Random crystal orientation and tensile strength of nanocrystalline dumbbell-shaped copper thick films electrodeposited from acidic aqueous solutions containing polyethylene glycol

Abstract

Nanocrystalline thick copper films with the thickness of ∼250 μm were electrochemically synthesized from an acidic aqueous solution containing polyethylene glycol (PEG) with the average molecular weight of 3,000 to investigate the preferential crystal orientation and mechanical properties such as microhardness and tensile strength. By addition of PEG to the electrolytic bath, the cathode potential was shifted to a less noble direction during the electrodeposition and the average crystallite size of electrodeposited copper thick films was decreased. The copper thick films electrodeposited from the solution without PEG exhibited a preferentially orientation in (220) texture while that obtained from the solution containing PEG was composed of nanocrystals with random crystal orientation that containing (111) and (200) textures. The micro-Vickers hardness, tensile strength, and elongation of the electrodeposited copper thick films reached up to 133 HV, 234 MPa, and 13.1%, respectively. These improvements in mechanical properties can be explained by the grain refinement effect and the random crystal orientation effect.