AVS 45th International Symposium
    Nanometer-scale Science and Technology Division Thursday Sessions
       Session NS-ThP

Paper NS-ThP8
Frictional Force Microscopy Study of Discrete Surface Functional Group Assembled by Langmuir-Blodgett Technique

Thursday, November 5, 1998, 5:30 pm, Room Hall A

Session: Nanometer-Scale Science and Technology Division Poster Session
Presenter: M. Nakamura, Toray Research Center, Inc., Japan
Authors: M. Nakamura, Toray Research Center, Inc., Japan
A. Shimizu, Toray Research Center, Inc., Japan
Y. Nakayama, Toray Research Center, Inc., Japan
Y. Nagasawa, Toray Research Center, Inc., Japan
Correspondent: Click to Email
Obtaining a flat surface which contains discrete functional groups with aimed density is doubtless valuable for nanometer science and technology. The functional groups can be used as nucleation sites for vacuum deposition or as adsorption sites for biomolecules. Furthermore, such a surface can be used as a test structure for scanning probe microscopy in terms of chemical identification. For this purpose, we have studied the Langmuir-Blodgett (LB) films formed with the mixture of stearic acid (SA) and stearyl mercaptan (SM) on atomically flat silicon substrates. The length of SM is approximately same as that of SA, but SM has a -SH group instead of a hydrophilic -COOH group. We therefore expect some part of the -SH groups in the bilayer film of the mixture to protrude from the surface. It was confirmed with atomic force microscopy (AFM) that flat and tight films were obtained with the mixtures which contain less than 10% of SM. Topographic and frictional force images showed that the surfaces contained number of protrusions exhibiting higher frictional force. The diameter of the higher friction spots was more than a few nanometer and varied with the AFM tip. Their density was nearly proportional to the concentration of SM. The distribution of the topographic height of these spots clearly exhibited two peaks around 1.6 and 2.6 Å, which can be explained by the models where the -SH shifts outward for one and two -(CH@sub 2@)- units of an alkyl chain. These results imply that the expected surface was successfully obtained. An interesting point is that the distribution of the maximum friction at these spots has only single peak in contrast to the height distribution.