Studies of Bis-(Sodium-Sulfopropyl)-Disulfide and 3-Mercapto-1-Propanesulfonate on/into the Copper Electrodeposited Layer by Time-of-Flight Secondary-Ion Mass Spectrometry

Abstract

Interactions of functional additives SPS (bis-(sodium-sulfopropyl)-disulfide), MPS (3‑Mercapto-1-Propanesulfonate), and Cl accumulated and incorporated on/into a copper electrodeposited layer were studied using time-of-flight secondary-ion mass spectrometry (TOF-SIMS) in combination with cyclic voltammetry measurements (CV). It was shown that the Cl and MPS surface coverage is dependent on the applied overpotential and concentration of Cl, SPS, or MPS in the solution. Detailed discussion on the mechanism of yielding CH2SO3−, C3H5SO3−, CuSC3H6SO3−, and CuS− fragments and their assignment to the gauche or trans conformation was proposed. The mechanism of the process of incorporation and re-adsorption of MPS on/into a copper surface under electrochemical conditions without and with chloride ions and its impact on electrochemical properties was proposed. Moreover, it was shown that the presence of chloride ions, the ratio gauche/trans of MPS molecules, as well as the ratio chloride/thiols demonstrate a high impact on the accelerating abilities. Comparative studies conducted under open circuit potential conditions on the nitinol and copper substrate allowed for the identification of specific reactions/interactions of MPS, or SPS and Cl ions on the nitinol and copper surface.

Interaction of Bis-(sodium-sulfopropyl)-Disulfide and Polyethylene Glycol on the Copper Electrodeposited Layer by Time-of-Flight Secondary-Ion Mass Spectrometry

“…For the base solution and after the addition of PEG, no characteristic fragments for PEG, SPS, or Cl were detected. Very few chloride ions in the form of Cu 2 Cl + were identified due to the accumulated impurities of chloride on the copper surface [ 22 , 62 , 63 ], and it was rather constant as a function of the applied overpotential.…”

“…However, an additional complementary mass spectrometry technique that provides molecular analysis of thin films on a copper surface is required. Time-of-flight secondary-ion mass spectrometry (TOF-SIMS) fulfills those expectations and was applied for electrodeposited copper surface analysis [ 22 , 50 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 ], serving very high detection limits (in the range of ppm) and a high lateral resolution for molecular imaging (below 1 µm).…”

“…Recently, we showed that static TOF-SIMS combined with cyclic voltammetry measurements can be successfully applied in molecular studies of polyethylene glycol in the presence of chloride ions during copper electrodeposition [ 22 ] and for investigations of MPS/SPS interactions with chloride ions [ 63 ]. In the latter study [ 63 ], it was shown that thiolate molecules were incorporated into the copper deposit. Moreover, the influence of thiolate and chloride surface coverage and the ratio of gauche/trans thiolate conformations on the accelerating abilities was studied.…”

“…Since the TOF-SIMS method cannot be used for in situ measurements due to the ultrahigh vacuum conditions in the analysis chamber, we designed and optimized an experimental condition that allowed us to evaluate the chemistry of the copper surface after electrodeposition. Instead of a flat substrate, which is routinely applied as a working electrode, nitinol wire was used and withdrawn at a controlled, constant speed from the electroplating bath during copper electrodeposition [ 22 , 63 ]. In this manner, the appropriate positions along the wire strictly corresponded to the applied overpotential points on the CV curve.…”

“…Moreover, due to the high concentration of copper sulfate in the solution, the method of rinsing the samples after the CV experiment was optimized to avoid, on the one hand, the crystallization of the copper sulfate and, on the other, to preserve a maximum amount of adsorbate material on the surface. More details can be found in our previous papers [ 22 , 63 ] and in Section 3 .…”