Transfer-free robust n-type graphene field-effect transistors for digital logic electronic devices

Graphene has been hailed as wonder materials for electronics due to its outstanding charge transport properties. However, its lack of an electronic bandgap has hindered its application to large-scale field-effect transistor (FET) circuits, thereby making bandgap opening a key priority. Further, the fabrication of graphene devices to date conventionally requires the transfer of graphene from its growth substrate to a target substrate, which introduces defects and deteriorates the device performance. To overcome these challenges, we demonstrate a transfer-free approach for the low-temperature growth (-100 degrees C) onto TiO2-x (-10 nm) buffer layer and in-situ nitrogen doping of monolayer graphene, which enables stretchable nitrogen-doped graphene-based FETs with cuttingedge performance and stability. Hybridizing a TiO2-x channel with the nitrogen-doped graphene, nitrogendoped graphene-based FETs could be achieved with an on-off ratio of -2 x 108 and an electron mobility of -1,500 cm2V- 1s- 1 for mainstream digital logic devices. Such devices exhibit high reproducibility and waferscale uniformity, thermal, bias-stress, long-term stability, and robust flexibility and stretchability. The scalability and versatility of this transfer-free approach for the flexible and stretchable FETs pave the way for highperformance nitrogen-doped graphene-based digital logic circuits.