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
Camouflage technology has garnered increasing attention for various applications.With the continuous advancement of detection technologies and the increasing variability of camouflage scenarios,the demand for multispe...Camouflage technology has garnered increasing attention for various applications.With the continuous advancement of detection technologies and the increasing variability of camouflage scenarios,the demand for multispectral dynamic camouflage has been steadily growing.In this work,we present a multispectral dynamic regulator based on phase-changing material vanadium dioxide(VO_(2))that can be dynamically and functional-independently regulated for reflective color and thermal radiation.It has been shown that the device can achieve a wide color gamut variation in visible band while simultaneously achieving highest emissivity tunability(Δε=-0.58)in the atmospheric window up to now,achieves multispectral camouflage spanning the visible and infrared spectra among VO_(2)-based devices.To go a step further,we advance the device featuring long-term cycling stability to achieve thermal-electric dual-mode response and flexibility for a series real-world camouflage performance evaluation.We have also demonstrated the digital camouflage based on multispectral dynamic regulator through Neighboring Color Block Camouflage Algorithm,highlighting its potential for practical implementation in different camouflage scenarios.The device achieves multispectral dynamic camouflage,opening a path for advancing the technology development in both the scientific field and practical applications.展开更多
Oxygen-containing rare-earth metal hydride YH_xO_y,is a newly found photochromic material showing fast photoresponse.While its preparation method,optical properties and structural features have been studied extensivel...Oxygen-containing rare-earth metal hydride YH_xO_y,is a newly found photochromic material showing fast photoresponse.While its preparation method,optical properties and structural features have been studied extensively,the photochromic mechanism in YH_xO_yremains unknown Here,using excited-state molecular dynamics simulation based on the recently developed real-time time-dependent density functional theory(RT-TDDFT)method,we study the photochemical reactions in YH_xO_y.We find that under photoexcitation,dihydrogen defects are formed within 100 fs.The dihydrogen defect behaves as a shallow donor and renders the material strongly n-type doped,which could be responsible for the photochromic effect observed in YH_xO_y.We also find that oxygen concentration affects the metastability of the dihydrogen species,meaning that the energy barrier for the dihydrogen to dissociate is related to the oxygen concentration The highest barrier of 0.28 eV is found in our model with O/Y=1:8.If the oxygen concentration is too low,the dihydrogen will quickly dissociate when the excitation is turned off.If the oxygen concentration is too high,the dihydrogen dissociates even when the excitation is still on.展开更多
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financially supported by the National Key Research and Development Program of China(No.2021YFA0718900)the National Natural Science Foundation of China(No.62175248)+1 种基金Shanghai Science and Technology Funds(No.23ZR1481900)the Major science and technology project of Yunnan Province(No.202302AB080023).
文摘Camouflage technology has garnered increasing attention for various applications.With the continuous advancement of detection technologies and the increasing variability of camouflage scenarios,the demand for multispectral dynamic camouflage has been steadily growing.In this work,we present a multispectral dynamic regulator based on phase-changing material vanadium dioxide(VO_(2))that can be dynamically and functional-independently regulated for reflective color and thermal radiation.It has been shown that the device can achieve a wide color gamut variation in visible band while simultaneously achieving highest emissivity tunability(Δε=-0.58)in the atmospheric window up to now,achieves multispectral camouflage spanning the visible and infrared spectra among VO_(2)-based devices.To go a step further,we advance the device featuring long-term cycling stability to achieve thermal-electric dual-mode response and flexibility for a series real-world camouflage performance evaluation.We have also demonstrated the digital camouflage based on multispectral dynamic regulator through Neighboring Color Block Camouflage Algorithm,highlighting its potential for practical implementation in different camouflage scenarios.The device achieves multispectral dynamic camouflage,opening a path for advancing the technology development in both the scientific field and practical applications.
基金the support by the National Natural Science Foundation of China(11774365)。
文摘Oxygen-containing rare-earth metal hydride YH_xO_y,is a newly found photochromic material showing fast photoresponse.While its preparation method,optical properties and structural features have been studied extensively,the photochromic mechanism in YH_xO_yremains unknown Here,using excited-state molecular dynamics simulation based on the recently developed real-time time-dependent density functional theory(RT-TDDFT)method,we study the photochemical reactions in YH_xO_y.We find that under photoexcitation,dihydrogen defects are formed within 100 fs.The dihydrogen defect behaves as a shallow donor and renders the material strongly n-type doped,which could be responsible for the photochromic effect observed in YH_xO_y.We also find that oxygen concentration affects the metastability of the dihydrogen species,meaning that the energy barrier for the dihydrogen to dissociate is related to the oxygen concentration The highest barrier of 0.28 eV is found in our model with O/Y=1:8.If the oxygen concentration is too low,the dihydrogen will quickly dissociate when the excitation is turned off.If the oxygen concentration is too high,the dihydrogen dissociates even when the excitation is still on.
