Rational fabrication of a gold-coated AFM TERS tip by pulsed electrodeposition

Abstract

Reproducible fabrication of sharp gold- or silver-coated tips has become the bottleneck issue in tip-enhanced Raman spectroscopy, especially for atomic force microscopy (AFM)-based TERS. Herein, we developed a novel method based on pulsed electrodeposition to coat a thin gold layer over atomic force microscopy (AFM) tips to produce plasmonic TERS tips with high reproducibility. We systematically investigated the influence of the deposition potential and step time on the surface roughness and sharpness. This method allows the rational control of the radii of gold-coated TERS tips from a few to hundreds of nanometers, which allows us to systematically study the dependence of the TERS enhancement on the radius of the gold-coated AFM tip. The maximum TERS enhancement was achieved for the tip radius in the range of 60-75 nm in the gap mode. The coated gold layer has a strong adhesion with the silicon tip surface, which is highly stable in water, showing the great potential for application in the aqueous environment.

Controllable Fabrication of Au-Coated AFM Probes via a Wet-Chemistry Procedure

“…After 70 nm, the Raman intensity begins to reduce. However, Ren’s group found that the optimized thickness of Au layer was about 60–75 nm, and the theory agreed with the experimental result [ 30 , 31 ]. According to their calculation model, the tip was regarded as a conical taper terminated by a hemisphere of various radii.…”

Tip‐Enhanced Raman Spectroscopy: A Tool for Nanoscale Chemical and Structural Characterization of Biomolecules

“…A buffer layer, either metallic (Ag or Cu) or dielectric (SiO x or AlF 3 ), can also be inserted to improve enhancement and adhesion properties of the metal coating, and reduce the peeling‐off process during scanning. Reproducible and cost‐effective Au and Ag metallization of AFM tips can alternatively be performed by using chemical deposition methods, such as electrodeposition or electroless deposition methods. These methods (the mirror reaction, for instance) are convenient to produce metal coatings on nonconductive surfaces (SiO 2 , Si, …) .…”

Applications of Raman spectroscopy in two-dimensional materials

“…They focus on obtaining a large enhancement while ensuring durability and stability. 58,59 Three techniques, including STM, AFM and SFM, were applied in SPM systems with di®erent nanotips (Fig. 3).…”