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Cobalt electrodeposition involves hydrogen reduction reaction, and the proton supply in feature filling varies depending on the location because of the topographical characteristics, thereby resulting in changes on the electrode surface, such as changes in pH and hydrogen adsorption. Based on this phenomenon, void-free trench filling was performed using benzimidazole (BZI) as an additive, which has different suppression effects depending on pH. Linear sweep voltammetry experiments confirmed the change in suppression behavior of the additive according to pH. Chronoamperometric transients were performed at a fixed BZI concentration to confirm the potential region, wherein actual cobalt deposition was suppressed. Chronoamperometric analysis with various rotation rates was also conducted to demonstrate the effect of proton concentration near the electrode on the suppression effect of BZI. Finally, a void-free filling working mechanism in a low aspect ratio trench using BZI was proposed. This study proposes, a single additive, whose suppression behavior changes according to the change in pH of the electrode surface, by considering the pH of the cobalt deposition solution and pK a value of the additive. Furthermore, it was demonstrated that void-free filling can be performed even in a trench with a low aspect ratio.

Nitrous oxide (N 2 O) is a notorious greenhouse gas because of its higher global warming potential and longer lifetime than those of CO 2 and CH 4 . Here, we present a rational design of a highly stable and active electrocatalyst that surpasses the activity of conventional Pd catalysts for N 2 O reduction. Theoretical calculations predicted that the catalytic activity of surface Pd atoms in an Au@Pd core−shell structure can be increased by optimizing the thickness of the Pd shell. This prediction was confirmed by the catalytic activity of an Au substrate on which Pd overlayers of different thicknesses were precisely deposited using the atomic layer deposition method. By applying these findings, we synthesized Au@Pd nanoparticles with an optimal shell thickness that exhibited excellent catalytic activity for electrochemical reduction of N 2 O. The catalytic activity of Au@Pd with a Tafel slope of 0.105 V/dec was much higher than that of Pd/C (0.126 V/dec). Moreover, even after 1000 cycles, the activity decreased by only 16%, whereas it decreased by 44% on the Pd/C catalyst.

In this study, superconformal cobalt filling of submicron trenches by electrodeposition is investigated in the presence of 2-mercaptobenzimidazole (MBI), which suppresses both cobalt deposition and the hydrogen evolution reaction (HER). The mechanism through which this single additive enables superconformal cobalt filling is investigated. The formation and breakdown of the suppression layer are characterized by linear sweep voltammetry and chronoamperometry. The convection-driven local concentration of MBI exerts different suppressing effects on cobalt reduction and the HER, leading to a change in the deposition rate and the current efficiency of cobalt. These phenomena induce a deposition rate differential between the top and bottom of the submicron trench, enabling bottom-up cobalt filling with a V-shape profile.