Single crystal silicon carbide(SiC)is widely used for optoelectronics applications.Due to the anisotropic characteristics of single crystal materials,the C face and Si face of single crystal SiC have different physica...Single crystal silicon carbide(SiC)is widely used for optoelectronics applications.Due to the anisotropic characteristics of single crystal materials,the C face and Si face of single crystal SiC have different physical properties,which may fit for particular application purposes.This paper presents an investigation of the material removal and associated subsurface defects in a set of scratching tests on the C face and Si face of 4H-SiC and 6H-SiC materials using molecular dynamics simulations.The investigation reveals that the sample material deformation consists of plastic,amorphous transformations and dislocation slips that may be prone to brittle split.The results showed that the material removal at the C face is more effective with less amorphous deformation than that at the Si face.Such a phenomenon in scratching relates to the dislocations on the basal plane(0001)of the SiC crystal.Subsurface defects were reduced by applying scratching cut depths equal to integer multiples of a half molecular lattice thickness,which formed a foundation for selecting machining control parameters for the best surface quality.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
A nonpolar SiC（1120） substrate has been used to fabricate epitaxial graphene （EG）. Two EGs with layer numbers of 8-10 （referred to as MLG） and 2-3 （referred to as FLG） were used as representative to study the ...A nonpolar SiC（1120） substrate has been used to fabricate epitaxial graphene （EG）. Two EGs with layer numbers of 8-10 （referred to as MLG） and 2-3 （referred to as FLG） were used as representative to study the substrate effect on EG through temperature-dependent Raman scattering. It is found that Raman lineshifts of G and 2D peaks of the MLG with temperature are consistent with that of free graphene, as predicted by theory calculation, indicating that the substrate influence on the MLG is undetectable. While Raman G peak lineshifts of the FLG to that of the free graphene are obvious, however, its lineshift rate （-0.016 cm-1/K） is almost one third of that （-0.043 cm-1/K） of an EG on 6H-SiC （0001） in the temperature range from 300 K to 400 K, indicating a weak substrate effect from SiC （1120） on the FLG. This renders the FLG with a high mobility around 1812 cm2.V-1 .s -1 at room temperature even with a very high carrier concentration about 2.95 × 10 ^13 cm-2 （p-type）. These suggest SiC （1120） is more suitable for fabricating EG with high performance.展开更多
基金financial support from National Natural Science Foundation of China(Grant No.51835004 and 51575197)Huaqiao University International Cultivation Program for Outstanding Postgraduates and Subsidized Projec for Postgraduates’Innovative Fund in Scientific Research of Huaqiao University(No.18011080010)。
文摘Single crystal silicon carbide(SiC)is widely used for optoelectronics applications.Due to the anisotropic characteristics of single crystal materials,the C face and Si face of single crystal SiC have different physical properties,which may fit for particular application purposes.This paper presents an investigation of the material removal and associated subsurface defects in a set of scratching tests on the C face and Si face of 4H-SiC and 6H-SiC materials using molecular dynamics simulations.The investigation reveals that the sample material deformation consists of plastic,amorphous transformations and dislocation slips that may be prone to brittle split.The results showed that the material removal at the C face is more effective with less amorphous deformation than that at the Si face.Such a phenomenon in scratching relates to the dislocations on the basal plane(0001)of the SiC crystal.Subsurface defects were reduced by applying scratching cut depths equal to integer multiples of a half molecular lattice thickness,which formed a foundation for selecting machining control parameters for the best surface quality.
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Project supported by the National Basic Research Program of China (Grant No. 2011CB932700)the Knowledge Innovation Project of the Chinese Academy of Sciences (Grant No. KJCX2-YW-W22)the National Natural Science Foundation of China (Grant Nos. 51072223 and 50972162)
文摘A nonpolar SiC（1120） substrate has been used to fabricate epitaxial graphene （EG）. Two EGs with layer numbers of 8-10 （referred to as MLG） and 2-3 （referred to as FLG） were used as representative to study the substrate effect on EG through temperature-dependent Raman scattering. It is found that Raman lineshifts of G and 2D peaks of the MLG with temperature are consistent with that of free graphene, as predicted by theory calculation, indicating that the substrate influence on the MLG is undetectable. While Raman G peak lineshifts of the FLG to that of the free graphene are obvious, however, its lineshift rate （-0.016 cm-1/K） is almost one third of that （-0.043 cm-1/K） of an EG on 6H-SiC （0001） in the temperature range from 300 K to 400 K, indicating a weak substrate effect from SiC （1120） on the FLG. This renders the FLG with a high mobility around 1812 cm2.V-1 .s -1 at room temperature even with a very high carrier concentration about 2.95 × 10 ^13 cm-2 （p-type）. These suggest SiC （1120） is more suitable for fabricating EG with high performance.
