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Nanomechanics of Self-Assembled Monolayers on Nanoscale Gold Films

Published online by Cambridge University Press:  01 February 2011

Milca I Aponte-Roman  and
Adrian B Mann
Milca I Aponte-Roman
Affiliation:
milcaa@eden.rutgers.edu, Rutgers, The State University of New Jersey, Materials Science & Engineering, 607 Taylor Road, Piscataway, NJ, 08854, United States
Adrian B Mann
Affiliation:
abmann@rci.rutgers.edu, Rutgers, The State University of New Jersey, Materials Science & Engineering, 607 Taylor Road, Piscataway, NJ, 08854, United States
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Abstract

Self-assembled monolayers (SAMs) are thin organic films formed by a single layer of molecules adsorbed on a substrate. Since their discovery the preparation of these molecular assemblies has attracted the attention of interfacial researchers interested in controlled wetting of surfaces, adhesion, friction, chemical sensing, and high resolution lithography. However, little effort has gone into understanding how this nano-layer affects the mechanics of the underlying surface. In this study the nanomechanics of alkanethiolate SAMs on Au (111) films has been investigated using nanoindentation techniques. The research is aimed at establishing the effect of a SAM on the measured mechanical properties of the Au film. The SAMs considered for this study were made from 1-decanethiol, 96% (CH3(CH2)9-SH). Nanoindentation experiments were performed using a Triboindenter (Hysitron Inc., MN) using displacement control mode. Comparisons were made between the mechanical behavior of the Au films, the Au films plus SAMs and the glass substrate. A range of maximum indentation displacements were used. During the nanoindentation tests the load-displacement curves and the apparent mechanical properties were found to depend on the presence of the SAM film. Surprisingly, the effects of the SAM layer are seen even when the nanoindentation displacement is orders of magnitude greater that the SAM thickness. Many of the effects of the SAM can be explained by changes in the contact geometry and the ability of the SAM to sustain compressive loads when it is in a confined volume. The results and conclusions are potentially relevant to all thin adsorbed organic films, including protein layers on biomaterial surfaces and lubricants on engineering components.

Keywords

nano-indentationself-assemblythin film
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 1086: Symposium U – Mechanics of Nanoscale Materials , 2008 , 1086-U08-27
Copyright
Copyright © Materials Research Society 2008

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