The metal-free synthesis of graphene on singlecrystal silicon substrates, the most common commercial semiconductor, is of paramount significance for many technological applications. In this work, we report the growth ...The metal-free synthesis of graphene on singlecrystal silicon substrates, the most common commercial semiconductor, is of paramount significance for many technological applications. In this work, we report the growth of graphene directly on an upside-down placed,single-crystal silicon substrate using metal-free, ambientpressure chemical vapor deposition. By controlling the growth temperature, in-plane propagation, edge-propagation, and core-propagation, the process of graphene growth on silicon can be identified. This process produces atomically flat monolayer or bilayer graphene domains, concave bilayer graphene domains, and bulging few-layer graphene domains. This work would be a significant step toward the synthesis of large-area and layer-controlled, high-quality graphene on single-crystal silicon substrates.展开更多
High-throughput powder X-ray diffraction(XRD)with white X-ray beam and an energy-dispersive detector array is demonstrated in this work on a CeO;powder sample on a bending magnet synchrotron beamline at the Shanghai S...High-throughput powder X-ray diffraction(XRD)with white X-ray beam and an energy-dispersive detector array is demonstrated in this work on a CeO;powder sample on a bending magnet synchrotron beamline at the Shanghai Synchrotron Radiation Facility(SSRF),using a simulated energy-dispersive array detector consisting of a spatially scanning silicon-drift detector(SDD).Careful analysis and corrections are applied to account for various experimental hardware-related and diffraction angle-related factors.The resulting diffraction patterns show that the relative strength between different diffraction peaks from energy-dispersive XRD(EDXRD)spectra is consistent with that from angle-resolved XRD(ARXRD),which is necessary for analyzing crystal structures for unknown samples.The X-ray fluorescence(XRF)signal is collected simultaneously.XRF counts from all pixels are integrated directly by energy,while the diffraction spectra are integrated by d-spacing,resulting in a much improved peak strength and signal-to-noise(S/N)ratio for the array detector.In comparison with ARXRD,the diffraction signal generated by a white X-ray beam over monochromic light under the experimental conditions is about 104 times higher.The full width at half maximum(FWHM)of the peaks in q-space is found to be dependent on the energy resolution of the detector,the angle span of the detector,and the diffraction angle.It is possible for EDXRD to achieve the same or even smaller FWHM as ARXRD under the energy resolution of the current detector if the experimental parameters are properly chosen.展开更多
The polarization and domain behavior on the surface of a ferroelectric material are significantly affected by the screening processes [1-12].Recently,there has been a notable increase in the theoretical calculations a...The polarization and domain behavior on the surface of a ferroelectric material are significantly affected by the screening processes [1-12].Recently,there has been a notable increase in the theoretical calculations and experiments investigating the dynamics of polarization and domain behaviors coexisting in phase transitions of ferroelectric materials.展开更多
As an alternative electrode material,transition metal oxides are promising candidates due to multivalent nature and oxygen vacancies present in the structure with facilitate redox reactions.The aim of this study is to...As an alternative electrode material,transition metal oxides are promising candidates due to multivalent nature and oxygen vacancies present in the structure with facilitate redox reactions.The aim of this study is to explore the intrinsic mechanism of oxygen evolution reaction(OER)using two-dimensional thin film La1-xSrxCoO3 electrode as a model.Herein,we report a planar two-dimensional model La1-xSrxCoO3 electrode grown on a Nb-SrTiO3 single-crystal substrate via pulsed laser deposition.The two-dimensional La1-xSrxCoO3 films offer different oxygen evolution activities at different pH electrolyte solutions.The mechanisms behind the variations of the oxygen evolution activity were discussed after comparing the oxygen evolution activity before and after treatments of the electrodes and measurements by various test methods.The results of this study offer a promising,low-cost electrode material for the efficient OER and a sustainable production of hydrogen fuel.展开更多
基金financially supported by the National Natural Science Foundation of China (NSFC) (Grant Nos. 11405253, 11225527, 11575283, 11205235, U1632129, U1332205)Shanghai Science Foundation (14YF1407500)the Youth Innovation Promotion Association CAS (2016237)
文摘The metal-free synthesis of graphene on singlecrystal silicon substrates, the most common commercial semiconductor, is of paramount significance for many technological applications. In this work, we report the growth of graphene directly on an upside-down placed,single-crystal silicon substrate using metal-free, ambientpressure chemical vapor deposition. By controlling the growth temperature, in-plane propagation, edge-propagation, and core-propagation, the process of graphene growth on silicon can be identified. This process produces atomically flat monolayer or bilayer graphene domains, concave bilayer graphene domains, and bulging few-layer graphene domains. This work would be a significant step toward the synthesis of large-area and layer-controlled, high-quality graphene on single-crystal silicon substrates.
基金supported by the National Key Research and Development Program of China,China(2017YFB0701900)High-Level Special Funds(G02256401 and G02256301)+1 种基金supported by the fund of the Guangdong Provincial Key Laboratory(2018B030322001)the Guangdong-Hong Kong-Macao Joint Laboratory(2019B121205001)。
文摘High-throughput powder X-ray diffraction(XRD)with white X-ray beam and an energy-dispersive detector array is demonstrated in this work on a CeO;powder sample on a bending magnet synchrotron beamline at the Shanghai Synchrotron Radiation Facility(SSRF),using a simulated energy-dispersive array detector consisting of a spatially scanning silicon-drift detector(SDD).Careful analysis and corrections are applied to account for various experimental hardware-related and diffraction angle-related factors.The resulting diffraction patterns show that the relative strength between different diffraction peaks from energy-dispersive XRD(EDXRD)spectra is consistent with that from angle-resolved XRD(ARXRD),which is necessary for analyzing crystal structures for unknown samples.The X-ray fluorescence(XRF)signal is collected simultaneously.XRF counts from all pixels are integrated directly by energy,while the diffraction spectra are integrated by d-spacing,resulting in a much improved peak strength and signal-to-noise(S/N)ratio for the array detector.In comparison with ARXRD,the diffraction signal generated by a white X-ray beam over monochromic light under the experimental conditions is about 104 times higher.The full width at half maximum(FWHM)of the peaks in q-space is found to be dependent on the energy resolution of the detector,the angle span of the detector,and the diffraction angle.It is possible for EDXRD to achieve the same or even smaller FWHM as ARXRD under the energy resolution of the current detector if the experimental parameters are properly chosen.
基金supported by the National Natural Science Foundation of China(Grant No.11574365)
文摘The polarization and domain behavior on the surface of a ferroelectric material are significantly affected by the screening processes [1-12].Recently,there has been a notable increase in the theoretical calculations and experiments investigating the dynamics of polarization and domain behaviors coexisting in phase transitions of ferroelectric materials.
基金the National Natural Science Foundation of China(Grant Nos.11574365,and 11974099)the Program for the Innovation Team of Science and Technology in University of Henan(Grant No.20IRTSTHN014)。
文摘As an alternative electrode material,transition metal oxides are promising candidates due to multivalent nature and oxygen vacancies present in the structure with facilitate redox reactions.The aim of this study is to explore the intrinsic mechanism of oxygen evolution reaction(OER)using two-dimensional thin film La1-xSrxCoO3 electrode as a model.Herein,we report a planar two-dimensional model La1-xSrxCoO3 electrode grown on a Nb-SrTiO3 single-crystal substrate via pulsed laser deposition.The two-dimensional La1-xSrxCoO3 films offer different oxygen evolution activities at different pH electrolyte solutions.The mechanisms behind the variations of the oxygen evolution activity were discussed after comparing the oxygen evolution activity before and after treatments of the electrodes and measurements by various test methods.The results of this study offer a promising,low-cost electrode material for the efficient OER and a sustainable production of hydrogen fuel.