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Yuwei Huang - One of the best experts on this subject based on the ideXlab platform.
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Significantly enhanced Breakdown Field in Ca 1-x Sr x Cu 3 Ti 4 O 12 ceramics by tailoring donor densities
Journal of the European Ceramic Society, 2018Co-Authors: Zhuang Tang, Yuwei HuangAbstract:Abstract Significantly enhanced Breakdown Field of 24.52 kV cm−1 as well as noteworthy nonlinear coefficient of 8.11 and low dielectric loss of 0.077 were obtained in Ca0.6Sr0.4Cu3Ti4O12 ceramic. It was proved from impedance spectra that improved Breakdown Field was attributed to enhanced grain boundary resistance and elevated Schottky barrier height, which was further found resulting from reduced donor densities in C-V measurements. In addition, it was found that the activation energy originated from oxygen vacancies was increased, indicating the generation of oxygen vacancies was suppressed. Since oxygen vacancies acted as donors in depletion layers, it is reasonable to deduce that the reduced donor density was mainly ascribed to the decreased oxygen vacancies. In conclusion, maximum integrated action of strong solid solution effect and weak Sr-stretching effect was achieved when Sr/Ca ratio is 40/60, leading to greatly elevated potential barrier height and enhanced Breakdown Field consequently.
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High Breakdown Field CaCu3Ti4O12 Ceramics: Roles of the Secondary Phase and of Sr Doping
Energies, 2017Co-Authors: Zhuang Tang, Yuwei HuangAbstract:In this work, two methods of CaCu3Ti4O12-CuAl2O4 composite and SrCu3Ti4O12-CaCu3Ti4O12 composite were prepared to improve the Breakdown Field in CaCu3Ti4O12 ceramics. CaCu3Ti4O12-0.5CuAl2O4 and 0.4SrCu3Ti4O12-0.6CaCu3Ti4O12 samples with proper sintering conditions were found to have greatly enhanced Breakdown Fields of more than 20 kV·cm−1 compared to the ordinary value of 1–2 kV·cm−1 in CaCu3Ti4O12 ceramics. In addition, reduced dielectric loss tangent of these samples remained about 0.1 at a low frequency of 0.1 Hz, indicating superior dielectric properties. No abnormal grain growth was found in either composite with a high Breakdown Field, which was attributed to the pining effect and consumption of Cu-rich phase at grain boundaries. Under analysis of the relaxation process by electric modulus, compared to conventional CaCu3Ti4O12 ceramics, interstitial Ali··· and increasing interfaces were responsible for variation in activation energy in CaCu3Ti4O12-0.5CuAl2O4 composites, while the integrated action of a strong solid solution effect and weak Sr-stretching effect contributed to the elevated potential barrier height and enhanced Breakdown Field in 0.4SrCu3Ti4O12-0.6CaCu3Ti4O12 composites.
Hisashi Furuya - One of the best experts on this subject based on the ideXlab platform.
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Simulation of degradation of dielectric Breakdown Field of thermal SiO/sub 2/ films due to voids in Si wafers
IEEE Transactions on Electron Devices, 2000Co-Authors: Y. Satoh, T. Shiota, Hisashi FuruyaAbstract:Degradation of the dielectric Breakdown Field of thermal SiO/sub 2/ film caused by voids that are formed during growth of silicon single crystal has been a serious problem with reliability of MOS devices. To understand the degradation of Breakdown Field, local thinning of oxide film grown on pits (i.e., voids exposed at the wafer surface) is simulated using a simple model, and the degradation of Breakdown Field expected from the thinning is compared with experimental reports. In the model, oxide film grown on the inner surface of a sphere is calculated by assuming that deformation of oxide film is visco-elastic and that oxidation reaction rate is reduced by compressional normal stress acting on the Si/SiO/sub 2/ interface. The calculated results show appreciable thinning of oxide film, which explains the low Breakdown Field observed experimentally. It also helps to understand the unique degradation characteristics reported for pits and voids: lower Breakdown Field for thicker oxide film and recovery of Breakdown Field by chemical etching. No clear pit size dependence observed in the experiments suggests that the oxide thinning is localized at corners of voids.
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Degradation of dielectric Breakdown Field of thermal SiO2 films due to structural defects in Czochralski silicon substrates
Journal of Applied Physics, 1996Co-Authors: Y. Satoh, T. Shiota, Yoshio Murakami, Takayuki Shingyouji, Hisashi FuruyaAbstract:We used heat treatment to intentionally introduce various structural defects in Czochralski silicon substrates. The type, size, and number density of the induced defects were surveyed with transmission electron microscopy, and the defects were then incorporated into SiO2 films (10–50 nm thick) during thermal oxidation in dry O2. The effect of the defects on dielectric strength of the SiO2 films was examined with a time zero dielectric Breakdown method. Larger platelet oxygen precipitates caused greater decreases of the Breakdown Field, and precipitates smaller than the SiO2 film thickness did not appreciably reduce the Breakdown Field. Every large platelet oxygen precipitate incorporated in the SiO2 film caused a degradation. Octahedral oxygen precipitates caused little degradation. The Breakdown Field was higher than 7 MV/cm and did not depend much on the SiO2 film thickness and precipitate size. We discussed possible mechanisms for the degradation due to both kinds of precipitates. Oxidation‐induced sta...
Zhuang Tang - One of the best experts on this subject based on the ideXlab platform.
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Significantly enhanced Breakdown Field in Ca 1-x Sr x Cu 3 Ti 4 O 12 ceramics by tailoring donor densities
Journal of the European Ceramic Society, 2018Co-Authors: Zhuang Tang, Yuwei HuangAbstract:Abstract Significantly enhanced Breakdown Field of 24.52 kV cm−1 as well as noteworthy nonlinear coefficient of 8.11 and low dielectric loss of 0.077 were obtained in Ca0.6Sr0.4Cu3Ti4O12 ceramic. It was proved from impedance spectra that improved Breakdown Field was attributed to enhanced grain boundary resistance and elevated Schottky barrier height, which was further found resulting from reduced donor densities in C-V measurements. In addition, it was found that the activation energy originated from oxygen vacancies was increased, indicating the generation of oxygen vacancies was suppressed. Since oxygen vacancies acted as donors in depletion layers, it is reasonable to deduce that the reduced donor density was mainly ascribed to the decreased oxygen vacancies. In conclusion, maximum integrated action of strong solid solution effect and weak Sr-stretching effect was achieved when Sr/Ca ratio is 40/60, leading to greatly elevated potential barrier height and enhanced Breakdown Field consequently.
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High Breakdown Field CaCu3Ti4O12 Ceramics: Roles of the Secondary Phase and of Sr Doping
Energies, 2017Co-Authors: Zhuang Tang, Yuwei HuangAbstract:In this work, two methods of CaCu3Ti4O12-CuAl2O4 composite and SrCu3Ti4O12-CaCu3Ti4O12 composite were prepared to improve the Breakdown Field in CaCu3Ti4O12 ceramics. CaCu3Ti4O12-0.5CuAl2O4 and 0.4SrCu3Ti4O12-0.6CaCu3Ti4O12 samples with proper sintering conditions were found to have greatly enhanced Breakdown Fields of more than 20 kV·cm−1 compared to the ordinary value of 1–2 kV·cm−1 in CaCu3Ti4O12 ceramics. In addition, reduced dielectric loss tangent of these samples remained about 0.1 at a low frequency of 0.1 Hz, indicating superior dielectric properties. No abnormal grain growth was found in either composite with a high Breakdown Field, which was attributed to the pining effect and consumption of Cu-rich phase at grain boundaries. Under analysis of the relaxation process by electric modulus, compared to conventional CaCu3Ti4O12 ceramics, interstitial Ali··· and increasing interfaces were responsible for variation in activation energy in CaCu3Ti4O12-0.5CuAl2O4 composites, while the integrated action of a strong solid solution effect and weak Sr-stretching effect contributed to the elevated potential barrier height and enhanced Breakdown Field in 0.4SrCu3Ti4O12-0.6CaCu3Ti4O12 composites.
Y. Satoh - One of the best experts on this subject based on the ideXlab platform.
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Simulation of degradation of dielectric Breakdown Field of thermal SiO/sub 2/ films due to voids in Si wafers
IEEE Transactions on Electron Devices, 2000Co-Authors: Y. Satoh, T. Shiota, Hisashi FuruyaAbstract:Degradation of the dielectric Breakdown Field of thermal SiO/sub 2/ film caused by voids that are formed during growth of silicon single crystal has been a serious problem with reliability of MOS devices. To understand the degradation of Breakdown Field, local thinning of oxide film grown on pits (i.e., voids exposed at the wafer surface) is simulated using a simple model, and the degradation of Breakdown Field expected from the thinning is compared with experimental reports. In the model, oxide film grown on the inner surface of a sphere is calculated by assuming that deformation of oxide film is visco-elastic and that oxidation reaction rate is reduced by compressional normal stress acting on the Si/SiO/sub 2/ interface. The calculated results show appreciable thinning of oxide film, which explains the low Breakdown Field observed experimentally. It also helps to understand the unique degradation characteristics reported for pits and voids: lower Breakdown Field for thicker oxide film and recovery of Breakdown Field by chemical etching. No clear pit size dependence observed in the experiments suggests that the oxide thinning is localized at corners of voids.
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Degradation of dielectric Breakdown Field of thermal SiO2 films due to structural defects in Czochralski silicon substrates
Journal of Applied Physics, 1996Co-Authors: Y. Satoh, T. Shiota, Yoshio Murakami, Takayuki Shingyouji, Hisashi FuruyaAbstract:We used heat treatment to intentionally introduce various structural defects in Czochralski silicon substrates. The type, size, and number density of the induced defects were surveyed with transmission electron microscopy, and the defects were then incorporated into SiO2 films (10–50 nm thick) during thermal oxidation in dry O2. The effect of the defects on dielectric strength of the SiO2 films was examined with a time zero dielectric Breakdown method. Larger platelet oxygen precipitates caused greater decreases of the Breakdown Field, and precipitates smaller than the SiO2 film thickness did not appreciably reduce the Breakdown Field. Every large platelet oxygen precipitate incorporated in the SiO2 film caused a degradation. Octahedral oxygen precipitates caused little degradation. The Breakdown Field was higher than 7 MV/cm and did not depend much on the SiO2 film thickness and precipitate size. We discussed possible mechanisms for the degradation due to both kinds of precipitates. Oxidation‐induced sta...
Xuetong Zhao - One of the best experts on this subject based on the ideXlab platform.
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Improvement of Breakdown Field and dielectric properties of CaCu3Ti4O12 ceramics by Bi and Al co-doping
Journal of Alloys and Compounds, 2018Co-Authors: Lulu Ren, Lijun Yang, Xuetong Zhao, Ruijin LiaoAbstract:Abstract Bi and Al co-doped CaCu3Ti4O12 (CCTO) ceramics with different doping concentration were fabricated by the solid-state sintering method. Great enhancements in dielectric and varistor properties of CCTO ceramic were achieved by co-doping at the concentration of 1 mol%. It is found that grain size distribution of co-doped sample is more uniform and the grain alignment is more compact. The improved morphologies could facilitate the macroscopic properties. Additionally, a relaxation peak, of activation energy at 0.39 eV, at relatively low frequency was characterized. It is likely to be originated from Cu-rich phase related defect in the grain boundary. This defect may be concomitantly aggravated by Bi and Al co-doping. The frequency dependence of the conductivity was interpreted with the Jonscher's law, indicating that the dc conduction loss at low frequency can be suppressed by additives. Comparing with the pure CCTO, the Breakdown Field Eb of co-doped sample at the concentration of 1 mol% was greatly enhanced from 2088 V/cm to 7839 V/cm due to the increase of Schottky barrier height (from 0.56 eV to 0.72 eV).
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Preparation, characterization and dielectric response of a high-Breakdown-Field ZnO-based varistor
Journal of Materials Science: Materials in Electronics, 2016Co-Authors: Xuetong Zhao, Ruijin Liao, Junyan Zhang, Kanglin LiuAbstract:In this study, ZnO-based varistors with a high Breakdown Field were obtained through BaCO3 doping and sintering at a low temperature of 950 °C. The grain size of the ZnO samples decreased to 1.28 μm, and the Breakdown Field was enhanced to 3845 V/mm, which is approximately one order of magnitude higher than that of ordinary ZnO-based varistors. The dielectric responses of the ZnO-based varistors were measured in a wide frequency and temperature range. At 193 K, two dielectric relaxation peaks with activation energies of 0.22 and 0.35 eV were observed and considered intrinsic defects; these peaks did not vary with the preparation process. Another dielectric relaxation peak observed in a wide temperature range (283–463 K) was characterized in an impedance plot. This relaxation peak was ascribed to extrinsic defects related to the grain boundary. The resistance values of the grain boundary increased by two orders of magnitude through BaCO3 doping and lowering of the sintering temperature. The corresponding activation energy also increased from 0.53 to 0.74 eV. A parallel resistance–capacitance circuit model was proposed to interpret the variation in the electrical properties of ZnO-based varistors.
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Enhanced electric Breakdown Field of CaCu3Ti4O12 ceramics: tuning of grain boundary by a secondary phase
Journal of Physics D: Applied Physics, 2013Co-Authors: Ran Jia, Xian Tang, Xuetong ZhaoAbstract:The electric Breakdown Field of CaCu3Ti4O12 ceramics has been enhanced by one order, i.e. from the conventional 1.0–2.0 kV cm−1 to 21 kV cm−1. Such great enhancement, associated with lower and relatively flat dielectric loss at low frequency, has arisen from optimum Al2O3 addition and sintering process. It is indicated that the addition of Al2O3 can affect the grain growth and the grain boundary characteristics via the distribution of a secondary phase of CuAl2O4, which is confirmed by x-ray diffraction and electron dispersive spectroscopy. The performance of grain boundary can be described well by the Schottky barrier model. It is found that the activation energy of hopping conduction at grain boundary is increased from 0.60 to 0.81 eV due to the secondary phase, which consequently leads to enhanced Breakdown Field.
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Large Breakdown Field and dielectric performance of CaCu 3 Ti 4 O 12 ceramics modified by Al 2 O 3
2013 IEEE International Conference on Solid Dielectrics (ICSD), 2013Co-Authors: Ran Jia, Xian Tang, Xuetong ZhaoAbstract:CaCu3Ti4O12 ceramics samples with varied Al2O3 additions have been prepared by a dispersion-precipitation-sintering method. The ceramics with nominal addition of 8 wt% Al2O3 sintered at 1100°C for 4 hours shows a Breakdown electric Field Eb of 21 kV/cm, compared with reported values of 1.0~2.0 kV/cm. Three energy levels of dielectric relaxation, two of which do not vary with either second phase addition or sintering condition, are found. The nearly constant levels of ~0.13 eV and ~0.33 eV are considered to relate to bulk and domain boundary relaxations. Another level varied from 0.61 to 0.84 eV is suggested to be Maxwell-Wagner relaxation of grain boundary, which correlates well with Breakdown electric Field Eb. It was proposed that the enhanced Breakdown Field is attributed to higher energy level of grain boundary relaxation and CuAl2O4 aggregation in the intergranular region.