Structure Specific Adsorbate Interactions at Electrodepositing Cu Interfaces

Abstract

Mechanistic understanding of interfaces during additive based electrochemical deposition of thin films is limited by lack of tools to discretely probe given features of deposits. Modern spectroelectrochemical methods that have enabled significant understanding, like surface-enhanced Raman and infrared spectroscopies (SERS and SEIRAS, respectively), are restricted by specimen geometry; SERS is closely linked to the use of rough plasmonically active surfaces while SEIRAS measurements is constrained to thin IR transparent metal films. More recently, the application of Au@SiO2 core-shell nanoparticles as “vibrational reporters” on plasmonically inactive surfaces has enabled collection of site-specific vibrational data on well-defined single crystal surfaces whereby the nanoparticle serves to channel the plasmonic energy to the nanoparticle-substrate interface. The present work utilizes this technique, Shell-Isolated Nanoparticle Enhanced Raman Spectroscopy (SHINERS) to track relative coverages of sulfonate, chloride and methylene moieties following super-conformal Cu electrodeposition on a patterned interface (Figure 1 a,b,d). Corroborated by computational finite-element results (Figure 1 c,d) and x-ray photoelectron spectroscopy measurements, the SHINERS measurements demonstrate that during early stages of electrodeposition, on an accelerator functionalized surface, the regions with more deposition have higher coverage of sulfonate species. As deposition continues dilation of the sulfonate concentration occurs following the continual decrease in surface area of the interface. Ultimately, this work reveals the benefit from the combined use of SHINERs, photoelectron spectroscopy and computational models to further our understanding of composite electroplating and resolve complex site-specific interfacial interactions. Figure 1