Image topography of alkyl-substituted carboxylates observed by noncontact atomic force microscopy

A series of carboxylates (HCOO-, CH3COO- and (CH3)(3)CCOO-) adsorbed on TiO 2(110) were observed by noncontact atomic force microscopy. Different carbo xylates were identified molecule-by-molecule in monolayers of mixed composi tion. The molecule-dependent image topography was quantitatively related to the atom geometry of alkyl group terminating the molecules. The image topo graphy exhibited a good correlation with the physical topography (altitude of topmost hydrogen atoms) of the alkyl groups. though the former was not a one-to-one projection of the latter. The deviation from the one-to-one rel ation indicates a long-range nature of tip-molecule force. (C) 2001 Elsevie r Science B.V. All rights reserved.