Estimating electrodeposition properties and processes: Cu-Ag alloy at n-Si(001) and Ru substrates from acidic sulfate bath

In alloy electrodeposition, estimations of the initial transient and the potential vs. composition trend of the film system is important for material design, deposition procedure and the deposit characterization. However, solving the diffusion-migration-convection problem based on common simulation methods is often too burdensome and too resource-consuming for ordinary tasks in the context of alloy electrodeposition works. In this work, based on a stagnant diffusion layer model, we have proposed simple estimates on (1) the potential-composition curve, (2) the thickness of the initial deposit, and (3) the time interval to reach the steady state deposition. These estimates were validated by using a Cu-Ag acidic sulfate electrolyte, which upon electrodeposition results in an immiscible Cu-Ag alloy, both at n-Si(001) or at polycrystallline Ru substrates. The limiting current of Cu-Ag electrodeposition is compared with the numerical results given by Selman and Newman in 1970s [17], whereas the film composition deposited at the limiting current from various electrolyte constitutions is compared with the model suggest by Brenner based on stagnant diffusion layer model [21]. The proposed estimation methods show good agreement with the observed values, despite being highly simplified, since they are compared with the actual mass-transfer problem of ions under convection and migration.