Application of Electrochemical Impedance Spectroscopy (EIS) to Study the Effect of Different Deposition Parameters During Electroplating

Abstract

Copper (Cu) electrochemical deposition (ECD) on graphite was studied using Cu (noble metal) and Ni (active metal) to investigate nucleation and growth processes. Cu deposition was analyzed under varying potentials, ion concentrations, and temperatures in acidic and alkaline baths. In acidic conditions, different anodes (Pt and Cu) were used. The electrodeposition was investigated by various techniques i.e., cyclic voltammetry (CV), chronoamperometry (CA), electrochemical impedance spectroscopy (EIS), X-ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscope (SEM). From cyclic voltammetry the redox potentials have been chosen. The selected potentials (-0.16 V, -0.26 V, -0.36 V, -0.46 V, -0.56 V and -0.66 V) are the input parameters for i-t curve and EIS. The Nyquist plots revealed that copper ion charge transfer happens at high frequencies and is represented by a single capacitive constant, while at low frequencies copper ion diffusion from the solution to the electrode surface is represented by a Warburg-type contribution. The corresponding Bode plots represent a decent ability between the experimental and fitting data. The effect of potential on double-layer capacitance, diffusion coefficient, and diffusion layer thickness along the interface of electrode and electrolyte has been discussed extensively. The morphologies of the copper particles depositing on the surface of electrode also studied and it shows that copper deposits during electrodeposition resulted in a transition from spherical to dendritic structure as a function of deposition potential. The current density-time (i-t) curve was recorded by the potentiostatic method for 300 sec various potentials, concentrations and temperatures. At low Potentials (-0.16, -0.26 and -0.36 V) Nyquist plots reveal that copper ion charge transfer occurs at high frequency, while at low frequency copper ion mass transfer occurs. At high Potentials (-0.46, -0.56 and -0.66 V) Nyquist plots reveal that copper ion charge transfer occurs at low and high frequency. A fitted equivalent circuit was utilised to determine EIS parameters. The Nyquist plots revealed that copper ion charge transfer happens at high frequencies and is represented by a single capacitive constant, while at low frequencies copper ion diffusion from the solution to the electrode surface is represented by a Warburg-type contribution. The corresponding Bode plots represent a decent ability between the experimental and fitting data. The effect of potential on double-layer capacitance, diffusion coefficient, and diffusion layer thickness along the interface of electrode and electrolyte has been discussed extensively. The morphologies of the copper particles depositing on the surface of electrode also studied and it shows that copper deposits during electrodeposition resulted in a transition from spherical to dendritic structure as a function of deposition potential. The effect of pH on copper electroplating from a cyanide-free alkali medium was studied using copper sulphate, glycine, and sodium hydroxide. Electrochemical impedance spectroscopy (EIS) was used to analyze phase transformations under varying ion concentrations (0.01, 0.05, and 0.1 M), temperatures (5–20 °C), and deposition potentials (-0.56 V, -0.66 V, -0.76 V) determined from cyclic voltammetry (CV). The initial CV and potentiostatic studies reveal that the system is mixed kinetics control one. EIS study further supplement to the observations and it was observed that at low ion concentration (0.01 M) mass transfer was dominated. To complement the EIS results, a thorough phase and morphological examination of the copper films was done by means of X-ray diffraction (XRD), FESEM and AFM. It was revealed that at low ion concentration and potential, the film was not uniform. The films were uniform and consisted of a thin oxide layer with increase of potential and concentration and decrease of temperature. Based on the findings of double layer capacitance and charge transfer resistance along with film resistance, a plausible deposition mechanism has been proposed. However, there can be further critical use of EIS to gain deeper insights into the electrochemical phenomena occurring at the electrode-electrolyte interface to manipulate the film properties as per the desired applications. Again, electrochemical impedance spectroscopy (EIS), chronoamperometry, and cyclic voltammetry are used to investigate Ni electroplating from three different types of electrolytic baths- sulphate, chloride, and watts at silent and ultrasonic conditions. The nucleation and growth mechanism were examined using the EIS method, and it was found that ultrasound had a discernible impact. After applying an applied potential of -1.4 V to deposit nickel, two unique depressed semicircles were observed in the impedance spectrum. These semicircles' frequency and capacitance varied according to the different electrolyte compositions, providing insight into the deposit morphology. According to X-ray diffraction studies, crystallite size decreased in sulphate to chloride bath. Atomic force microscopy and scanning electron microscopy were used to analyse the surface morphology of films produced in the presence of ultrasound and silent condition.