Alkaline metal-doped n-type semiconducting nanotubes as quantum dots

A 0.4 μm long semiconducting single-walled carbon nanotube is doped into n type by potassium (K) vapor. Electrical measurements of the doped nanotube reveal single-electron charging at temperatures up to 160 K. The K-doped sample manifests as a single quantum dot or multiple quantum dots in series depending on the range of applied gate voltage. This is explained by an inhomogeneous doping profile along the nanotube length. Similarities between K-doped nanotubes and silicon-based quantum dots and the possibility of room-temperature nanotube single-electron transistors are discussed.