Electrocrystallization of metallic thin films on different substrates: Effect of operating parameters

Abstract

Thin films are two dimensional layers with a thickness usually in the order of nanometers to microns, which is negligible when compared to the bulk of a material. Thin films play a vital role in many prospective fields like energy, mechanical and metallurgical solutions. The current work focuses on the grain growth, crystallinity and induced stress in copper thin films synthesized by electrodeposition on graphite and stainless steel (SS) substrates. Cu thin film deposition was carried out (i) at a constant voltage (0.35V) with varying temperature of deposition and (ii) at constant (room) temperature with varying voltage for each substrate. The nucleation and grain growth behavior of Cu on Graphite was studied by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). Induced stress of the film was calculated from Stoney formula from the surface profilometer data. It was observed that in case of fixed voltage tests, low temperature (10°C) was not favorable for the grain growth and higher grain growth was observed with increase in bath temperature (18 & 20°C). Similarly, for fixed temperature tests, higher deposition voltage (1.3V) resulted in high nucleation rate and grain growth than low voltage values (0.7 & 1.0 V). XRD analysis revealed that crystallinity of the Cu film was much better in case of graphite substrate compared to SS substrate. It may be due to the favorable crystal structure of the SS substrate. Stress condition obtained by profilometer tests revealed the trend of varying stress condition based on the temperature and substrate. Tensile stress condition is detrimental for thin film as compressive nature prevents cracking.