Difference in chemical reactions in bulk plasma and sheath regions during surface modification of graphene oxide film using capacitively coupled NH3 plasma

Abstract

Reduced graphene oxide (r-GO) films were obtained from capacitively coupled NH3 plasma treatment of spin-coated graphene oxide (GO) films at room temperature. Variations were evaluated according to the two plasma treatment regions: the bulk plasma region (Rbulk) and the sheath region (Rsheath). Reduction and nitridation of the GO films began as soon as the NH3 plasma was exposed to both regions. However, with the increase in treatment time, the reduction and nitridation reactions differed in each region. In the Rbulk, NH3 plasma ions reacted chemically with oxygen functional groups on the GO films, which was highly effective for reduction and nitridation. While in the Rsheath, physical reactions by ion bombardment were dominant because plasma ions were accelerated by the strong electrical field. The accelerated plasma ions reacted not only with the oxygen functional groups but also with the broken carbon chains, which caused the removal of the GO films by the formation of hydrocarbon gas species. These results showed that reduction and nitridation in the Rbulk using capacitively coupled NH3 plasma were very effective for modifying the properties of r-GO films for application as transparent conductive films.