Morphological Surface Study of Silver Electrodeposition by Kinetic Monte Carlo‐Embedded Atom Method

Abstract

Herein, a kinetic Monte Carlo (KMC) simulation of the 3D electrodeposition of Ag metal on Ag cathode surface is carried out under galvanostatic, different substrate temperatures, and current density conditions. Both deposition and diffusion processes are considered during the film electrodeposition, where each adatom diffuses via nearest‐neighbor hopping, exchange, and step‐edge atom exchange mechanisms. The interatomic interaction is described within the well‐known embedded atomic method (EAM) framework. The number of hopping, exchange, and step‐edge exchange mechanisms is evaluated using a power law of time n hop ∝ t α , n exch ∝ t β , and n step ∝ t γ , respectively. However, the step‐edge exchange mechanism depends on current density. The effects of deposited atom number, current density, and substrate temperature on the transitions of surface morphologies of the electrodeposited thin film are studied considering different combinations of the mechanisms. The results indicate that surface roughness increases when the number of deposited atoms and the current density increase, but when the substrate temperature increases the roughness decreases. In addition, the resulting surface has been found to be smooth if all diffusion mechanisms are involved in the electrodeposition phenomenon, while roughness occurs when diffusion takes place only via hopping mechanism. Furthermore, the surface roughness behavior is found to be related to clusters and islands distribution.

Kinetic Monte Carlo simulation of polycrystalline silver metal electrodeposition: scaling of roughness and effects of deposition parameters

“…This observation is in agreement with our previous simulation results on the surface roughness evolution of Ag/Ag(100) when three surface diffusion mechanisms are included. 49 Also, the same morphology evolution of iridium electrodeposition was observed experimentally. 67…”

“…For this reason, it is interesting to understand the effect of these conditions on the microstructure and growth morphology of the deposited film structures. Based on previous works, 49,61,66–69 the surface roughness can be calculated using the root mean square (RMS)where h i is the height of each surface atom i , h̄ is the average height for all atoms containing the surface, and N is the number of surface atoms. Dynamic scaling theory has been applied to analyze the evolution of surface roughness and the growth mechanism.…”

“…In this study, the surface roughness values calculated are higher when compared to a single crystal system. 49 This was due to the crystal defects found in the polycrystalline system such as grain boundaries and surface misorientation. The same behavior was observed experimentally for silver 73 and iridium 67 electrodeposition.…”

“…The diffusion of adatoms on the substrate surface is evaluated according to the exponential law which is written as an Arrhenius-type relationship 25,30,49,50 where ν is the atomic vibrational frequency (s −1 ), k B is the Boltzmann's constant (eV K −1 ), T is the temperature (K), Δ E is the change in the system's energy (eV) due to diffusion of an adatom from one stable adsorption site to the next one on the surface and E diff is the activation energy (eV) through one of surface diffusion mechanisms namely hopping, exchange, step-edge atom exchange, and grain boundary. The propensity function for the deposition process is written as followswhere i dep is the current density, e is the elementary charge (1.602 × 10 −19 C ), z 0 is the number of transferred electrons in reduction reaction and n dep is the number of possible deposition sites per unit area (sites m −2 ).…”

“…The propensity function for the deposition process is written as followswhere i dep is the current density, e is the elementary charge (1.602 × 10 −19 C ), z 0 is the number of transferred electrons in reduction reaction and n dep is the number of possible deposition sites per unit area (sites m −2 ). 49…”