title: Direct observation of localized defect States in semiconductor nanotube junctions.
abstract: We report scanning tunneling microscopy of semiconductor-semiconductor carbon nanotube junctions with different band gaps. Characteristic features of the wave functions at different energy levels, such as a localized defect state, are clearly exhibited in the atomically resolved scanning tunneling spectroscopy. The peaks of the Van Hove singularity on each side penetrate and decay into the opposite side across the junction over a distance of approximately 2 nm. These experimental features are accounted for, with the help of tight-binding calculation, by the presence of pentagon-heptagon pair defects at the junction.
authors.affiliation: School of Physics and Center for Science in Nanometer Scale, Seoul National University, Seoul 151-742, Korea.
authors.forename: Hajin
authors.initials: H
authors.lastname: Kim
authors.forename: J
authors.initials: J
authors.lastname: Lee
authors.forename: S-J
authors.initials: SJ
authors.lastname: Kahng
authors.forename: Y-W
authors.initials: YW
authors.lastname: Son
authors.forename: S B
authors.initials: SB
authors.lastname: Lee
authors.forename: C-K
authors.initials: CK
authors.lastname: Lee
authors.forename: J
authors.initials: J
authors.lastname: Ihm
authors.forename: Young
authors.initials: Y
authors.lastname: Kuk