Hydrogen Co-Deposition Induced Phase and Microstructure Evolution of Cobalt Nanowires Electrodeposited in Acidic Baths

Abstract

The growth and deposition mechanism of electrodeposited cobalt nanowires (NWs) at different bath temperatures (25°C–60°C) in strongly acidic bath (pH of 2.0) is studied. CV scans show that hydrogen co-deposition is most pronounced in 50°C bath. X-ray diffraction patterns of Co NWs show that a mixture of hcp and fcc phases grows at 25°C, (200) textured fcc-Co phase grows at 50°C, and and (110) textured hcp-Co phase at 60°C, with these planes normal to the NW-axis. The magnetic properties studied by vibrating sample magnetometer show the change in coercivity, saturation field and magnetization reversal behavior is consistent with the phase of NW. Nucleation mechanism is explained on the basis of intermediates formation induced by the extent of hydrogen co-deposition leading to the change in nucleation overpotential and linked selection of the growth plane as per bath pH and temperature. Chronoamperometry study has confirmed the instantaneous and progressive growth mechanisms operative at 50°C and 60°C respectively and hydrogen co-deposition controlled grain size growth model is also put forth to understand the growth kinetics of fcc and hcp phase Co NWs. The suggested growth mechanism also consistently explains the growth in less acidic bath of pH 4.5.