Appealing optoelectronic properties of p-type Cu-G transparent conductor prepared by Cu sputtering and thermal reduction of graphene oxide

Abstract

This article discusses the optoelectronic performance of Cu-graphene (Cu-G) film prepared by the sputtering of the Cu layer on graphene oxide (GO) before the thermal reduction process. Surface diffusion of Cu intervenes with the reduction mechanism of GO in a good way if the Cu is sufficiently thick after 120 s sputtering. The best crystal quality of Cu-G is indicated by the Raman spectra lowest Γ_G = 69 cm^–1 and highest I_D/I_G = 1.63. Originally, the thickness of Cu after 120 s sputtering is 12 nm while the thickness of spin-coated GO is 5.52 nm. After the thermal reduction, Cu-G is 2.1 nm with an additional 0.3 nm residual layer underneath. The optical transmittance of Cu-G film at λ = 550 nm is 89.3% and it has two surface plasmon resonances at 4.58 eV and 5.28 eV. The peaks of absorption at high energy UV possibly allow Cu-G to boost its electrical conductivity without costing its transmittance in visible light. In a dark condition, the measured sheet resistance is 54.07 Ω sq^–1, Hall mobility of holes majority carriers is 37.48 cm² V^–1 s^–1, and dc conductivity is 7.88 × 10⁴ S cm^–1. They can be translated into a relatively high figure-of-merit of transparent conductor equivalent to 59.9. The stable processing of Cu-G film makes it promising to integrate this process into the fabrication of relevant optoelectronic devices.