Program for JLU Science and Technology Innovative Research Team(JLUSTIRT,2021TD-39).
文摘Strain modulation is crucial for heteroepitaxy such as GaN on foreign substrates.Here,the epitaxy of strain-relaxed GaN films on graphene/SiC substrates by metal-organic chemical vapor deposition is demonstrated.Graphene was directly prepared on SiC substrates by thermal decomposition.Its pre-treatment with nitrogen-plasma can introduce C–N dangling bonds,which provides nucleation sites for subsequent epitaxial growth.The scanning transmission electron microscopy measurements confirm that part of graphene surface was etched by nitrogen-plasma.We study the growth behavior on different areas of graphene surface after pre-treatment,and propose a growth model to explain the epitaxial growth mechanism of GaN films on graphene.Significantly,graphene is found to be effective to reduce the biaxial stress in GaN films and the strain relaxation improves indium-atom incorporation in InGaN/GaN multiple quantum wells(MQWs)active region,which results in the obvious red-shift of light-emitting wavelength of InGaN/GaN MQWs.This work opens up a new way for the fabrication of GaN-based long wavelength light-emitting diodes.
基金supported by Natural Science Foundation of China under Grant Nos.10671060 and 10871061the Youth Foundation of Hunan Education Bureau under Grant No.06B037+1 种基金the Natural Science Foundation of Hunan Province under Grant No.09JJ6015the Construct Program of the Key Discipline in Hunan Province
文摘It is presented in this paper that the new design and its analysis of finite difference domain decomposition algorithms for the two-dimensional heat equation, and the numerical results have shown the stability and accuracy of the algorithms, where SauFyev asymmetric schemes have been used at the interface points. The Algorithm II in this paper has further extended those developed by Dawson and the others, Zhang and Shen.
文摘By using the concept of multigraphs, the difference graphs of a class of alternating block Crank-Nicolson methods are defined and described, which extends the results on difference graphs of parallel computing for the finite difference method.