Antimony-based anodes have attracted wide attention in potassium-ion batteries due to their high theoretical specific capacities(∼660 mA h g^(-1))and suitable voltage platforms.However,severe capacity fading caused b...Antimony-based anodes have attracted wide attention in potassium-ion batteries due to their high theoretical specific capacities(∼660 mA h g^(-1))and suitable voltage platforms.However,severe capacity fading caused by huge volume change and limited ion transportation hinders their practical applications.Recently,strategies for controlling the morphologies of Sb-based materials to improve the electrochemical performances have been proposed.Among these,the two-dimensional Sb(2D-Sb)materials present excellent properties due to shorted ion immigration paths and enhanced ion diffusion.Nevertheless,the synthetic methods are usually tedious,and even the mechanism of these strategies remains elusive,especially how to obtain large-scale 2D-Sb materials.Herein,a novel strategy to synthesize 2D-Sb material using a straightforward solvothermal method without the requirement of a complex nanostructure design is provided.This method leverages the selective adsorption of aldehyde groups in furfural to induce crystal growth,while concurrently reducing and coating a nitrogen-doped carbon layer.Compared to the reported methods,it is simpler,more efficient,and conducive to the production of composite nanosheets with uniform thickness(3–4 nm).The 2D-Sb@NC nanosheet anode delivers an extremely high capacity of 504.5 mA h g^(-1) at current densities of 100 mA g^(-1) and remains stable for more than 200 cycles.Through characterizations and molecular dynamic simulations,how potassium storage kinetics between 2D Sb-based materials and bulk Sb-based materials are explored,and detailed explanations are provided.These findings offer novel insights into the development of durable 2D alloy-based anodes for next-generation potassium-ion batteries.展开更多
The chirality structure of a single-walled carbon nanotube(SWNT)strongly depends on the composition of catalyst used in the chemical vapor deposition process.In this study,we develop a porous magnesia supported mangan...The chirality structure of a single-walled carbon nanotube(SWNT)strongly depends on the composition of catalyst used in the chemical vapor deposition process.In this study,we develop a porous magnesia supported manganese-rhenium(MnRe/MgO)catalyst for chirality-selective synthesis of SWNTs.Detailed characterizations reveal that(6,5)tubes with a selectivity higher than 70%are grown from the Re-rich MnRe/MgO catalyst.By comparing the SWNT growth results with those of monometallic Mn or Re,the formation of sigma phase,an intermetallic compound occurring in transition-metal alloy systems,is revealed to be crucial for the dominant synthesis of(6,5)SWNTs.This work not only extends the application of sigma phase alloy for catalytic synthesis of SWNTs,but also sheds lights on the growth of SWNTs with a high chirality selectivity.展开更多
Heterostructures combined by different individual two-dimensional(2D)materials are essential building blocks to realize unique electronic,optoelectronic properties and multifunctional applications.To date,the direct g...Heterostructures combined by different individual two-dimensional(2D)materials are essential building blocks to realize unique electronic,optoelectronic properties and multifunctional applications.To date,the direct growth of 2D/2D atomic van der Waals heterostructures(vdWHs)have been extensively investigated.However,the heterostructures from 2D inorganic molecular crystals and atomic crystals have been rarely reported.Here we report two-step direct epitaxial growth of the inorganic molecular-atomic Sb2O3/WS2 vdWHs.The thickness of Sb2O3 nanosheets on WS2 nanosheets can be tuned by variable growth temperatures.Oriented growth behavior of Sb2O3 on WS2 was determined through statistics.Optical images,Raman spectra,Raman mappings and selected-area electron diffraction(SAED),etc.,reveal that Sb2O3/WS2 heterostructures are vertically stacked with high crystal quality.Electrical transport measurements demonstrate that the heterotransistors based on the heterostructures possess high current on/off ratio of 5 × 10^5,obvious gate-tunable and current rectification output characteristics.Optoelectronic characterizations show that the heterostructures have a clear photoresponse with high responsivity of 16.4 AW.The growth of vdWHs from 2D inorganic molecular-atomic crystals may open up new opportunities in 2D functional electronics and optoelectronics.展开更多
A promising strategy for the selective growth of ZnO nanorods on SiO2/Si substrates using a graphene buffer layer in a low temperature solution process is described. High densities of ZnO nanorods were grown over a la...A promising strategy for the selective growth of ZnO nanorods on SiO2/Si substrates using a graphene buffer layer in a low temperature solution process is described. High densities of ZnO nanorods were grown over a large area and most ZnO nanorods were vertically well-aligned on graphene. Furthermore, selective growth of ZnO nanorods on graphene was realized by applying a simple mechanical treatment, since ZnO nanorods formed on graphene are mechanically stable on an atomic level. These results were confirmed by first principles calculations which showed that the ZnO-graphene binding has a low destabilization energy. In addition, it was found that ZnO nanorods grown on SiO2/Si with a graphene buffer layer have better optical properties than ZnO nanorods grown on bare SiO2/Si. The nanostructured ZnO-graphene materials have promising applications in future flexible electronic and optical devices.展开更多
Cone-shaped patterned sapphire substrate was prepared by inductively coupled plasma etching and GaN nucleation layer was grown on it by metal-organic chemical vapor deposition.A selective growth of GaN nucleation laye...Cone-shaped patterned sapphire substrate was prepared by inductively coupled plasma etching and GaN nucleation layer was grown on it by metal-organic chemical vapor deposition.A selective growth of GaN nucleation layer was found on the slope of the cone-shaped patterned sapphire substrat,and the distribution morphology of GaN had significantly changed after it was recrystallized.GaN selective growth and redistribution were analyzed by investigating the distribution of crystallographic planes on the cone surface and the atom array of specific planes at atom level.展开更多
CaN nanorods are successfully fabricated by adjusting the flow rate ratio of hydrogen （H2）/nitrogen （N2） and growth temperature of the selective area growth （SAG） method with metal organic chemical vapor deposit...CaN nanorods are successfully fabricated by adjusting the flow rate ratio of hydrogen （H2）/nitrogen （N2） and growth temperature of the selective area growth （SAG） method with metal organic chemical vapor deposition （MOCVD）. The SAG template is obtained by nanospherical-lens photolithography. It is found that increasing the flow rate of 1-12 will change the CaN crystal shape from pyramid to vertical rod, while increasing the growth temperature will reduce the diameters of GaN rods to nanometer scale. Finally the CaN nanorods with smooth lateral surface and relatively good quality are obtained under the condition that the H2：N2 ratio is 1：1 and the growth temperature is 1030℃. The good crystal quality and orientation of GaN nanorods are confirmed by high resolution transmission electron microscopy. The cathodoluminescence spectrum suggests that the crystal and optical quality is also improved with increasing the temperature.展开更多
A 32 Gb/s monolithically integrated electroabsorption modulated laser is fabricated by selective area growth technology. The threshold current of the device is below 13mA. The output power exceeds 10mW at 0V bias when...A 32 Gb/s monolithically integrated electroabsorption modulated laser is fabricated by selective area growth technology. The threshold current of the device is below 13mA. The output power exceeds 10mW at 0V bias when the injection current of the distributed feedback laser is 100mA at 25℃. The side mode suppression ratio is over 50 dB. A 32Gb/s eye diagram is measured with a 3.SVpp nonreturn-to-zero pseudorandom modulation signal at -2.3 V bias. A clearly opening eyediagram with a dynamic extinction ratio of 8.01 dB is obtained.展开更多
A high quality of GaAs crystal growth in nanoscale V-shape trenches on Si（O01） substrates is achieved by using the aspect-ratio trapping method. GaAs thin films are deposited via metal-organic chemical vapor deposit...A high quality of GaAs crystal growth in nanoscale V-shape trenches on Si（O01） substrates is achieved by using the aspect-ratio trapping method. GaAs thin films are deposited via metal-organic chemical vapor deposition by using a two-step growth process. Threading disJocations arising from lattice mismatch are trapped by laterally confining sidewalls, and antiphase domains boundaries are completely restricted by V-groove trenches with Si { 111} facets. Material quality is confirmed by scanning electron microscopy （SEM）, transmission electron microscopy （TEM） and high resolution X-ray diffraction. Low temperature photoluminescence （PL） measurement is used to analyze the thermal strain relaxation in GaAs layers. This approach shows great promise for the realization of high mobility devices or optoelectronie integrated circuits on Si substrates.展开更多
High performance 1 57μm spotsize converter monolithically integrated DFB is fabricated by the technique of self aligned selective area growth.The upper optical confinement layer and the butt coupled tapered thickn...High performance 1 57μm spotsize converter monolithically integrated DFB is fabricated by the technique of self aligned selective area growth.The upper optical confinement layer and the butt coupled tapered thickness waveguide are regrown simultaneously,which not only offeres the separated optimization of the active region and the integrated spotsize converter,but also reduces the difficulty of the butt joint selective regrowth.The threshold current is as low as 4 4mA.The output power at 49mA is 10 1mW.The side mode suppression ratio (SMSR) is 33 2dB.The vertical and horizontal far field divergence angles are as small as 9° and 15° respectively,the 1dB misalignment tolerance are 3 6μm and 3 4μm.展开更多
Migration characterizations of Ga and In adatoms on the dielectric surface in selective metal organic vapor phase epitaxy （MOVPE） were investigated. In the typical MOVPE environment, the selectivity of growth is pre...Migration characterizations of Ga and In adatoms on the dielectric surface in selective metal organic vapor phase epitaxy （MOVPE） were investigated. In the typical MOVPE environment, the selectivity of growth is preserved for GaN, and the growth rate of GaN micro-pyramids is sensitive to the period of the patterned SiO2 mask. A surface migration induced model was adopted to figure out the effective migration length of Ga adatoms on the dielectric surface. Different from the growth of GaN, the selective area growth of InGaN on the patterned template would induce the deposition of InGaN polycrystalline particles on the patterned Si02 mask with a long period. It was demonstrated with a scanning electron microscope and energy dispersive spectroscopy that the In adatoms exhibit a shorter migration length on the dielectric surface.展开更多
Ga N micro-pyramids with AlGaN capping layer are grown by selective metal–organic–vapor phase epitaxy（MOVPE）. Compared with bare Ga N micro-pyramids, AlGaN/Ga N micro-pyramids show wrinkling morphologies at the bo...Ga N micro-pyramids with AlGaN capping layer are grown by selective metal–organic–vapor phase epitaxy（MOVPE）. Compared with bare Ga N micro-pyramids, AlGaN/Ga N micro-pyramids show wrinkling morphologies at the bottom of the structure. The formation of those special morphologies is associated with the spontaneously formed AlGaN polycrystalline particles on the dielectric mask, owing to the much higher bond energy of Al–N than that of Ga–N. When the sizes of the polycrystalline particles are larger than 50 nm, the uniform source supply behavior is disturbed, thereby leading to unsymmetrical surface morphology. Analysis reveals that the scale of surface wrinkling is related to the migration length of Ga adatoms along the AlGaN {1ī01} facet. The migration properties of Al and Ga further affect the distribution of Al composition along the sidewalls, characterized by the μ-PL measurement.展开更多
In perinatal medicine,intrauterine growth restriction(IUGR)is one of the greatest challenges.The etiology of IUGR is multifactorial,but most cases are thought to arise from placental insufficiency.However,identifying ...In perinatal medicine,intrauterine growth restriction(IUGR)is one of the greatest challenges.The etiology of IUGR is multifactorial,but most cases are thought to arise from placental insufficiency.However,identifying the placental cause of IUGR can be difficult due to numerous confounding factors.Selective IUGR(sIUGR)would be a good model to investigate how impaired placentation affects fetal development,as the growth discordance between monochorionic twins cannot be explained by confounding genetic or maternal factors.Herein,we constructed and analyzed the placental proteomic profiles of IUGR twins and normal cotwins.Specifically,we identified a total of 5481 proteins,of which 233 were differentially expressed(57 up-regulated and 176 down-regulated)in IUGR twins.Bioinformatics analysis indicates that these differentially expressed proteins(DEPs)are mainly associated with cardiovascular system development and function,organismal survival,and organismal development.Notably,34 DEPs are significantly enriched in angiogenesis,and diminished placental angiogenesis in IUGR twins has been further elaborately confirmed.Moreover,we found decreased expression of metadherin(MTDH)in the placentas of IUGR twins and demonstrated that MTDH contributes to placental angiogenesis and fetal growth in vitro.Collectively,our findings reveal the comprehensive proteomic signatures of placentas for sIUGR twins,and the DEPs identified may provide in-depth insights into the pathogenesis of placental dysfunction and subsequent impaired fetal growth.展开更多
We provide a new way to prepare ZnO nanorods pattern from the solution composed of hexamethylenetetramine （HMT） and Zn（NO3）2. The substrate is ITO substrate covered by well ordered Au islands. Since Au and the und...We provide a new way to prepare ZnO nanorods pattern from the solution composed of hexamethylenetetramine （HMT） and Zn（NO3）2. The substrate is ITO substrate covered by well ordered Au islands. Since Au and the underneath ITO substrate have two different nucleation rates in the initial stage of heterogeneous nucleation process, the subsequent ZnO growth on the quick nucleating area takes place under diffusion control and is able to confine the synthesis of ZnO nanorods to specific locations. The concentrations of zinc nitrate and HMT are well adjusted to show the possibility of the new route for the patterning of the ZnO nanorods. Furthermore, the nanorods pattern was characterized by X-ray diffraction and photoluminescence and the performance of field emission property from ZnO nanorod patterns was investigated. The ZnO nanorods pattern with a good alignment also shows a good field enhancement behavior with a high value of the field enhancement factor.展开更多
We report a wavelength tunable electro-absorption modulated DBR laser based on a combined method of SAG and QWI. The threshold current is 37mA and the output power at 100mA gain current is 3.5mW. When coupled to a sin...We report a wavelength tunable electro-absorption modulated DBR laser based on a combined method of SAG and QWI. The threshold current is 37mA and the output power at 100mA gain current is 3.5mW. When coupled to a single-mode fiber with a coupling efficiency of 15% ,more than a 20dB extinction ratio is observed over the change of EAM bias from 0 to -2V. The 4.4nm continuous wavelength tuning range covers 6 channels on a 100GHz grid for WDM telecommunications.展开更多
A semiconductor optical amplifier and electroabsorption modulator monolithically integrated with a spotsize converter input and output is fabricated by means of selective area growth,quantum well intermixing,and asymm...A semiconductor optical amplifier and electroabsorption modulator monolithically integrated with a spotsize converter input and output is fabricated by means of selective area growth,quantum well intermixing,and asymmetric twin waveguide technology. A 1550-1600nm lossless operation with a high DC extinction ratio of 25dB and more than 10GHz 3dB bandwidth are successfully achieved. The output beam divergence angles of the device in the horizontal and vertical directions are as small as 7.3°× 18.0°, respectively, resulting in a 3.0dB coupling loss with a cleaved single-mode optical fiber.展开更多
Selective fetal growth restriction (sFGR) is a severe condition that complicates 10% to 15% of all monochorionic diamniotic (MCDA) twin pregnancies. Pregnancies complicated with sFGR are at high risk of intrauterine d...Selective fetal growth restriction (sFGR) is a severe condition that complicates 10% to 15% of all monochorionic diamniotic (MCDA) twin pregnancies. Pregnancies complicated with sFGR are at high risk of intrauterine demise or adverse perinatal outcome for the twins. Three clinical types have been described according to the umbilical artery (UA) Doppler pattern observed in the smaller twin: type I, when the UA Doppler is normal;type II, when there is persistent absent or reversed end-diastolic blood flow in the UA Doppler;and type III, when there is intermittent absent and/or reversed end-diastolic blood flow in the UA Doppler. Clinical evolution and management options mainly depend on the type of sFGR. Type I is usually associated with a good prognosis and is managed conservatively. There is no consensus on the management of types II and III, but in earlier and more severe presentations, fetal interventions such as selective laser photocoagulation of placental anastomoses or selective fetal cord occlusion of the smaller twin may be considered. This review aims to provide updated information about the diagnosis, evaluation, follow-up, and management of sFGR in MCDA twin pregnancies.展开更多
A high crystalline quality of SiGe fin with an Si-rich composition area using the replacement fin processing is systematically demonstrated in this paper.The fin replacement process based on a standard FinFET process ...A high crystalline quality of SiGe fin with an Si-rich composition area using the replacement fin processing is systematically demonstrated in this paper.The fin replacement process based on a standard FinFET process is developed.A width of less than 20-nm SiGe fin without obvious defect impact both in the direction across the fin and in the direction along the fin is verified by using the high angle annular dark field scanning transmission electron microscopy and the scanning moiréfringe imaging technique.Moreover,the SiGe composition is inhomogenous in the width of the fin.This is induced by the formation of 111 facets.Due to the atomic density of the 111 facets being higher,the epitaxial growth in the direction perpendicular to these facets is slower than in the direction perpendicular to 001.The Ge incorporation is then higher on the 111 facets than on the 001 facets.So,an Si-rich area is observed in the central area and on the bottom of SiGe fin.展开更多
InP-based photonics integration is becoming a competi- tive candidate for realizing optical modules with enhanced functionality at a reduced cost, especially in optical com- munication systems, since the proposal of w...InP-based photonics integration is becoming a competi- tive candidate for realizing optical modules with enhanced functionality at a reduced cost, especially in optical com- munication systems, since the proposal of wavelength division multiplexing （WDM）. In recent years, network traffic has raised demands for high capacity, high speed transmission systems.展开更多
Heterostructured bimetal nanocrystals with a component having localized surface plasmon resonance(LSPR)property are promising photocatalysts for a series of reactions.In this work,kinetic products of Pd-Ag with a scre...Heterostructured bimetal nanocrystals with a component having localized surface plasmon resonance(LSPR)property are promising photocatalysts for a series of reactions.In this work,kinetic products of Pd-Ag with a screwdriver-like heterostructure have been successfully fabricated via the selective epitaxial growth of Ag on Pd nanowires(NWs).It was confirmed that the deposition rate(Vdeposition)of Ag is much more sensitive to the temperature,compared to the surface diffusion rate(Vdiffusion)which can be effectively reduced by the binding of poly(vinylpyrrolidone)(PVP)molecules.Then the magnitude of Vdeposition/Vdiffusion has been well tailored for the formation of a kinetic growth environment.The interactions between the components of the as-prepared Pd-Ag heterostructures resulted in intensified LSPR effects.As a result,they gained better photocatalytic performance toward solvent free aerobic oxidation of toluene than Pd NWs,Ag NWs and the mixture of them.Additionally,the Pd-Ag heterostructured nanocrystals exhibited excellent catalytic stability for recycling.This work not only presents an idea for realizing kinetic growth but also supports that LSPR effect is a good tool for improving the photocatalytic activity.展开更多
We report a selective area growth（SAG） method to define the p-GaN gate of AlGaN/GaN high electron mobility transistors（HEMTs） by metal-organic chemical vapor deposition.Compared with Schottky gate HEMTs,the SAG p-...We report a selective area growth（SAG） method to define the p-GaN gate of AlGaN/GaN high electron mobility transistors（HEMTs） by metal-organic chemical vapor deposition.Compared with Schottky gate HEMTs,the SAG p-GaN gate HEMTs show more positive threshold voltage（Vth） and better gate control ability.The influence of Cp2Mg flux of SAG p-GaN gate on the AlGaN/GaN HEMTs has also been studied.With the increasing Cp2Mg from 0.16 μmol/min to 0.20 μmol/min,the Vth raises from-0.67 V to-0.37 V.The maximum transconductance of the SAG HEMT at a drain voltage of 10 V is 113.9 mS/mm while that value of the Schottky HEMT is 51.6 mS/mm.The SAG method paves a promising way for achieving p-GaN gate normally-off AlGaN/GaN HEMTs without dry etching damage.展开更多
基金financially supported by the Science and Technology Development Program of Jilin Province(YDZJ202101ZYTS185)the National Natural Science Foundation of China(21975250)。
文摘Antimony-based anodes have attracted wide attention in potassium-ion batteries due to their high theoretical specific capacities(∼660 mA h g^(-1))and suitable voltage platforms.However,severe capacity fading caused by huge volume change and limited ion transportation hinders their practical applications.Recently,strategies for controlling the morphologies of Sb-based materials to improve the electrochemical performances have been proposed.Among these,the two-dimensional Sb(2D-Sb)materials present excellent properties due to shorted ion immigration paths and enhanced ion diffusion.Nevertheless,the synthetic methods are usually tedious,and even the mechanism of these strategies remains elusive,especially how to obtain large-scale 2D-Sb materials.Herein,a novel strategy to synthesize 2D-Sb material using a straightforward solvothermal method without the requirement of a complex nanostructure design is provided.This method leverages the selective adsorption of aldehyde groups in furfural to induce crystal growth,while concurrently reducing and coating a nitrogen-doped carbon layer.Compared to the reported methods,it is simpler,more efficient,and conducive to the production of composite nanosheets with uniform thickness(3–4 nm).The 2D-Sb@NC nanosheet anode delivers an extremely high capacity of 504.5 mA h g^(-1) at current densities of 100 mA g^(-1) and remains stable for more than 200 cycles.Through characterizations and molecular dynamic simulations,how potassium storage kinetics between 2D Sb-based materials and bulk Sb-based materials are explored,and detailed explanations are provided.These findings offer novel insights into the development of durable 2D alloy-based anodes for next-generation potassium-ion batteries.
基金supported by the Key Basic Research Project of Shandong Province,China(No.ZR2019ZD49)the National Natural Science Foundation of China(Nos.51972184 and 51802316)the Natural Science Foundation of Liaoning Province,China(No.2020-MS-009).
文摘The chirality structure of a single-walled carbon nanotube(SWNT)strongly depends on the composition of catalyst used in the chemical vapor deposition process.In this study,we develop a porous magnesia supported manganese-rhenium(MnRe/MgO)catalyst for chirality-selective synthesis of SWNTs.Detailed characterizations reveal that(6,5)tubes with a selectivity higher than 70%are grown from the Re-rich MnRe/MgO catalyst.By comparing the SWNT growth results with those of monometallic Mn or Re,the formation of sigma phase,an intermetallic compound occurring in transition-metal alloy systems,is revealed to be crucial for the dominant synthesis of(6,5)SWNTs.This work not only extends the application of sigma phase alloy for catalytic synthesis of SWNTs,but also sheds lights on the growth of SWNTs with a high chirality selectivity.
基金We acknowledge the financial support from the Fundamental Research Funds of the Central Universities(No.531118010112)the Double First-Class University Initiative of Hunan University(No.531109100004)+2 种基金We also acknowledge the support from the National Natural Science Foundation of China(No.751214296)Hunan Key Laboratory of Two-Dimensional Materials(No.801200005)Strategic Priority Research Program of Chinese Academy of Science(No.XDB30000000).
文摘Heterostructures combined by different individual two-dimensional(2D)materials are essential building blocks to realize unique electronic,optoelectronic properties and multifunctional applications.To date,the direct growth of 2D/2D atomic van der Waals heterostructures(vdWHs)have been extensively investigated.However,the heterostructures from 2D inorganic molecular crystals and atomic crystals have been rarely reported.Here we report two-step direct epitaxial growth of the inorganic molecular-atomic Sb2O3/WS2 vdWHs.The thickness of Sb2O3 nanosheets on WS2 nanosheets can be tuned by variable growth temperatures.Oriented growth behavior of Sb2O3 on WS2 was determined through statistics.Optical images,Raman spectra,Raman mappings and selected-area electron diffraction(SAED),etc.,reveal that Sb2O3/WS2 heterostructures are vertically stacked with high crystal quality.Electrical transport measurements demonstrate that the heterotransistors based on the heterostructures possess high current on/off ratio of 5 × 10^5,obvious gate-tunable and current rectification output characteristics.Optoelectronic characterizations show that the heterostructures have a clear photoresponse with high responsivity of 16.4 AW.The growth of vdWHs from 2D inorganic molecular-atomic crystals may open up new opportunities in 2D functional electronics and optoelectronics.
文摘A promising strategy for the selective growth of ZnO nanorods on SiO2/Si substrates using a graphene buffer layer in a low temperature solution process is described. High densities of ZnO nanorods were grown over a large area and most ZnO nanorods were vertically well-aligned on graphene. Furthermore, selective growth of ZnO nanorods on graphene was realized by applying a simple mechanical treatment, since ZnO nanorods formed on graphene are mechanically stable on an atomic level. These results were confirmed by first principles calculations which showed that the ZnO-graphene binding has a low destabilization energy. In addition, it was found that ZnO nanorods grown on SiO2/Si with a graphene buffer layer have better optical properties than ZnO nanorods grown on bare SiO2/Si. The nanostructured ZnO-graphene materials have promising applications in future flexible electronic and optical devices.
基金Supported by the National Natural Science Foundation of China（Nos.61223005, 61376046）, the Program for New Century Excellent Talents in University of China（Nos.NCET-12-0236, NCET-13-0254）, the Science and Technology Developing Project of Jilin Province, China （No.20130204032GX） and the Opening Project of Science and Technology on Reliability Physics and Application Technology of Electronic Component Laboratory in the Fifth Electronics Research Institute of Ministry of Industry and Information Technology of China（No.ZHD201204）.
文摘Cone-shaped patterned sapphire substrate was prepared by inductively coupled plasma etching and GaN nucleation layer was grown on it by metal-organic chemical vapor deposition.A selective growth of GaN nucleation layer was found on the slope of the cone-shaped patterned sapphire substrat,and the distribution morphology of GaN had significantly changed after it was recrystallized.GaN selective growth and redistribution were analyzed by investigating the distribution of crystallographic planes on the cone surface and the atom array of specific planes at atom level.
基金Supported by the Key Program of the National Natural Science Foundation of China under Grant No 61334009the National High Technology Research and Development Program of China under Grant No 2014AA032604
文摘CaN nanorods are successfully fabricated by adjusting the flow rate ratio of hydrogen （H2）/nitrogen （N2） and growth temperature of the selective area growth （SAG） method with metal organic chemical vapor deposition （MOCVD）. The SAG template is obtained by nanospherical-lens photolithography. It is found that increasing the flow rate of 1-12 will change the CaN crystal shape from pyramid to vertical rod, while increasing the growth temperature will reduce the diameters of GaN rods to nanometer scale. Finally the CaN nanorods with smooth lateral surface and relatively good quality are obtained under the condition that the H2：N2 ratio is 1：1 and the growth temperature is 1030℃. The good crystal quality and orientation of GaN nanorods are confirmed by high resolution transmission electron microscopy. The cathodoluminescence spectrum suggests that the crystal and optical quality is also improved with increasing the temperature.
基金Supported by the National High-Technology Research and Development Program of China under Grant Nos 2011AA010303and 2012AA012203the National Basic Research Program of China under Grant No 2011CB301702the National Natural Science Foundation of China under Grant Nos 61321063 and 6132010601
文摘A 32 Gb/s monolithically integrated electroabsorption modulated laser is fabricated by selective area growth technology. The threshold current of the device is below 13mA. The output power exceeds 10mW at 0V bias when the injection current of the distributed feedback laser is 100mA at 25℃. The side mode suppression ratio is over 50 dB. A 32Gb/s eye diagram is measured with a 3.SVpp nonreturn-to-zero pseudorandom modulation signal at -2.3 V bias. A clearly opening eyediagram with a dynamic extinction ratio of 8.01 dB is obtained.
基金Supported by the National Science and Technology Major Project of China under Grant No 2011ZX02708
文摘A high quality of GaAs crystal growth in nanoscale V-shape trenches on Si（O01） substrates is achieved by using the aspect-ratio trapping method. GaAs thin films are deposited via metal-organic chemical vapor deposition by using a two-step growth process. Threading disJocations arising from lattice mismatch are trapped by laterally confining sidewalls, and antiphase domains boundaries are completely restricted by V-groove trenches with Si { 111} facets. Material quality is confirmed by scanning electron microscopy （SEM）, transmission electron microscopy （TEM） and high resolution X-ray diffraction. Low temperature photoluminescence （PL） measurement is used to analyze the thermal strain relaxation in GaAs layers. This approach shows great promise for the realization of high mobility devices or optoelectronie integrated circuits on Si substrates.
文摘High performance 1 57μm spotsize converter monolithically integrated DFB is fabricated by the technique of self aligned selective area growth.The upper optical confinement layer and the butt coupled tapered thickness waveguide are regrown simultaneously,which not only offeres the separated optimization of the active region and the integrated spotsize converter,but also reduces the difficulty of the butt joint selective regrowth.The threshold current is as low as 4 4mA.The output power at 49mA is 10 1mW.The side mode suppression ratio (SMSR) is 33 2dB.The vertical and horizontal far field divergence angles are as small as 9° and 15° respectively,the 1dB misalignment tolerance are 3 6μm and 3 4μm.
基金supported by the National Natural Science Foundation of China(Grant Nos.61274039 and 51177175)the National Basic Research Program of China(Grant No.2011CB301903)+5 种基金the Ph.D.Programs Foundation of Ministry of Education of China(Grant No.20110171110021)the International Sci.&Tech.Collaboration Program of China(Grant No.2012DFG52260)the International Sci.&Tech.Collaboration Program of Guangdong Province,China(Grant No.2013B051000041)the Science and Technology Plan of Guangdong Province,China(Grant No.2013B010401013)the National High Technology Research and Development Program of China(Grant No.2014AA032606)the Opened Fund of the State Key Laboratory on Integrated Optoelectronics,China(Grant No.IOSKL2014KF17)
文摘Migration characterizations of Ga and In adatoms on the dielectric surface in selective metal organic vapor phase epitaxy （MOVPE） were investigated. In the typical MOVPE environment, the selectivity of growth is preserved for GaN, and the growth rate of GaN micro-pyramids is sensitive to the period of the patterned SiO2 mask. A surface migration induced model was adopted to figure out the effective migration length of Ga adatoms on the dielectric surface. Different from the growth of GaN, the selective area growth of InGaN on the patterned template would induce the deposition of InGaN polycrystalline particles on the patterned Si02 mask with a long period. It was demonstrated with a scanning electron microscope and energy dispersive spectroscopy that the In adatoms exhibit a shorter migration length on the dielectric surface.
基金supported by the National Natural Science Foundation of China(Grant Nos.61274039 and 61574173)the National Key Research and Development Program,China(Grant No.2016YFB0400105)+9 种基金the International Science and Technology Collaboration Program of Guangdong Province,China(Grant No.2013B051000041)the International Science and Technology Collaboration Program of Guangzhou City,China(Grant No.2016201604030055)the National High Technology Research and Development Program of China(Grant No.2014AA032606)Guangdong Provincial Natural Science Foundation,China(Grant No.2015A030312011)the Science&Technology Plan of Guangdong Province,China(Grant Nos.2015B090903062,2015B010132007,and2015B010129010)the Science and Technology Plan of Guangzhou,China(Grant No.201508010048)the Science and Technology Plan of Foshan,China(Grant No.201603130003)Guangdong–Hong Kong Joint Innovation Project of Guangdong Province,China(Grant No.2014B050505009)the Opened Fund of the State Key Laboratory on Integrated Optoelectronics(Grant No.IOSKL2014KF17)the Zhuhai Key Technology Laboratory of Wide Bandgap Semiconductor Power Electronics,Sun Yat-sen University(Grant No.20167612042080001)
文摘Ga N micro-pyramids with AlGaN capping layer are grown by selective metal–organic–vapor phase epitaxy（MOVPE）. Compared with bare Ga N micro-pyramids, AlGaN/Ga N micro-pyramids show wrinkling morphologies at the bottom of the structure. The formation of those special morphologies is associated with the spontaneously formed AlGaN polycrystalline particles on the dielectric mask, owing to the much higher bond energy of Al–N than that of Ga–N. When the sizes of the polycrystalline particles are larger than 50 nm, the uniform source supply behavior is disturbed, thereby leading to unsymmetrical surface morphology. Analysis reveals that the scale of surface wrinkling is related to the migration length of Ga adatoms along the AlGaN {1ī01} facet. The migration properties of Al and Ga further affect the distribution of Al composition along the sidewalls, characterized by the μ-PL measurement.
基金supported by the National Natural Science Foundation of China(Grant Nos.81971399 and 82171661).
文摘In perinatal medicine,intrauterine growth restriction(IUGR)is one of the greatest challenges.The etiology of IUGR is multifactorial,but most cases are thought to arise from placental insufficiency.However,identifying the placental cause of IUGR can be difficult due to numerous confounding factors.Selective IUGR(sIUGR)would be a good model to investigate how impaired placentation affects fetal development,as the growth discordance between monochorionic twins cannot be explained by confounding genetic or maternal factors.Herein,we constructed and analyzed the placental proteomic profiles of IUGR twins and normal cotwins.Specifically,we identified a total of 5481 proteins,of which 233 were differentially expressed(57 up-regulated and 176 down-regulated)in IUGR twins.Bioinformatics analysis indicates that these differentially expressed proteins(DEPs)are mainly associated with cardiovascular system development and function,organismal survival,and organismal development.Notably,34 DEPs are significantly enriched in angiogenesis,and diminished placental angiogenesis in IUGR twins has been further elaborately confirmed.Moreover,we found decreased expression of metadherin(MTDH)in the placentas of IUGR twins and demonstrated that MTDH contributes to placental angiogenesis and fetal growth in vitro.Collectively,our findings reveal the comprehensive proteomic signatures of placentas for sIUGR twins,and the DEPs identified may provide in-depth insights into the pathogenesis of placental dysfunction and subsequent impaired fetal growth.
文摘We provide a new way to prepare ZnO nanorods pattern from the solution composed of hexamethylenetetramine （HMT） and Zn（NO3）2. The substrate is ITO substrate covered by well ordered Au islands. Since Au and the underneath ITO substrate have two different nucleation rates in the initial stage of heterogeneous nucleation process, the subsequent ZnO growth on the quick nucleating area takes place under diffusion control and is able to confine the synthesis of ZnO nanorods to specific locations. The concentrations of zinc nitrate and HMT are well adjusted to show the possibility of the new route for the patterning of the ZnO nanorods. Furthermore, the nanorods pattern was characterized by X-ray diffraction and photoluminescence and the performance of field emission property from ZnO nanorod patterns was investigated. The ZnO nanorods pattern with a good alignment also shows a good field enhancement behavior with a high value of the field enhancement factor.
文摘We report a wavelength tunable electro-absorption modulated DBR laser based on a combined method of SAG and QWI. The threshold current is 37mA and the output power at 100mA gain current is 3.5mW. When coupled to a single-mode fiber with a coupling efficiency of 15% ,more than a 20dB extinction ratio is observed over the change of EAM bias from 0 to -2V. The 4.4nm continuous wavelength tuning range covers 6 channels on a 100GHz grid for WDM telecommunications.
文摘A semiconductor optical amplifier and electroabsorption modulator monolithically integrated with a spotsize converter input and output is fabricated by means of selective area growth,quantum well intermixing,and asymmetric twin waveguide technology. A 1550-1600nm lossless operation with a high DC extinction ratio of 25dB and more than 10GHz 3dB bandwidth are successfully achieved. The output beam divergence angles of the device in the horizontal and vertical directions are as small as 7.3°× 18.0°, respectively, resulting in a 3.0dB coupling loss with a cleaved single-mode optical fiber.
文摘Selective fetal growth restriction (sFGR) is a severe condition that complicates 10% to 15% of all monochorionic diamniotic (MCDA) twin pregnancies. Pregnancies complicated with sFGR are at high risk of intrauterine demise or adverse perinatal outcome for the twins. Three clinical types have been described according to the umbilical artery (UA) Doppler pattern observed in the smaller twin: type I, when the UA Doppler is normal;type II, when there is persistent absent or reversed end-diastolic blood flow in the UA Doppler;and type III, when there is intermittent absent and/or reversed end-diastolic blood flow in the UA Doppler. Clinical evolution and management options mainly depend on the type of sFGR. Type I is usually associated with a good prognosis and is managed conservatively. There is no consensus on the management of types II and III, but in earlier and more severe presentations, fetal interventions such as selective laser photocoagulation of placental anastomoses or selective fetal cord occlusion of the smaller twin may be considered. This review aims to provide updated information about the diagnosis, evaluation, follow-up, and management of sFGR in MCDA twin pregnancies.
基金the Beijing Municipal Natural Science Foundation,China(Grant No.4202078)the National Key Project of Science and Technology of China(Grant No.2017ZX02315001-002).
文摘A high crystalline quality of SiGe fin with an Si-rich composition area using the replacement fin processing is systematically demonstrated in this paper.The fin replacement process based on a standard FinFET process is developed.A width of less than 20-nm SiGe fin without obvious defect impact both in the direction across the fin and in the direction along the fin is verified by using the high angle annular dark field scanning transmission electron microscopy and the scanning moiréfringe imaging technique.Moreover,the SiGe composition is inhomogenous in the width of the fin.This is induced by the formation of 111 facets.Due to the atomic density of the 111 facets being higher,the epitaxial growth in the direction perpendicular to these facets is slower than in the direction perpendicular to 001.The Ge incorporation is then higher on the 111 facets than on the 001 facets.So,an Si-rich area is observed in the central area and on the bottom of SiGe fin.
基金supported by the National High-Tech Research and Development Program of China(No.2015AA016902)the National Natural Science Foundation of China(Nos.61635010,61674136,and 61435002)
文摘InP-based photonics integration is becoming a competi- tive candidate for realizing optical modules with enhanced functionality at a reduced cost, especially in optical com- munication systems, since the proposal of wavelength division multiplexing （WDM）. In recent years, network traffic has raised demands for high capacity, high speed transmission systems.
基金This work was supported by the Natural Science Foundation of Zhejiang Province(No.LY20B010004)the National Natural Science Foundation of China(Nos.21671152,51672193,and 51420105002).
文摘Heterostructured bimetal nanocrystals with a component having localized surface plasmon resonance(LSPR)property are promising photocatalysts for a series of reactions.In this work,kinetic products of Pd-Ag with a screwdriver-like heterostructure have been successfully fabricated via the selective epitaxial growth of Ag on Pd nanowires(NWs).It was confirmed that the deposition rate(Vdeposition)of Ag is much more sensitive to the temperature,compared to the surface diffusion rate(Vdiffusion)which can be effectively reduced by the binding of poly(vinylpyrrolidone)(PVP)molecules.Then the magnitude of Vdeposition/Vdiffusion has been well tailored for the formation of a kinetic growth environment.The interactions between the components of the as-prepared Pd-Ag heterostructures resulted in intensified LSPR effects.As a result,they gained better photocatalytic performance toward solvent free aerobic oxidation of toluene than Pd NWs,Ag NWs and the mixture of them.Additionally,the Pd-Ag heterostructured nanocrystals exhibited excellent catalytic stability for recycling.This work not only presents an idea for realizing kinetic growth but also supports that LSPR effect is a good tool for improving the photocatalytic activity.
基金Project supported by the National Natural Sciences Foundation of China(Nos.61376090,61306008)the National High Technology Program of China(No.2014AA032606)
文摘We report a selective area growth（SAG） method to define the p-GaN gate of AlGaN/GaN high electron mobility transistors（HEMTs） by metal-organic chemical vapor deposition.Compared with Schottky gate HEMTs,the SAG p-GaN gate HEMTs show more positive threshold voltage（Vth） and better gate control ability.The influence of Cp2Mg flux of SAG p-GaN gate on the AlGaN/GaN HEMTs has also been studied.With the increasing Cp2Mg from 0.16 μmol/min to 0.20 μmol/min,the Vth raises from-0.67 V to-0.37 V.The maximum transconductance of the SAG HEMT at a drain voltage of 10 V is 113.9 mS/mm while that value of the Schottky HEMT is 51.6 mS/mm.The SAG method paves a promising way for achieving p-GaN gate normally-off AlGaN/GaN HEMTs without dry etching damage.
