Modulated chemical doping of individual carbon nanotubes

Modulation doping of a semiconducting single-walled carbon nanotube along i ts length leads to an intramolecular wire electronic device. The nanotube i s doped n-type for half of Its length and p-type for the other half. Electr ostatic gating can tune the system into p-n junctions, causing it to exhibi t rectifying characteristics or negative differential conductance. The syst em can also be tuned into n-type, exhibiting single-electron charging and n egative differential conductance at low temperatures. The low-temperature b ehavior is manifested by a quantum dot formed by chemical inhomogeneity alo ng the tube.