Deposition of oxygen-functionalized graphene on copper by conventional and modified electrophoretic deposition with bipolar high-impulses

Abstract

The present paper investigated the deposition of oxygen-functionalized graphene (GO) on copper (Cu) substrates using a low-voltage electrophoretic deposition (EPD) compared to a bipolar high-impulse electrophoretic deposition (HI-EPD) as a function of electrode distance and deposition time. The conventional deposition was conducted with a constant voltage of +10 V. Bipolar HI-EPD used 1.0 μs period pulses, alternating pulses of +600 and −600 V. The pulses train consisted of four individual pulses, two positive and two negative (2p+ and 2p−), with a 20.0 μs off-time between the pulse sets. GO films were characterized by scanning electron microscopy, water contact angle, atomic force microscopy, relative sheet resistance, Raman, x-ray photoelectron spectroscopy, and adhesion tests. For conventional EPD, the minimal deposition time necessary to obtain homogeneous GO films was 10 min with a distance between electrodes of 1.0 cm. When bipolar HI-EPD was used, a homogeneous deposition was obtained in 5.0 min. The samples with GO films had an average reduction in the contact angle by 28% in comparison to the Cu surface, showing hydrophilic behavior, and an increase in relative sheet resistance compared to Cu by 104 times for deposition through conventional EPD and up to 105 times for deposition through bipolar HI-EPD. The presence of GO increased the surface roughness. The bipolar HI-EPD showed no apparent water electrolysis even under high-voltage pulse deposition. Thus, the bipolar HI-EPD demonstrates a promising process for producing homogeneous film depositions of GO nanoparticles in an aqueous medium with lower deposition time.