Microscopy, 2014, Vol. 63, No. S1
i22 Irradiation damage in multicomponent equimolar alloys and high entropy alloys (HEAs)
2
Rutgers Center for Emergent Materials and Department of Physics & Astronomy, Rutgers University, Piscataway, New Jersey 08854, USA
Takeshi Nagasea,b, Philip D. Rackc,d, and Takeshi Egamic,d,e a
Research Center for Ultra-High Voltage Electron Microscopy, Osaka University, 7-1, Mihogaoka, Ibaraki, Osaka 567-0047, Japan, b Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University, 2-1, Yamada-Oka, Suita, Osaka 565-0871, Japan, cOak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831, U.S, dDepartment of Materials Science and Engineering, University of Tennessee, Knoxville, TN 37996, U.S, and e Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996, U.S
(1) ZrHfNb equimolar alloys [1, 2] A multicomponent ZrHfNb alloy was prepared by a co-sputtering process using elemental Zr, Hf, and Nb targets using an AJA International ATC 2000-V system. A single-phase bcc solid solution was obtained in the ZrHfNb alloy with an approximately equiatomic ratio of its constituent elements. The irradiation-induced structural change in the ZrHfNb equimolar alloys with the bcc solid solution structure was investigated by HVEM using the Hitachi H-3000 installed at Osaka University. The polycrystalline bcc phase shows high phase stability against irradiation damage at 298 K; the bcc solid solution phase, whose grain size was about 20 nm, remained as a main constituent phase even after the severe irradiation damage that reached 10 dpa. (2) CoCrCuFeNi HEAs [3] A single-phase fcc solid solution was obtained in a CoCrCuFeNi alloy. The microstructure of the alloy depended on the preparation technique: a nanocrystalline CoCrCuFeNi alloy with an approximately equiatomic ratio of its constituent elements was obtained by a co-sputtering process with multi-targets, while polycrystalline structures were formed when the arc-melting method was used. Both nanocrystalline and polycrystalline structures showed high phase stability against fast electron irradiation at temperatures ranging from 298 K to 973 K; a fcc phase remained as the main constituent phase over 40 dpa of irradiation. The grain coarsening of the crystalline phase can be seen during the annealing in a nanocrystalline CoCrCuFeNi alloy, while the irradiation-induced grain coarsening did not occur at 773 K as well as at 298 K.
References 1. Fiebig M., et al., Nature 419, 818 (2002). 2. Choi T. J., et al., Nature Materials 9, 253 (2010) doi: 10.1093/jmicro/dfu067
Observation of the potential distribution in GaN-based devices by a scanning electron microscope Takahiro Karumi1, Shigeyasu Tanaka2, and Takayoshi Tanji2 1
Department of Electrical Engineering and Computer Science, Nagoya University, and 2EcoTopia Science Institute, Nagoya University
References 1. Nagase T., Anada S., Rack P. D., Noh J. H., Yasuda H., Mori H., Egami T.: Intermetallics, 26 (2012) 122–130. 2. Nagase T., Anada S., Rack P. D., Noh J. H., Yasuda H., Mori H., Egami T.: Intermetallics, 38 (2013) 70–79. 3. Nagase T., Rack P. D., Noh J. H., Egami T.: Intermetallics, to be submitted. 4. Egami T., Guo W., Rack P. D., Nagase T.: Metall. Mater. Trans. A, 45 (2014) 180–183. doi: 10.1093/jmicro/dfu054 Observation of vortex domain structures in multiferroic hexagonal manganites RMnO3 by transmission electron microscopy Yoichi Horibe1, Fei-Ting Huang2, Taekjib Choi2, Nara Lee2, and Sang-Wook Cheong2 1
Department of Materials Science & Engineering, Kyushu Institute of Technology, Kita-kyushu, Fukuoka 804-8550, Japan, and
Mapping of the potential distribution using a scanning electron microscope (SEM) has been reported in recent years [1,2] for semiconductors such as Si, GaAs and InP. But, there are no such studies on GaN-based devices, to our knowledge. In this study, we observed two types of GaN-based devices by SEM to see if there is a condition that the contrast matches the potential distribution of the devices. The first device we studied was GaN p-n junction ( p, n ∼5 × 1017 cm−3). The device was cut, and polished from the cross-section to a flat surface. The cross-section was observed by SEM. Fig. 1(a) shows an SEM image taken at 3 kV. The p-region appears bright and the n-region appears dark. The image intensity changes at the position of p-n junction, for which we used electron beam induced current (EBIC) technique to determine the p-n junction position. Fig. 1(b) is a line profile across the p-n junction (broken line) of the SEM image together with a calculated potential distribution (solid line) using p and n concentrations. It can be seen that the contrast profile matches the potential distribution very well. The SEM observations were carried out for several accelerating voltages. But, best result was obtained at 3 kV. For lower accelerating voltages, the image seemed to reflect the surface potential. On the other hand, higher accelerating voltages resulted in blurred images. The second sample was a light emitting diode structure based on AlN where a multiple quantum
Downloaded from http://jmicro.oxfordjournals.org/ at University of Ulster on October 4, 2015
To maintain sustainable energy supply and improve the safety and efficiency of nuclear reactors, development of new and advanced nuclear materials with superior resistance to irradiation damage is necessary. Recently, a new generation of structural materials, termed as multicomponent equimolar alloys and/or high entropy alloys (HEAs), are being developed. These alloys consist of multicomponent elements for maximizing the compositional entropy, which stabilizes the solid solution phase. In this paper, preliminary studies on the irradiation damage in equimolar alloys and HEAs by High Voltage Electron Microscopy (HVEM) are reported [1–4].
Multiferroic hexagonal manganite RMnO3 (R = rare-earth elements) shows improper ferroelectricity accompanied by tilting of MnO5 hexahedra as the primary order parameter. The ferroelectricity is originated from displacements of rare-earth ions along c-axis triggered by the MnO5 hexahedra tilting. Although coupling between ferroelectric and antiferromagnetic domains below the magnetic transition temperature of ∼90 K has been reported from previous work[1], the relationship between the ferroelectric domains and structural domains due to the MnO5 hexahedra tilting has not been wellstudied. In this talk, we will report our studies on unique patterns of ferroelectric antiphase domains with a vorticity in hexagonal RMnO3, obtained from the results of transmission electron microscopy [2]. The electron diffraction patterns obtained at room temperature exhibit superlattice reflection spots due to the MnO5 hexahedra tilting and displacements of rare-earth ions along c-axis, in addition to the fundamental reflections associated with the high symmetry structure with the space group of P63/mmc. Unique antiphase/ferroelectric "cloverleaf-like" domain patterns are clearly observed in dark-field images taken using superlattice spots. The fundamental and superlattice dark-field imaging combined with high-resolution imaging clearly demonstrates that in the cloverleaf-like domain patterns the antiphase and ferroelectric domains arrange periodically with certain rotation direction. In addition, there exist two types of cloverleaf-like domain patterns with the opposite rotations next to each other in the superlattice dark-field images. These results indicate that the cloverleaf-like domain patterns can be considered as the aggregation of vortices and antivortices consisting of ferroelectric and antiphase domains.
Microscopy, 2014, Vol. 63, No. S1
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Fig. 1. (a) SEM image of p-n GaN. (b) Comparison of line profile across the p-n junction (broken line) and a calculated potential distribution (solid line).
well (MQW) structure was sandwiched by p- and n-AlGaN materials. In this case, the sample was obliquely polished from the surface (∼10°) to improve the lateral resolution. The SEM image could reveal the structure of MQW.
References 1. Sealy C. P., Castell M. R., Wilshaw P. R., J. Electron Microscopy 49, 311 (2000). 2. Kaestner B., Schönjahn C., Humphreys C. J., Appl. Physics Letters 84, 2109 (2004). doi: 10.1093/jmicro/dfu051
Three-dimensional characterization of ODS ferritic steel using by FIB-SEM serial sectioning method T. Endo, Y. Sugino, N. Ohono, S. Ukai, N. Miyazaki, Y. Wang, and S. Ohnuki Dept. of Materials Science, Faculty of Engineering, Hokkaido University kita 13, Nishi 8, Kitaku, Sapporo, Hokkaido, Japan Considerable attention has been paid to the research of the electron tomography due to determine the three-dimensional (3D) structure of materials [1]. One of the electron tomography techniques, focused ion beam/scanning electron microscopy (FIB-SEM) imaging has advantages of high resolutions (10 nm), large area observation (μm order) and simultaneous energy dispersive x- ray microanalysis (EDS)/ electron backscatter diffraction (EBSD) analysis. The purpose of this study, three-dimensional EBSD analysis of ODS ferritic steel which carried out cold work using FIB-SEM equipment was conducted, and it aimed at analyzing the microstructure obtained there. The zone annealing tests were conducted for ferritic steel [2,3], which
were produced through mechanical alloying and hot-extrusion. After zone annealing, specimens were mechanically polished with #400∼4000 emery paper, 1 µm diamond paste and alumina colloidal silica. The serial sectioning and the 3D-electron backscattering
References 1. Schneid P., Meier M., Wepf R., Mülleret R.: Bone 49 (2011) 304–311. 2. Ukai S., Okuda T., Fujiwara M., Kobayashi T., Mizuta S., Nakashima H.: J. Nucl. Sci. Technol., 39 (2002), No. 8, 872. 3. Sugino Y., Ukai S., Leng B., Tang Q., Hayashi S., Kaito T., Ohtsuka S.,: ISIJ International, 51 (2011), 982. doi: 10.1093/jmicro/dfu052 A new field-of-view autotracking method based on back-projected ray image cross-correlation for online tomography reconstruction Sachihiko Tomonaga1, Misuzu Baba1,2, and Norio Baba1 1
Major of Informatics, Graduate School, Kogakuin University, 2665-1 Nakano, Hachioji, Japan, and 2Research Institute for Science and Technology, Kogakuin University, 2665-1 Nakano, Hachioji, Japan In general, a tomogram cannot be observed immediately after the acquisition of a series of specimen tilt images, but is instead observed after the post-processing of the tilt series alignment, which often requires a substantial amount of time. Moreover, for general specimens, the automatic acquisition of the tilt series is difficult because field-of-view tracking frequently fails as the tilt angle or specimen thickness increases. In this study, we focus on the improvement of the field-of-view autotracking technique for the purpose of online tomography reconstruction and propose a new alternative technique [1,2]. The method we proposed uses a so-called ‘back-projected ray image’ instead of a specimen tilt image. The back-projected ray image is a cross-section image calculated from each projection image only during reconstruction. As a result of a study on ‘ray images’, the quality and accuracy of the cross-correlation between a pair of neighboring ray images among the tilt series were observed to be very high compared with those between a pair of projection images. We observed that a back projected ray image reliably cross-correlates with other neighboring ray images at the position of an existing three-dimensional object. The proposed method can therefore consistently track the
Downloaded from http://jmicro.oxfordjournals.org/ at University of Ulster on October 4, 2015
Acknowledgement We thank professor H. Amano (Nagoya University) for providing the samples.
diffraction (3D-EBSD) analysis were carried out. We made the micro pillar (30 x 30 x 15 µm). The EBSD measurements were carried out in each layer after serial sectioning at a step size and milling depth was 80 nm with 30 slices. After EBSD analysis, the series of crosssectional images were aligned according to arbitrarily specified areas and then stacked up to form a volume. Consequently, we obtained the 3D-IPF maps for ODS ferritic steel. In this specimen, the {111} and {001} grains are layered by turns. In addition, the volume fraction value of both plane are similar. The aspect ratio increases with specimen depth. The 3D-EBSD mapping is useful to analysis of the bulk material since this method obtain many microstructure information, such a shape, volume and orientation of the crystal, grain boundary.
i22 Irradiation damage in multicomponent equimolar alloys and high entropy alloys (HEAs)
2
Rutgers Center for Emergent Materials and Department of Physics & Astronomy, Rutgers University, Piscataway, New Jersey 08854, USA
Takeshi Nagasea,b, Philip D. Rackc,d, and Takeshi Egamic,d,e a
Research Center for Ultra-High Voltage Electron Microscopy, Osaka University, 7-1, Mihogaoka, Ibaraki, Osaka 567-0047, Japan, b Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University, 2-1, Yamada-Oka, Suita, Osaka 565-0871, Japan, cOak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831, U.S, dDepartment of Materials Science and Engineering, University of Tennessee, Knoxville, TN 37996, U.S, and e Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996, U.S
(1) ZrHfNb equimolar alloys [1, 2] A multicomponent ZrHfNb alloy was prepared by a co-sputtering process using elemental Zr, Hf, and Nb targets using an AJA International ATC 2000-V system. A single-phase bcc solid solution was obtained in the ZrHfNb alloy with an approximately equiatomic ratio of its constituent elements. The irradiation-induced structural change in the ZrHfNb equimolar alloys with the bcc solid solution structure was investigated by HVEM using the Hitachi H-3000 installed at Osaka University. The polycrystalline bcc phase shows high phase stability against irradiation damage at 298 K; the bcc solid solution phase, whose grain size was about 20 nm, remained as a main constituent phase even after the severe irradiation damage that reached 10 dpa. (2) CoCrCuFeNi HEAs [3] A single-phase fcc solid solution was obtained in a CoCrCuFeNi alloy. The microstructure of the alloy depended on the preparation technique: a nanocrystalline CoCrCuFeNi alloy with an approximately equiatomic ratio of its constituent elements was obtained by a co-sputtering process with multi-targets, while polycrystalline structures were formed when the arc-melting method was used. Both nanocrystalline and polycrystalline structures showed high phase stability against fast electron irradiation at temperatures ranging from 298 K to 973 K; a fcc phase remained as the main constituent phase over 40 dpa of irradiation. The grain coarsening of the crystalline phase can be seen during the annealing in a nanocrystalline CoCrCuFeNi alloy, while the irradiation-induced grain coarsening did not occur at 773 K as well as at 298 K.
References 1. Fiebig M., et al., Nature 419, 818 (2002). 2. Choi T. J., et al., Nature Materials 9, 253 (2010) doi: 10.1093/jmicro/dfu067
Observation of the potential distribution in GaN-based devices by a scanning electron microscope Takahiro Karumi1, Shigeyasu Tanaka2, and Takayoshi Tanji2 1
Department of Electrical Engineering and Computer Science, Nagoya University, and 2EcoTopia Science Institute, Nagoya University
References 1. Nagase T., Anada S., Rack P. D., Noh J. H., Yasuda H., Mori H., Egami T.: Intermetallics, 26 (2012) 122–130. 2. Nagase T., Anada S., Rack P. D., Noh J. H., Yasuda H., Mori H., Egami T.: Intermetallics, 38 (2013) 70–79. 3. Nagase T., Rack P. D., Noh J. H., Egami T.: Intermetallics, to be submitted. 4. Egami T., Guo W., Rack P. D., Nagase T.: Metall. Mater. Trans. A, 45 (2014) 180–183. doi: 10.1093/jmicro/dfu054 Observation of vortex domain structures in multiferroic hexagonal manganites RMnO3 by transmission electron microscopy Yoichi Horibe1, Fei-Ting Huang2, Taekjib Choi2, Nara Lee2, and Sang-Wook Cheong2 1
Department of Materials Science & Engineering, Kyushu Institute of Technology, Kita-kyushu, Fukuoka 804-8550, Japan, and
Mapping of the potential distribution using a scanning electron microscope (SEM) has been reported in recent years [1,2] for semiconductors such as Si, GaAs and InP. But, there are no such studies on GaN-based devices, to our knowledge. In this study, we observed two types of GaN-based devices by SEM to see if there is a condition that the contrast matches the potential distribution of the devices. The first device we studied was GaN p-n junction ( p, n ∼5 × 1017 cm−3). The device was cut, and polished from the cross-section to a flat surface. The cross-section was observed by SEM. Fig. 1(a) shows an SEM image taken at 3 kV. The p-region appears bright and the n-region appears dark. The image intensity changes at the position of p-n junction, for which we used electron beam induced current (EBIC) technique to determine the p-n junction position. Fig. 1(b) is a line profile across the p-n junction (broken line) of the SEM image together with a calculated potential distribution (solid line) using p and n concentrations. It can be seen that the contrast profile matches the potential distribution very well. The SEM observations were carried out for several accelerating voltages. But, best result was obtained at 3 kV. For lower accelerating voltages, the image seemed to reflect the surface potential. On the other hand, higher accelerating voltages resulted in blurred images. The second sample was a light emitting diode structure based on AlN where a multiple quantum
Downloaded from http://jmicro.oxfordjournals.org/ at University of Ulster on October 4, 2015
To maintain sustainable energy supply and improve the safety and efficiency of nuclear reactors, development of new and advanced nuclear materials with superior resistance to irradiation damage is necessary. Recently, a new generation of structural materials, termed as multicomponent equimolar alloys and/or high entropy alloys (HEAs), are being developed. These alloys consist of multicomponent elements for maximizing the compositional entropy, which stabilizes the solid solution phase. In this paper, preliminary studies on the irradiation damage in equimolar alloys and HEAs by High Voltage Electron Microscopy (HVEM) are reported [1–4].
Multiferroic hexagonal manganite RMnO3 (R = rare-earth elements) shows improper ferroelectricity accompanied by tilting of MnO5 hexahedra as the primary order parameter. The ferroelectricity is originated from displacements of rare-earth ions along c-axis triggered by the MnO5 hexahedra tilting. Although coupling between ferroelectric and antiferromagnetic domains below the magnetic transition temperature of ∼90 K has been reported from previous work[1], the relationship between the ferroelectric domains and structural domains due to the MnO5 hexahedra tilting has not been wellstudied. In this talk, we will report our studies on unique patterns of ferroelectric antiphase domains with a vorticity in hexagonal RMnO3, obtained from the results of transmission electron microscopy [2]. The electron diffraction patterns obtained at room temperature exhibit superlattice reflection spots due to the MnO5 hexahedra tilting and displacements of rare-earth ions along c-axis, in addition to the fundamental reflections associated with the high symmetry structure with the space group of P63/mmc. Unique antiphase/ferroelectric "cloverleaf-like" domain patterns are clearly observed in dark-field images taken using superlattice spots. The fundamental and superlattice dark-field imaging combined with high-resolution imaging clearly demonstrates that in the cloverleaf-like domain patterns the antiphase and ferroelectric domains arrange periodically with certain rotation direction. In addition, there exist two types of cloverleaf-like domain patterns with the opposite rotations next to each other in the superlattice dark-field images. These results indicate that the cloverleaf-like domain patterns can be considered as the aggregation of vortices and antivortices consisting of ferroelectric and antiphase domains.
Microscopy, 2014, Vol. 63, No. S1
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Fig. 1. (a) SEM image of p-n GaN. (b) Comparison of line profile across the p-n junction (broken line) and a calculated potential distribution (solid line).
well (MQW) structure was sandwiched by p- and n-AlGaN materials. In this case, the sample was obliquely polished from the surface (∼10°) to improve the lateral resolution. The SEM image could reveal the structure of MQW.
References 1. Sealy C. P., Castell M. R., Wilshaw P. R., J. Electron Microscopy 49, 311 (2000). 2. Kaestner B., Schönjahn C., Humphreys C. J., Appl. Physics Letters 84, 2109 (2004). doi: 10.1093/jmicro/dfu051
Three-dimensional characterization of ODS ferritic steel using by FIB-SEM serial sectioning method T. Endo, Y. Sugino, N. Ohono, S. Ukai, N. Miyazaki, Y. Wang, and S. Ohnuki Dept. of Materials Science, Faculty of Engineering, Hokkaido University kita 13, Nishi 8, Kitaku, Sapporo, Hokkaido, Japan Considerable attention has been paid to the research of the electron tomography due to determine the three-dimensional (3D) structure of materials [1]. One of the electron tomography techniques, focused ion beam/scanning electron microscopy (FIB-SEM) imaging has advantages of high resolutions (10 nm), large area observation (μm order) and simultaneous energy dispersive x- ray microanalysis (EDS)/ electron backscatter diffraction (EBSD) analysis. The purpose of this study, three-dimensional EBSD analysis of ODS ferritic steel which carried out cold work using FIB-SEM equipment was conducted, and it aimed at analyzing the microstructure obtained there. The zone annealing tests were conducted for ferritic steel [2,3], which
were produced through mechanical alloying and hot-extrusion. After zone annealing, specimens were mechanically polished with #400∼4000 emery paper, 1 µm diamond paste and alumina colloidal silica. The serial sectioning and the 3D-electron backscattering
References 1. Schneid P., Meier M., Wepf R., Mülleret R.: Bone 49 (2011) 304–311. 2. Ukai S., Okuda T., Fujiwara M., Kobayashi T., Mizuta S., Nakashima H.: J. Nucl. Sci. Technol., 39 (2002), No. 8, 872. 3. Sugino Y., Ukai S., Leng B., Tang Q., Hayashi S., Kaito T., Ohtsuka S.,: ISIJ International, 51 (2011), 982. doi: 10.1093/jmicro/dfu052 A new field-of-view autotracking method based on back-projected ray image cross-correlation for online tomography reconstruction Sachihiko Tomonaga1, Misuzu Baba1,2, and Norio Baba1 1
Major of Informatics, Graduate School, Kogakuin University, 2665-1 Nakano, Hachioji, Japan, and 2Research Institute for Science and Technology, Kogakuin University, 2665-1 Nakano, Hachioji, Japan In general, a tomogram cannot be observed immediately after the acquisition of a series of specimen tilt images, but is instead observed after the post-processing of the tilt series alignment, which often requires a substantial amount of time. Moreover, for general specimens, the automatic acquisition of the tilt series is difficult because field-of-view tracking frequently fails as the tilt angle or specimen thickness increases. In this study, we focus on the improvement of the field-of-view autotracking technique for the purpose of online tomography reconstruction and propose a new alternative technique [1,2]. The method we proposed uses a so-called ‘back-projected ray image’ instead of a specimen tilt image. The back-projected ray image is a cross-section image calculated from each projection image only during reconstruction. As a result of a study on ‘ray images’, the quality and accuracy of the cross-correlation between a pair of neighboring ray images among the tilt series were observed to be very high compared with those between a pair of projection images. We observed that a back projected ray image reliably cross-correlates with other neighboring ray images at the position of an existing three-dimensional object. The proposed method can therefore consistently track the
Downloaded from http://jmicro.oxfordjournals.org/ at University of Ulster on October 4, 2015
Acknowledgement We thank professor H. Amano (Nagoya University) for providing the samples.
diffraction (3D-EBSD) analysis were carried out. We made the micro pillar (30 x 30 x 15 µm). The EBSD measurements were carried out in each layer after serial sectioning at a step size and milling depth was 80 nm with 30 slices. After EBSD analysis, the series of crosssectional images were aligned according to arbitrarily specified areas and then stacked up to form a volume. Consequently, we obtained the 3D-IPF maps for ODS ferritic steel. In this specimen, the {111} and {001} grains are layered by turns. In addition, the volume fraction value of both plane are similar. The aspect ratio increases with specimen depth. The 3D-EBSD mapping is useful to analysis of the bulk material since this method obtain many microstructure information, such a shape, volume and orientation of the crystal, grain boundary.
