Molecular Tailoring of Interfaces using Self-Assembled Monolayers (SAM)

PROJECT TITLE:
MULTISCALE ANALYSIS OF IMPACT OF SELF-ASSEMBLED MONOLAYERS ON THE MECHANICAL PROPERTIES OF FILM/SUBSTRATE INTERFACES

PARTICIPANTS: CHEN ZHANG (PhD), DR. AMNAYA AWASTHI (Postdoctoral Research Associate), PROF. NANCY R. SOTTOS (MatSE, U. Illinois), AND PROF. PHILIPPE GEUBELLE

SUPPORT: NSF CMMI


PROJECT DESCRIPTION: In this project, we performed simulations using tools ranging from molecular dynamics to continuum-level cohesive finite element methods to investigate how the presence of nanometer-thick self-assembled monolayers affect the failure strength of the interface between a metallic film (typically made of gold) and a silicon substrate. Emphasis is placed in capturing the effect of the surface roughness of the SAM-enhanced substrate. This modeling work is performed in collaboration with members of Prof. Nancy Sottos’ research group (M. Grady and J. Sung) in the MatSE Department at the University of Illinois, who use a laser-induced spallation technique to extract the interface properties of the film/SAM/substrate system.

Manufacturing of SAM-enhanced thin film/substrate interface using a transfer printing technique.

Experimental observation of effect of SAM composition on the delimitation failure of patterned gold films on a silicon substrate. M and D respectively denote MUTMS (11-mercapto-undecyltrimethoxysilane) and DTES (Dodecyltriethoxysilane), whose concentration is varied from 100% MUTMS/0% DTES (left) to 25% MUTMS/75% DTES (right). A longer delamination zone denotes a weaker interface.

Cohesive/plate model of the effect of substrate roughness on the failure properties of SAM-enhanced thin films. Note that the roughness profiles, which are taken from experimental measurements, is greatly exaggerated in this figure.

 

RELATED PUBLICATIONS:

  1. Awasthi, A. P., Grady, M. E., Kim, I. H., Sottos, N. R., and Geubelle, P. H. (2016) “Nanoscale mechanical tailoring of interfaces using self-assembled monolayers.” Mechanics of Materials, 98, 71-80. DOI: http://dx.doi.org/10.1016/j.mechmat.2016.04.003.
  2. Zhang, C., Awasthi, A. P., Geubelle, P. H., Sung, J., and Sottos, N. R. (2017) “Multi-scale model of effects of roughness on the cohesive strength of self-assembled monolayers”. International Journal of Fracture, in press. doi:10.1007/s10704-017-0221-3.
  3. Zhang, C., Awasthi, A. P., Geubelle, P. H., Grady, M. E., and Sottos, N. R. (2017) “Effects of interface roughness on the cohesive strength of self-assembled monolayers.” Applied Surface Science, 397, 192-198. DOI: http://dx.doi.org/10.1016/j.apsusc.2016.10.089.