Lateral force microscopy study of functionalized self-assembled monolayer surfaces

Patterned self-assembly of functionalized alkanethiols on the gold surface on a submicron scale was achieved by microcontact printing with elastomeric poly(dimethylsiloxane) (PDMS) stamps. Atomic force microscopy (AFM) and lateral force microscopy (LFM) were used to examine the topography and properties of the self-assembled. monolayer (SAM) surface containing Br and OH groups. Au-coated probe rips were modified with alkanethiolates of such functional groups as CH3, NHCOCH3 and NHCOCF3. LFM images were examined to elucidate the adhesive interaction between modified probe tips and SAM surfaces. AFM images scanned by normal and modified probe tips clearly show that the height difference of the alternating lines on the exposed surface is attributed to the size differences of Br and OH groups. With an NHCOCH3 probe the image contrast of the lines due to the friction is almost indistinguishable or inverted in the LFM image. LFM image by a normal and NHCOCF3 probes exhibit the same contrast as topography in AFM images. Therefore, the specific functional group in this system could be recognized by the comparison of the adhesive interaction between tip and sample surfaces. (C) 1999 Elsevier Science S.A. All rights reserved.