We experimentally evaluated the interface state density of GaN MIS-HEMTs during time-dependent dielectric breakdown(TDDB).Under a high forward gate bias stress,newly increased traps generate both at the SiNx/AlGaN int...We experimentally evaluated the interface state density of GaN MIS-HEMTs during time-dependent dielectric breakdown(TDDB).Under a high forward gate bias stress,newly increased traps generate both at the SiNx/AlGaN interface and the SiNx bulk,resulting in the voltage shift and the increase of the voltage hysteresis.When prolonging the stress duration,the defects density generated in the SiNx dielectric becomes dominating,which drastically increases the gate leakage current and causes the catastrophic failure.After recovery by UV light illumination,the negative shift in threshold voltage(compared with the fresh one)confirms the accumulation of positive charge at the SiNx/AlGaN interface and/or in SiNx bulk,which is possibly ascribed to the broken bonds after long-term stress.These results experimentally confirm the role of defects in the TDDB of GaN-based MIS-HEMTs.展开更多
Ferroelectric ceramics have the potential to be widely applied in the modern industry and military power systems due to their ultrafast charging/discharging speed and high energy density.Considering the structural des...Ferroelectric ceramics have the potential to be widely applied in the modern industry and military power systems due to their ultrafast charging/discharging speed and high energy density.Considering the structural design and electrical properties of ferroelectric capacitor,it is still a challenge to ffnd out the optimal energy storage of ferroelectric ceramics during the phase-transition process of amorphous/nanocrystalline and polycrystalline.In this work,a ffnite element model suitable for the multiphase ceramic system is constructed based on the phase ffeld breakdown theory.The nonlinear coupling relationship of multiple physical ffelds between multiphase ceramics was taken into account in this model.The basic structures of multiphase ceramics are generated by using the Voronoi diagram construction method.The speciffed structure of multiphase ceramics in the phase-transition process of amorphous/nanocrystalline and polycrystalline was further obtained through the grain boundary diffusion equation.The simulation results show that the multiphase ceramics have an optimal energy storage in the process of amorphous polycrystalline transformation,and the energy storage density reaches the maximum when the crystallinity is 13.96%and the volume fraction of grain is 2.08%.It provides a research plan and idea for revealing the correlation between microstructure and breakdown characteristics of multiphase ceramics.This simulation model realizes the nonlinear coupling of the multiphase ceramic mesoscopic structure and the phase ffeld breakdown.It provides a reference scheme for the structural design and performance optimization of ferroelectric ceramics.展开更多
In contrast to conventional transformers, power electronic transformers, as an integral component of new energy power system, are often subjected to high-frequency and transient electrical stresses, leading to heighte...In contrast to conventional transformers, power electronic transformers, as an integral component of new energy power system, are often subjected to high-frequency and transient electrical stresses, leading to heightened concerns regarding insulation failures. Meanwhile, the underlying mechanism behind discharge breakdown failure and nanofiller enhancement under high-frequency electrical stress remains unclear. An electric-thermal coupled discharge breakdown phase field model was constructed to study the evolution of the breakdown path in polyimide nanocomposite insulation subjected to high-frequency stress. The investigation focused on analyzing the effect of various factors, including frequency, temperature, and nanofiller shape, on the breakdown path of Polyimide(PI) composites. Additionally, it elucidated the enhancement mechanism of nano-modified composite insulation at the mesoscopic scale. The results indicated that with increasing frequency and temperature, the discharge breakdown path demonstrates accelerated development, accompanied by a gradual dominance of Joule heat energy. This enhancement is attributed to the dispersed electric field distribution and the hindering effect of the nanosheets. The research findings offer a theoretical foundation and methodological framework to inform the optimal design and performance management of new insulating materials utilized in high-frequency power equipment.展开更多
The dielectric breakdown(DB) model for a penny-shaped crack under a semipermeable boundary condition in a three-dimensional piezoelectric medium is studied.An approximate analytical solution is derived by using the bo...The dielectric breakdown(DB) model for a penny-shaped crack under a semipermeable boundary condition in a three-dimensional piezoelectric medium is studied.An approximate analytical solution is derived by using the boundary integral equation with extended displacement discontinuity,and the corresponding boundary element method with double iterative approaches is developed to analyze the semi-permeable crack.The effect of electric boundary conditions on crack faces is discussed on the basis of DB model.By comparing the DB model with the polarization saturation(PS) model for different piezoelectric materials,some interesting phenomena related to the electric yielding zone and local J-integral are observed.展开更多
Annealing and firing in wet hydrogen are widely used steps in the processing alumina.ceramic insulators that may affect their dielectric breakdown strengths(DBS).In this study,the effects of annealing(at 1300℃for 7 h...Annealing and firing in wet hydrogen are widely used steps in the processing alumina.ceramic insulators that may affect their dielectric breakdown strengths(DBS).In this study,the effects of annealing(at 1300℃for 7 h)and firing in wet hydrogen on the DBS of alumina ceramics(all sintered at 1650℃)were studied,and the underlying mechanisms were analyzed by material characterizations.Annealing reduced the DBS of the 95%alumina ceramics due to the inter-granular phase crystallization,and the reduction in the DBS could be correlated to the reduction in mechanical strength.In contrast,annealing improved the DBS of the 99%alumina ceramic without intergranular phase transformation.Firing in wet hydrogen at 1500℃caused the DBS increment,which can be ascribed to the reduction in the concentrations of point defects and electrical carriers.展开更多
Glass-free MgO-based microwave dielectric ceramics(1-x)wt%(0.98 MgO-0.02 Al2O3)-x wt%LiF(x=0.5,1,2,3,4)were synthesized where LiF and Al2O3 were utilized as sintering additive and reinforcement phase in MgO matrix res...Glass-free MgO-based microwave dielectric ceramics(1-x)wt%(0.98 MgO-0.02 Al2O3)-x wt%LiF(x=0.5,1,2,3,4)were synthesized where LiF and Al2O3 were utilized as sintering additive and reinforcement phase in MgO matrix respectively.It was found that ion substitution is apt to occur between LiF and MgO,leading to the formation of oxygen vacancies and MgF2.Nevertheless,different from ordinary liquidphase sintering,morphologies of ceramics were distinctly altered with grains changing from polyhedron to sphere-like shape and densities underwent obvious decrease when excessive amount of LiF was introduced and we call it excessive liquid-phase sintering.Grain boundary weakening caused by this circumstance would exert an adverse effect on physical properties.Moreover,LiF addition dramatically reduced dielectric breakdown strength and altered the dielectric breakdown behavior of MgO-based ceramics,which is dominated by electrical breakdown mechanism.Combination of good properties were achieved in 1 wt%LiF modified MgO-based ceramics sintered at 950℃ which exhibited superior microwave properties(εr=9.56,tanδ=9.2×10^(-5),Qf=124,600 GHz),high flexural strength(184.5 MPa),high thermal conductivity(21.3 W/(m,K)),high coefficient of thermal expansion(-12 ppm/℃)and moderate electrical properties(Eb=35.9 kV/mm,r=4.9×10^(12) U cm).展开更多
A large number of insulation/dielectric failures in power systems are related to thermally-induced dielectrical breakdown,also known as‘thermal breakdown’,at higher operating temperatures.In this work,the thermal br...A large number of insulation/dielectric failures in power systems are related to thermally-induced dielectrical breakdown,also known as‘thermal breakdown’,at higher operating temperatures.In this work,the thermal breakdown behavior of typical silicone formulations,used as dielectrics in stretchable electronic devices,is analyzed at practically relevant operating temperatures ranging from 20℃ to 80℃.An effective way of delaying the thermal breakdown of insulating materials is to blend micro-or nano-sized inorganic particles with high thermal conductivity,to dissipate better any losses generated during energy transduction.Therefore,two types of commercial silicone formulations,blended with two types of rutile hydrophobic,high-dielectric TiO_(2) fillers,are investigated in relation to their dielectric properties,namely,relative permittivity,the dissipation factor,and electrical breakdown strength.The breakdown strengths of these silicone composites are subsequently evaluated using Weibull analysis,which indicates a negative correlation between temperature and shape parameter for all compositions,thus illustrating that the homogeneity of the samples decreases in line with temperature,but the breakdown strengths nevertheless increase initially due to the trapping effect from the high-permittivity fillers.展开更多
For many years, a Lorentz factor of L = 1/3 has been used to describe the local electric field in thin amorphous dielectrics. However, the exact meaning of thin has been unclear. The local electric field E<sub>l...For many years, a Lorentz factor of L = 1/3 has been used to describe the local electric field in thin amorphous dielectrics. However, the exact meaning of thin has been unclear. The local electric field E<sub>loc</sub> modeling presented in this work indicates that L = 1/3 is indeed valid for very thin solid dielectrics (t<sub>diel</sub> ≤ 20 monolayers) but significant deviations from L = 1/3 start to occur for thicker dielectrics. For example, L ≈ 2/3 for dielectric thicknesses of t<sub>diel</sub> = 50 monolayers and increases to L ≈ 1 for dielectric thicknesses t<sub>diel</sub> > 200 monolayers. The increase in L with t<sub>diel</sub> means that the local electric fields are significantly higher in thicker dielectrics and explains why the breakdown strength E<sub>bd</sub> of solid polar dielectrics generally reduces with dielectric thickness t<sub>diel</sub>. For example, E<sub>bd</sub> for SiO<sub>2</sub> reduces from approximately E<sub>bd</sub> ≈ 25 MV/cm at t<sub>diel</sub> = 2 nm to E<sub>bd</sub> ≈ 10 MV/cm at t<sub>diel</sub> = 50 nm. However, while E<sub>bd</sub> for SiO<sub>2</sub> reduces with t<sub>diel</sub>, all SiO<sub>2</sub> thicknesses are found to breakdown at approximately the same local electric field (E<sub>loc</sub>)<sub>bd</sub> ≈ 40 MV/cm. This corresponds to a coordination bond strength of 2.7 eV for the silicon-ion to transition from four-fold to three-fold coordination in the tetrahedral structure.展开更多
High-k materials as an alternative dielectric layer for SiC power devices have the potential to reduce interfacial state defects and improve MOS channel conduction capability.Besides,under identical conditions of gate...High-k materials as an alternative dielectric layer for SiC power devices have the potential to reduce interfacial state defects and improve MOS channel conduction capability.Besides,under identical conditions of gate oxide thickness and gate voltage,the high-k dielectric enables a greater charge accumulation in the channel region,resulting in a larger number of free electrons available for conduction.However,the lower energy band gap of high-k materials leads to significant leakage currents at the interface with Si C,which greatly affects device reliability.By inserting a layer of SiO_(2)between the high-k material and Si C,the interfacial barrier can be effectively widened and hence the leakage current will be reduced.In this study,the optimal thickness of the intercalated SiO_(2)was determined by investigating and analyzing the gate dielectric breakdown voltage and interfacial defects of a dielectric stack composed of atomic-layer-deposited Al_(2)O_(3)layer and thermally nitride SiO_(2).Current-voltage and high-frequency capacitance-voltage measurements were performed on metal-oxide-semiconductor test structures with 35 nm thick Al_(2)O_(3)stacked on 1 nm,2 nm,3 nm,6 nm,or 9 nm thick nitride SiO_(2).Measurement results indicated that the current conducted through the oxides was affected by the thickness of the nitride oxide and the applied electric field.Finally,a saturation thickness of stacked SiO_(2)that contributed to dielectric breakdown and interfacial band offsets was identified.The findings in this paper provide a guideline for the SiC gate dielectric stack design with the breakdown strength and the interfacial state defects considered.展开更多
Controlled breakdown has recently emerged as a highly accessible technique to fabricate solid-state nanopores.However,in its most common form,controlled breakdown creates a single nanopore at an arbitrary location in ...Controlled breakdown has recently emerged as a highly accessible technique to fabricate solid-state nanopores.However,in its most common form,controlled breakdown creates a single nanopore at an arbitrary location in the membrane.Here,we introduce a new strategy whereby breakdown is performed by applying the electric field between an on-chip electrode and an electrolyte solution in contact with the opposite side of the membrane.We demonstrate two advantages of this method.First,we can independently fabricate multiple nanopores at given positions in the membrane by localising the applied field to the electrode.Second,we can create nanopores that are self-aligned with complementary nanoelectrodes by applying voltages to the on-chip electrodes to locally heat the membrane during controlled breakdown.This new controlled breakdown method provides a path towards the affordable,rapid,and automatable fabrication of arrays of nanopores self-aligned with complementary on-chip nanostructures.展开更多
A phase-field model is developed in this paper based on the similarity between mechanical fracture and dielectric breakdown.Electrical treeing is associated with the dielectric breakdown in solid dielectrics by the ap...A phase-field model is developed in this paper based on the similarity between mechanical fracture and dielectric breakdown.Electrical treeing is associated with the dielectric breakdown in solid dielectrics by the application of high voltages.Instead of explicitly tracing the propagation of conductive channel,this model initializes a continuous phase field to characterize the extent of damage.So far,limited research has been conducted for simulating the effect of nanofiller dispersion on electrical treeing.No study has modeled the effect of uniform and nonuniform dispersion of nanofillers with varying filler concentration on treeing.Since electrical treeing tends to decrease the breakdown strength of solid dielectrics therefore,nanofillers are widely used to distract the tree from a straight channel to distribute its energy in multiple paths.Diverting a straight treeing channel into mul-tiple paths reduces the chances of its propagation from live to dead-end hence,improving the breakdown strength.The physical and chemical nature of nanofillers has a crucial impact on increasing the resistance to treeing.In this paper,phase-field model is developed and used to simulate electrical treeing in polyethylene for varying concentrations of alumina nanofiller using COM-SOL Multiphysics.Tree inception time,tree-growth patterns,and corresponding changes in dielectric strength is studied for both dispersions.Electrical treeing under different concentrations of alumina nanofillers with uniform and nonuniform dispersion is investigated in polyethylene as a base material.It is observed that fillers with uniform dispersion increases the resistance to tree-ing and tree inception time.Highest resistance to treeing is observed by adding 1%nanoalumina uniformly in raw polyethylene.Moreover,in uniform dispersion the tree deflects into multiple branches earlier than nonuniform dispersion impeding the damage speed as well.展开更多
基金National Key Research and Development Program of China(Grant No.2017YFB0402800)the Key Research and Development Program of Guangdong Province,China(Grant Nos.2019B010128002 and 2020B010173001)+2 种基金the National Natural Science Foundation of China(Grant Nos.U1601210 and 61904207)the Natural Science Foundation of Guangdong Province of China(Grant No.2015A030312011)the China Postdoctoral Science Foundation(Grant No.2019M663233).
文摘We experimentally evaluated the interface state density of GaN MIS-HEMTs during time-dependent dielectric breakdown(TDDB).Under a high forward gate bias stress,newly increased traps generate both at the SiNx/AlGaN interface and the SiNx bulk,resulting in the voltage shift and the increase of the voltage hysteresis.When prolonging the stress duration,the defects density generated in the SiNx dielectric becomes dominating,which drastically increases the gate leakage current and causes the catastrophic failure.After recovery by UV light illumination,the negative shift in threshold voltage(compared with the fresh one)confirms the accumulation of positive charge at the SiNx/AlGaN interface and/or in SiNx bulk,which is possibly ascribed to the broken bonds after long-term stress.These results experimentally confirm the role of defects in the TDDB of GaN-based MIS-HEMTs.
基金supported by the youth project of Guangdong Foshan joint fund of Guangdong Natural Science Foundation(Grant No.2020A1515110601 and Grant No.2019A1515110444)the National Natural Science Foundation of China(No:61804029)the Project of Foshan Science and Technology Innovation Team(No:FS0AA-KJ919-4402-0062).
文摘Ferroelectric ceramics have the potential to be widely applied in the modern industry and military power systems due to their ultrafast charging/discharging speed and high energy density.Considering the structural design and electrical properties of ferroelectric capacitor,it is still a challenge to ffnd out the optimal energy storage of ferroelectric ceramics during the phase-transition process of amorphous/nanocrystalline and polycrystalline.In this work,a ffnite element model suitable for the multiphase ceramic system is constructed based on the phase ffeld breakdown theory.The nonlinear coupling relationship of multiple physical ffelds between multiphase ceramics was taken into account in this model.The basic structures of multiphase ceramics are generated by using the Voronoi diagram construction method.The speciffed structure of multiphase ceramics in the phase-transition process of amorphous/nanocrystalline and polycrystalline was further obtained through the grain boundary diffusion equation.The simulation results show that the multiphase ceramics have an optimal energy storage in the process of amorphous polycrystalline transformation,and the energy storage density reaches the maximum when the crystallinity is 13.96%and the volume fraction of grain is 2.08%.It provides a research plan and idea for revealing the correlation between microstructure and breakdown characteristics of multiphase ceramics.This simulation model realizes the nonlinear coupling of the multiphase ceramic mesoscopic structure and the phase ffeld breakdown.It provides a reference scheme for the structural design and performance optimization of ferroelectric ceramics.
基金supported in part by the National Key R&D Program of China (No.2021YFB2601404)Beijing Natural Science Foundation (No.3232053)National Natural Science Foundation of China (Nos.51929701 and 52127812)。
文摘In contrast to conventional transformers, power electronic transformers, as an integral component of new energy power system, are often subjected to high-frequency and transient electrical stresses, leading to heightened concerns regarding insulation failures. Meanwhile, the underlying mechanism behind discharge breakdown failure and nanofiller enhancement under high-frequency electrical stress remains unclear. An electric-thermal coupled discharge breakdown phase field model was constructed to study the evolution of the breakdown path in polyimide nanocomposite insulation subjected to high-frequency stress. The investigation focused on analyzing the effect of various factors, including frequency, temperature, and nanofiller shape, on the breakdown path of Polyimide(PI) composites. Additionally, it elucidated the enhancement mechanism of nano-modified composite insulation at the mesoscopic scale. The results indicated that with increasing frequency and temperature, the discharge breakdown path demonstrates accelerated development, accompanied by a gradual dominance of Joule heat energy. This enhancement is attributed to the dispersed electric field distribution and the hindering effect of the nanosheets. The research findings offer a theoretical foundation and methodological framework to inform the optimal design and performance management of new insulating materials utilized in high-frequency power equipment.
基金Project supported by the National Natural Science Foundation of China(Nos.11102186 and 11272290)the Science and Technology Key Project of Henan(No.132102210412)
文摘The dielectric breakdown(DB) model for a penny-shaped crack under a semipermeable boundary condition in a three-dimensional piezoelectric medium is studied.An approximate analytical solution is derived by using the boundary integral equation with extended displacement discontinuity,and the corresponding boundary element method with double iterative approaches is developed to analyze the semi-permeable crack.The effect of electric boundary conditions on crack faces is discussed on the basis of DB model.By comparing the DB model with the polarization saturation(PS) model for different piezoelectric materials,some interesting phenomena related to the electric yielding zone and local J-integral are observed.
基金The study was financially supported by the Science Development Foundation of China Academy of Engineering Physics(2014A0302012)the Funding Support by Laboratory of Precision Manufacturing Technology,CAEP(ZD18001).
文摘Annealing and firing in wet hydrogen are widely used steps in the processing alumina.ceramic insulators that may affect their dielectric breakdown strengths(DBS).In this study,the effects of annealing(at 1300℃for 7 h)and firing in wet hydrogen on the DBS of alumina ceramics(all sintered at 1650℃)were studied,and the underlying mechanisms were analyzed by material characterizations.Annealing reduced the DBS of the 95%alumina ceramics due to the inter-granular phase crystallization,and the reduction in the DBS could be correlated to the reduction in mechanical strength.In contrast,annealing improved the DBS of the 99%alumina ceramic without intergranular phase transformation.Firing in wet hydrogen at 1500℃caused the DBS increment,which can be ascribed to the reduction in the concentrations of point defects and electrical carriers.
基金supported by National Natural Science Foundation of China(Grant No.11774366)International Partnership Program of Chinese Academy of Sciences(Grant No.GJHZ1821)。
文摘Glass-free MgO-based microwave dielectric ceramics(1-x)wt%(0.98 MgO-0.02 Al2O3)-x wt%LiF(x=0.5,1,2,3,4)were synthesized where LiF and Al2O3 were utilized as sintering additive and reinforcement phase in MgO matrix respectively.It was found that ion substitution is apt to occur between LiF and MgO,leading to the formation of oxygen vacancies and MgF2.Nevertheless,different from ordinary liquidphase sintering,morphologies of ceramics were distinctly altered with grains changing from polyhedron to sphere-like shape and densities underwent obvious decrease when excessive amount of LiF was introduced and we call it excessive liquid-phase sintering.Grain boundary weakening caused by this circumstance would exert an adverse effect on physical properties.Moreover,LiF addition dramatically reduced dielectric breakdown strength and altered the dielectric breakdown behavior of MgO-based ceramics,which is dominated by electrical breakdown mechanism.Combination of good properties were achieved in 1 wt%LiF modified MgO-based ceramics sintered at 950℃ which exhibited superior microwave properties(εr=9.56,tanδ=9.2×10^(-5),Qf=124,600 GHz),high flexural strength(184.5 MPa),high thermal conductivity(21.3 W/(m,K)),high coefficient of thermal expansion(-12 ppm/℃)and moderate electrical properties(Eb=35.9 kV/mm,r=4.9×10^(12) U cm).
基金supported by the Independent Research Fund Denmark.
文摘A large number of insulation/dielectric failures in power systems are related to thermally-induced dielectrical breakdown,also known as‘thermal breakdown’,at higher operating temperatures.In this work,the thermal breakdown behavior of typical silicone formulations,used as dielectrics in stretchable electronic devices,is analyzed at practically relevant operating temperatures ranging from 20℃ to 80℃.An effective way of delaying the thermal breakdown of insulating materials is to blend micro-or nano-sized inorganic particles with high thermal conductivity,to dissipate better any losses generated during energy transduction.Therefore,two types of commercial silicone formulations,blended with two types of rutile hydrophobic,high-dielectric TiO_(2) fillers,are investigated in relation to their dielectric properties,namely,relative permittivity,the dissipation factor,and electrical breakdown strength.The breakdown strengths of these silicone composites are subsequently evaluated using Weibull analysis,which indicates a negative correlation between temperature and shape parameter for all compositions,thus illustrating that the homogeneity of the samples decreases in line with temperature,but the breakdown strengths nevertheless increase initially due to the trapping effect from the high-permittivity fillers.
文摘For many years, a Lorentz factor of L = 1/3 has been used to describe the local electric field in thin amorphous dielectrics. However, the exact meaning of thin has been unclear. The local electric field E<sub>loc</sub> modeling presented in this work indicates that L = 1/3 is indeed valid for very thin solid dielectrics (t<sub>diel</sub> ≤ 20 monolayers) but significant deviations from L = 1/3 start to occur for thicker dielectrics. For example, L ≈ 2/3 for dielectric thicknesses of t<sub>diel</sub> = 50 monolayers and increases to L ≈ 1 for dielectric thicknesses t<sub>diel</sub> > 200 monolayers. The increase in L with t<sub>diel</sub> means that the local electric fields are significantly higher in thicker dielectrics and explains why the breakdown strength E<sub>bd</sub> of solid polar dielectrics generally reduces with dielectric thickness t<sub>diel</sub>. For example, E<sub>bd</sub> for SiO<sub>2</sub> reduces from approximately E<sub>bd</sub> ≈ 25 MV/cm at t<sub>diel</sub> = 2 nm to E<sub>bd</sub> ≈ 10 MV/cm at t<sub>diel</sub> = 50 nm. However, while E<sub>bd</sub> for SiO<sub>2</sub> reduces with t<sub>diel</sub>, all SiO<sub>2</sub> thicknesses are found to breakdown at approximately the same local electric field (E<sub>loc</sub>)<sub>bd</sub> ≈ 40 MV/cm. This corresponds to a coordination bond strength of 2.7 eV for the silicon-ion to transition from four-fold to three-fold coordination in the tetrahedral structure.
基金Project supported by the Key Area Research and Development Program of Guangdong Province of China(Grant No.2021B0101300005)the National Key Research and Development Program of China(Grant No.2021YFB3401603)。
文摘High-k materials as an alternative dielectric layer for SiC power devices have the potential to reduce interfacial state defects and improve MOS channel conduction capability.Besides,under identical conditions of gate oxide thickness and gate voltage,the high-k dielectric enables a greater charge accumulation in the channel region,resulting in a larger number of free electrons available for conduction.However,the lower energy band gap of high-k materials leads to significant leakage currents at the interface with Si C,which greatly affects device reliability.By inserting a layer of SiO_(2)between the high-k material and Si C,the interfacial barrier can be effectively widened and hence the leakage current will be reduced.In this study,the optimal thickness of the intercalated SiO_(2)was determined by investigating and analyzing the gate dielectric breakdown voltage and interfacial defects of a dielectric stack composed of atomic-layer-deposited Al_(2)O_(3)layer and thermally nitride SiO_(2).Current-voltage and high-frequency capacitance-voltage measurements were performed on metal-oxide-semiconductor test structures with 35 nm thick Al_(2)O_(3)stacked on 1 nm,2 nm,3 nm,6 nm,or 9 nm thick nitride SiO_(2).Measurement results indicated that the current conducted through the oxides was affected by the thickness of the nitride oxide and the applied electric field.Finally,a saturation thickness of stacked SiO_(2)that contributed to dielectric breakdown and interfacial band offsets was identified.The findings in this paper provide a guideline for the SiC gate dielectric stack design with the breakdown strength and the interfacial state defects considered.
基金J.P.F.thanks the Oxford Australia Scholarship committee and the University of Western Australia for fundingJ.R.Y.was funded by an FCT contract according to DL57/2016,[SFRH/BPD/80071/2011]+6 种基金J.R.Y.’s lab was funded by national funds through FCT-Fundação para a Ciência e a Tecnologia,I.P.,Project MOSTMICRO-ITQB with refs UIDB/04612/2020 and UIDP/04612/2020 and Project PTDC/NAN-MAT/31100/2017J.M.was supported through the UKRI Future Leaders Fellowship,Grant No.MR/S032541/1with in-kind support from the Royal Academy of Engineering.A.P.I.and J.B.E.acknowledge support from BBSRC grant BB/R022429/1,EPSCR grant EP/P011985/1Analytical Chemistry Trust Fund grant 600322/05This project has also received funding from the European Research Council(ERC)under the European Union’s Horizon 2020 research and innovation programme(Nos.724300 and 875525)O.D.and STEM investigations were supported by the Center for Nanophase Materials Sciences(CNMS)a U.S.Department of Energy,Office of Science User Facility.
文摘Controlled breakdown has recently emerged as a highly accessible technique to fabricate solid-state nanopores.However,in its most common form,controlled breakdown creates a single nanopore at an arbitrary location in the membrane.Here,we introduce a new strategy whereby breakdown is performed by applying the electric field between an on-chip electrode and an electrolyte solution in contact with the opposite side of the membrane.We demonstrate two advantages of this method.First,we can independently fabricate multiple nanopores at given positions in the membrane by localising the applied field to the electrode.Second,we can create nanopores that are self-aligned with complementary nanoelectrodes by applying voltages to the on-chip electrodes to locally heat the membrane during controlled breakdown.This new controlled breakdown method provides a path towards the affordable,rapid,and automatable fabrication of arrays of nanopores self-aligned with complementary on-chip nanostructures.
文摘A phase-field model is developed in this paper based on the similarity between mechanical fracture and dielectric breakdown.Electrical treeing is associated with the dielectric breakdown in solid dielectrics by the application of high voltages.Instead of explicitly tracing the propagation of conductive channel,this model initializes a continuous phase field to characterize the extent of damage.So far,limited research has been conducted for simulating the effect of nanofiller dispersion on electrical treeing.No study has modeled the effect of uniform and nonuniform dispersion of nanofillers with varying filler concentration on treeing.Since electrical treeing tends to decrease the breakdown strength of solid dielectrics therefore,nanofillers are widely used to distract the tree from a straight channel to distribute its energy in multiple paths.Diverting a straight treeing channel into mul-tiple paths reduces the chances of its propagation from live to dead-end hence,improving the breakdown strength.The physical and chemical nature of nanofillers has a crucial impact on increasing the resistance to treeing.In this paper,phase-field model is developed and used to simulate electrical treeing in polyethylene for varying concentrations of alumina nanofiller using COM-SOL Multiphysics.Tree inception time,tree-growth patterns,and corresponding changes in dielectric strength is studied for both dispersions.Electrical treeing under different concentrations of alumina nanofillers with uniform and nonuniform dispersion is investigated in polyethylene as a base material.It is observed that fillers with uniform dispersion increases the resistance to tree-ing and tree inception time.Highest resistance to treeing is observed by adding 1%nanoalumina uniformly in raw polyethylene.Moreover,in uniform dispersion the tree deflects into multiple branches earlier than nonuniform dispersion impeding the damage speed as well.