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Processing Examples
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Copyright© 2006, University of Washington, used with permission
A 2 nm gold-palladium film was used as a substrate for microcontact printing octadecanethiol. Although barely visibile in TEM, there are a series of alternating bands running up and down the image with a 2 nm periodicity, matching the pattern of the polydimethylsiloxane (PDMS) stamp. As in example #1, the grid needed to be "glued" to a surface to support the delicate film during the contacting procedure and many of the grid windows are damaged in the process. Note that the patterns which are darker do not represent octadecanethiol, as was later discovered when using asymettric patterns. George Whitesides and others also reported this in SEM observations that the noble metal surface which is not coated actually becomes dirty with adventitious carbon more rapidly over time than the functionalized regions. Thus, the darker regions here are actually the bare substrate, opposite what one might expect.
