Given the carbon peak and carbon neutrality era,there is an urgent need to develop high-strength steel with remarkable hydrogen embrittlement resistance.This is crucial in enhancing toughness and ensuring the utilizat...Given the carbon peak and carbon neutrality era,there is an urgent need to develop high-strength steel with remarkable hydrogen embrittlement resistance.This is crucial in enhancing toughness and ensuring the utilization of hydrogen in emerging iron and steel materials.Simultaneously,the pursuit of enhanced metallic materials presents a cross-disciplinary scientific and engineering challenge.Developing high-strength,toughened steel with both enhanced strength and hydrogen embrittlement(HE)resistance holds significant theoretical and practical implications.This ensures secure hydrogen utilization and further carbon neutrality objectives within the iron and steel sector.Based on the design principles of high-strength steel HE resistance,this review provides a comprehensive overview of research on designing surface HE resistance and employing nanosized precipitates as intragranular hydrogen traps.It also proposes feasible recommendations and prospects for designing high-strength steel with enhanced HE resistance.展开更多
航天器运行在恶劣的空间环境中容易引发充放电现象,而叠加电磁场会导致其在较低的充电电位下发生放电,严重威胁航天器的安全运行。为揭示强电磁场诱发真空沿面放电的机理并提出抑制方法,该文采用离子交换方法对聚酰亚胺(polyimide,PI)...航天器运行在恶劣的空间环境中容易引发充放电现象,而叠加电磁场会导致其在较低的充电电位下发生放电,严重威胁航天器的安全运行。为揭示强电磁场诱发真空沿面放电的机理并提出抑制方法,该文采用离子交换方法对聚酰亚胺(polyimide,PI)薄膜表面进行改性处理,并基于搭建的强电磁场诱发真空沿面放电平台,结合表面陷阱、二次电子发射系数(secondary electron emission yields,SEEY)等表征手段,系统分析表面改性对抑制强电磁场诱发PI薄膜沿面放电的机理。结果表明:改性后的PI表面引入大量浅陷阱,显著降低PI薄膜的表面电阻率和SEEY,并提升了材料表面电荷的积聚与消散速率。同时,浅陷阱的引入降低了PI薄膜的SEEY和直流场下的极化能,抑制气体的解吸附与电离及二次电子倍增过程,从而显著提升了PI薄膜在抑制强电磁场诱发真空沿面放电方面的能力。该研究有望为强电磁场诱发航天器表面沿面放电的防护设计提供参考。展开更多
AlGaN/GaN high electron mobility transistors （HEMTs） are fabricated by employing SiN passivation, this paper investigates the degradation due to the high-electric-field stress. After the stress, a recoverable degrad...AlGaN/GaN high electron mobility transistors （HEMTs） are fabricated by employing SiN passivation, this paper investigates the degradation due to the high-electric-field stress. After the stress, a recoverable degradation has been found, consisting of the decrease of saturation drain current IDsat, maximal transconductance gm, and the positive shift of threshold voltage VTH at high drain-source voltage VDS. The high-electric-field stress degrades the electric characteristics of AlGaN/GaN HEMTs because the high field increases the electron trapping at the surface and in AlGaN barrier layer. The SiN passivation of AlGaN/GaN HEMTs decreases the surface trapping and 2DEC depletion a little during the high-electric-field stress. After the hot carrier stress with VDS = 20 V and VGS= 0 V applied to the device for 104 sec, the SiN passivation decreases the stress-induced degradation of IDsat from 36% to 30%. Both on-state and pulse-state stresses produce comparative decrease of IDsat, which shows that although the passivation is effective in suppressing electron trapping in surface states, it does not protect the device from high-electric-field degradation in nature. So passivation in conjunction with other technological solutions like cap layer, prepassivation surface treatments, or field-plate gate to weaken high-electric-field degradation should be adopted.展开更多
The two frequently observed phenomena,photoluminescence(PL)blinking and quantum-confined Stark effect(QCSE)-induced spectral diffusion,are not conducive to the applications of colloidal quantum dots(QDs).It remains el...The two frequently observed phenomena,photoluminescence(PL)blinking and quantum-confined Stark effect(QCSE)-induced spectral diffusion,are not conducive to the applications of colloidal quantum dots(QDs).It remains elusive how these two phenomena are linked to each other.Unraveling the potential link between blinking and QCSE could facilitate the adoption of appropriate strategies that can simultaneously suppress both PL blinking and spectral diffusion.In this work,we investigated the blinking mechanism and QCSE of single CdSe/CdS/ZnS QDs in the presence of positive and negative surface charges using single-dot PL spectroscopy.We found that the negative surface charges can simultaneously suppress PL blinking and spectral diffusion of single QDs.On the other hand,the positive surface charges could change the blinking mechanisms of QDs from Auger-blinking to band-edge carrier(BC)-blinking.Two types of QCSE were observed,and a significant QCSE-induced spectral broadening of 5.25 nm was measured,which could be attributed to the hopping of surface charges between different surface-trap sites.Based on these findings,several theoretical models are proposed to explain various phenomena observed.展开更多
It has been reported that the gate leakage currents are described by the Frenkel-Poole emission(FPE) model,at temperatures higher than 250 K.However,the gate leakage currents of our passivated devices do not accord wi...It has been reported that the gate leakage currents are described by the Frenkel-Poole emission(FPE) model,at temperatures higher than 250 K.However,the gate leakage currents of our passivated devices do not accord with the FPE model.Therefore,a modified FPE model is developed in which an additional leakage current,besides the gate(ⅠⅡ),is added.Based on the samples with different passivations,the ⅠⅡcaused by a large number of surface traps is separated from total gate currents,and is found to be linear with respect to(φB-Vg)0.5.Compared with these from the FPE model,the calculated results from the modified model agree well with the Ig-Vgmeasurements at temperatures ranging from 295 K to 475 K.展开更多
NiO has a perfect-aligned energy level with CH3 NH3 Pb I3 perovskite such that it serves as a hole transport layer(HTL),but Ni O-based perovskite solar cells(PSCs)still suffer from low efficiency due to the poor inter...NiO has a perfect-aligned energy level with CH3 NH3 Pb I3 perovskite such that it serves as a hole transport layer(HTL),but Ni O-based perovskite solar cells(PSCs)still suffer from low efficiency due to the poor interface contact between the perovskite layer and the Ni O HTL,and haphazardly stacked perovskite grains.Herein,poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-co-(1,4-benzo-{2,1,3}-thiadiazole)](PFBT)is introduced between the Ni O and perovskite layers in the form of a polymer aggregate to enhance perovskite crystallinity and decrease the interface charge recombination between perovskite and Ni O in PSCs,resulting in an improved performance.Moreover,PFBT modified perovskite films showed sharper,smoother,and more compact crystalline grains with fewer grain boundaries,leading to the decreased nonradiative recombination.This study offers a simple strategy to achieve highly efficient PSCs with the incorporation of polymer semiconductor aggregates to passivate the interface between the perovskite and Ni O layers.展开更多
The effect of phosphorus passivation on 4H-SiC（0001） silicon （Si） dangling bonds is investigated using ab initio atomistic thermodynamic calculations. Phosphorus passivation commences with chemisorption of phospho...The effect of phosphorus passivation on 4H-SiC（0001） silicon （Si） dangling bonds is investigated using ab initio atomistic thermodynamic calculations. Phosphorus passivation commences with chemisorption of phosphorus atoms at high-symmetry coordinated sites. To determine the most stable structure during the passivation process of phosphorus, a surface phase diagram of phosphorus adsorption on SiC （0001） surface is constructed over a coverage range of 1/9-1 monolayer （ML）. The calculated results indicate that the 1/3 ML configuration is most energetically favorable in a reasonable environment. At this coverage, the total electron density of states demonstrates that phosphorus may effectively reduce the interface state density near the conduction band by removing 4H-SiC （0001） Si dangling bonds. It provides an atomic level insight into how phosphorus is able to reduce the near interface traps.展开更多
Deep level transient spectroscopy（DLTS） as a method to investigate deep traps in AlGaN/GaN heterostructure or high electron mobility transistors（HEMTs） has been widely utilized.The DLTS measurements under differen...Deep level transient spectroscopy（DLTS） as a method to investigate deep traps in AlGaN/GaN heterostructure or high electron mobility transistors（HEMTs） has been widely utilized.The DLTS measurements under different bias conditions are carried out in this paper.Two hole-like traps with active energies of E_v ＋ 0.47 eV,and E_v ＋ 0.10 eV are observed,which are related to surface states.The electron traps with active energies of E_c-0.56 eV are located in the channel,those with E_c-0.33 eV and E_c-0.88 eV are located in the AlGaN layer.The presence of surface states has a strong influence on the detection of electron traps,especially when the electron traps are low in density.The DLTS signal peak height of the electron trap is reduced and even disappears due to the presence of plentiful surface state.展开更多
基金the National Key Research and Development Program of China(No.2022YFB3709000)the National Natural Science Foundation of China(Nos.52201060 and 51922002)+2 种基金the China Postdoctoral Science Foundation(Nos.BX20220035 and 2022M710347)Science Center for Gas Turbine Project(No.P2022-B-IV-008-001)the Open Fund of State Key Laboratory of New Metal Materials,University of Science and Technology Beijing(No.2022Z-18)。
文摘Given the carbon peak and carbon neutrality era,there is an urgent need to develop high-strength steel with remarkable hydrogen embrittlement resistance.This is crucial in enhancing toughness and ensuring the utilization of hydrogen in emerging iron and steel materials.Simultaneously,the pursuit of enhanced metallic materials presents a cross-disciplinary scientific and engineering challenge.Developing high-strength,toughened steel with both enhanced strength and hydrogen embrittlement(HE)resistance holds significant theoretical and practical implications.This ensures secure hydrogen utilization and further carbon neutrality objectives within the iron and steel sector.Based on the design principles of high-strength steel HE resistance,this review provides a comprehensive overview of research on designing surface HE resistance and employing nanosized precipitates as intragranular hydrogen traps.It also proposes feasible recommendations and prospects for designing high-strength steel with enhanced HE resistance.
文摘航天器运行在恶劣的空间环境中容易引发充放电现象,而叠加电磁场会导致其在较低的充电电位下发生放电,严重威胁航天器的安全运行。为揭示强电磁场诱发真空沿面放电的机理并提出抑制方法,该文采用离子交换方法对聚酰亚胺(polyimide,PI)薄膜表面进行改性处理,并基于搭建的强电磁场诱发真空沿面放电平台,结合表面陷阱、二次电子发射系数(secondary electron emission yields,SEEY)等表征手段,系统分析表面改性对抑制强电磁场诱发PI薄膜沿面放电的机理。结果表明:改性后的PI表面引入大量浅陷阱,显著降低PI薄膜的表面电阻率和SEEY,并提升了材料表面电荷的积聚与消散速率。同时,浅陷阱的引入降低了PI薄膜的SEEY和直流场下的极化能,抑制气体的解吸附与电离及二次电子倍增过程,从而显著提升了PI薄膜在抑制强电磁场诱发真空沿面放电方面的能力。该研究有望为强电磁场诱发航天器表面沿面放电的防护设计提供参考。
基金Project supported by the State Key Program of National Natural Science Foundation of China (Grant No 60736033)the State Key Development Program (973 Program) for Basic Research of China (Grant No 513270407)the Advanced Research Foundation of China (Grant Nos 51311050112, 51308030102 and 51308040301)
文摘AlGaN/GaN high electron mobility transistors （HEMTs） are fabricated by employing SiN passivation, this paper investigates the degradation due to the high-electric-field stress. After the stress, a recoverable degradation has been found, consisting of the decrease of saturation drain current IDsat, maximal transconductance gm, and the positive shift of threshold voltage VTH at high drain-source voltage VDS. The high-electric-field stress degrades the electric characteristics of AlGaN/GaN HEMTs because the high field increases the electron trapping at the surface and in AlGaN barrier layer. The SiN passivation of AlGaN/GaN HEMTs decreases the surface trapping and 2DEC depletion a little during the high-electric-field stress. After the hot carrier stress with VDS = 20 V and VGS= 0 V applied to the device for 104 sec, the SiN passivation decreases the stress-induced degradation of IDsat from 36% to 30%. Both on-state and pulse-state stresses produce comparative decrease of IDsat, which shows that although the passivation is effective in suppressing electron trapping in surface states, it does not protect the device from high-electric-field degradation in nature. So passivation in conjunction with other technological solutions like cap layer, prepassivation surface treatments, or field-plate gate to weaken high-electric-field degradation should be adopted.
基金the National Key Research and Development Program of China(No.2017YFA0304203)the National Natural Science Foundation of China(Nos.62127817,62075120,62075122,61875109,91950109,and 62105193),NSFCSTINT(No.62011530133)+3 种基金PCSIRT(No.IRT_17R70)Natural Science Foundation of Shanxi Province(No.201901D111010(ZD))Research Project Supported by Shanxi Scholarship Council of China(No.HGKY2019002)PTIT,Shanxi“1331 Project”,and 111 project(No.D18001).
文摘The two frequently observed phenomena,photoluminescence(PL)blinking and quantum-confined Stark effect(QCSE)-induced spectral diffusion,are not conducive to the applications of colloidal quantum dots(QDs).It remains elusive how these two phenomena are linked to each other.Unraveling the potential link between blinking and QCSE could facilitate the adoption of appropriate strategies that can simultaneously suppress both PL blinking and spectral diffusion.In this work,we investigated the blinking mechanism and QCSE of single CdSe/CdS/ZnS QDs in the presence of positive and negative surface charges using single-dot PL spectroscopy.We found that the negative surface charges can simultaneously suppress PL blinking and spectral diffusion of single QDs.On the other hand,the positive surface charges could change the blinking mechanisms of QDs from Auger-blinking to band-edge carrier(BC)-blinking.Two types of QCSE were observed,and a significant QCSE-induced spectral broadening of 5.25 nm was measured,which could be attributed to the hopping of surface charges between different surface-trap sites.Based on these findings,several theoretical models are proposed to explain various phenomena observed.
基金supported by the National Natural Science Foundation of China(Grant No.61306113)
文摘It has been reported that the gate leakage currents are described by the Frenkel-Poole emission(FPE) model,at temperatures higher than 250 K.However,the gate leakage currents of our passivated devices do not accord with the FPE model.Therefore,a modified FPE model is developed in which an additional leakage current,besides the gate(ⅠⅡ),is added.Based on the samples with different passivations,the ⅠⅡcaused by a large number of surface traps is separated from total gate currents,and is found to be linear with respect to(φB-Vg)0.5.Compared with these from the FPE model,the calculated results from the modified model agree well with the Ig-Vgmeasurements at temperatures ranging from 295 K to 475 K.
基金National Natural Science Foundation of China(61875072)National Postdoctoral Program for Innovative Talents(BX20190135)+2 种基金the Special Project of the Province-University Co-constructing Program of Jilin Province(SXGJXX2017-3)Project of Graduate Innovation Fund of Jilin University(101832018C018)International Cooperation and Exchange Project of Jilin Province(20170414002GH,20180414001GH)for the support to the work。
文摘NiO has a perfect-aligned energy level with CH3 NH3 Pb I3 perovskite such that it serves as a hole transport layer(HTL),but Ni O-based perovskite solar cells(PSCs)still suffer from low efficiency due to the poor interface contact between the perovskite layer and the Ni O HTL,and haphazardly stacked perovskite grains.Herein,poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-co-(1,4-benzo-{2,1,3}-thiadiazole)](PFBT)is introduced between the Ni O and perovskite layers in the form of a polymer aggregate to enhance perovskite crystallinity and decrease the interface charge recombination between perovskite and Ni O in PSCs,resulting in an improved performance.Moreover,PFBT modified perovskite films showed sharper,smoother,and more compact crystalline grains with fewer grain boundaries,leading to the decreased nonradiative recombination.This study offers a simple strategy to achieve highly efficient PSCs with the incorporation of polymer semiconductor aggregates to passivate the interface between the perovskite and Ni O layers.
基金Project supported by the National High Technology Research and Development Program of China(Grant No.2014AA052401)the National Natural Science Foundation of China(Grant No.61474013)the National Grid Science&Technology Project,China(Grant No.5455DW150006)
文摘The effect of phosphorus passivation on 4H-SiC（0001） silicon （Si） dangling bonds is investigated using ab initio atomistic thermodynamic calculations. Phosphorus passivation commences with chemisorption of phosphorus atoms at high-symmetry coordinated sites. To determine the most stable structure during the passivation process of phosphorus, a surface phase diagram of phosphorus adsorption on SiC （0001） surface is constructed over a coverage range of 1/9-1 monolayer （ML）. The calculated results indicate that the 1/3 ML configuration is most energetically favorable in a reasonable environment. At this coverage, the total electron density of states demonstrates that phosphorus may effectively reduce the interface state density near the conduction band by removing 4H-SiC （0001） Si dangling bonds. It provides an atomic level insight into how phosphorus is able to reduce the near interface traps.
基金Project supported by the National Key Basic Research Program of China(Grant No.2011CBA00606)the Program for New Century Excellent Talents in University,China(Grant No.NCET-12-0915)the National Natural Science Foundation of China(Grant Nos.61334002 and 61404097)
文摘Deep level transient spectroscopy（DLTS） as a method to investigate deep traps in AlGaN/GaN heterostructure or high electron mobility transistors（HEMTs） has been widely utilized.The DLTS measurements under different bias conditions are carried out in this paper.Two hole-like traps with active energies of E_v ＋ 0.47 eV,and E_v ＋ 0.10 eV are observed,which are related to surface states.The electron traps with active energies of E_c-0.56 eV are located in the channel,those with E_c-0.33 eV and E_c-0.88 eV are located in the AlGaN layer.The presence of surface states has a strong influence on the detection of electron traps,especially when the electron traps are low in density.The DLTS signal peak height of the electron trap is reduced and even disappears due to the presence of plentiful surface state.
