Carbon and oxygen-rich corrosion barrier layer formed on Mg by a simple and scalable CO_(2) atmospheric plasma(CO_(2)-AP)process.The reactive CO_(2)-AP interacts with the Mg surface and forms a unique layered structur...Carbon and oxygen-rich corrosion barrier layer formed on Mg by a simple and scalable CO_(2) atmospheric plasma(CO_(2)-AP)process.The reactive CO_(2)-AP interacts with the Mg surface and forms a unique layered structure with the top MgCO_(3)/MgO-intermixed particulates pillars and the bottom dense layer.The surface features were simultaneously formed on the nano-/micro-structured MgO layer by carbonate molecules,plasma-active CO_(2) molecules,and/or other volatile organic compounds on the nano-/micro-structured MgO particle layer.The resulting surfaces after CO_(2)-AP were either hydrophobic or hydrophilic and exhibited lower anodic current or high resistance for Mg corrosion.For the hydrophobic surfaces of CO_(2)-AP treated Mg,molecular dynamic simulations were performed to understand the origin of hydrophobicity and identified that the amorphous carbon layers formed on the Mg surface are the source.The environmentally benign abundant-gas-based process enables the cost reduction associated with waste treatment,generation of by-product,and supply of raw material.展开更多
Highly sensitive phototransistors based on two-dimensional （2D） GaTe nanosheet have been demonstrated. The performance （photoresponsivity, detectivity） of the GaTe nanosheet phototransistor can be efficiently adju...Highly sensitive phototransistors based on two-dimensional （2D） GaTe nanosheet have been demonstrated. The performance （photoresponsivity, detectivity） of the GaTe nanosheet phototransistor can be efficiently adjusted by using the applied gate voltage. The devices exhibit an ultrahigh photoresponsivity of 274.3 AW^-1. The detectivity of 2D GaTe devices is -10^12 Jones, which surpasses that of currently-exploited InGaAs photodetectors （10^11-10^12 Jones）. To reveal the origin of the enhanced photocurrent in GaTe nanosheets, theoretical modeling of the electronic structures was performed to show that GaTe nanosheets also have a direct bandgap structure, which contributes to the promotion of photon absorption and generation of excitons. This work shows that GaTe nanosheets are promising materials for high performance photodetectors.展开更多
Recent experiments identified Co_(3)Sn_(2)S_(2) as the first magnetic Weyl semimetal(MWSM).Using first-principles calculation with a global optimization approach,we explore the structural stabilities and topological e...Recent experiments identified Co_(3)Sn_(2)S_(2) as the first magnetic Weyl semimetal(MWSM).Using first-principles calculation with a global optimization approach,we explore the structural stabilities and topological electronic properties of cobalt(Co)-based shandite and alloys,Co_(3)MM’X_(2)(M/M’=Ge,Sn,Pb,X=S,Se,Te),and identify stable structures with different Weyl phases.Using a tight-binding model,for the first time,we reveal that the physical origin of the nodal lines of a Co-based shandite structure is the interlayer coupling between Co atoms in different Kagome layers,while the number of Weyl points and their types are mainly governed by the interaction between Co and the metal atoms,Sn,Ge,and Pb.The Co_(3)SnPbS_(2) alloy exhibits two distinguished topological phases,depending on the relative positions of the Sn and Pb atoms:a three-dimensional quantum anomalous Hall metal,and a MWSM phase with anomalous Hall conductivity(~1290Ω^(−1) cm^(−1))that is larger than that of Co_(2)Sn_(2)S_(2).Our work reveals the physical mechanism of the origination of Weyl fermions in Co-based shandite structures and proposes topological quantum states with high thermal stability.展开更多
基金the US Department of Energy’s(DOE’s)Office of Energy Efficiency and Renewable Energy,Vehicle Technology Office,Powertrain Materials Core and Light Metals Core ProgramsSample characterization is also partially supported by the Technology Commercialization Fund Fiscal Year 2020 of DOE’s Office of Technology Transitionsby the Creative Materials Discovery Program through the National Research Foundation of Korea,with computational modeling of amorphous carbons funded by the Ministry of Science,ICT and Future Planning(NRF-2016M3D1A1919181)。
文摘Carbon and oxygen-rich corrosion barrier layer formed on Mg by a simple and scalable CO_(2) atmospheric plasma(CO_(2)-AP)process.The reactive CO_(2)-AP interacts with the Mg surface and forms a unique layered structure with the top MgCO_(3)/MgO-intermixed particulates pillars and the bottom dense layer.The surface features were simultaneously formed on the nano-/micro-structured MgO layer by carbonate molecules,plasma-active CO_(2) molecules,and/or other volatile organic compounds on the nano-/micro-structured MgO particle layer.The resulting surfaces after CO_(2)-AP were either hydrophobic or hydrophilic and exhibited lower anodic current or high resistance for Mg corrosion.For the hydrophobic surfaces of CO_(2)-AP treated Mg,molecular dynamic simulations were performed to understand the origin of hydrophobicity and identified that the amorphous carbon layers formed on the Mg surface are the source.The environmentally benign abundant-gas-based process enables the cost reduction associated with waste treatment,generation of by-product,and supply of raw material.
文摘Highly sensitive phototransistors based on two-dimensional （2D） GaTe nanosheet have been demonstrated. The performance （photoresponsivity, detectivity） of the GaTe nanosheet phototransistor can be efficiently adjusted by using the applied gate voltage. The devices exhibit an ultrahigh photoresponsivity of 274.3 AW^-1. The detectivity of 2D GaTe devices is -10^12 Jones, which surpasses that of currently-exploited InGaAs photodetectors （10^11-10^12 Jones）. To reveal the origin of the enhanced photocurrent in GaTe nanosheets, theoretical modeling of the electronic structures was performed to show that GaTe nanosheets also have a direct bandgap structure, which contributes to the promotion of photon absorption and generation of excitons. This work shows that GaTe nanosheets are promising materials for high performance photodetectors.
基金The research was supported by the U.S.Department of Energy,Office of Science,Office of Basic Energy Sciences,Materials Sciences and Engineering Divisionby the Creative Materials Discovery Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Science,ICT and Future Planning(NRF-2016M3D1A1919181).
文摘Recent experiments identified Co_(3)Sn_(2)S_(2) as the first magnetic Weyl semimetal(MWSM).Using first-principles calculation with a global optimization approach,we explore the structural stabilities and topological electronic properties of cobalt(Co)-based shandite and alloys,Co_(3)MM’X_(2)(M/M’=Ge,Sn,Pb,X=S,Se,Te),and identify stable structures with different Weyl phases.Using a tight-binding model,for the first time,we reveal that the physical origin of the nodal lines of a Co-based shandite structure is the interlayer coupling between Co atoms in different Kagome layers,while the number of Weyl points and their types are mainly governed by the interaction between Co and the metal atoms,Sn,Ge,and Pb.The Co_(3)SnPbS_(2) alloy exhibits two distinguished topological phases,depending on the relative positions of the Sn and Pb atoms:a three-dimensional quantum anomalous Hall metal,and a MWSM phase with anomalous Hall conductivity(~1290Ω^(−1) cm^(−1))that is larger than that of Co_(2)Sn_(2)S_(2).Our work reveals the physical mechanism of the origination of Weyl fermions in Co-based shandite structures and proposes topological quantum states with high thermal stability.
