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
The energy transfer and upconversion of Er 3+ /Yb 3+ co-doped TeO2-TiO2-K2O glasses upon excitation with 976nm lasers diode were studied. The tellurite glasses were prepared by conventional melting methods. Their opti...The energy transfer and upconversion of Er 3+ /Yb 3+ co-doped TeO2-TiO2-K2O glasses upon excitation with 976nm lasers diode were studied. The tellurite glasses were prepared by conventional melting methods. Their optical properties and sensitization upconversion spectra were performed. The dependence of green upconversion luminescence intensity on the mole ratio of Yb 3+ to Er 3+ and Er 3+ concentration were discussed in detail. When the mole ratio of Yb 3+ to Er 3+ is 25/1 and Er 3+ concentration is 0.1% （mole fraction）, or when the mole ratio of Yb 3+ to Er 3+ is 10/1 and Er 3+ concentration is 0.15%, the optimal upconversion luminescence intensity is obtained. The obtained glasses can be one of the potential candidates for lasers-diode pumping microchip solid-state lasers.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Projects(2004Z2-D0131 and 2004A10602002) supported by the Science and Technology Programof Guangzhou , Guang-dong Province project(60307004 and 50472053) supported by the National Natural Science Foundation of China project(04200036) sup-ported by the Natural Foundation of Guangdong Province
文摘The energy transfer and upconversion of Er 3+ /Yb 3+ co-doped TeO2-TiO2-K2O glasses upon excitation with 976nm lasers diode were studied. The tellurite glasses were prepared by conventional melting methods. Their optical properties and sensitization upconversion spectra were performed. The dependence of green upconversion luminescence intensity on the mole ratio of Yb 3+ to Er 3+ and Er 3+ concentration were discussed in detail. When the mole ratio of Yb 3+ to Er 3+ is 25/1 and Er 3+ concentration is 0.1% （mole fraction）, or when the mole ratio of Yb 3+ to Er 3+ is 10/1 and Er 3+ concentration is 0.15%, the optimal upconversion luminescence intensity is obtained. The obtained glasses can be one of the potential candidates for lasers-diode pumping microchip solid-state lasers.
