AVS 51st International Symposium
    Surface Science Wednesday Sessions
       Session SS+OF-WeA

Paper SS+OF-WeA10
Time-Evolution and Stability of Metal-Molecule Contacts

Wednesday, November 17, 2004, 5:00 pm, Room 213B

Session: Contacts to Molecules and Molecular Films
Presenter: A.V. Walker, Washington University in St. Louis
Authors: G. Nagy, Washington University in St. Louis
A.V. Walker, Washington University in St. Louis
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Understanding the nature of metal-molecule interactions is important for many technologies, including organic and molecular electronics. It has already been demonstrated using vapor-deposited metals on self-assembled monolayers (SAMs) that many interactions are possible, ranging from destruction of the SAM to organometallic formation to penetration through the SAM to the Au/S interface. We apply time-of-flight secondary ion mass spectrometry (TOF SIMS) experiments and density functional theory (DFT) calculations to investigate the time-evolution and the energetics of vapor-deposited metallic contacts. As model systems we are employing vapor-deposition of copper on alkanethiolate SAMs with -CH3, -OCH@sub 3@, -COOH, -OH and -COOCH@sub 3@ terminal groups. We observe at room temperature that vapor-deposited Cu on -COOH and -OCH@sub 3@ SAMs initially both penetrates to the Au/S interface and forms a weak complex with the terminal group. However, Cu at the vacuum interface is not stable in the long term and slowly penetrates through the monolayer. We demonstrate that the stability of metal-molecule contacts is dependent on a number of factors including the strengths of the metal-metal and the metal-molecule interactions and the rate of penetration through the monolayer, which itself is dependent on the diffusion of the SAM molecules on the Au substrate.