Synergistic study on electrochemically deposited thin film with a spectrum from micro to nano range structures

Abstract

Thin films are deposited onto bulk materials (substrates) to achieve properties unattainable or not easily attainable in the substrates alone. The film thickness usually varies from few nanometers to a maximum value of 1 μm. Cavitation, irradiation of liquid with high intensity ultrasound, as a means of altering the crystallization process is achieved by the repeated creation and collapse of microscopic bubbles inside the solution. It is at the solid-liquid interface that electrochemical techniques may be employed to detect the possible influence of sonication on electrochemical nucleation and growth of clusters. In this work we prepare the copper thin film by sonoelectrosynthesis method at different temperature, acid and concentration of electrolyte. Films are characterized by XRD, SEM, AFM, and study of the mechanical properties is done by nanaoidentation. Scahifker and Hills model was used for study of nucleation and growth phenomena for electrochemically deposited thin film by cyclic voltammetry and chronoamperometry. A potential of 450 mV (100 mV negative than the Nernst potential) was selected for the deposition procedure for all the conditions. The sole impact of sonication was experimented before the study of the coupling effect and was found to favor nucleation ahead of growth. The evidence of secondary nucleation in ultrasonic condition was also observed. The thickness of films lies in the range of 400-500 nm. The phases of the deposits are confirmed by the XRD analysis. The nucleation population density got increased from a low value to high value of acid concentrations. Comparison with the theoretical models, it is apparent that copper follows progressive nucleation mode in increasing acid concentration. Hydrogen evolution was also imperative at increasing acid concentrations, however, ultrasound capable of degassing produced hydrogen free adherent surfaces. The facts are also confirmed by the morphological analysis by SEM and AFM. The same trend is observed for the films with low temperatures. Among all the depositions copper films at – 4 °C is the smoothest. Increasing metal ion concentrations produces finer and harder deposits. Films are rougher at 0.1 M as compared to that of 0.025 M. The grains are found to vary from 400 nm to 50 nm at various conditions with the average roughness factors from 300 nm to 14 nm.