Electrochemical Etching of Gold within Nanoshaved Self-Assembled Monolayers

Abstract

Wet etching of metal substrates with patterned self-assembled monolayers (SAMs) is an inexpensive and convenient method to produce metal nanostructures. For this method to be relevant to the fabrication of high precision plasmonic structures, the kinetics of nanoscale etching process, particularly in the lateral direction, must be elucidated and controlled. We herein describe an in situ atomic force microscopy (AFM) study to characterize the etching process within patterned SAMs with nanometer resolution and in real time. The in situ study was enabled by several unique elements, including single crystalline substrates to minimize the variability of facet-dependent etch rate, high-resolution nanoshaved SAM patterns, electrochemical-potential-controlled etching, and AFM kymographs to improve temporal resolution. Our approach has successfully quantified the extent of both lateral etching and vertical etching at different potentials. Our study reveals the presence of an induction period prior to the onset of significant lateral etching, which would be difficult to observe with the limited time resolution and sample-to-sample variation of ex situ studies. By increasing the vertical etch rate during this induction period with higher potentials, gold was etched up to 40 nm in the vertical direction with minimal lateral etching. High-resolution etching was also demonstrated on single crystal gold microplates, which are high quality gold thin films suitable for plasmonics studies.

An integrated experimental-theoretical approach to understand the electron transfer mechanism of adsorbed ferrocene-terminated alkanethiol monolayers

“…In particular, ferrocene-terminated alkanethiol (FcCnSH) molecules on gold substrates has provided with a simple and stable way to prepare tuneable films [4][5][6]. Furthermore, the presence of this electroactive moiety on the substrate has put forward significant advances to improve the protection against corrosion [7,8], to understand the electron transfer mechanisms [9][10][11], to enhance the performance of bioelectrochemical devices [12][13][14][15][16], and to exploit molecular electronics [17][18][19][20][21][22]. The stability of this surface modification relies on the strong interaction between the thiolated adsorbate and the gold substrate.…”

Facet selective etching of Au microcrystallites

“…Jana et al [18] have reported the anisotropic etching of Au spheroid to spherical nanoparticles using CN -. Electrochemical oxidation to Au crystals also has been reported [19,20]. Pradeep et al have used CuCl2 as an etchant for the anisotropic etching of Au nanorods, and selective etching of body and tip of the nanorods have been demonstrated [21].…”

Intermolecular Interactions in Mixed Self‐Assembled Monolayers of Ferrocene

“…Researches on the electrochemical behavior of redox active self‐assembled monolayers (SAMs) have been coming up since much time. The study of the interfacial electron transfer has derived in relevant advances concerning the protection against corrosion 1, electron transfer theory 2, bioelectrochemistry 3, and molecular electronics 4. Mixed SAMs, i.e.…”