A convenient fabrication technique for samarium hexaboride（SmB6） nanostructures（nanowires and nanopencils） is developed, combining magnetron-sputtering and chemical vapor deposition. Both nanostructures are proven...A convenient fabrication technique for samarium hexaboride（SmB6） nanostructures（nanowires and nanopencils） is developed, combining magnetron-sputtering and chemical vapor deposition. Both nanostructures are proven to be single crystals with cubic structure, and they both grow along the [001] direction. Formation of both nanostructures is attributed to the vapor-liquid-solid（VLS） mechanism, and the content of boron vapor is proposed to be the reason for their different morphologies at various evaporation distances. Field emission（FE） measurements show that the maximum current density of both the as-grown nanowires and nanopencils can be several hundred μA/cm^2, and their FN plots deviate only slightly from a straight line. Moreover, we prefer the generalized Schottky-Nordheim（SN） model to comprehend the difference in FE properties between the nanowires and nanopencils. The results reveal that the nonlinearity of FN plots is attributable to the effect of image potential on the FE process, which is almost independent of the morphology of the nanostructures.All the research results suggest that the SmB6 nanostructures would have a more promising future in the FE area if their surface oxide layer was eliminated in advance.展开更多
The conductances of two typical metallic graphene nanoribbons with one and two defects are studied using the tight binding model with the surface Green＇s function method. The weak scattering impurities, U - 1 eV, ind...The conductances of two typical metallic graphene nanoribbons with one and two defects are studied using the tight binding model with the surface Green＇s function method. The weak scattering impurities, U - 1 eV, induce a dip in the conductance near the Fermi energy for the narrow zigzag graphene nanoribbons. As the impurity scattering strength increases, the conductance behavior at the Fermi energy becomes more complicated and depends on the impurity location, the AA and AB sites. The impurity effect then becomes weak and vanishes with the increase in the width of the zigzag graphene nanoribbons （150 nm）. For the narrow armchair graphene nanoribbons, the conductance at tile Fermi energy is suppressed by the impurities and becomes zero with the increase in impurity scattering strength, U 〉 100 eV, for two impurities at the AA sites, but becomes constant for the two impurities at the AB sites. As the width of the graphene nanoribbons increases, the impurity effect on the conductance at the Fermi energy depends sensitively on the vacancy location at the AA or AB sites.展开更多
基金Project supported by the National Key Basic Research Program of China(Grant No.2013CB933601)National Project for the Development of Key Scientific Apparatus of China(Grant No.2013YQ12034506)+3 种基金the Fundamental Research Funds for the Central Universities of Chinathe Science and Technology Department of Guangdong Province,Chinathe Education Department of Guangdong Province,Chinathe Natural Science Foundation of Guangdong Province,China(Grant No.2016A030313313)
文摘A convenient fabrication technique for samarium hexaboride（SmB6） nanostructures（nanowires and nanopencils） is developed, combining magnetron-sputtering and chemical vapor deposition. Both nanostructures are proven to be single crystals with cubic structure, and they both grow along the [001] direction. Formation of both nanostructures is attributed to the vapor-liquid-solid（VLS） mechanism, and the content of boron vapor is proposed to be the reason for their different morphologies at various evaporation distances. Field emission（FE） measurements show that the maximum current density of both the as-grown nanowires and nanopencils can be several hundred μA/cm^2, and their FN plots deviate only slightly from a straight line. Moreover, we prefer the generalized Schottky-Nordheim（SN） model to comprehend the difference in FE properties between the nanowires and nanopencils. The results reveal that the nonlinearity of FN plots is attributable to the effect of image potential on the FE process, which is almost independent of the morphology of the nanostructures.All the research results suggest that the SmB6 nanostructures would have a more promising future in the FE area if their surface oxide layer was eliminated in advance.
基金supported by the National Natural Science Foundation of China (Grants Nos. 10774194 and 51072236)the Elite Student Program from National Education Departmentthe Fundamental Research Funds for the Central Universities
文摘The conductances of two typical metallic graphene nanoribbons with one and two defects are studied using the tight binding model with the surface Green＇s function method. The weak scattering impurities, U - 1 eV, induce a dip in the conductance near the Fermi energy for the narrow zigzag graphene nanoribbons. As the impurity scattering strength increases, the conductance behavior at the Fermi energy becomes more complicated and depends on the impurity location, the AA and AB sites. The impurity effect then becomes weak and vanishes with the increase in the width of the zigzag graphene nanoribbons （150 nm）. For the narrow armchair graphene nanoribbons, the conductance at tile Fermi energy is suppressed by the impurities and becomes zero with the increase in impurity scattering strength, U 〉 100 eV, for two impurities at the AA sites, but becomes constant for the two impurities at the AB sites. As the width of the graphene nanoribbons increases, the impurity effect on the conductance at the Fermi energy depends sensitively on the vacancy location at the AA or AB sites.
