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Toru Ujihara - One of the best experts on this subject based on the ideXlab platform.
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immobilization of partial dislocations bounding double shockley stacking faults in 4h sic observed by in situ synchrotron x ray Topography
Social Science Research Network, 2021Co-Authors: Fumihiro Fujie, Balaji Raghothamachar, Michael Dudley, Hiromasa Suo, Tomohisa Kato, Shunta Harada, Miho Tagawa, Kenji Hanada, Haruhiko Koizumi, Toru UjiharaAbstract:The expansion of double Shockley stacking faults (DSFs) in an n-type 4H-SiC substrate with a nitrogen concentration of 3.9×10 19 cm −3 was investigated using in situ synchrotron X-Ray Topography. DSF expansion was observed to be suppressed and immobilized above 1590 K, along with the partial dislocation (PD) shape being changed from a straight to zig-zag configuration. For a different heating process (higher heating rate), the PDs could continue to expand, even above 1590 K. Ex situ Topography experiments revealed that the DSFs close to the specimen surface expanded widely, although those expanding toward the specimen interior became immobile. One possible mechanism for this immobilization was proposed, where the core structural changes from a Si-core to the C-core by climb motion induced by the interaction between the PDs and point defects (C interstitials).
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temperature dependence of double shockley stacking fault behavior in nitrogen doped 4h sic studied by in situ synchrotron x ray Topography
Acta Materialia, 2020Co-Authors: Fumihiro Fujie, Hiromasa Suo, Tomohisa Kato, Toru Ujihara, Shunta Harada, Miho Tagawa, Kenji Hanada, Haruhiko KoizumiAbstract:Abstract We observed the behavior of double Shockley stacking faults (DSFs) in 4H-SiC crystals with nitrogen concentrations of 1.0 × 1019–2.6 × 1019 cm−3 over an extensive temperature range (1380–1910 K) by in-situ synchrotron X-Ray Topography. For a nitrogen concentration of 2.6 × 1019 cm−3, the expansion velocity of the DSFs exponentially increased with temperature in the range from 1370 to 1650 K. In contrast, at a nitrogen concentration of 1.0 × 1019 cm−3, this velocity decreased above 1610 K and the DSFs shrank above 1730 K. The DSF energy, the magnitude of which is the driving force on partial dislocation (PD) movement, was quantitatively estimated from the radius of the curvature of bowed-out partial PDs pinned by threading screw dislocations (TSDs), showing a positive temperature dependence and lying in the range from −0.6 to 0.8 mJ/m2 for 1630–1910 K at a nitrogen concentration of 1.0 × 1019 cm−3. The DSF expansion and shrinkage behavior can be understood by the simple temperature and nitrogen concentration dependence of the DSF energy.
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temperature dependence of double shockley stacking fault behavior in nitrogen doped 4h sic studied by in situ synchrotron x ray Topography
Social Science Research Network, 2020Co-Authors: Fumihiro Fujie, Hiromasa Suo, Tomohisa Kato, Shunta Harada, Miho Tagawa, Kenji Hanada, Haruhiko Koizumi, Toru UjiharaAbstract:We observed the behavior of double Shockley stacking faults (DSFs) in 4H-SiC crystals with nitrogen concentrations of 1.0×1019-2.6×1019 cm−3 over an extensive temperature range (1380-1910 K) by in-situ synchrotron X-Ray Topography. For a nitrogen concentration of 2.6×1019 cm−3, the expansion velocity of the DSFs exponentially increased with temperature for temperatures in the range from 1370 to 1650 K. In contrast, at a nitrogen concentration of 1.0×1019 cm−3, this velocity decreased above 1610 K and the DSFs shrank above 1730 K. The DSF energy, considered to be the driving force for DSF expansion, was quantitatively estimated from the radius of the curvature of bowed-out partial dislocations (PDs) pinned by threading screw dislocations (TSDs), showing a positive temperature dependence and lying in the range from −0.6 to 0.8 mJ/m2 at a nitrogen concentration of 1.0×1019 cm−3. The DSF expansion and shrinkage behavior can be understood by the simple temperature and nitrogen concentration dependence of the DSF energy.
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direct observation of stacking fault shrinkage in 4h sic at high temperatures by in situ x ray Topography using monochromatic synchrotron radiation
Applied Physics Letters, 2018Co-Authors: Fumihiro Fujie, Toru Ujihara, Shunta Harada, Kenta Murayama, Miho Tagawa, Kenji Hanada, Haruhiko KoizumiAbstract:An in-situ X-Ray Topography system using monochromatic synchrotron radiation for the observation of the stacking faults in 4H-SiC during a high-temperature annealing process was developed. We demonstrated that the stacking faults in nitrogen-doped 4H-SiC not only expand but also shrink at high temperatures. Furthermore, it was confirmed that the types of the core structure of partial dislocations enclosing the stacking fault can be determined at high temperatures.An in-situ X-Ray Topography system using monochromatic synchrotron radiation for the observation of the stacking faults in 4H-SiC during a high-temperature annealing process was developed. We demonstrated that the stacking faults in nitrogen-doped 4H-SiC not only expand but also shrink at high temperatures. Furthermore, it was confirmed that the types of the core structure of partial dislocations enclosing the stacking fault can be determined at high temperatures.
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conversion behavior of threading screw dislocations on c face with different surface morphology during 4h sic solution growth
Crystal Growth & Design, 2016Co-Authors: Shiyu Xiao, Shunta Harada, Kenta Murayama, Miho Tagawa, Toru UjiharaAbstract:The conversion of threading screw dislocations (TSDs) to defects on the basal plane during SiC solution growth caused by macrostep advance is a key factor to improve crystal quality. We realized the TSD conversion in 4H-SiC C face solution growth by modification of the surface morphology including macrosteps by addition of 5 atom % Ti into pure Si solvent. Synchrotron X-Ray Topography revealed that the possibility of TSD conversion increased to about 10% with the addition of 5 atom % Ti. In addition, the TSD conversion ratio depends on the shape of the macrostep edge. The gentle slope hardly made TSD conversion. The elastic energy of dislocations in anisotropy crystals was postulated as an explanation for the influence of step shape on TSD conversion behavior.
Shunta Harada - One of the best experts on this subject based on the ideXlab platform.
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immobilization of partial dislocations bounding double shockley stacking faults in 4h sic observed by in situ synchrotron x ray Topography
Social Science Research Network, 2021Co-Authors: Fumihiro Fujie, Balaji Raghothamachar, Michael Dudley, Hiromasa Suo, Tomohisa Kato, Shunta Harada, Miho Tagawa, Kenji Hanada, Haruhiko Koizumi, Toru UjiharaAbstract:The expansion of double Shockley stacking faults (DSFs) in an n-type 4H-SiC substrate with a nitrogen concentration of 3.9×10 19 cm −3 was investigated using in situ synchrotron X-Ray Topography. DSF expansion was observed to be suppressed and immobilized above 1590 K, along with the partial dislocation (PD) shape being changed from a straight to zig-zag configuration. For a different heating process (higher heating rate), the PDs could continue to expand, even above 1590 K. Ex situ Topography experiments revealed that the DSFs close to the specimen surface expanded widely, although those expanding toward the specimen interior became immobile. One possible mechanism for this immobilization was proposed, where the core structural changes from a Si-core to the C-core by climb motion induced by the interaction between the PDs and point defects (C interstitials).
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temperature dependence of double shockley stacking fault behavior in nitrogen doped 4h sic studied by in situ synchrotron x ray Topography
Acta Materialia, 2020Co-Authors: Fumihiro Fujie, Hiromasa Suo, Tomohisa Kato, Toru Ujihara, Shunta Harada, Miho Tagawa, Kenji Hanada, Haruhiko KoizumiAbstract:Abstract We observed the behavior of double Shockley stacking faults (DSFs) in 4H-SiC crystals with nitrogen concentrations of 1.0 × 1019–2.6 × 1019 cm−3 over an extensive temperature range (1380–1910 K) by in-situ synchrotron X-Ray Topography. For a nitrogen concentration of 2.6 × 1019 cm−3, the expansion velocity of the DSFs exponentially increased with temperature in the range from 1370 to 1650 K. In contrast, at a nitrogen concentration of 1.0 × 1019 cm−3, this velocity decreased above 1610 K and the DSFs shrank above 1730 K. The DSF energy, the magnitude of which is the driving force on partial dislocation (PD) movement, was quantitatively estimated from the radius of the curvature of bowed-out partial PDs pinned by threading screw dislocations (TSDs), showing a positive temperature dependence and lying in the range from −0.6 to 0.8 mJ/m2 for 1630–1910 K at a nitrogen concentration of 1.0 × 1019 cm−3. The DSF expansion and shrinkage behavior can be understood by the simple temperature and nitrogen concentration dependence of the DSF energy.
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temperature dependence of double shockley stacking fault behavior in nitrogen doped 4h sic studied by in situ synchrotron x ray Topography
Social Science Research Network, 2020Co-Authors: Fumihiro Fujie, Hiromasa Suo, Tomohisa Kato, Shunta Harada, Miho Tagawa, Kenji Hanada, Haruhiko Koizumi, Toru UjiharaAbstract:We observed the behavior of double Shockley stacking faults (DSFs) in 4H-SiC crystals with nitrogen concentrations of 1.0×1019-2.6×1019 cm−3 over an extensive temperature range (1380-1910 K) by in-situ synchrotron X-Ray Topography. For a nitrogen concentration of 2.6×1019 cm−3, the expansion velocity of the DSFs exponentially increased with temperature for temperatures in the range from 1370 to 1650 K. In contrast, at a nitrogen concentration of 1.0×1019 cm−3, this velocity decreased above 1610 K and the DSFs shrank above 1730 K. The DSF energy, considered to be the driving force for DSF expansion, was quantitatively estimated from the radius of the curvature of bowed-out partial dislocations (PDs) pinned by threading screw dislocations (TSDs), showing a positive temperature dependence and lying in the range from −0.6 to 0.8 mJ/m2 at a nitrogen concentration of 1.0×1019 cm−3. The DSF expansion and shrinkage behavior can be understood by the simple temperature and nitrogen concentration dependence of the DSF energy.
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direct observation of stacking fault shrinkage in 4h sic at high temperatures by in situ x ray Topography using monochromatic synchrotron radiation
Applied Physics Letters, 2018Co-Authors: Fumihiro Fujie, Toru Ujihara, Shunta Harada, Kenta Murayama, Miho Tagawa, Kenji Hanada, Haruhiko KoizumiAbstract:An in-situ X-Ray Topography system using monochromatic synchrotron radiation for the observation of the stacking faults in 4H-SiC during a high-temperature annealing process was developed. We demonstrated that the stacking faults in nitrogen-doped 4H-SiC not only expand but also shrink at high temperatures. Furthermore, it was confirmed that the types of the core structure of partial dislocations enclosing the stacking fault can be determined at high temperatures.An in-situ X-Ray Topography system using monochromatic synchrotron radiation for the observation of the stacking faults in 4H-SiC during a high-temperature annealing process was developed. We demonstrated that the stacking faults in nitrogen-doped 4H-SiC not only expand but also shrink at high temperatures. Furthermore, it was confirmed that the types of the core structure of partial dislocations enclosing the stacking fault can be determined at high temperatures.
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conversion behavior of threading screw dislocations on c face with different surface morphology during 4h sic solution growth
Crystal Growth & Design, 2016Co-Authors: Shiyu Xiao, Shunta Harada, Kenta Murayama, Miho Tagawa, Toru UjiharaAbstract:The conversion of threading screw dislocations (TSDs) to defects on the basal plane during SiC solution growth caused by macrostep advance is a key factor to improve crystal quality. We realized the TSD conversion in 4H-SiC C face solution growth by modification of the surface morphology including macrosteps by addition of 5 atom % Ti into pure Si solvent. Synchrotron X-Ray Topography revealed that the possibility of TSD conversion increased to about 10% with the addition of 5 atom % Ti. In addition, the TSD conversion ratio depends on the shape of the macrostep edge. The gentle slope hardly made TSD conversion. The elastic energy of dislocations in anisotropy crystals was postulated as an explanation for the influence of step shape on TSD conversion behavior.
Michael Dudley - One of the best experts on this subject based on the ideXlab platform.
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immobilization of partial dislocations bounding double shockley stacking faults in 4h sic observed by in situ synchrotron x ray Topography
Social Science Research Network, 2021Co-Authors: Fumihiro Fujie, Balaji Raghothamachar, Michael Dudley, Hiromasa Suo, Tomohisa Kato, Shunta Harada, Miho Tagawa, Kenji Hanada, Haruhiko Koizumi, Toru UjiharaAbstract:The expansion of double Shockley stacking faults (DSFs) in an n-type 4H-SiC substrate with a nitrogen concentration of 3.9×10 19 cm −3 was investigated using in situ synchrotron X-Ray Topography. DSF expansion was observed to be suppressed and immobilized above 1590 K, along with the partial dislocation (PD) shape being changed from a straight to zig-zag configuration. For a different heating process (higher heating rate), the PDs could continue to expand, even above 1590 K. Ex situ Topography experiments revealed that the DSFs close to the specimen surface expanded widely, although those expanding toward the specimen interior became immobile. One possible mechanism for this immobilization was proposed, where the core structural changes from a Si-core to the C-core by climb motion induced by the interaction between the PDs and point defects (C interstitials).
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mapping of lattice strain in 4h sic crystals by synchrotron double crystal x ray Topography
Journal of Electronic Materials, 2018Co-Authors: Jianqiu Guo, Balaji Raghothamachar, Michael Dudley, Yu Yang, Stanislav StoupinAbstract:The presence of lattice strain in n-doped 4H-SiC substrate crystals grown by a physical vapor transport method can strongly influence the performance of related power devices that are fabricated on them. Information on the level and the variation of lattice strain in these wafer crystals is thus important. In this study, a non-destructive method is developed based on synchrotron double-crystal X-Ray Topography to map lattice strains in 4H-SiC wafers. Measurements are made on two 4H-SiC substrate crystals—one is an unprocessed commercial wafer while the other was subject to a post-growth high-temperature heat treatment. Maps of different strain components are generated from the equi-misorientation contour maps recorded using synchrotron monochromatic radiation. The technique is demonstrated to be a powerful tool in estimating strain fields in 4H-SiC crystals. Analysis of the strain maps also shows that the normal strain components vary much more significantly than do the shear/rotation components, indicating that lattice dilation/compression rather than lattice tilt is the major type of deformation caused by both the incorporation of nitrogen dopants and the nucleation of basal plane dislocations.
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studying the impact of stress strain on cracks in laminated crystalline silicon cells opening the doors of synchrotron facilities to the pv module industry
Photovoltaic Specialists Conference, 2016Co-Authors: Alessandra Colli, Balaji Raghothamachar, Klaus Attenkofer, Michael DudleyAbstract:In this paper we present and discuss the capabilities of synchrotron X-Ray Topography for the direct imaging and analysis of defects, stress and strain affecting the cell within the laminated photovoltaic module. The results of the initial synchrotron experiment done at Brookhaven National Laboratory-NSLS II and the following Topography campaign run at the Advanced Photon Source at Argonne National Laboratory will be presented and discussed. Cracks originating from grain boundaries and strain affecting the cell in the module package are clearly revealed on the X-Ray topographs of a commercial single-cell mini-module — also known as reference cell. With this experiment we demonstrate that the use of synchrotron facilities is promising for the non-destructive analysis of the entire PV module structure.
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correlation of lifetime mapping of 4h sic epilayers with structural defects using synchrotron x ray Topography
Materials Science Forum, 2016Co-Authors: Ouloide Yannick Goue, Balaji Raghothamachar, Michael Dudley, Jianqiu Guo, Yu Yang, J L Hosteller, Rachael L Myersward, P B Klein, Kurt D GaskillAbstract:Lifetime maps for two 4H-SiC epi-wafers (samples 1 and 2) were recorded using microwave photoconductive decay (μPCD) measurements and correlated with the type and distribution of structural defects mapped by synchrotron X-Ray Topography (white beam and monochromatic). Sample 1 showed lower lifetime inside one of its higher doped facet regions and along its edges. The low lifetime in the facet region was associated with the presence of a high density of multi-layered Shockley stacking faults (SFs) and low angle grain boundaries (LAGBs). These stacking faults are likely double Shockley stacking faults (DSSFs) and probably nucleated from scratches present on the substrate surface and LAGBs present in that region, propagating during epilayer growth. In contrast, sample 2 showed a reduced carrier lifetime in the middle region associated with a network of interfacial dislocations (IDs) and half loop arrays (HLAs) originating from 3C inclusions that are generated during epilayer growth. Along the edges of both samples, overlapping triangular defects, microcracks and BPD loops lowered lifetime.
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study of defect structures in 6h sic a m plane pseudofiber crystals grown by hot wall cvd epitaxy
Journal of Electronic Materials, 2016Co-Authors: Ouloide Yannick Goue, Balaji Raghothamachar, Michael Dudley, Philip G Neudeck, Jianqiu Guo, Yu Yang, Kim Kisslinger, Andrew J Trunek, David J Spry, Andrew A WoodworthAbstract:Structural perfection of silicon carbide (SiC) single crystals is essential to achieve high-performance power devices. A new bulk growth process for SiC proposed by researchers at NASA Glenn Research Center, called large tapered crystal (LTC) growth, based on axial fiber growth followed by lateral expansion, could produce SiC boules with potentially as few as one threading screw dislocation per wafer. In this study, the lateral expansion aspect of LTC growth is addressed through analysis of lateral growth of 6H-SiC a/m-plane seed crystals by hot-wall chemical vapor deposition. Preliminary synchrotron white-beam X-Ray Topography (SWBXT) indicates that the as-grown boules match the polytype structure of the underlying seed and have a faceted hexagonal morphology with a strain-free surface marked by steps. SWBXT Laue diffraction patterns of transverse and axial slices of the boules reveal streaks suggesting the existence of stacking faults/polytypes, and this is confirmed by micro-Raman spectroscopy. Transmission X-Ray Topography of both transverse and axial slices reveals inhomogeneous strains at the seed–epilayer interface and linear features propagating from the seed along the growth direction. Micro-Raman mapping of an axial slice reveals that the seed contains high stacking disorder, while contrast extinction analysis (g·b and g·b×l) of the linear features reveals that these are mostly edge-type basal plane dislocations. Further high-resolution transmission electron microscopy investigation of the seed–homoepilayer interface also reveals nanobands of different SiC polytypes. A model for their formation mechanism is proposed. Finally, the implication of these results for improving the LTC growth process is addressed.
Miho Tagawa - One of the best experts on this subject based on the ideXlab platform.
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immobilization of partial dislocations bounding double shockley stacking faults in 4h sic observed by in situ synchrotron x ray Topography
Social Science Research Network, 2021Co-Authors: Fumihiro Fujie, Balaji Raghothamachar, Michael Dudley, Hiromasa Suo, Tomohisa Kato, Shunta Harada, Miho Tagawa, Kenji Hanada, Haruhiko Koizumi, Toru UjiharaAbstract:The expansion of double Shockley stacking faults (DSFs) in an n-type 4H-SiC substrate with a nitrogen concentration of 3.9×10 19 cm −3 was investigated using in situ synchrotron X-Ray Topography. DSF expansion was observed to be suppressed and immobilized above 1590 K, along with the partial dislocation (PD) shape being changed from a straight to zig-zag configuration. For a different heating process (higher heating rate), the PDs could continue to expand, even above 1590 K. Ex situ Topography experiments revealed that the DSFs close to the specimen surface expanded widely, although those expanding toward the specimen interior became immobile. One possible mechanism for this immobilization was proposed, where the core structural changes from a Si-core to the C-core by climb motion induced by the interaction between the PDs and point defects (C interstitials).
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temperature dependence of double shockley stacking fault behavior in nitrogen doped 4h sic studied by in situ synchrotron x ray Topography
Acta Materialia, 2020Co-Authors: Fumihiro Fujie, Hiromasa Suo, Tomohisa Kato, Toru Ujihara, Shunta Harada, Miho Tagawa, Kenji Hanada, Haruhiko KoizumiAbstract:Abstract We observed the behavior of double Shockley stacking faults (DSFs) in 4H-SiC crystals with nitrogen concentrations of 1.0 × 1019–2.6 × 1019 cm−3 over an extensive temperature range (1380–1910 K) by in-situ synchrotron X-Ray Topography. For a nitrogen concentration of 2.6 × 1019 cm−3, the expansion velocity of the DSFs exponentially increased with temperature in the range from 1370 to 1650 K. In contrast, at a nitrogen concentration of 1.0 × 1019 cm−3, this velocity decreased above 1610 K and the DSFs shrank above 1730 K. The DSF energy, the magnitude of which is the driving force on partial dislocation (PD) movement, was quantitatively estimated from the radius of the curvature of bowed-out partial PDs pinned by threading screw dislocations (TSDs), showing a positive temperature dependence and lying in the range from −0.6 to 0.8 mJ/m2 for 1630–1910 K at a nitrogen concentration of 1.0 × 1019 cm−3. The DSF expansion and shrinkage behavior can be understood by the simple temperature and nitrogen concentration dependence of the DSF energy.
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temperature dependence of double shockley stacking fault behavior in nitrogen doped 4h sic studied by in situ synchrotron x ray Topography
Social Science Research Network, 2020Co-Authors: Fumihiro Fujie, Hiromasa Suo, Tomohisa Kato, Shunta Harada, Miho Tagawa, Kenji Hanada, Haruhiko Koizumi, Toru UjiharaAbstract:We observed the behavior of double Shockley stacking faults (DSFs) in 4H-SiC crystals with nitrogen concentrations of 1.0×1019-2.6×1019 cm−3 over an extensive temperature range (1380-1910 K) by in-situ synchrotron X-Ray Topography. For a nitrogen concentration of 2.6×1019 cm−3, the expansion velocity of the DSFs exponentially increased with temperature for temperatures in the range from 1370 to 1650 K. In contrast, at a nitrogen concentration of 1.0×1019 cm−3, this velocity decreased above 1610 K and the DSFs shrank above 1730 K. The DSF energy, considered to be the driving force for DSF expansion, was quantitatively estimated from the radius of the curvature of bowed-out partial dislocations (PDs) pinned by threading screw dislocations (TSDs), showing a positive temperature dependence and lying in the range from −0.6 to 0.8 mJ/m2 at a nitrogen concentration of 1.0×1019 cm−3. The DSF expansion and shrinkage behavior can be understood by the simple temperature and nitrogen concentration dependence of the DSF energy.
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direct observation of stacking fault shrinkage in 4h sic at high temperatures by in situ x ray Topography using monochromatic synchrotron radiation
Applied Physics Letters, 2018Co-Authors: Fumihiro Fujie, Toru Ujihara, Shunta Harada, Kenta Murayama, Miho Tagawa, Kenji Hanada, Haruhiko KoizumiAbstract:An in-situ X-Ray Topography system using monochromatic synchrotron radiation for the observation of the stacking faults in 4H-SiC during a high-temperature annealing process was developed. We demonstrated that the stacking faults in nitrogen-doped 4H-SiC not only expand but also shrink at high temperatures. Furthermore, it was confirmed that the types of the core structure of partial dislocations enclosing the stacking fault can be determined at high temperatures.An in-situ X-Ray Topography system using monochromatic synchrotron radiation for the observation of the stacking faults in 4H-SiC during a high-temperature annealing process was developed. We demonstrated that the stacking faults in nitrogen-doped 4H-SiC not only expand but also shrink at high temperatures. Furthermore, it was confirmed that the types of the core structure of partial dislocations enclosing the stacking fault can be determined at high temperatures.
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conversion behavior of threading screw dislocations on c face with different surface morphology during 4h sic solution growth
Crystal Growth & Design, 2016Co-Authors: Shiyu Xiao, Shunta Harada, Kenta Murayama, Miho Tagawa, Toru UjiharaAbstract:The conversion of threading screw dislocations (TSDs) to defects on the basal plane during SiC solution growth caused by macrostep advance is a key factor to improve crystal quality. We realized the TSD conversion in 4H-SiC C face solution growth by modification of the surface morphology including macrosteps by addition of 5 atom % Ti into pure Si solvent. Synchrotron X-Ray Topography revealed that the possibility of TSD conversion increased to about 10% with the addition of 5 atom % Ti. In addition, the TSD conversion ratio depends on the shape of the macrostep edge. The gentle slope hardly made TSD conversion. The elastic energy of dislocations in anisotropy crystals was postulated as an explanation for the influence of step shape on TSD conversion behavior.
Fumihiro Fujie - One of the best experts on this subject based on the ideXlab platform.
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immobilization of partial dislocations bounding double shockley stacking faults in 4h sic observed by in situ synchrotron x ray Topography
Social Science Research Network, 2021Co-Authors: Fumihiro Fujie, Balaji Raghothamachar, Michael Dudley, Hiromasa Suo, Tomohisa Kato, Shunta Harada, Miho Tagawa, Kenji Hanada, Haruhiko Koizumi, Toru UjiharaAbstract:The expansion of double Shockley stacking faults (DSFs) in an n-type 4H-SiC substrate with a nitrogen concentration of 3.9×10 19 cm −3 was investigated using in situ synchrotron X-Ray Topography. DSF expansion was observed to be suppressed and immobilized above 1590 K, along with the partial dislocation (PD) shape being changed from a straight to zig-zag configuration. For a different heating process (higher heating rate), the PDs could continue to expand, even above 1590 K. Ex situ Topography experiments revealed that the DSFs close to the specimen surface expanded widely, although those expanding toward the specimen interior became immobile. One possible mechanism for this immobilization was proposed, where the core structural changes from a Si-core to the C-core by climb motion induced by the interaction between the PDs and point defects (C interstitials).
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temperature dependence of double shockley stacking fault behavior in nitrogen doped 4h sic studied by in situ synchrotron x ray Topography
Acta Materialia, 2020Co-Authors: Fumihiro Fujie, Hiromasa Suo, Tomohisa Kato, Toru Ujihara, Shunta Harada, Miho Tagawa, Kenji Hanada, Haruhiko KoizumiAbstract:Abstract We observed the behavior of double Shockley stacking faults (DSFs) in 4H-SiC crystals with nitrogen concentrations of 1.0 × 1019–2.6 × 1019 cm−3 over an extensive temperature range (1380–1910 K) by in-situ synchrotron X-Ray Topography. For a nitrogen concentration of 2.6 × 1019 cm−3, the expansion velocity of the DSFs exponentially increased with temperature in the range from 1370 to 1650 K. In contrast, at a nitrogen concentration of 1.0 × 1019 cm−3, this velocity decreased above 1610 K and the DSFs shrank above 1730 K. The DSF energy, the magnitude of which is the driving force on partial dislocation (PD) movement, was quantitatively estimated from the radius of the curvature of bowed-out partial PDs pinned by threading screw dislocations (TSDs), showing a positive temperature dependence and lying in the range from −0.6 to 0.8 mJ/m2 for 1630–1910 K at a nitrogen concentration of 1.0 × 1019 cm−3. The DSF expansion and shrinkage behavior can be understood by the simple temperature and nitrogen concentration dependence of the DSF energy.
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temperature dependence of double shockley stacking fault behavior in nitrogen doped 4h sic studied by in situ synchrotron x ray Topography
Social Science Research Network, 2020Co-Authors: Fumihiro Fujie, Hiromasa Suo, Tomohisa Kato, Shunta Harada, Miho Tagawa, Kenji Hanada, Haruhiko Koizumi, Toru UjiharaAbstract:We observed the behavior of double Shockley stacking faults (DSFs) in 4H-SiC crystals with nitrogen concentrations of 1.0×1019-2.6×1019 cm−3 over an extensive temperature range (1380-1910 K) by in-situ synchrotron X-Ray Topography. For a nitrogen concentration of 2.6×1019 cm−3, the expansion velocity of the DSFs exponentially increased with temperature for temperatures in the range from 1370 to 1650 K. In contrast, at a nitrogen concentration of 1.0×1019 cm−3, this velocity decreased above 1610 K and the DSFs shrank above 1730 K. The DSF energy, considered to be the driving force for DSF expansion, was quantitatively estimated from the radius of the curvature of bowed-out partial dislocations (PDs) pinned by threading screw dislocations (TSDs), showing a positive temperature dependence and lying in the range from −0.6 to 0.8 mJ/m2 at a nitrogen concentration of 1.0×1019 cm−3. The DSF expansion and shrinkage behavior can be understood by the simple temperature and nitrogen concentration dependence of the DSF energy.
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direct observation of stacking fault shrinkage in 4h sic at high temperatures by in situ x ray Topography using monochromatic synchrotron radiation
Applied Physics Letters, 2018Co-Authors: Fumihiro Fujie, Toru Ujihara, Shunta Harada, Kenta Murayama, Miho Tagawa, Kenji Hanada, Haruhiko KoizumiAbstract:An in-situ X-Ray Topography system using monochromatic synchrotron radiation for the observation of the stacking faults in 4H-SiC during a high-temperature annealing process was developed. We demonstrated that the stacking faults in nitrogen-doped 4H-SiC not only expand but also shrink at high temperatures. Furthermore, it was confirmed that the types of the core structure of partial dislocations enclosing the stacking fault can be determined at high temperatures.An in-situ X-Ray Topography system using monochromatic synchrotron radiation for the observation of the stacking faults in 4H-SiC during a high-temperature annealing process was developed. We demonstrated that the stacking faults in nitrogen-doped 4H-SiC not only expand but also shrink at high temperatures. Furthermore, it was confirmed that the types of the core structure of partial dislocations enclosing the stacking fault can be determined at high temperatures.