Conductive copper patterning by nanotransfer printing

In this paper, we report a solventless, additive approach for patterning conductive copper in the 1-100 μm range at ambient conditions. A freshly-etched GaAs substrate is treated with 1,8-octanedithiol molecules, resulting in covalent bonds between the GaAs substrate and one of the thiol functionalities. A poly(dimethylsiloxane), PDMS, elastomeric stamp, freshly evaporated with Cu, is then brought into contact with the substrate. Intimate molecular contact between the raised regions of the stamp and the substrate facilitates the permanent attachment of Cu to the GaAs substrate via the formation of covalent bonds between the unreacted thiol endgroups of octanedithiol and Cu. Pattern transfer is completed upon stamp removal; this process occurs at ambient conditions with less than 30 seconds of contact time. Currently, this technique permits large-area patterning of features with sizes ranging from 1 μm to 500 μm.