Monolayers by Combination of Underpotential Deposition and Scanning Tunneling Microscopy:

A novel method for imaging individual defect structures contained within thin, insulating layers that cover atomically smooth conducting substrates is described. The technique relies upon imaging metal islands electrochemically deposited within defects that penetrate the insulating layer by scanning tunneling microscopy. The method is illustrated by measuring the rate of self-ass-embly of a monolayer of CH3(CH2)17SH on a Au (111) substrate. The results are found to be in accord with those obtained by spec-troscopic and contact angle measurements. Self-organizing chemical systems represent a versatile ap-proach for the rational modification of surfaces (1), and during the past several years considerable ffort has been directed to-wards the synthesis and characterization of ideal, defect-free mono- and multilayers (2-7). However, little emphasis has been placed on the characterization of adventitious defect struc-tures, or on the synthesis of intentionally formed defect struc-tures, because the techniques that are presently used for studying self-assembled organic surfaces generally rely upo