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(a) Schematic of copper pattern transfer by nTP. Copper is deposited onto a PDMS stamp by e-beam evaporation. The PDMS stamp is then contacted for at room temperature against a substrate that was pretreated with 1,8-octanedithiol. After removing the stamp, the copper patterns are bound to the substrate in the areas of contact. (b) Optical micrograph of a printed copper film revealing the large-area printing capability of nTP. Light regions correspond to copper, dark regions correspond to .
(a) Copper LMM spectra of pure copper (II) oxide (bottom), a printed nonconductive copper pattern beneath the surface (middle), and pure copper (top). spectra of (b) gold and (c) copper printed with as-cast PDMS stamps, and (d) copper printed with a toluene-leached stamp. All spectra are offset for clarity. In graphs b through d, the top spectra were obtained on the printed surfaces, while the middle and the bottom spectra were obtained below the surface and at the metal/GaAs interface, respectively (note differences in -axis scale).
Normalized integrated peak intensities of oxygen along the depth of the patterns. All peaks were also normalized by the appropriate atomic sensitivity factor. (See Ref. 20). The PDMS oligomers reside only on the surface of gold, but permeate through the copper patterns.
Resistance measured along the length of printed continuous copper lines. The slope yields an average resistivity of . Top inset: Optical micrograph of one of the printed copper lines. Light regions correspond to copper.
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