Silver deposition on silicon and glassy carbon. A comparative study in cyanide medium

Abstract

Nucleation and growth during Ag deposition on n-Si (111) have been studied and compared with results obtained on glassy carbon (GC). The initial stages of metal deposition from a cyanide electrolyte (pH 14) were investigated using conventional electrochemical techniques combined with AFM and SEM. Relevant kinetic parameters were obtained from the analysis of current transients on the basis of existing models for electrochemical nucleation and diffusion controlled growth. On n-Si a clear change in the Ag deposition mechanism from progressive ( E=−0.80 V vs. standard hydrogen electrode, SHE) to instantaneous ( E=−0.90 V vs. SHE) nucleation is observed, while on GC an intermediate behaviour is found at both potentials. A strong dependence of the nucleation site density N 0 with potential E was observed on both Si and GC, being this effect particularly important in the case of the semiconductor. Therefore, the driving force for Ag nucleation (supersaturation) on Si was varied both by changing the electrode potential E at c AgCN =constant and the concentration c AgCN at E=constant. On silicon, the critical silver nucleus was found to be composed by one atom within the studied potential range. The stability of the Ag clusters in the cyanide electrolyte was found to be strongly influenced by the presence of oxygen. Studies of the solid state n-Si/Ag contact indicate an ideal Schottky behaviour and the formation of a high quality junction.