Electrodeposition of CoWP film II. Effect of electrolyte concentration

Abstract

CoWP films were electrodeposited on copper-coated silicon wafers from citrate electrolyte containing cobalt sulphate, sodium tungstate and sodium hypophosphite at room temperature potentiostatically. The effects of electrolyte concentration on thickness, composition and microstructure of the films were studied. It was observed that the deposition current density and thickness increased with increasing cobalt and hypophosphite ion concentrations, whereas an increase in tungstate ion concentration resulted in a decrease in current density and thickness. Films with larger variations of cobalt (from 64 to 83 at.%), tungsten (from 0.5 to 24 at.%) and phosphorus (from 6 to 21 at.%) were electrodeposited by controlling the concentrations of the electrolytes. X-ray diffraction studies suggested that films containing ∼20 at.% phosphorus were amorphous while films with lower phosphorus content were crystalline. SEM and AFM examinations showed that the size of crystallites and surface roughness were mainly dependent on the amount of phosphorus present in the films.