Discrimination of dislocations is critical to the statistics of dislocation densities in 4H silicon carbide(4H-SiC),which are routinely used to evaluate the quality of 4H-SiC single crystals and homoepitaxial layers.I...Discrimination of dislocations is critical to the statistics of dislocation densities in 4H silicon carbide(4H-SiC),which are routinely used to evaluate the quality of 4H-SiC single crystals and homoepitaxial layers.In this work,we show that the inclination angles of the etch pits of molten-alkali etched 4H-SiC can be adopted to discriminate threading screw dislocations(TSDs),threading edge dislocations(TEDs)and basal plane dislocations(BPDs)in 4H-SiC.In n-type 4H-SiC,the inclination angles of the etch pits of TSDs,TEDs and BPDs in molten-alkali etched 4H-SiC are in the ranges of 27°−35°,8°−15°and 2°−4°,respectively.In semi-insulating 4H-SiC,the inclination angles of the etch pits of TSDs and TEDs are in the ranges of 31°−34°and 21°−24°,respectively.The inclination angles of dislocation-related etch pits are independent of the etching duration,which facilitates the discrimination and statistic of dislocations in 4H-SiC.More significantly,the inclination angle of a threading mixed dislocations(TMDs)is found to consist of characteristic angles of both TEDs and TSDs.This enables to distinguish TMDs from TSDs in 4H-SiC.展开更多
In this work,we propose to reveal the subsurface damage(SSD)of 4H-SiC wafers by photo-chemical etching and identify the nature of SSD by molten-alkali etching.Under UV illumination,SSD acts as a photoluminescence-blac...In this work,we propose to reveal the subsurface damage(SSD)of 4H-SiC wafers by photo-chemical etching and identify the nature of SSD by molten-alkali etching.Under UV illumination,SSD acts as a photoluminescence-black defect.The selective photo-chemical etching reveals SSD as the ridge-like defect.It is found that the ridge-like SSD is still crystalline 4H-SiC with lattice distortion.The molten-KOH etching of the 4H-SiC wafer with ridge-like SSD transforms the ridge-like SSD into groove lines,which are typical features of scratches.This means that the underlying scratches under mechanical stress give rise to the formation of SSD in 4H-SiC wafers.SSD is incorporated into 4H-SiC wafers during the lapping,rather than the chemical mechanical polishing(CMP).展开更多
β-Si Al ON-Si C composites were prepared using SiC particles and fines,silicon powder,AlN powder,α-Al_(2)O_(3)micropowder and flake graphite as starting materials.The influence of the graphite(particle size of≤45 ...β-Si Al ON-Si C composites were prepared using SiC particles and fines,silicon powder,AlN powder,α-Al_(2)O_(3)micropowder and flake graphite as starting materials.The influence of the graphite(particle size of≤45 and≤300μm,addition of 3.0%,5.5%,7.5%,and 10.0%,by mass)on the molten-alkali corrosion resistance was investigated.The results show that the moltenalkali resistance for theβ-Si Al ON-Si C sample with 7.5%of graphite(≤300μm)is optimal,showing the lowest mass change rate after corrosion and the highest retention ratios of cold modulus of rupture and hot modulus of rupture.展开更多
Silica white was prepared with the method of molten NaOH-carbonation decomposition from the laterite nickel ore,and the content of NiO in the residue reached 2.71%.The results showed that the extraction ratio of SiO2 ...Silica white was prepared with the method of molten NaOH-carbonation decomposition from the laterite nickel ore,and the content of NiO in the residue reached 2.71%.The results showed that the extraction ratio of SiO2 increased with increasing reaction time and mass ratio of alkali to ore,and with decreasing particle size of the laterite nickel ore.Furthermore,the extraction ratio of SiO2 increased firstly and then decreased with increasing reaction temperature.XRD analysis indicated that the product was amorphous.FT-IR analysis indicated that the product was hydrated silicon dioxide.SEM morphology showed that the product was of uniform particle size with average particle size about 100 nm.The physical and chemical properties of the product conformed with the national standards of chemical industry.展开更多
基金supported by“Pioneer”and“Leading Goose”R&D Program of Zhejiang(Grant No.2022C01021)National Key Research and Development Program of China(Grant Nos.2018YFB2200101)+3 种基金Natural Science Foundation of China(Grant Nos.61774133)Fundamental Research Funds for the Central Universities(Grant No.2018XZZX003-02)Natural Science Foundation of China for Innovative Research Groups(Grant No.61721005)Zhejiang University Education Foundation Global Partnership Fund.
文摘Discrimination of dislocations is critical to the statistics of dislocation densities in 4H silicon carbide(4H-SiC),which are routinely used to evaluate the quality of 4H-SiC single crystals and homoepitaxial layers.In this work,we show that the inclination angles of the etch pits of molten-alkali etched 4H-SiC can be adopted to discriminate threading screw dislocations(TSDs),threading edge dislocations(TEDs)and basal plane dislocations(BPDs)in 4H-SiC.In n-type 4H-SiC,the inclination angles of the etch pits of TSDs,TEDs and BPDs in molten-alkali etched 4H-SiC are in the ranges of 27°−35°,8°−15°and 2°−4°,respectively.In semi-insulating 4H-SiC,the inclination angles of the etch pits of TSDs and TEDs are in the ranges of 31°−34°and 21°−24°,respectively.The inclination angles of dislocation-related etch pits are independent of the etching duration,which facilitates the discrimination and statistic of dislocations in 4H-SiC.More significantly,the inclination angle of a threading mixed dislocations(TMDs)is found to consist of characteristic angles of both TEDs and TSDs.This enables to distinguish TMDs from TSDs in 4H-SiC.
基金supported by “Pioneer” and “Leading Goose”R&D Program of Zhejiang (Grant No. 2022C01021)National Key Research and Development Program of China (Grant No.2018YFB2200101)+3 种基金National Natural Science Foundation of China (Grant Nos. 91964107, 61774133)Fundamental Research Funds for the Central Universities (Grant No.2018XZZX003-02)Natural Science Foundation of China for Innovative Research Groups (Grant No. 61721005)Zhejiang University Education Foundation Global Partnership Fund
文摘In this work,we propose to reveal the subsurface damage(SSD)of 4H-SiC wafers by photo-chemical etching and identify the nature of SSD by molten-alkali etching.Under UV illumination,SSD acts as a photoluminescence-black defect.The selective photo-chemical etching reveals SSD as the ridge-like defect.It is found that the ridge-like SSD is still crystalline 4H-SiC with lattice distortion.The molten-KOH etching of the 4H-SiC wafer with ridge-like SSD transforms the ridge-like SSD into groove lines,which are typical features of scratches.This means that the underlying scratches under mechanical stress give rise to the formation of SSD in 4H-SiC wafers.SSD is incorporated into 4H-SiC wafers during the lapping,rather than the chemical mechanical polishing(CMP).
文摘β-Si Al ON-Si C composites were prepared using SiC particles and fines,silicon powder,AlN powder,α-Al_(2)O_(3)micropowder and flake graphite as starting materials.The influence of the graphite(particle size of≤45 and≤300μm,addition of 3.0%,5.5%,7.5%,and 10.0%,by mass)on the molten-alkali corrosion resistance was investigated.The results show that the moltenalkali resistance for theβ-Si Al ON-Si C sample with 7.5%of graphite(≤300μm)is optimal,showing the lowest mass change rate after corrosion and the highest retention ratios of cold modulus of rupture and hot modulus of rupture.
文摘Silica white was prepared with the method of molten NaOH-carbonation decomposition from the laterite nickel ore,and the content of NiO in the residue reached 2.71%.The results showed that the extraction ratio of SiO2 increased with increasing reaction time and mass ratio of alkali to ore,and with decreasing particle size of the laterite nickel ore.Furthermore,the extraction ratio of SiO2 increased firstly and then decreased with increasing reaction temperature.XRD analysis indicated that the product was amorphous.FT-IR analysis indicated that the product was hydrated silicon dioxide.SEM morphology showed that the product was of uniform particle size with average particle size about 100 nm.The physical and chemical properties of the product conformed with the national standards of chemical industry.
