Solvent-Resistant Ultraflat Gold Using Liquid Glass

Abstract

Templating against atomically flat materials allows creation of smooth metallic surfaces. The process of adding the backing (superstrate) to the deposited metals has proven to be the most difficult part in producing reliable, large-area, solvent-resistant substrates and has been the subject of recent research. In this paper we describe a simple and inexpensive liquid glass template-stripping (lgTS) method for the fabrication of large area ultraflat gold surfaces. Using our lgTS method, ultraflat gold surfaces with normals aligned along the <111> crystal plane and with a root-mean-square roughness of 0.275 nm (over 1 μm(2)) were created. The surfaces are fabricated on silica-based substrates which are highly solvent resistant and electrically insulating using silicate precursor solution (commonly known as "liquid glass") and concomitant mild heat treatment. We demonstrate the capabilities of such ultraflat gold surfaces by imaging nanoscale objects on top and fabricating microelectrodes as an example application. Because of the simplicity and versatility of the fabrication process, lgTS will have wide-ranging application in imaging, catalysis, electrochemistry, and surface science.

Metal Oxide Nanoparticle Mediated Enhanced Raman Scattering and Its Use in Direct Monitoring of Interfacial Chemical Reactions

“…To rule out the possibility that roughness might play a role in the enhancement, Au surfaces with a very high degree of flatness were prepared by a templatestripping method against mica. 25 These Au surfaces, with a root-mean-square (rms) roughness of 0.3 nm, showed similar levels of enhancement to the normal flat Au surfaces fabricated by thermal evaporation (Supporting Information Figure S1). Neither type of Au substrate showed any molecular signal in the absence of MONPs, confirming that Raman enhancements indeed only arise from the interaction between the MONPs and Au surfaces.…”

Optical and Structural Properties of Ultra‐thin Gold Films

“…[13] Later, Hatton et al [14] reported optical transmission measurements on ultra-thin gold films deposited on silanized glass, but did not compare the results to a detailed structural analysis or theoretically expected transmission spectra. The method of surface activation with mercapto-silane is easier and less costly than some other fabrication procedures reported recently [15,16] and does not compromise the optical quality of ultra-thin films, as is the case when metallic adhesion/seeding layers (typically Ti, Cr, Ge or Ni) are used. [17] It should be noted that a substantial amount of research has also been devoted to ultra-thin silver films and their optical properties, where many of the same problems and applications are encountered.…”

Ultra-thin films for plasmonics: a technology overview

“…A different approach involves evaporating Au on a mica substrate and then peeling it off from the initial substrate and attaching to a silica one [55,56]. This approach allows for extremely flat layers (RMS = 0.275 nm [55]) to be created (Figure 3), but it does not preclude the use of Reproduced with permission from [55].…”

“…This approach allows for extremely flat layers (RMS = 0.275 nm [55]) to be created (Figure 3), but it does not preclude the use of Reproduced with permission from [55]. metallic adhesion layers in order to insure good adhesion between the silica superstrate and the gold.…”

“…As with gold [55], a promising technique for obtaining thin smooth silver layers consists of silver deposition on smooth substrates with poor adhesion (mica, silica, silicon) and covering them with strongly adhesive materials like epoxy. Peeling off the obtained layer from the initial substrate -so-called template stripping [80], produces a metal layer with roughness dictated by that of the initial substrates.…”