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811 results on '"Hu, Zhigao"'

8. Effect of oxygen defects on ferroelectric oxides: Correlation between linear and nonlinear dielectric responses.

Author

Cao, Zixin, Li, Yawei, Shang, Liyan, Jiang, Kai, Zhu, Liangqing, Zhang, Jinzhong, and Hu, Zhigao

Subjects
DIELECTRICS, FREQUENCY spectra, OXYGEN, PERMITTIVITY, FERROELECTRIC thin films, ELECTRIC fields, BARIUM titanate
Abstract

Oxygen defects are introduced into PbZr0.5Ti0.5O3 films and their impact on ferroelectric behavior, linear dielectric response (LDR), and nonlinear dielectric response (NDR) is studied. Apart from a notable decrease in both polarization and LDR permittivity, the frequency spectra of LDR exhibit a distinctive loss peak. The peak position varies with temperature and oxygen defect concentration. NDR parameters, including the Rayleigh coefficient (α1), the slope (α2) correlating the imaginary part of permittivity with the ac electric field, and the slope (k) between the real and the imaginary parts of permittivity, demonstrate diverse behaviors in response to temperature and oxygen defect concentration. The similarity in the frequency spectra of tanδ and 1/k reveals the correlation between LDR and NDR induced by the presence of oxygen defects. These observations are attributed to the behavior of the single and composite defects associated with oxygen vacancies. [ABSTRACT FROM AUTHOR]

Published
2024
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14. Flux periodic oscillations and phase-coherent transport in GeTe nanowire-based devices

Author

Zhang, Jinzhong, Tse, Pok-Lam, Jalil, Abdur-Rehman, Kölzer, Jonas, Rosenbach, Daniel, Luysberg, Martina, Panaitov, Gregory, Lüth, Hans, Hu, Zhigao, Grützmacher, Detlev, Lu, Jia Grace, and Schäpers, Thomas

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

Despite the fact that GeTe is known to be a very interesting material for applications in thermoelectrics and for phase-change memories, the knowledge on its low-temperature transport properties is only limited. Here, we report on phase-coherent phenomena in the magnetotransport of GeTe nanowires. From universal conductance fluctuations, a phase-coherence length of about 200nm at 0.5K is determined for the hole carriers. The distinct phase-coherence is confirmed by the observation of Aharonov--Bohm type oscillations for magnetic fields applied along the nanowire axis. We interpret the occurrence of these magnetic flux-periodic oscillations by the formation of a tubular hole accumulation layer on the nanowire surface. In addition, for Nb/GeTe-nanowire/Nb Josephson junctions, we obtained a proximity-induced critical current of about 0.2$\mu$A at 0.4K. By applying a magnetic field perpendicular to the nanowire axis, the critical current decreases monotonously with increasing magnetic field, which indicates that the structure is in the small-junction-limit. Whereas, by applying a parallel magnetic field the critical current oscillates with a period of the magnetic flux quantum indicating once again the presence of a tubular hole channel., Comment: 9 pages, 4 figures

Published
2020
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26. Origin of Improved Photoelectrochemical Water Splitting in Mixed Perovskite Oxides

Author

Li, Weiwei, Jiang, Kai, Li, Zhongguo, Gong, Shijing, Hoye, Robert L. Z., Hu, Zhigao, Song, Yinglin, Tian, Chuanmu, Kim, Jongkyoung, Zhang, Kelvin H. L., Cho, Seungho, and MacManus-Driscoll, Judith L.

Subjects
Condensed Matter - Materials Science
Abstract

Owing to the versatility in their chemical and physical properties, transition metal perovskite oxides have emerged as a new category of highly efficient photocatalysts for photoelectrochemical water splitting. Here, to understand the underlying mechanism for the enhanced photoelectrochemical water splitting in mixed perovskites, we explore ideal epitaxial thin films of the BiFeO3-SrTiO3 system. The electronic struture and carrier dynamics are determined from both experiment and density-functional theory calculations. The intrinsic phenomena are measured in this ideal sytem, contrasting to commonly studied polycrstalline solid solutions where extrinsic structural features obscure the intrinsic phenomena. We determined that when SrTiO3 is added to BiFeO3 the conduction band minimum position is raised and an exponential tail of trap states from hybridized Ti 3d and Fe 3d orbitals emerges near the conduction band edge. The presence of these trap states strongly suppresses the fast electron-hole recombination and improves the photocurrent density in the visible-light region, up to 16 times at 0 VRHE compared to the pure end member compositions. Our work provides a new design approach for optimising the photoelectrochemical performance in mixed perovksite oxides., Comment: 7 pages and 5 figures

Published
2018
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30. Improvement of the energy storage performance of antiferroelectric Pb,La(Zr,Ti)O3 thin films by the LaNiO3 buffer layer on the metal electrode.

Author

Cao, Zixin, Li, Yawei, Shang, Liyan, Jiang, Kai, Zhu, Liangqing, and Hu, Zhigao

Abstract

Conductive LaNiO3 (LNO) buffer layers are grown on silicon and Pt-covered silicon and the effects on Pb0.94La0.04(Zr0.95Ti0.05)O3 (PLZT) thin films are studied. The PLZT films on LNO-buffered Si and LNO-buffered Pt show different preferred orientations with the film on Pt. The LNO buffer layer not only induces the columnar growth of PLZT, but also reduces the surface roughness of the PLZT films. By introducing the LNO buffer layer on Pt, the PLZT thin film can achieve high polarization while reducing the window width of the hysteresis loop. The PLZT film on LNO/Pt exhibits the best energy storage performance in all samples. The recoverable energy density (WRec) of 15.66 J cm−3 is obtained, which is 19% higher than the WRec of the PLZT film on LNO/Si and twice higher than the maximum WRec of the PLZT film on Pt. Moreover, the PLZT on LNO/Pt has an energy storage efficiency of 73% and exhibits better voltage stability. The nonlinear dielectric response results are used to analyze the different performances of the samples. This study suggests that the energy storage performance of the capacitors based on the antiferroelectric films can be further improved by adding the buffer layer on metal electrodes. [ABSTRACT FROM AUTHOR]

Published
2024
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40. Direct observation of Landau level resonance and mass generation in Dirac semimetal Cd3As2 thin films

Author

Yuan, Xiang, Cheng, Peihong, Zhang, Longqiang, Zhang, Cheng, Wang, Junyong, Liu, Yanwen, Sun, Qingqing, Zhou, Peng, Zhang, David Wei, Hu, Zhigao, Wan, Xiangang, Yan, Hugen, Li, Zhiqiang, and Xiu, Faxian

Subjects
Condensed Matter - Materials Science, Condensed Matter - Mesoscale and Nanoscale Physics, Physics - Optics
Abstract

Three-dimensional topological Dirac semimetals have hitherto stimulated unprecedented research interests as a new class of quantum materials. Breaking certain types of symmetries has been proposed to enable the manipulation of Dirac fermions; and that was soon realized by external modulations such as magnetic fields. However, an intrinsic manipulation of Dirac states, which is more efficient and desirable, remains a significant challenge. Here, we report a systematic study of quasi-particle dynamics and band evolution in Cd3As2 thin films with controlled Chromium (Cr) doping by both magneto-infrared spectroscopy and electrical transport. For the first time, we observe square-root-B relation of inter-Landau-level resonance in undoped Cd3As2 Dirac semimetal, an important signature of ultra-relativistic Dirac state inaccessible in previous optical experiments. A crossover from quantum to quasi-classical behavior makes it possible to directly probe the mass of Dirac fermions. Importantly, Cr doping allows for a Dirac mass acquisition and topological phase transition enabling a desired dynamic control of Dirac fermions. Corroborating with the density-functional theory calculations, we show that the mass generation is essentially driven by explicit C4 rotation symmetry breaking and the resultant Dirac gap engineering through Cr substitution for Cd atoms. The manipulation of the system symmetry and Dirac mass in Cd3As2 thin films provides a tuning knob to explore the exotic states stemming from the parent phase of Dirac semimetals.

Published
2016
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46. Low-loss strong index modulated ultra-thermally stable optical phase-change material for broadband nonvolatile photonics.

Author

Li, Ming, Li, Shubing, Deng, Menghan, Xu, Xionghu, Dai, Kai, Cui, Anyang, Zhou, Xin, Jiang, Kai, Shang, Liyan, Li, Yawei, Zhang, Jinzhong, Zhu, Liangqing, Chu, Junhao, and Hu, Zhigao

Subjects
OPTICAL materials, OPTICAL modulation, PHASE transitions, PULSED laser deposition, TRANSMISSION electron microscopes, WAVEGUIDES, PHASE change materials
Abstract

Optical phase change materials (O-PCMs) have attracted increasing attention and provide promising solutions for non-volatile reconfigurable photonics due to their large index contrast and non-volatile switching characteristics. In this work, we have explored the optical phase change properties of a dozen different O-PCMs and established the corresponding gene bank. Among these O-PCMs, Ge 1 Sb 2 Se 3 Te 1 (G1S2S3T1) films exhibit unprecedented low-loss, strong light modulation capability, and ultra-thermal stability capability, which are prepared by pulsed laser deposition. Meanwhile, we investigate the phase transition kinetic mechanism of G1S2S3T1 films by transmission electron microscope, temperature dependent transmission spectroscopy, and temperature dependent Raman spectroscopy. It is found that the wide bandgap (1.09 eV) in the amorphous state, the large bandgap variation (0.51 eV) between amorphous and crystalline states, the needle-like configuration of its crystalline state, and the special phase change process contribute to strong refractive index modulation. Moreover, we find that their ultra-thermal stability is from a strong Sb–Se bond. Through the simulation, we found that G1S2S3T1 can be applied to prepare ultra-low loss waveguide devices. The present work represents a significant step in the development of broadband nonvolatile photonics derived from O-PCMs. [ABSTRACT FROM AUTHOR]

Published
2023
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49. Prognostic Value of Alpha-Fetoprotein in Unresectable Hepatocellular Carcinoma Treated with Hepatic Artery Infusion Chemotherapy Combined with Lenvatinib and Camrelizumab.

Author

Xiao, Yongqiang, Chen, Wanqing, Deng, Wei, Zhu, Guoqing, Xie, Jin, Luo, Laihui, Lin, Liucong, Tao, Jiahao, Hu, Zhigao, and Shan, Renfeng

Subjects
HEPATIC artery, HEPATOCELLULAR carcinoma, PROGNOSIS, MULTIVARIATE analysis, ALPHA fetoproteins
Abstract

Objective response rates compared to AFP non-responders, as determined by RECIST v1.1 or mRECIST criteria (45.5 vs. 18.2%, p=0.014, or 81.8 vs. 48.5%, p=0.013). Furthermore, early AFP responders demonstrated prolonged OS (not reached vs. 8.0 months, p< 0.001) and PFS (13.3 vs. 3.0 months, p= 0.018) relative to early AFP non-responders. Similarly, AFP responders exhibited improved OS (not reached vs. 9.0 months, p< 0.001) and PFS (19.3 vs. 5.1 months, p=0.002) compared to AFP non-responders. Multivariate analysis results indicated that both early AFP response and AFP response independently predicted OS [hazard ratio (HR) 2.963, 95% confidence interval (CI) 1.333– 6.585, p=0.008, and HR 6.182, 95% CI 1.780– 21.466, p=0.004] and PFS (HR 2.186, 95% CI 1.107– 4.318, p=0.024, and HR 3.078, 95% CI 1.407– 6.730, p=0.005), serving as significant prognostic values. Conclusion: Early AFP response and AFP response serve as predictive biomarkers for the effectiveness of HAIC combined with lenvatinib and camrelizumab in patients with u-HCC. [ABSTRACT FROM AUTHOR]

Published
2024
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