Abstract Organic additives play an important role in regulating film growth and properties in Cu electrodeposition. 3‑Mercapto‑1‑propane sulfonate (MPS) and its dimer bis(3‑sulfopropyl) disulfide (SPS) are representative accelerators that promote Cu electrodeposition rate. In this study, the formal reduction potential of SPS to MPS was determined by measuring the equilibrium constants of thiol–disulfide interchange reactions with the reference thiol/disulfide pairs by 1H nuclear magnetic resonance (1H NMR) spectroscopy. The calculated formal reduction potential of SPS to MPS was 0.153 V (vs. standard hydrogen electrode). Based on this calculation, the cell potentials of Cu(I)(thiolate) formation reaction with either SPS or MPS, which is a key reaction in accelerating mechanism, were also estimated by ultraviolet–visible absorption and 1H NMR spectroscopies: they were found to be 0.202 V and 0.214 V for SPS and MPS, respectively. The positive cell potential indicates that the formation of Cu(I)(thiolate) complexes is thermodynamically favorable in the presence of additives.

中文翻译：

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双（3-磺丙基）二硫化物和 3-巯基-1-丙磺酸在铜电沉积中的热力学特性

摘要 有机添加剂在调节铜电沉积薄膜的生长和性能方面起着重要作用。3-巯基-1-丙烷磺酸盐 (MPS) 及其二聚体双（3-磺丙基）二硫化物 (SPS) 是促进铜电沉积速率的代表性加速剂。在这项研究中，SPS 对 MPS 的正式还原电位是通过 1H 核磁共振（1H NMR）光谱测量硫醇-二硫化物交换反应与参考硫醇/二硫化物对的平衡常数来确定的。SPS 到 MPS 的计算形式还原电位为 0.153 V（相对于标准氢电极）。基于此计算，Cu(I)(硫醇盐)与 SPS 或 MPS 形成反应的细胞电位，这是加速机制中的关键反应，还通过紫外 - 可见吸收和 1 H NMR 光谱估计：发现它们对于 SPS 和 MPS 分别为 0.202 V 和 0.214 V。正电池电位表明，在添加剂存在下，Cu(I)(硫醇盐)配合物的形成在热力学上是有利的。