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52. Segregation mechanism of arsenic dopants at grain boundaries in silicon

Author

Ohno, Yutaka, Yokoi, Tatsuya, Shimizu, Yasuo, Ren, Jie, Inoue, Koji, Nagai, Yasuyoshi, Kutsukake, Kentaro, Fujiwara, Kozo, Nakamura, Atsutomo, Matsunaga, Katsuyuki, and Yoshida, Hideto

Abstract

Three-dimensional distribution of arsenic (As) dopants at Σ3{111}, Σ9{221}, Σ9{114}, and Σ9{111}/{115} grain boundaries (GBs) in silicon (Si) is examined by correlative analytical methods using atom probe tomography (APT) combined with low-temperature focused ion beam (LT-FIB), scanning transmission electron microscopy, and ab initio calculations. Σ3{111} GBs, consisting of only 6-membered rings with small bond distortions, do not exhibit an apparent As segregation. Meanwhile, it is hypothesized that As atoms would segregate at 5-membered rings in the other GBs via anisotropic bond distortions spontaneously introduced so as to lower the donor level, as Jahn-Teller distortions. In addition, APT combined with LT-FIB suggests preferential As segregation around stretched 11‾0 bonds reconstructed in Σ9{114} and Σ9{111}/{115} GBs, that are inevitably introduced in the 11‾0 tilt GBs with the tilt angle larger than 70.5°. It is hypothesized that As atoms would form As dimers at stretched 11‾0 bonds and the adjacent ⟨111⟩ bonds, due to the tendency of As with five valence electrons to form a three-coordinated configuration, which is efficiently attained by an As dimer of a long length. This work provides important insights into As segregation at GBs; it is mainly determined by electronic interactions depending on the characteristics of valence electrons of As atoms, as well as on local bond distortions at GBs, via anisotropic bond distortions and dimerization.

Published
2021
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53. Bridging the Gap between Bulk Compression and Indentation Test on Room-Temperature Plasticity in Oxides: Case Study on SrTiO3

Author

Fang, Xufei, Porz, Lukas, Ding, Kuan, Nakamura, Atsutomo, Fang, Xufei, Porz, Lukas, Ding, Kuan, and Nakamura, Atsutomo

Abstract

Dislocation-based functionalities in inorganic ceramics and semiconductors are drawing increasing attention, contrasting the conventional belief that the majority of ceramic materials are brittle at room temperature. Understanding the dislocation behavior in ceramics and advanced semiconducting materials is therefore critical for the mechanical reliability of such materials and devices designed for harvesting the dislocation-based functionalities. Here we compare the mechanical testing between indentation at nano-/microscale and bulk uniaxial deformation at macroscale and highlight the dislocation plasticity in single crystal SrTiO3, a model perovskite. The similarities and differences as well as the advantages and limitations of both testing protocols are discussed based on the experimental outcome of the crystal plasticity, with a focus on the pre-existing defect population being probed with different volumes across the length scales (“size effect”). We expect this work to pave the road for studying dislocation-based plasticity in various advanced functional ceramics and semiconductors.

Published
2021

54. Dislocation-toughened ceramics

Author

Porz, Lukas, Klomp, Arne J., Fang, Xufei, Li, Ning, Yildirim, Can, Detlefs, Carsten, Bruder, Enrico, Höfling, Marion, Rheinheimer, Wolfgang, Patterson, Eric A., Gao, Peng, Durst, Karsten, Nakamura, Atsutomo, Albe, Karsten, Simons, Hugh, Rödel, Jürgen, Porz, Lukas, Klomp, Arne J., Fang, Xufei, Li, Ning, Yildirim, Can, Detlefs, Carsten, Bruder, Enrico, Höfling, Marion, Rheinheimer, Wolfgang, Patterson, Eric A., Gao, Peng, Durst, Karsten, Nakamura, Atsutomo, Albe, Karsten, Simons, Hugh, and Rödel, Jürgen

Abstract

Functional and structural ceramics have become irreplaceable in countless high-tech applications. However, their inherent brittleness tremendously limits the application range and, despite extensive research efforts, particularly short cracks are hard to combat. While local plasticity carried by mobile dislocations allows desirable toughness in metals, high bond strength is widely believed to hinder dislocation-based toughening of ceramics. Here, we demonstrate the possibility to induce and engineer a dislocation microstructure in ceramics that improves the crack tip toughness even though such toughening does not occur naturally after conventional processing. With modern microscopy and simulation techniques, we reveal key ingredients for successful engineering of dislocation-based toughness at ambient temperature. For many ceramics a dislocation-based plastic zone is not impossible due to some intrinsic property (e.g. bond strength) but limited by an engineerable quantity, i.e. the dislocation density. The impact of dislocation density is demonstrated in a surface near region and suggested to be transferrable to bulk ceramics. Unexpected potential in improving mechanical performance of ceramics could be realized with novel synthesis strategies.

Published
2021

58. Bridging the Gap between Bulk Compression and Indentation Test on Room-Temperature Plasticity in Oxides: Case Study on SrTiO3

Author

Fang, Xufei, Porz, Lukas, Ding, Kuan, and Nakamura, Atsutomo

Subjects
nanoindentation, bulk deformation, dislocation plasticity, lcsh:QD901-999, SrTiO3, lcsh:Crystallography, ceramics
Abstract

Dislocation-based functionalities in inorganic ceramics and semiconductors are drawing increasing attention, contrasting the conventional belief that the majority of ceramic materials are brittle at room temperature. Understanding the dislocation behavior in ceramics and advanced semiconducting materials is therefore critical for the mechanical reliability of such materials and devices designed for harvesting the dislocation-based functionalities. Here we compare the mechanical testing between indentation at nano-/microscale and bulk uniaxial deformation at macroscale and highlight the dislocation plasticity in single crystal SrTiO3, a model perovskite. The similarities and differences as well as the advantages and limitations of both testing protocols are discussed based on the experimental outcome of the crystal plasticity, with a focus on the pre-existing defect population being probed with different volumes across the length scales (&ldquo, size effect&rdquo, ). We expect this work to pave the road for studying dislocation-based plasticity in various advanced functional ceramics and semiconductors.

Published
2020
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61. Segregation mechanism of arsenic dopants at grain boundaries in silicon

Author

Ohno, Yutaka, primary, Yokoi, Tatsuya, additional, Shimizu, Yasuo, additional, Ren, Jie, additional, Inoue, Koji, additional, Nagai, Yasuyoshi, additional, Kutsukake, Kentaro, additional, Fujiwara, Kozo, additional, Nakamura, Atsutomo, additional, Matsunaga, Katsuyuki, additional, and Yoshida, Hideto, additional

Published
2021
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62. Dislocation-toughened ceramics

Author

Porz, Lukas, primary, Klomp, Arne J., additional, Fang, Xufei, additional, Li, Ning, additional, Yildirim, Can, additional, Detlefs, Carsten, additional, Bruder, Enrico, additional, Höfling, Marion, additional, Rheinheimer, Wolfgang, additional, Patterson, Eric A., additional, Gao, Peng, additional, Durst, Karsten, additional, Nakamura, Atsutomo, additional, Albe, Karsten, additional, Simons, Hugh, additional, and Rödel, Jürgen, additional

Published
2021
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63. Conceptual Framework for Dislocation-Modified Conductivity in Oxide Ceramics Deconvoluting Mesoscopic Structure, Core, and Space Charge Exemplified for SrTiO3

Author

Porz, Lukas, primary, Frömling, Till, additional, Nakamura, Atsutomo, additional, Li, Ning, additional, Maruyama, Ryohei, additional, Matsunaga, Katsuyuki, additional, Gao, Peng, additional, Simons, Hugh, additional, Dietz, Christian, additional, Rohnke, Marcus, additional, Janek, Jürgen, additional, and Rödel, Jürgen, additional

Published
2020
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72. Deform to perform: Dislocation-tuned properties of ceramics.

Author

Xufei Fang, Nakamura, Atsutomo, and Rödel, Jürgen

Subjects
*SPACE charge, *TITANIUM powder, *CERAMICS, *SUPERCONDUCTING transition temperature
Abstract

The article summarizes developments led by methods for engineering dislocations into ceramics and considers what is next for the field of dislocations in ceramics. Topics discussed include comparison between ceramics and metals in terms of fracture toughness; opportunities brought by the charges of the dislocation core, together with the high local strain field surrounding dislocations; and ways dislocation engineering in ceramics can be achieved.

Published
2023

77. Conceptual Framework for Dislocation-Modified Conductivity in Oxide Ceramics Deconvoluting Mesoscopic Structure, Core, and Space Charge Exemplified for SrTiO3

Author

Porz, Lukas, Frömling, Till, Nakamura, Atsutomo, Li, Ning, Maruyama, Ryohei, Matsunaga, Katsuyuki, Gao, Peng, Simons, Hugh, Dietz, Christian, Rohnke, Marcus, Janek, Jürgen, and Rödel, Jürgen

Abstract

The introduction of dislocations is a recently proposed strategy to tailor the functional and especially the electrical properties of ceramics. While several works confirm a clear impact of dislocations on electrical conductivity, some studies raise concern in particular when expanding to dislocation arrangements beyond a geometrically tractable bicrystal interface. Moreover, the lack of a complete classification on pertinent dislocation characteristics complicates a systematic discussion and hampers the design of dislocation-modified electrical conductivity. We proceed by mechanically introducing dislocations with three different mesoscopic structures into the model material single-crystal SrTiO3and extensively characterizing them from both a mechanical as well as an electrical perspective. As a final result, a deconvolution of mesoscopic structure, core structure,and space chargeenables us to obtain the complete picture of the effect of dislocations on functional properties, focusing here on electric properties.

Published
2021
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83. Structure of the Basal Edge Dislocation in ZnO

Author

Nakamura, Atsutomo, primary, Tochigi, Eita, additional, Nagahara, Ryota, additional, Furushima, Yuho, additional, Oshima, Yu, additional, Ikuhara, Yuichi, additional, Yokoi, Tatsuya, additional, and Matsunaga, Katsuyuki, additional

Published
2018
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86. Room-Temperature Plastic Deformation of Strontium Titanate Crystals Grown from Different Chemical Compositions

Author

60590172, Nakamura, Atsutomo, Yasufuku, Kensuke, Furushima, Yuho, Toyoura, Kazuaki, Lagerlöf, K., Matsunaga, Katsuyuki, 60590172, Nakamura, Atsutomo, Yasufuku, Kensuke, Furushima, Yuho, Toyoura, Kazuaki, Lagerlöf, K., and Matsunaga, Katsuyuki

Abstract

Oxide materials have the potential to exhibit superior mechanical properties in terms of high yield point, high melting point, and high chemical stability. Despite this, they are not widely used as a structural material due to their brittle nature. However, this study shows enhanced room-temperature plasticity of strontium titanate (SrTiO3) crystals through the control of the chemical composition. It is shown that the deformation behavior of SrTiO3 crystals at room temperature depends on the Sr/Ti ratio. It was found that flow stresses in deforming SrTiO3 crystals grown from a powder with the particular ratio of Sr/Ti = 1.04 are almost independent of the strain rate because of the high mobility of dislocations in such crystals. As a result, the SrTiO3 crystals can deform by dislocation slip up to a strain of more than 10%, even at a very high strain rate of 10% per second. It is thus demonstrated that SrTiO3 crystals can exhibit excellent plasticity when chemical composition in the crystal is properly controlled.

Published
2017

87. Dislocation-toughened ceramicsElectronic supplementary information (ESI) available. See DOI: 10.1039/d0mh02033h

Author

Porz, Lukas, Klomp, Arne J., Fang, Xufei, Li, Ning, Yildirim, Can, Detlefs, Carsten, Bruder, Enrico, Höfling, Marion, Rheinheimer, Wolfgang, Patterson, Eric A., Gao, Peng, Durst, Karsten, Nakamura, Atsutomo, Albe, Karsten, Simons, Hugh, and Rödel, Jürgen

Abstract

Functional and structural ceramics have become irreplaceable in countless high-tech applications. However, their inherent brittleness tremendously limits the application range and, despite extensive research efforts, particularly short cracks are hard to combat. While local plasticity carried by mobile dislocations allows desirable toughness in metals, high bond strength is widely believed to hinder dislocation-based toughening of ceramics. Here, we demonstrate the possibility to induce and engineer a dislocation microstructure in ceramics that improves the crack tip toughness even though such toughening does not occur naturally after conventional processing. With modern microscopy and simulation techniques, we reveal key ingredients for successful engineering of dislocation-based toughness at ambient temperature. For many ceramics a dislocation-based plastic zone is not impossible due to some intrinsic property (e.g.bond strength) but limited by an engineerable quantity, i.e.the dislocation density. The impact of dislocation density is demonstrated in a surface near region and suggested to be transferrable to bulk ceramics. Unexpected potential in improving mechanical performance of ceramics could be realized with novel synthesis strategies.

Published
2021
Full Text
View/download PDF

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