Edge Spreading Lithography and Its Application to the Fabrication of Mesoscopic Gold and Silver Rings

Abstract

A new form of edge lithography, edge spreading lithography (ESL), has been demonstrated and applied to the formation of coinage metal rings. In this process, alkanethiols are delivered from a flat PDMS stamp to the surface of a metal film through a two-dimensional array of spherical silica colloids. The thiols further spread on the metal surface, forming highly ordered SAMs in the form of a ring pattern. Following lift-off of beads, the pattern in the SAMs can be transferred into the metal film through wet chemical etching, with SAMs serving as the resist. The dimensions of the rings can be readily controlled by several parameters such as the beads diameter, the concentration of the thiol solution, and the contact time between the stamp and the silica beads.

Gold nanorings synthesized via a stress-driven collapse and etching mechanism

“…10 To date, Au or Ag NPs with various shapes, such as nanospheres, nanobars, nanorods, nanorices, nanoneedles, nanowires, nanocubes, nanoprisms, bipyramids, nanocarrots, nanoplates, nanodisks and nanobelts, have been successfully prepared. 11 However, the fabrication of ring-like Au or Ag nanostructures is limited to either electron beam lithography or template techniques. 12 The electron beam lithography approach not only involves costly and complex processes but also leads to nanorings anchored onto solid supports, which limits their feasibility for further applications.…”

Colloidal Lithography

“…Combining microcontact printing with colloidal crystal masking, Xia et al have developed a simple method -edge spreading lithography (ESL) -to generate mesoscopic structures on substrates [59]. As the name suggests, ESL utilizes the edges of masks -the perimeters of the footprint of particles on substrates -to define the features of resultant structures.…”

“…As the name suggests, ESL utilizes the edges of masks -the perimeters of the footprint of particles on substrates -to define the features of resultant structures. The ESL procedure begins with formation of 2D colloidal crystals of silica beads on the surfaces of gold or silver thin films [59]. As shown in Fig.…”

“…The area of the thiol SAM could expand laterally via reactive spreading as long as the thiols were continuously supplies. Upon removal of the stamp and lift-off of the beads, the ring pattern was developed by wet etching with aqueous Fe 3+ /thiourea using the patterned SAM as a resist [59]. Of importance is that ESL allows generation of the concentric rings of different alkanethiol SAMs by successive printing different thiol inks, and the removal of silica particle templates and selective etching yield concentric gold rings and the width of the rings were determined by the printing period (Fig.…”

Sub-Micrometer Patterning Using Soft Lithography

“…Edge-spreading lithography (ESL) [132][133][134][135] is suitable for the patterning of alkanethiol monolayers on coinage metals at sub-micrometer length scales. This technique relies on two key features: a mesoscopic relief structure on the metal substrate and reactive spreading.…”