Dewetting-induced formation of periodic dot arrays of polymer/Au composites by capillary force lithography

This paper demonstrates that simple cross-stamping in capillary force lithography (CFL) enables the fabrication of periodic dots, rings, and line patterns of the metal/polymer composites. The key to the success was the compatibility of polymer/inorganic precursor composite liquids on substrates. As a model study, the composites consisting of poly(ethylene oxide) (PEO) and the gold precursor (HAuCl₄) were investigated. The contact angle of the composite liquid on the Si substrate significantly increased when the fractional composition of the precursor was over a critical value, while the contact angle on poly(dimethylsiloxane) (PDMS) molds decreased. The reduced wettability on the substrate resulted in isolated dot patterns upon cross-stamping on the line patterns fabricated by CFL. The shape, size, and number of the dots could be controlled by adjusting the thickness of the composite films. Small coupled dots were obtained from dual-line patterns and large single dots were obtained from single-line patterns. When the initial film thickness was ∼60 nm, the cross-stamping resulted in donutlike composite patterns. Chemical reduction of the precursor could generate periodic arrays of Au rings or solid nanodots.