Selective Atomic Layer Deposition of Metals on Graphene for Transparent Conducting Electrode Application.

Although graphene has considerable potential as a next-generation transparent conducting electrode (TCE) material owing to its excellent optical transparency and flexibility, its electrical properties require further improvement for an industrial application. This study reports a pathway of doping graphene by selective atomic layer deposition (ALD) of metals to elevate electrical conductivity of graphene. The introduction of a novel Pt precursor [Dimethyl(N,N-dimethyl-3-butene-1-amine-N)platinum(II); CHNPt; DDAP] facilitates a low-temperature (165 °C) process. The sheet resistance (R) of graphene is reduced significantly from 471 Ωsq to 86.8 Ωsq after 200 cycles of Pt ALD, while the optical transmittance at 550 nm (T) is maintained above 90% up to 200 cycles due to the selective growth of Pt on the defects of graphene. Furthermore, comprehensive analysis, including metal (Ru, Pt, and Ni) ALD on graphene, metal (Ru, Pt, Ni, Au, and Co) evaporation on graphene, and change in the ALD chemicals, demonstrates that ALD allows efficient graphene doping and the oxygen affinity of metal is one of the key properties for efficient graphene doping. Finally, Pt ALD is applied to a multi-layer graphene to further reduce R down to 75.8 Ωsq, yet to be highly transparent (T: 87.3%) after 200 cycles. In summary, the selective ALD of metals opens a way of improving the electrical properties of graphene to a level required for the industrial TCE application and has a potential to promote a development of other types of functional metal-graphene composites.