OBSERVATION OF 1-DODECANETHIOL MOLECULES ON GRAPHITE BY SCANNING-TUNNELING-MICROSCOPY

Molecular-resolution images of 1-dodecanethiol on the graphite substra te are successfully observed with a scanning tunneling microscope in a ir. The image reveals a two-dimensional ordering with the molecules ly ing down and arranged in rows on the graphite surface. A 5.5 nm period icity observed suggests that there are three molecules arranged in ser ies along the molecular axis. Two kinds of molecular arrangements exis t within a single row, with one subrow about 1.5 nm wide with one 1-do decanethiol and the other subrow about 3.5 nm in width approximately d ouble the length of the molecule. The periodicity vertical to the mole cular axis is about 0.55 nm, comparable with the Van der Waals diamete r of the molecule. A model for the possible arrangement of the molecul es on graphite surface is proposed. (C) 1998 Elsevier Science B.V. All rights reserved.