title: Temporal Stability of Metal-Chloride-Doped Chemical-Vapour-Deposited Graphene.
abstract: 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 (Mx Cly The sheet resistance (RS ) 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 RS 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 RS was found to be negligible (ΔRS AuCl3 =0.06 kΩ sq(-1) ), indicating that, of the considered Mx Cly species, AuCl3 doping offered the highest degree of time stability under ambient conditions. There appears a tendency of increasing RS 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.
authors.affiliation: Electrical Engineering Division, Department of Engineering, University of Cambridge, CB3 0FA, Cambridge, United Kingdom. mhk29@cam.ac.uk.
authors.forename: Moon H
authors.initials: MH
authors.lastname: Kang
authors.affiliation: Electrical Engineering Division, Department of Engineering, University of Cambridge, CB3 0FA, Cambridge, United Kingdom.|College of Information Science and Electronic Engineering, Zhejiang University, 310027, Hangzhou, P. R. China.
authors.forename: William I
authors.initials: WI
authors.lastname: Milne
authors.affiliation: Electrical Engineering Division, Department of Engineering, University of Cambridge, CB3 0FA, Cambridge, United Kingdom. mtc35@cam.ac.uk.
authors.forename: Matthew T
authors.identifier: http://orcid.org/0000-0001-8631-3259
authors.initials: MT
authors.lastname: Cole
keywords: adsorption; chemical doping; graphene; surface energy; transparent flexible conductors