A commercial epi-ready(201)β-Ga_(2)O_(3) wafer was investigated upon diamond sawing into pieces measuring 2.5×3 mm^(2).The defect structure and crystallinity in the cut samples has been studied by X-ray diffract...A commercial epi-ready(201)β-Ga_(2)O_(3) wafer was investigated upon diamond sawing into pieces measuring 2.5×3 mm^(2).The defect structure and crystallinity in the cut samples has been studied by X-ray diffraction and a selective wet etching technique.The density of defects was estimated from the average value of etch pits calculated,including near-edge regions,and was obtained close to 109 cm^(-2).Blocks with lattice orientation deviated by angles of 1-3 arcmin,as well as non-stoichiometric fractions with a relative strain about(1.0-1.5)×10^(-4)in the[201]direction,were found.Crystal perfection was shown to decrease significantly towards the cutting lines of the samples.To reduce the number of structural defects and increase the crystal perfection of the samples via increasing defect motion mobility,the thermal annealing was employed.Polygonization and formation of a mosaic structure coupled with dislocation wall appearance upon 3 h of annealing at 1100℃ was observed.The fractions characterized by non-stoichiometry phases and the block deviation disappeared.The annealing for 11 h improved the homogeneity and perfection in the crystals.The average density of the etch pits dropped down significantly to 8×10^(6) cm^(-2).展开更多
Electrochemical nitrogen reduction reaction(NRR)is a promising method for the synthesis of ammonia(NH3).However,the electrochemical NRR process remains a great challenge in achieving a high NH3 yield rate and a high F...Electrochemical nitrogen reduction reaction(NRR)is a promising method for the synthesis of ammonia(NH3).However,the electrochemical NRR process remains a great challenge in achieving a high NH3 yield rate and a high Faradaic efficiency(FE)due to the extremely strong N≡N bonds and the competing hydrogen evolution reaction(HER).Recently,bismuth telluride(Bi_(2)Te_(3))with two-dimensional layered structure has been reported as a promising catalyst for N_(2)fixation.Herein,to further enhance its NRR activity,a general doping strategy is developed to introduce and modulate the crystal defects of Bi_(2)Te_(3)nanosheets by adjusting the amount of Ce dopant(denoted as Ce_(x)-Bi_(2)Te_(3),where x represents the designed molar ratio of Ce/Bi).Meanwhile,the crystal defects can be designed and controlled by means of ion substitution and charge compensation.At−0.60 V versus the reversible hydrogen electrode(RHE),Ce_(0.3)-Bi_(2)Te_(3)exhibits a high NH_(3) yield(78.2μg·h^(−1)·mgcat^(−1)),a high FE(19.3%),excellent structural and electrochemical stability.Its outstanding catalytic activity is attributed to the tunable crystal defects by Ce doping.This work not only contributes to enhancing the NRR activity of Bi_(2)Te_(3)nanosheets,but also provides a reliable approach to prepare high-performance electrocatalysts by controlling the type and concentration of crystal defects for artificial N_(2)fixation.展开更多
Owing to their attractive structure and mechanical properties,high-entropy alloys(HEAs) and mediumentropy alloys(MEAs) have attracted considerable research interest.The strength of HEAs/MEAs with a single face-centere...Owing to their attractive structure and mechanical properties,high-entropy alloys(HEAs) and mediumentropy alloys(MEAs) have attracted considerable research interest.The strength of HEAs/MEAs with a single face-centered cubic(FCC) phase,on the other hand,requires improvement.Therefore,in this study,we demonstrate a strategy for increasing the room-temperature strength of FCC-phase HEAs/MEAs by tuning cryo-pre-straining-induced crystal defects via the temperature-dependent stacking fault energyregulated plasticity mechanism.Through neutron diffraction line profile analysis and electron microscope observation,the effect of the tuned defects on the tensile strength was clarified.Due to the cryorolling-induced high dislocation density,mechanical twins,and stacking faults,the room-temperature yield strength of an equiatomic CoCrFeNi HEA was increased by ~290%,from 243 MPa(as-recrystallized)to 941.6 MPa(30% cryo-rolled),while maintaining a tensile elongation of 18%.After partial recovery via heat treatment,the yield strength and ultimate tensile strength decreased slightly to 869 and 936 MPa,respectively.Conversely,the elongation increased to 25.6%,The dislocation density and distribution of the dislocations were found to contribute to the strengthening caused by forest dislocations,which warrants further investigation.This study discussed the possibility of developing single-phase high-performance HEAs by tuning pre-straining-induced crystal defects.展开更多
Single photonic crystal defects based on an air-bridge structure were fabricated. We obtained sharp defect modes with quality factors higher than 600 and observed their response to ultrashort optical pulses by utilizi...Single photonic crystal defects based on an air-bridge structure were fabricated. We obtained sharp defect modes with quality factors higher than 600 and observed their response to ultrashort optical pulses by utilizing two-photon absorption.展开更多
Crystal defect engineering is widely used as an effective approach to regulate the optical and optoelectronic properties of semiconductor nanostructures.However,photogenerated electron-hole pair recombination centers ...Crystal defect engineering is widely used as an effective approach to regulate the optical and optoelectronic properties of semiconductor nanostructures.However,photogenerated electron-hole pair recombination centers caused by structural defects usually lead to the reduction of optoelectronic performance.In this work,a high-performance photodetector based on(GaN)_(1-x)(ZnO)_(x)solid solution nanowire with bicrystal structure is fabricated and it shows excellent photoresponse to ultraviolet and visible light.The highest responsivity of the photodetector is as high as 60,86 and 43 A/W under the irradiation of365 nm,532 nm and 650 nm,respectively.The corresponding response time is as fast as 170,320 and 160 ms.Such wide spectral responses can be attributed to various intermediate energy levels induced by the introduction of various structural defects and dopants in the solid solution nanowire.Moreover,the peculiar bicrystal boundary along the axial direction of the nanowire provides two parallel and fast transmission channels for photo-generated carriers,reducing the recombination of photo-generated carriers.Our findings provide a valued example using crystal defect engineering to broaden the photoresponse range and improve the photodetector performance and thus can be extended to other material systems for various optoelectronic applications.展开更多
Inorganic perovskite wafers with good stability and adjustable sizes are promising in X-ray detection but the high synthetic temperature is a hindrance.Herein,dimethyl sulfoxide(DMSO)is used to prepare the CsPbBr_(3)m...Inorganic perovskite wafers with good stability and adjustable sizes are promising in X-ray detection but the high synthetic temperature is a hindrance.Herein,dimethyl sulfoxide(DMSO)is used to prepare the CsPbBr_(3)micro-bricks powder at room temperature.The CsPbBr_(3)powder has a cubic shape with few crystal defects,small charge trap density,and high crystallinity.A trace amount of DMSO attaches to the surface of the CsPbBr_(3)micro-bricks via Pb-O bonding,forming the CsPbBr_(3)-DMSO adduct.During hot isostatic processing,the released DMSO vapor merges the CsPbBr_(3)micro-bricks,producing a compact and dense CsPbBr_(3)wafer with minimized grain boundaries and excellent charge transport properties.The CsPbBr_(3)wafer shows a large mobility-lifetime(μτ)product of 5.16×10^(-4)cm^(2)·V^(-1),high sensitivity of 14,430μC·Gyair^(-1)·cm^(-2),low detection limit of 564 nGyair·s^(-1),as well as robust stability in X-ray detection.The results reveal a novel strategy with immense practical potential pertaining to high-contrast X-ray detection.展开更多
Hydroxyapatite(HA)synthesized by a wet chemical route was subjected to heavy ion irradiation,using4 Me V Krypton ion(Kr17+)with ion fluence ranging from 1×1013 to 1×1015 ions/cm2.Glancing incidence X-ray dif...Hydroxyapatite(HA)synthesized by a wet chemical route was subjected to heavy ion irradiation,using4 Me V Krypton ion(Kr17+)with ion fluence ranging from 1×1013 to 1×1015 ions/cm2.Glancing incidence X-ray diffraction(GIXRD)results confirmed the phase purity of irradiated HA with a moderate contraction in lattice parameters,and further indicated the irradiation-induced structural disorder,evidenced by broadening of the diffraction peaks.High-resolution transmission electron microscopy(HRTEM)observations indicated that the applied Kr irradiation induced significant damage in the hydroxyapatite lattice.Specifically,cavities were observed with their diameter and density varying with the irradiation fluences,while a radiation-induced crystalline-to-amorphous transition with increasing ion dose was identified.Raman and X-ray photoelectron spectroscopy(XPS)analysis further indicated the presence of irradiationinduced defects.Ion release from pristine and irradiated materials following immersion in Tris(p H 7.4,37?)buffer showed that dissolution in vitro was enhanced by irradiation,reaching a peak at 0.1 dpa.We examined the effects of irradiation on the early stages of the mouse osteoblast-like cells(MC3 T3-E)response.A cell counting kit-8 assay(CCK-8 test)was carried out to investigate the cytotoxicity of samples,and viable cells can be observed on the irradiated materials.展开更多
Due to a radioactive decay Pu is vulnerable to aging.The behavior of He in Pu is the foundation for understanding Pu self-radiation damage aging.Molecular dynamics technique is performed to investigate the behavior of...Due to a radioactive decay Pu is vulnerable to aging.The behavior of He in Pu is the foundation for understanding Pu self-radiation damage aging.Molecular dynamics technique is performed to investigate the behavior of defects,the interaction between He and defects,the processes of initial nucleation and growth of He bubble and the dependence of He bubble on the macroscopical properties of Pu.Modified embedded atom method,Morse pair potential and the Lennard-Jones pair potential are used for describing the interactions of Pu-Pu,Pu-He and He-He,respectively.The main calculated results show that He atoms can combine with vacancies to form Hevacancy cluster(i.e.,the precursor of He bubble)during the process of self-radiation as a result of high binding energy of an interstitial He atom to vacancy;He bubble’s growth can be dominated by the mechanism of punching out of dislocation loop;the swelling induced by He bubble is very small;grain boundaries give rise to an energetically more favorable zone for the interstitial He atom and self-interstitial atom accumulation than for vacancy accumulation;the process of He release can be identified as the formation of release channel induced by the cracking of He bubble and surface structure.展开更多
基金funded by the Russian Science Foundation,project#23-29-10196。
文摘A commercial epi-ready(201)β-Ga_(2)O_(3) wafer was investigated upon diamond sawing into pieces measuring 2.5×3 mm^(2).The defect structure and crystallinity in the cut samples has been studied by X-ray diffraction and a selective wet etching technique.The density of defects was estimated from the average value of etch pits calculated,including near-edge regions,and was obtained close to 109 cm^(-2).Blocks with lattice orientation deviated by angles of 1-3 arcmin,as well as non-stoichiometric fractions with a relative strain about(1.0-1.5)×10^(-4)in the[201]direction,were found.Crystal perfection was shown to decrease significantly towards the cutting lines of the samples.To reduce the number of structural defects and increase the crystal perfection of the samples via increasing defect motion mobility,the thermal annealing was employed.Polygonization and formation of a mosaic structure coupled with dislocation wall appearance upon 3 h of annealing at 1100℃ was observed.The fractions characterized by non-stoichiometry phases and the block deviation disappeared.The annealing for 11 h improved the homogeneity and perfection in the crystals.The average density of the etch pits dropped down significantly to 8×10^(6) cm^(-2).
基金the National Natural Science Foundation of China(Nos.22074137 and 21721003).
文摘Electrochemical nitrogen reduction reaction(NRR)is a promising method for the synthesis of ammonia(NH3).However,the electrochemical NRR process remains a great challenge in achieving a high NH3 yield rate and a high Faradaic efficiency(FE)due to the extremely strong N≡N bonds and the competing hydrogen evolution reaction(HER).Recently,bismuth telluride(Bi_(2)Te_(3))with two-dimensional layered structure has been reported as a promising catalyst for N_(2)fixation.Herein,to further enhance its NRR activity,a general doping strategy is developed to introduce and modulate the crystal defects of Bi_(2)Te_(3)nanosheets by adjusting the amount of Ce dopant(denoted as Ce_(x)-Bi_(2)Te_(3),where x represents the designed molar ratio of Ce/Bi).Meanwhile,the crystal defects can be designed and controlled by means of ion substitution and charge compensation.At−0.60 V versus the reversible hydrogen electrode(RHE),Ce_(0.3)-Bi_(2)Te_(3)exhibits a high NH_(3) yield(78.2μg·h^(−1)·mgcat^(−1)),a high FE(19.3%),excellent structural and electrochemical stability.Its outstanding catalytic activity is attributed to the tunable crystal defects by Ce doping.This work not only contributes to enhancing the NRR activity of Bi_(2)Te_(3)nanosheets,but also provides a reliable approach to prepare high-performance electrocatalysts by controlling the type and concentration of crystal defects for artificial N_(2)fixation.
基金supported by a Grant-in-Aid for Scientific Research from the Japan Society for the Promotion of Science(JSPS)KAKENHI(Nos.19K14838 and 21K03766)the“Creation of Life Innovation Materials for Interdisciplinary and International Researcher Development”project。
文摘Owing to their attractive structure and mechanical properties,high-entropy alloys(HEAs) and mediumentropy alloys(MEAs) have attracted considerable research interest.The strength of HEAs/MEAs with a single face-centered cubic(FCC) phase,on the other hand,requires improvement.Therefore,in this study,we demonstrate a strategy for increasing the room-temperature strength of FCC-phase HEAs/MEAs by tuning cryo-pre-straining-induced crystal defects via the temperature-dependent stacking fault energyregulated plasticity mechanism.Through neutron diffraction line profile analysis and electron microscope observation,the effect of the tuned defects on the tensile strength was clarified.Due to the cryorolling-induced high dislocation density,mechanical twins,and stacking faults,the room-temperature yield strength of an equiatomic CoCrFeNi HEA was increased by ~290%,from 243 MPa(as-recrystallized)to 941.6 MPa(30% cryo-rolled),while maintaining a tensile elongation of 18%.After partial recovery via heat treatment,the yield strength and ultimate tensile strength decreased slightly to 869 and 936 MPa,respectively.Conversely,the elongation increased to 25.6%,The dislocation density and distribution of the dislocations were found to contribute to the strengthening caused by forest dislocations,which warrants further investigation.This study discussed the possibility of developing single-phase high-performance HEAs by tuning pre-straining-induced crystal defects.
文摘Single photonic crystal defects based on an air-bridge structure were fabricated. We obtained sharp defect modes with quality factors higher than 600 and observed their response to ultrashort optical pulses by utilizing two-photon absorption.
基金partially supported by the National Natural Science Foundation of China(Nos.51702326 and 51872296)the Liaoning Province Natural Science Foundation(No.2019-MS333)+3 种基金the Youth Innovation Promotion Association of the Chinese Academy of Sciences(No.2019197)the Shenyang National Laboratory for Materials Science(No.L2019F36)the Shenyang Planning Project of Science and Technology(No.18-013-0-52)Tomsk Polytechnic University Competitiveness Enhancement Program grant with project number TPU CEP NOC N.M.Kizhnera188/2020。
文摘Crystal defect engineering is widely used as an effective approach to regulate the optical and optoelectronic properties of semiconductor nanostructures.However,photogenerated electron-hole pair recombination centers caused by structural defects usually lead to the reduction of optoelectronic performance.In this work,a high-performance photodetector based on(GaN)_(1-x)(ZnO)_(x)solid solution nanowire with bicrystal structure is fabricated and it shows excellent photoresponse to ultraviolet and visible light.The highest responsivity of the photodetector is as high as 60,86 and 43 A/W under the irradiation of365 nm,532 nm and 650 nm,respectively.The corresponding response time is as fast as 170,320 and 160 ms.Such wide spectral responses can be attributed to various intermediate energy levels induced by the introduction of various structural defects and dopants in the solid solution nanowire.Moreover,the peculiar bicrystal boundary along the axial direction of the nanowire provides two parallel and fast transmission channels for photo-generated carriers,reducing the recombination of photo-generated carriers.Our findings provide a valued example using crystal defect engineering to broaden the photoresponse range and improve the photodetector performance and thus can be extended to other material systems for various optoelectronic applications.
基金This work was financially supported by the National Natural Science Foundation of China(Nos.21975280,62004091,and 12235006)the Shenzhen Excellent Science and Technology Innovation Talent Training Project-Outstanding Youth Project(No.RCJC20200714114435061)+5 种基金the Shenzhen Basic Research Program(No.JCYJ20200109115212546)the Chinese Academy of Sciences Special Research Assistant Project(Nos.Y95909 and E15907)the Chinese Academy of Sciences Excellent Youth Innovation Fund grade B(No.E2G0161001)the Youth Innovation Promotion Association Chinese Academy of Sciences(No.2020354)the Hong Kong ITC(Innovation and Technology Commission)ITF(Innovation and Technology Fund)(Nos.GHP/149/20SZ and CityU 9440296)the City University of Hong Kong Donation Research Grant(DON-RMG No.9229021).
文摘Inorganic perovskite wafers with good stability and adjustable sizes are promising in X-ray detection but the high synthetic temperature is a hindrance.Herein,dimethyl sulfoxide(DMSO)is used to prepare the CsPbBr_(3)micro-bricks powder at room temperature.The CsPbBr_(3)powder has a cubic shape with few crystal defects,small charge trap density,and high crystallinity.A trace amount of DMSO attaches to the surface of the CsPbBr_(3)micro-bricks via Pb-O bonding,forming the CsPbBr_(3)-DMSO adduct.During hot isostatic processing,the released DMSO vapor merges the CsPbBr_(3)micro-bricks,producing a compact and dense CsPbBr_(3)wafer with minimized grain boundaries and excellent charge transport properties.The CsPbBr_(3)wafer shows a large mobility-lifetime(μτ)product of 5.16×10^(-4)cm^(2)·V^(-1),high sensitivity of 14,430μC·Gyair^(-1)·cm^(-2),low detection limit of 564 nGyair·s^(-1),as well as robust stability in X-ray detection.The results reveal a novel strategy with immense practical potential pertaining to high-contrast X-ray detection.
基金supported by the Science Challenge Project[No:TZ2018004]National Natural Science Foundation of China[Nos.51072159,51273159]+1 种基金Science and technology program of Shaanxi Province[No:2014K10-07]Technology Foundation for Selected Overseas Chinese Scholar,Department of Human Resources and Social Security of Shaanxi Province[No:2014-27].
文摘Hydroxyapatite(HA)synthesized by a wet chemical route was subjected to heavy ion irradiation,using4 Me V Krypton ion(Kr17+)with ion fluence ranging from 1×1013 to 1×1015 ions/cm2.Glancing incidence X-ray diffraction(GIXRD)results confirmed the phase purity of irradiated HA with a moderate contraction in lattice parameters,and further indicated the irradiation-induced structural disorder,evidenced by broadening of the diffraction peaks.High-resolution transmission electron microscopy(HRTEM)observations indicated that the applied Kr irradiation induced significant damage in the hydroxyapatite lattice.Specifically,cavities were observed with their diameter and density varying with the irradiation fluences,while a radiation-induced crystalline-to-amorphous transition with increasing ion dose was identified.Raman and X-ray photoelectron spectroscopy(XPS)analysis further indicated the presence of irradiationinduced defects.Ion release from pristine and irradiated materials following immersion in Tris(p H 7.4,37?)buffer showed that dissolution in vitro was enhanced by irradiation,reaching a peak at 0.1 dpa.We examined the effects of irradiation on the early stages of the mouse osteoblast-like cells(MC3 T3-E)response.A cell counting kit-8 assay(CCK-8 test)was carried out to investigate the cytotoxicity of samples,and viable cells can be observed on the irradiated materials.
基金This work was supported by the National Natural Science Foundation of China(Grant No.20801007).
文摘Due to a radioactive decay Pu is vulnerable to aging.The behavior of He in Pu is the foundation for understanding Pu self-radiation damage aging.Molecular dynamics technique is performed to investigate the behavior of defects,the interaction between He and defects,the processes of initial nucleation and growth of He bubble and the dependence of He bubble on the macroscopical properties of Pu.Modified embedded atom method,Morse pair potential and the Lennard-Jones pair potential are used for describing the interactions of Pu-Pu,Pu-He and He-He,respectively.The main calculated results show that He atoms can combine with vacancies to form Hevacancy cluster(i.e.,the precursor of He bubble)during the process of self-radiation as a result of high binding energy of an interstitial He atom to vacancy;He bubble’s growth can be dominated by the mechanism of punching out of dislocation loop;the swelling induced by He bubble is very small;grain boundaries give rise to an energetically more favorable zone for the interstitial He atom and self-interstitial atom accumulation than for vacancy accumulation;the process of He release can be identified as the formation of release channel induced by the cracking of He bubble and surface structure.
