High-resolution imaging of organic monolayers using noncontact AFM

Noncontact atomic force microscopy (AFM) provides useful technique for imag ing organic molecules in high resolution. Here we present our recent advanc es in the noncontact AFM imaging of organic materials. (I) Molecular packin g structures, defects and domain boundaries were clearly observed on adenin e and thymine films. The noncontact AFM images revealed detailed features o f the individual nucleic acid base molecules, thus allowing us to distingui sh between adenine and thymine. (II) Both (root 3 X root 3)R30 degrees stru ctures and c(4 X 2) superlattice structures were resolved on alkanethiolate self-assembled monolayer (SAM) [CH3(CH2)(8)SH] (nonanethiol) on Au(111). W e found that the c(4 X 2) superlattice structures changed into (root 3 X ro ot 3)R30 degrees structures when the tip-surface distance decreased. (C) 20 00 Elsevier Science B.V. All rights reserved.