Local electronic properties of carbon nanotube heterojunctions

Local electronic properties of metallic-semiconducting carbon nanotube hete rostructures are investigated by studying the behavior of the one-electron local density of states (LDOS) along the tubes. We determine how these prop erties change from the metallic to the semiconducting side of a nanotube ju nction. We show that Friedel oscillations may not always be evident on the metallic side, and we found clear exponential decay of the LDOS on the semi conducting side. The exponential rates of decay as well as the absence of t he oscillations are explained in terms of a simple picture that relates the LDOS to the bulk electronic structure of the constituent parts of the hete rostructures.