Vapour transport deposition of fluorographene oxide films and electro-optical device applications

Fluorographene is one of the most interesting 2D materials owing to its span of electronic properties, from a conductor to wide-gap insulator, controlled by the compositional carbon to fluorine ratio. Unlike the chemically inert graphene, fluorographene is recognized for its rich chemistry, particularly at ambient, allowing tailoring its physical properties. Here, we report on single step, catalyst free, wafer-scale synthesis of fluorographene oxide (FGO) ultra-thin films (∼4 nm thickness) by physical vapour deposition. The FGO, possessing 7% fluorine content, comprises few-nanometer domains of sp²-sp³ carbon with high thermal stability, as confirmed by several analytical methods. We show that FGO can be utilized as an active hetero-layer on a few-layer MoS₂ field effect transistor (FET), significantly improving the performance of MoS₂ optoelectronic devices with an extended spectral response towards the near infrared and responsivity of up to 6 A/W. The FGO-MoS₂ band alignment, as derived from the measured work function of FGO (4.69 eV), indicates a plausible photoconductive gain mechanism with a fast transit time of holes mediated by FGO quasi-continuous defect states.