Molecular-Scale Quantum Dots from Carbon Nanotube Heterojunctions

Carbon nanotube heterojunctions (HJs), which seamlessly connect nanotubes of different chiral structure using a small number of atomic-scale defects, represent the ultimate scaling of electronic interfaces. Here we report the first electrical transport measurements on a HJ formed between semiconducting and metallic nanotubes of known chiralities. These measurements reveal asymmetric IV-characteristics and the presence of a quantum dot (QD) with ∼60 meV charging energy and ∼75 meV level spacing. A detailed atomistic and electronic model of the HJ enables the identification of specific defect arrangements that lead to the QD behavior consistent with the experiment.