Micro-Vickers Hardness of Cu and Cu2O Dual Phase Composite Films Electrodeposited from Acidic Aqueous Solutions Containing Polyethylene Glycol

Abstract

Metallic copper (Cu) and copper oxide (Cu2O) dual phase composite films were fabricated via a cathodic reduction process in an acidic aqueous solution dissolving polyethylene glycol (PEG) to investigate the structure and micro-Vickers hardness. By dissolving PEG in an aqueous electrolyte, the cathode potential was depolarized to the noble region during the electrodeposition, and the average crystallite size of electrodeposited Cu/Cu2O composite films was decreased down to around 40 nm. The metallic copper films electrodeposited from the solution without PEG was preferentially orientated in (220), while that containing PEG was composed of Cu and Cu2O dual phase composite films with random crystal orientation. The micro-Vickers hardness of the Cu/Cu2O composite films that were electrodeposited from the solution containing PEG was achieved up to 2.53 GPa. This improvement in mechanical performance can be explained by the grain refinement effect and the electrochemical phase transformation effect from a copper metallic state to the oxide.