Application of Atom Manipulation for Fabricating Nanoscale and Atomic-Scale Structures on Si Surfaces: Fid-Bau Portal

Application of Atom Manipulation for Fabricating Nanoscale and Atomic-Scale Structures on Si Surfaces

Hashizume, T. / Heike, S. / Hitosugi, T. / Kitazawa, K.

Summary Scanning Tunneling Microscopy/Spectroscopy (STM/STS) and atom manipulation have been used to fabricate and characterize nanoscale and atomic-scale structures on Si(111)−7x7 and hydrogen-terminated Si(100)−2x1−H surfaces. We first fabricate 0.2–0.6 nm deep and 10 nm wide trench lines by applying a high voltage and/or a large tunneling current between the STM tip and the Si(111)−7x7 surface. When the trench lines form a closed figure such as a circle or a square, the apparent height of the surface area inside the closed trench becomes 0.1–0.3 nm lower than outside. This phenomenon is explained by a naturally formed Schottky barrier between metallic surface states and substrate, and by electronic conduction through the surface states. Atom manipulation is then applied on a hydrogen-terminated Si(100)−2x1−H surface to extract hydrogen atoms one by one and to fabricate atomic-scale dangling bond (DB) structures. Electronic structures of DB wires are studied using STS. The wires composed of both unpaired DBs and paired DBs show a finite density of states at the Fermi level and do not show semiconductive band gaps. The results agree well with first-principles theoretical calculations. The hydrogen-terminated Si(100)−2x1−H surface and its interaction with thermally deposited Ga atoms and C60 molecules is investigated. They migrate on the hydrogen-terminated area and preferentially adsorb on DBs. Several methods for manipulating hydrogen atoms (detaching, attaching and moving) are also tested. Atomic-scale Ga wires on the Si surface are fabricated for the first time by thermally depositing Ga atoms on the DB wires.