IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Nanometer Structures Wednesday Sessions
       Session NS+EL-WeA

Paper NS+EL-WeA8
Diffusion of Alkanethiols in the Presence of Water

Wednesday, October 31, 2001, 4:20 pm, Room 133

Session: Molecular Electronics and Patterning
Presenter: P.E. Sheehan, Naval Research Laboratory
Authors: P.E. Sheehan, Naval Research Laboratory
M.L. Stevens, Naval Research Laboratory
L.J. Whitman, Naval Research Laboratory
Correspondent: Click to Email
The patterning of alkanethiols has become a cornerstone in the burgeoning field of nanotechnology. Several patterning techniques have been developed, the more popular of which include stamping using polymer masters, known as microcontact printing (mCP) and, more recently, the direct writing of the thiols using an AFM tip, known as Dip Pen Nanolithography (DPN). Importantly, in both techniques, diffusion of the thiol away from the contact area fundamentally limits the spatial resolution obtained. Obtaining the highest resolution possible from these techniques will require a full understanding of the rate and nature of thiol diffusion. To address this need, the radii of octadecanethiol spots deposited via DPN were studied as a function of tip-surface contact time and relative humidity. The increase in spot size with time was well described by two-dimensional radial diffusion from a constant source of finite radius. Fits using this formula revealed a diffusion constant of approximately 2500 nm2/sec with little dependence on humidity. Analysis of published images@footnote 1@ showing the spread of hexadecanethiol on gold after microcontact printing leads to comparable diffusion constants. Significantly, these values are four orders of magnitude smaller than that expected for diffusion through bulk water. Mechanisms that would explain such a low diffusion coefficient will be discussed. @FootnoteText@ @footnote 1@ Y. Xia and G.M. Whitesides, J. Am. Chem. Soc. 117 (1995) 3274.