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
A high-quality Ga2O3 thin film is deposited on an SiC substrate to form a heterojunction structure. The band alignment of the Ga2O3/6H-SiC heterojunction is studied by using synchrotron radiation photoelectron spectro...A high-quality Ga2O3 thin film is deposited on an SiC substrate to form a heterojunction structure. The band alignment of the Ga2O3/6H-SiC heterojunction is studied by using synchrotron radiation photoelectron spectroscopy, The energy band diagram of the Ga2O3/6H-SiC heterojunction is obtained by analysing the binding energies of Ga 3d and Si 2p at the surface and the interface of the heterojunction. The valence band offset is experimentally determined to be 2.8 eV and the conduction band offset is calculated to be 0.89 eV, which indicate a type-II band alignment. This provides useful guidance for the application of Ga2O3/6H-SiC electronic devices.展开更多
The effect of surface morphology of 6H-SiC substrate on the ohmic contact properties of Ti/6H-SiC structure is studied. The H-terminated surface on Si-face 6H-SiC is obtained by both dipping SiC into HF acid solution ...The effect of surface morphology of 6H-SiC substrate on the ohmic contact properties of Ti/6H-SiC structure is studied. The H-terminated surface on Si-face 6H-SiC is obtained by both dipping SiC into HF acid solution for 15 s and thermal heating SiC in hydrogen atmosphere at 1100 ℃ for 10 min, while the H-terminated surface on C-face 6H-SiC could be obtained only by the latter method. Ti is deposited on Si-face and C-face SiC substrates with H-terminated surfaces and ohmic contact is obtained without high-temperature annealing.展开更多
β-FeSi2 thin films have been successfully prepared by magnetron sputtering and post rapid thermal annealing method on 6H-SiC （0001） substrates using a FeSi2 target and a Si target. X-ray diffraction （XRD） and Ram...β-FeSi2 thin films have been successfully prepared by magnetron sputtering and post rapid thermal annealing method on 6H-SiC （0001） substrates using a FeSi2 target and a Si target. X-ray diffraction （XRD） and Raman spectroscopy are applied to analyze the formation of/%FeSi2 films. XRD spectra reveal that the amorphous FeSi2 films are transformed to%FeSi2 phase as the annealing temperature is increased from 500 to 900 ℃ for 5 min and the optimal annealing temperature is 900 ℃. The formation of β-FeSi2 is also confirmed by Raman spectroscopy. Scanning electron microscope （SEM） observations indicate that the film is βat, relatively compact and the interface between β-FeSi2 and 6H-SiC is clear. Atomic force microscope （AFM） measurements demonstrate that the surface roughness confirmed by the root mean square （RMS） of the tJ-FeSi2 film is 0.87 nm. Near-infrared spectrophotometer observation shows that the absorption coefficient is of the order of 105 cm-1 and the optical band-gap of the β-FeSi2 film is 0.88 eV. The β-FeSi2 film with high crystal quality is fabricated by co-sputtering a FeSi2 target and a Si target for 60 min and annealing at 900 ℃ for 5 min.展开更多
Hydrous minerals in the subducting slabs are potential water carriers into the deep mantle,and thus the synthesis of new hydrous phases is significant in our understanding of water circulation throughout the Earth’s ...Hydrous minerals in the subducting slabs are potential water carriers into the deep mantle,and thus the synthesis of new hydrous phases is significant in our understanding of water circulation throughout the Earth’s interior.In this study,we report the two new hydrous phases,Al_(2)SiO_(6)H_(2)and Al_(5.5)Si_(4)O_(18)H_(3.5)(hereafter referred to simply as phases Psi and Phi,respectively),which are synthesized in the Al_(2)O_(3)-SiO_(2)-H_(2)O system at 15.5 GPa,1400℃and 17.5 GPa,1600℃ by using Sakura2500-ton multi-anvil apparatus.The luminescence spectra of Cr3+show the phase Psi has characteristic peaks at 687,693 and705 nm,while phase Phi has characteristic peaks at 691,696 and 708 nm.Single-crystal X-ray diffraction (SCXRD) refinements yield a monoclinic structure of both phases (space group P2_(1)) with ideal chemical formulae of Al_(2)SiO6H2and Al5.5Si4O18H3.5respectively.The determined lattice parameters for phase Psi are a=9.4168±0.0016Å,b=4.3441±0.0007Å,c=9.4360±0.002Åand β=119.726±0.005°at ambient pressure and 300 K,while the phase Phi has a=7.2549±0.0018Å,b=4.3144±0.001Å,c=8.0520±0.002Å,and β=101.740±0.009°at ambient pressure and 250 K.Electron microprobe analyses (EPMA) show the chemical compositions of phases Psi and Phi to be Al_(1.99)Si_(0.85)O_(6)H_(2.62)and Al_(5.58)Si_(2.81)O_(18)H_(8.03),respectively,which slightly deviate from the ideal formulae inferred from SCXRD measurements.This may result from the disorder or substitution of Al and Si by H in the crystal structures under our synthesis conditions.Our study suggests that phases Psi and Phi are the two potential water carriers at the upper part of the mantle transitions zone,providing new insights into how deep water is stored in this region.展开更多
Owing to their outstanding optoelectronic properties,all-inorganic CsPbBr_(3) perovskite nanocrystals(NCs)are regarded as excellent materials for various optoelectronic applications.Unfortunately,their practical appli...Owing to their outstanding optoelectronic properties,all-inorganic CsPbBr_(3) perovskite nanocrystals(NCs)are regarded as excellent materials for various optoelectronic applications.Unfortunately,their practical applications are limited by poor stability against water,heat,and polar solvents.Here,we propose a facile synthesis strategy for CsPbBr_(3)@Cs_(4)PbBr_(6) NCs via tetraoctylammonium bromide ligand induction at room temperature.The resulting CsPbBr_(3)@Cs_(4)PbBr_(6) NCs show a high photoluminescence quantum yield of 94%.In order to prevent Cs4PbBr6 from being converted back to CsPbBr_(3) NCs when exposed to water,a second coating layer of SiO2 is formed on the surface of the CsPbBr_(3)@Cs_(4)PbBr_(6) NCs by the facile hydrolysis of tetramethoxysilane.The resulting CsPbBr_(3)@Cs_(4)PbBr_(6)/SiO_(2) NCs with their double coating structure have outstanding stability against not only a polar solvent(ethanol)but also water and heat.The as-prepared CsPbBr_(3)@Cs_(4)PbBr_(6)/SiO_(2) NCs serve as green emitters in efficient white light-emitting diodes(WLEDs)with a high color rendering index(CRI)of 91 and a high power efficiency 59.87 lm W−1.Furthermore,the use of these WLEDs in visible light communication(VLC)results in a maximum rate of 44.53 Mbps,suggesting the great potential of the reported methods and materials for solid-state illumination and VLC.展开更多
The effect of amorphous film on the deformation mechanism and mechanical properties of 6 H-SiC were systematically explored by a combination of both experiments and molecular dynamic(MD)simulations in nanoindentation....The effect of amorphous film on the deformation mechanism and mechanical properties of 6 H-SiC were systematically explored by a combination of both experiments and molecular dynamic(MD)simulations in nanoindentation.The experimental results showed that the plastic deformation of surface-modified6 H-SiC is mainly accommodated by dislocation activities in the subsurface and an amorphous layer with uniform thickness.The MD results indicated that the amorphous layer on the surface of the residual indentation mark consists of both amorphous SiO_(2)and SiC due to direct amorphization.In addition,the amorphous SiO_(2)film undergoes densification and then ruptures with the indentation depth increases.The modulus and hardness increase with increasing the indentation depth at the initial stage but will reach their stable values equivalent to monocrystalline 6 H-SiC.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supported by the National Natural Science Foundation of China(Grant Nos.50702071 and 50772122)the Young Scientists Fund of the National Natural Science Foundation of China(Grant No.51002176)
文摘A high-quality Ga2O3 thin film is deposited on an SiC substrate to form a heterojunction structure. The band alignment of the Ga2O3/6H-SiC heterojunction is studied by using synchrotron radiation photoelectron spectroscopy, The energy band diagram of the Ga2O3/6H-SiC heterojunction is obtained by analysing the binding energies of Ga 3d and Si 2p at the surface and the interface of the heterojunction. The valence band offset is experimentally determined to be 2.8 eV and the conduction band offset is calculated to be 0.89 eV, which indicate a type-II band alignment. This provides useful guidance for the application of Ga2O3/6H-SiC electronic devices.
基金Project supported by the Innovation Program of the Chinese Academy of Sciences (Grant No. KJCX2-EW-W10)the Shanghai Municipal Science and Technology Commission, China (Grant Nos. 09DZ1141400 and 09520714900)the Young Scientists Fund of the National Natural Science Foundation of China (Grant No. 51002176)
文摘The effect of surface morphology of 6H-SiC substrate on the ohmic contact properties of Ti/6H-SiC structure is studied. The H-terminated surface on Si-face 6H-SiC is obtained by both dipping SiC into HF acid solution for 15 s and thermal heating SiC in hydrogen atmosphere at 1100 ℃ for 10 min, while the H-terminated surface on C-face 6H-SiC could be obtained only by the latter method. Ti is deposited on Si-face and C-face SiC substrates with H-terminated surfaces and ohmic contact is obtained without high-temperature annealing.
基金Project supported by the National Natural Science Foundation of China(No.51177134)the Natural Science Basic Research Plan in Shaanxi Province of China(No.2015JM6286)
文摘β-FeSi2 thin films have been successfully prepared by magnetron sputtering and post rapid thermal annealing method on 6H-SiC （0001） substrates using a FeSi2 target and a Si target. X-ray diffraction （XRD） and Raman spectroscopy are applied to analyze the formation of/%FeSi2 films. XRD spectra reveal that the amorphous FeSi2 films are transformed to%FeSi2 phase as the annealing temperature is increased from 500 to 900 ℃ for 5 min and the optimal annealing temperature is 900 ℃. The formation of β-FeSi2 is also confirmed by Raman spectroscopy. Scanning electron microscope （SEM） observations indicate that the film is βat, relatively compact and the interface between β-FeSi2 and 6H-SiC is clear. Atomic force microscope （AFM） measurements demonstrate that the surface roughness confirmed by the root mean square （RMS） of the tJ-FeSi2 film is 0.87 nm. Near-infrared spectrophotometer observation shows that the absorption coefficient is of the order of 105 cm-1 and the optical band-gap of the β-FeSi2 film is 0.88 eV. The β-FeSi2 film with high crystal quality is fabricated by co-sputtering a FeSi2 target and a Si target for 60 min and annealing at 900 ℃ for 5 min.
基金supported by the Special Research Fund for the Doctoral Program of Tongren University(Grant No.trxyDH2201)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB42000000)the National Key Research and Development Program of China(Grant No.2019YFA0708502)。
文摘Hydrous minerals in the subducting slabs are potential water carriers into the deep mantle,and thus the synthesis of new hydrous phases is significant in our understanding of water circulation throughout the Earth’s interior.In this study,we report the two new hydrous phases,Al_(2)SiO_(6)H_(2)and Al_(5.5)Si_(4)O_(18)H_(3.5)(hereafter referred to simply as phases Psi and Phi,respectively),which are synthesized in the Al_(2)O_(3)-SiO_(2)-H_(2)O system at 15.5 GPa,1400℃and 17.5 GPa,1600℃ by using Sakura2500-ton multi-anvil apparatus.The luminescence spectra of Cr3+show the phase Psi has characteristic peaks at 687,693 and705 nm,while phase Phi has characteristic peaks at 691,696 and 708 nm.Single-crystal X-ray diffraction (SCXRD) refinements yield a monoclinic structure of both phases (space group P2_(1)) with ideal chemical formulae of Al_(2)SiO6H2and Al5.5Si4O18H3.5respectively.The determined lattice parameters for phase Psi are a=9.4168±0.0016Å,b=4.3441±0.0007Å,c=9.4360±0.002Åand β=119.726±0.005°at ambient pressure and 300 K,while the phase Phi has a=7.2549±0.0018Å,b=4.3144±0.001Å,c=8.0520±0.002Å,and β=101.740±0.009°at ambient pressure and 250 K.Electron microprobe analyses (EPMA) show the chemical compositions of phases Psi and Phi to be Al_(1.99)Si_(0.85)O_(6)H_(2.62)and Al_(5.58)Si_(2.81)O_(18)H_(8.03),respectively,which slightly deviate from the ideal formulae inferred from SCXRD measurements.This may result from the disorder or substitution of Al and Si by H in the crystal structures under our synthesis conditions.Our study suggests that phases Psi and Phi are the two potential water carriers at the upper part of the mantle transitions zone,providing new insights into how deep water is stored in this region.
基金National Natural Science Foundation of China(11974063,61904023)Key Program Science Foundation of Natural Science Foundation of Chongqing(cstc2020jcyj-jqX0028)Chongqing Special Postdoctoral Science Foundation(cstc2019jcyj-54bsh0026).
文摘Owing to their outstanding optoelectronic properties,all-inorganic CsPbBr_(3) perovskite nanocrystals(NCs)are regarded as excellent materials for various optoelectronic applications.Unfortunately,their practical applications are limited by poor stability against water,heat,and polar solvents.Here,we propose a facile synthesis strategy for CsPbBr_(3)@Cs_(4)PbBr_(6) NCs via tetraoctylammonium bromide ligand induction at room temperature.The resulting CsPbBr_(3)@Cs_(4)PbBr_(6) NCs show a high photoluminescence quantum yield of 94%.In order to prevent Cs4PbBr6 from being converted back to CsPbBr_(3) NCs when exposed to water,a second coating layer of SiO2 is formed on the surface of the CsPbBr_(3)@Cs_(4)PbBr_(6) NCs by the facile hydrolysis of tetramethoxysilane.The resulting CsPbBr_(3)@Cs_(4)PbBr_(6)/SiO_(2) NCs with their double coating structure have outstanding stability against not only a polar solvent(ethanol)but also water and heat.The as-prepared CsPbBr_(3)@Cs_(4)PbBr_(6)/SiO_(2) NCs serve as green emitters in efficient white light-emitting diodes(WLEDs)with a high color rendering index(CRI)of 91 and a high power efficiency 59.87 lm W−1.Furthermore,the use of these WLEDs in visible light communication(VLC)results in a maximum rate of 44.53 Mbps,suggesting the great potential of the reported methods and materials for solid-state illumination and VLC.
基金financially supported by the Guangdong Specific Discipline Project(No.2020ZDZX2006)Shenzhen Key Laboratory of Cross-scale Manufacturing Mechanics Project(No.ZDSYS20200810171201007)undertaken with the assistance of the resources provided at the NCI National Facility systems through the National Computational Merit Allocation Scheme supported by the Australian Government。
文摘The effect of amorphous film on the deformation mechanism and mechanical properties of 6 H-SiC were systematically explored by a combination of both experiments and molecular dynamic(MD)simulations in nanoindentation.The experimental results showed that the plastic deformation of surface-modified6 H-SiC is mainly accommodated by dislocation activities in the subsurface and an amorphous layer with uniform thickness.The MD results indicated that the amorphous layer on the surface of the residual indentation mark consists of both amorphous SiO_(2)and SiC due to direct amorphization.In addition,the amorphous SiO_(2)film undergoes densification and then ruptures with the indentation depth increases.The modulus and hardness increase with increasing the indentation depth at the initial stage but will reach their stable values equivalent to monocrystalline 6 H-SiC.
