Nitrogen doping in chemical vapor deposition-derived ultrananocrystalline diamond(UNCD)films in-creases the electronic conductivity,yet its microstructural effects on electron transport are insufficiently understood.W...Nitrogen doping in chemical vapor deposition-derived ultrananocrystalline diamond(UNCD)films in-creases the electronic conductivity,yet its microstructural effects on electron transport are insufficiently understood.We investigated the formation of nitrogen-induced diaph-ite structures(hybrid diamond-graphite phases)and their role in changing the conductivity.Nitrogen doping in a hy-drogen-rich plasma environment promotes the emergence of unique sp^(3)-sp^(2)bonding interfaces,where diamond grains are covalently integrated with graphitic domains,facilitating a structure-driven electronic transition.High-resolution transmis-sion electron microscopy and selected area electron diffraction reveal five-fold,six-fold and twelve-fold symmetries,along with an atypical{200}crystallographic reflection,confirming diaphite formation in 5%and 10%N-doped UNCD films,while high-er doping levels(15%and 20%)result in extensive graphitization.Raman spectroscopy tracks the evolution of sp^(2)bonding with increasing nitrogen content,while atomic force microscopy and X-ray diffraction indicate a consistent diamond grain size of~8 nm.Cryogenic electronic transport measurements reveal a conductivity increase from 8.72 to 708 S/cm as the nitrogen dop-ing level increases from 5%to 20%,which is attributed to defect-mediated carrier transport and 3D weak localization.The res-ulting conductivity is three orders of magnitude higher than previously reported.These findings establish a direct correlation between diaphite structural polymorphism and tunable electronic properties in nitrogen-doped UNCD films,offering new ways for defect-engineering diamond-based electronic materials.展开更多
Silicon is considered one of the most promising candidates for incorporation into carbon-based anodes in lithium-ion batteries(LIBs)due to its high specific capacity.However,the significant volume changes during charg...Silicon is considered one of the most promising candidates for incorporation into carbon-based anodes in lithium-ion batteries(LIBs)due to its high specific capacity.However,the significant volume changes during charge and discharge cycles lead to repeated reconstruction of the solid electrolyte interface(SEI)film and continuous loss of active lithium.Pre-lithiation method is regarded as a highly attractive approach for effectively compensating for active lithium loss during the charge and discharge cycles of LIBs.Constructing a stable SEI film is particularly crucial in the pre-lithiation process.In this study,we developed a direct contact pre-lithiation(DC-Pr)method to create a temperature-tailored robust SEI film interface on silicon-carbon(Si@C)electrodes.By investigating the morphology,structure,and composition of the SEI formed on Si@C electrodes at different pre-lithiation temperatures(50,25,0,and-25℃),we demonstrated that controlling the lithiation temperature to regulate the migration rate of lithium ions within the Si@C electrode yields a lithiated Si@C anode(25-Pr-Si@C)at 25℃ with a continuous,uniform SEI film(~3.65 nm)enriched with Li_(2)O-LiF,which exhibits synergistic effects.Importantly,the initial Coulombic efficiency(ICE)of 25-Pr-Si@C significantly improved from 85.4% in the unlithiated Si@C electrode(Blank-Si@C)to 106.1%.Additionally,the full cell configuration using a high areal loading of lithiated Si@C(~5.5 mA h cm^(-2))as the anode and NCM811 as the cathode(NCM811||25-Pr-Si@C)demonstrated superior cycling performance,maintaining 69.4% of capacity retention and achieving a Coulombic efficiency of over 99.7% after 150 cycles(0.5 C).Therefore,this simple and efficient experimental design provides a high-performance,controllable,and scalable pre-lithiation method for LIBs,paving the way for the commercialization of LIBs utilizing pre-lithiation techniques.展开更多
The negatively charged nitrogen vacancy(NV^(−))center ensemble in as-grown chemical vapor deposition(CVD)diamond is a promising candidate for quantum sensing due to its long coherence time and excellent optical proper...The negatively charged nitrogen vacancy(NV^(−))center ensemble in as-grown chemical vapor deposition(CVD)diamond is a promising candidate for quantum sensing due to its long coherence time and excellent optical properties.However,achieving a high concentration of NV^(−)centers in as-grown CVD diamond remains a critical challenge,which constrains the performance of NV^(−)based sensors.In this study,we observe that NV^(−)center formation efficiency is significantly enhanced during the initial growth phase,with a coherence time T_(2)^(*)of 1.1μs.These findings demonstrate that high-concentration NV^(−)centers can be achieved in as-grown diamonds,greatly enhancing their utility in high-performance magnetometers and quantum sensing.展开更多
文摘Nitrogen doping in chemical vapor deposition-derived ultrananocrystalline diamond(UNCD)films in-creases the electronic conductivity,yet its microstructural effects on electron transport are insufficiently understood.We investigated the formation of nitrogen-induced diaph-ite structures(hybrid diamond-graphite phases)and their role in changing the conductivity.Nitrogen doping in a hy-drogen-rich plasma environment promotes the emergence of unique sp^(3)-sp^(2)bonding interfaces,where diamond grains are covalently integrated with graphitic domains,facilitating a structure-driven electronic transition.High-resolution transmis-sion electron microscopy and selected area electron diffraction reveal five-fold,six-fold and twelve-fold symmetries,along with an atypical{200}crystallographic reflection,confirming diaphite formation in 5%and 10%N-doped UNCD films,while high-er doping levels(15%and 20%)result in extensive graphitization.Raman spectroscopy tracks the evolution of sp^(2)bonding with increasing nitrogen content,while atomic force microscopy and X-ray diffraction indicate a consistent diamond grain size of~8 nm.Cryogenic electronic transport measurements reveal a conductivity increase from 8.72 to 708 S/cm as the nitrogen dop-ing level increases from 5%to 20%,which is attributed to defect-mediated carrier transport and 3D weak localization.The res-ulting conductivity is three orders of magnitude higher than previously reported.These findings establish a direct correlation between diaphite structural polymorphism and tunable electronic properties in nitrogen-doped UNCD films,offering new ways for defect-engineering diamond-based electronic materials.
基金the financial support from the Shanghai Oriental Talent Program(QNDS2024007)On-Campus Scene Verification Project of Tongji University(kh0170020242359)+4 种基金Shanghai Research Institute of China Shenhua Coal-to-Liquids Chemical Co.,Ltd.the National Natural Science Foundation of China(52307249)National Science Foundation of Shanghai Province(23ZR1465900)Fundamental Research Funds for the Central Universities at Tongji University(PA2022000668,22120220426)Nanchang Automotive Institute of Intelligence&New Energy of Tongji University(TPDTC202211-02)。
文摘Silicon is considered one of the most promising candidates for incorporation into carbon-based anodes in lithium-ion batteries(LIBs)due to its high specific capacity.However,the significant volume changes during charge and discharge cycles lead to repeated reconstruction of the solid electrolyte interface(SEI)film and continuous loss of active lithium.Pre-lithiation method is regarded as a highly attractive approach for effectively compensating for active lithium loss during the charge and discharge cycles of LIBs.Constructing a stable SEI film is particularly crucial in the pre-lithiation process.In this study,we developed a direct contact pre-lithiation(DC-Pr)method to create a temperature-tailored robust SEI film interface on silicon-carbon(Si@C)electrodes.By investigating the morphology,structure,and composition of the SEI formed on Si@C electrodes at different pre-lithiation temperatures(50,25,0,and-25℃),we demonstrated that controlling the lithiation temperature to regulate the migration rate of lithium ions within the Si@C electrode yields a lithiated Si@C anode(25-Pr-Si@C)at 25℃ with a continuous,uniform SEI film(~3.65 nm)enriched with Li_(2)O-LiF,which exhibits synergistic effects.Importantly,the initial Coulombic efficiency(ICE)of 25-Pr-Si@C significantly improved from 85.4% in the unlithiated Si@C electrode(Blank-Si@C)to 106.1%.Additionally,the full cell configuration using a high areal loading of lithiated Si@C(~5.5 mA h cm^(-2))as the anode and NCM811 as the cathode(NCM811||25-Pr-Si@C)demonstrated superior cycling performance,maintaining 69.4% of capacity retention and achieving a Coulombic efficiency of over 99.7% after 150 cycles(0.5 C).Therefore,this simple and efficient experimental design provides a high-performance,controllable,and scalable pre-lithiation method for LIBs,paving the way for the commercialization of LIBs utilizing pre-lithiation techniques.
基金supported by the National Natural Science Foundation of China(Grant Nos.11374280 and 50772110).
文摘The negatively charged nitrogen vacancy(NV^(−))center ensemble in as-grown chemical vapor deposition(CVD)diamond is a promising candidate for quantum sensing due to its long coherence time and excellent optical properties.However,achieving a high concentration of NV^(−)centers in as-grown CVD diamond remains a critical challenge,which constrains the performance of NV^(−)based sensors.In this study,we observe that NV^(−)center formation efficiency is significantly enhanced during the initial growth phase,with a coherence time T_(2)^(*)of 1.1μs.These findings demonstrate that high-concentration NV^(−)centers can be achieved in as-grown diamonds,greatly enhancing their utility in high-performance magnetometers and quantum sensing.
