Temporal Stability of Metal-Chloride-Doped Chemical-Vapour-Deposited Graphene

Graphene has proven to be a promising material for transparent flexible electronics. In this study, we report the development of a transfer and doping scheme of large-area chemical vapour deposited (CVD) graphene. A technique to transfer the as-grown material onto mechanically flexible and optically transparent polymeric substrates using an ultraviolet adhesive (UVA) is outlined, along with the temporal stability of the sheet resistance and optical transparency following chemical doping with various metal chlorides (M_xCl_yThe sheet resistance (R_S) and 550 nm optical transparency (%T₅₅₀) of the transferred un-doped graphene was 3.5 kΩ sq⁻¹ (±0.2 kΩ sq⁻¹) and 84.1 % (±2.9 %), respectively. Doping with AuCl₃ showed a notable reduction in R_S by some 71.4 % (to 0.93 kΩ sq⁻¹) with a corresponding %T₅₅₀ of 77.0 %. After 200 h exposure to air at standard temperature and pressure, the increase in R_S was found to be negligible (ΔR_S AuCl₃=0.06 kΩ sq⁻¹), indicating that, of the considered M_xCl_y species, AuCl₃ doping offered the highest degree of time stability under ambient conditions. There appears a tendency of increasing R_S with time for the remaining metal chlorides studied. We attribute the observed temporal shift to desorption of molecular dopants. We find that desorption was most significant in RhCl₃-doped samples whereas, in contrast, after 200 h in ambient conditions, AuCl₃-doped graphene showed only marginal desorption. The results of this study demonstrate that chemical doping of UVA-transferred graphene is a promising means for enhancing large-area CVD graphene in order to realise a viable platform for next-generation optically transparent and mechanically flexible electronics.