The influence of 3,5-diamino-1,2,4-triazole (DAT) on the electrochemical reduction of carbon dioxide to carbon monoxide on a silver electrode was studied via in situ surface-enhanced Raman spectroscopy (SERS). SERS bands obtained in the absence of DAT indicate potentialdependent adsorption of the CO product to bridge and 3-fold hollow sites. With the addition of DAT, CO adsorption to less-coordinated surface sites was found, including a physisorbed or non-coordinating site that exhibited no significant Stark vibrational shift. Raman peaks associated with adsorbed DAT observed at the same potentials as this species suggest that the ligand promotes weaker CO adsorption, which may be responsible for the high efficiency of the AgDAT catalyst. The observation of potential-dependent methylene stretching vibrations indicates the presence of surface hydrocarbon species while the presence of C-D stretches in deuterated electrolyte confirm that these hydrocarbons are generated as a CO 2 reduction byproduct.1.90 V 9 , indicating a large activation barrier to product formation. This large activation barrier has led to suggestions that other species might be involved in CO 2 reduction in aqueous solution, particularly HCO 3 -, since CO 2 dissolved in water exists in equilibrium with HCO 3 -, which is far For Ar control trials, the pH was reduced through the addition of HClO 4 (Optima, Fischer Scientific) to match. A 1 M KOD deuterated electrolyte was prepared by diluting 40 wt % KOD (98 atom % D, Aldrich) in D 2 O (99.9% D, Cambridge Isotope Laboratories).

We evaluate the effect of chain length for a series of alkyl sulfonic acid additives on Cu electrodeposition by using a combination of electrochemical and Raman spectroscopic methods.

We investigate the mechanism of 3-mercapto-1-propanesulfonate (MPS) acceleration of Cu electrodeposition in the presence of Cl– through comparison with the inactive but related model compounds 1-butanesulfonate and 1-butanethiol (BuSH). In situ shell-isolated nanoparticle-enhanced Raman spectroscopy was used to evaluate these additives as a function of potential. MPS adsorbs to the Cu electrode in the presence of Cl– through the thiol functional group. Density functional theory calculations reveal that the adsorption of thiol has a depolarizing effect on the strength of the interaction between adsorbed Cl– and the electrode surface, the consequences of which are observed spectroscopically. The sulfonate moiety does not interact directly with the electrode. However, cyclic voltammetry used to assess the permeability of adsorbed MPS and BuSH adlayers indicates that the sulfonate group has a more direct role in Cu deposition beyond simple disruption of the surface layer.

We investigate the behavior of Cu plating bath suppressor additives poly(ethylene glycol) (PEG) and poly(propylene glycol) (PPG) using normal Raman spectroscopy, surface-enhanced Raman spectroscopy (SERS), and electrochemical quartz crystal microbalance (QCM) measurements. Raman and SERS show a clear spectroscopic trend of increased intensity in higher wavenumber modes in the CH stretching region as the environment is changed from pure material to solution to surface for both PEG and PPG. The spectral changes associated with PEG are larger than those associated with PPG, suggesting that the relatively more hydrophilic PEG undergoes more conformational changes upon surface association relative to the more hydrophobic PPG. Calculations show that the observed spectroscopic trend is associated with increased gauche character in the polymer backbone. QCM measurements show PEG adsorbs to the surface only in the presence of Cl − , while PPG adsorbs to the surface both with and without Cl − present. In the presence of Cl − , PPG forms a denser surface layer (0.598 μg/cm 2 ) compared to PEG (0.336 μg/cm 2 ) on a Cu underpotential deposition (UPD) layer on Au. These differences are consistent with the increased hydrophobicity of PPG relative to PEG.

We evaluate the effect of chain length for a series of alkyl sulfonic acid additives on Cu electrodeposition by using a combination of electrochemical and Raman spectroscopic methods. The combination of these methods suggests that effective Cu electrodeposition acceleration processes require: 1) direct tethering of mercaptoalkylsulfonate species to the electrode, 2) partial desolvation of Cu2+ by the sulfonate group to minimize its solvent reorganization energy, and 3) stabilization of Cu+ adjacent to the electrode surface by addition of halide. Finally, we use the cis-trans ratio idea developed for SPS to examine the effect of inhibitors on SPS activity. We also investigate the behavior of Cu plating bath suppressor additives poly(ethylene glycol) (PEG) and poly(propylene glycol) (PPG) using normal Raman spectroscopy, surface-enhanced Raman spectroscopy (SERS), and electrochemical quartz crystal microbalance (QCM) measurements. Raman and SERS show a clear spectroscopic trend of increased intensity in higher wavenumber modes in the CH stretching region as the environment is changed from pure material to solution to surface for both PEG and PPG. The spectral changes associated with PEG are larger than those associated with PPG, suggesting that the relatively more hydrophilic PEG undergoes more conformational changes upon surface association relative to the more hydrophobic PPG. In the presence of Cl-, PPG forms a denser surface layer compared to PEG on a Cu underpotential deposition (UPD) layer on Au. These differences are consistent with the increased hydrophobicity of PPG relative to PEG.

Damascene processing of copper interconnects for integrated circuits requires void-free filling of high aspect ratio trenches and vias.  A combination of organic additives is commonly used to achieve bottom-up or superfilling of these features by electrochemical plating.  To better understand the surface interactions of brightening agents, 3-mercapto-1-propanesulfonate (MPS) was studied by in situ shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS).  The influence of each functional group was discerned by individually testing butanethiol and butanesulfonate as model compounds.  In an acidic solution of copper sulfate, MPS coadsorbs with sulfate.  Butanethiol displays similar adsorption behavior, but butanesulfonate demonstrates no Raman bands attributed to surface adsorption.  This strongly suggests that the sulfonate moiety does not interact significantly with the Cu substrate, and MPS adsorption occurs through the thiol linkage.  When chloride is added, sulfate is displaced and both MPS and butanethiol coadsorb with the halide.  However, the Cu-Cl stretching vibration is weaker in the presence of these additives than it is with Cl- alone.  In addition to spectroelectrochemical experiments, Cu deposition processes with these additives were also monitored by electrochemical quartz crystal microbalance measurements.  Butanethiol is more resistant than MPS to both Cu deposition and stripping, which confirms that the sulfonate group plays an important role in facilitating Cu deposition.