Cesium encapsulation in single-walled carbon nanotubes via plasma ion irradiation: Application to junction formation and ab initio investigation

Using an approach different from the conventional vapor doping methods, Cs positive ions in a magnetized-plasma column are irradiated upon a negatively biased substrate which is covered with dispersed single-walled carbon nanotubes (SWNTs). The Cs ions are evidently observed inside SWNTs by the Z-contrast method in scanning transmission electron microscopy, demonstrating the formation of alkali-metal encapsulating SWNTs. Ab initio band structures and density of states for the light and heavy doping regimes indicate the possibility of using Cs-doped SWNTs as doped junctions, with potential application in nanoelectronics. This is supported by the direct experimental observation of an actual junction.