Lanthanide complexes as molecular dopants for realizing air-stable n-type graphene logic inverters with symmetric transconductance

Abstract

An unprecedented air-stable, n-doped graphene field-effect transistor (GFET) with exceptionally enhanced mobility (500%), and concomitantly increased current density (∼10⁵ A cm⁻²), using lanthanide macrocyclic complexes [Ln(L₁)(NO₃)₃] (where Ln = La (1) or Ce (2)) is demonstrated. Such n-doped GFETs (n-GFETs) exhibit ambient stability for up to 7200 h, attributed to the inherent robustness of 1 and 2. Achieving stable and symmetric n-GFETs is mutually exclusive and elusive, underlining the significance of both high stability and symmetric electron- and hole-currents illustrated here. Interestingly, the influence of C–H⋯π interaction for the non-covalent charge-transfer between the dopant and GFET is established experimentally for the first time and strongly corroborated through computational investigations. Besides stabilizing n-doped GFETs, the C–H⋯π interaction unravels a previously unknown direction for electronic tuning of graphene. Importantly, spatial selectivity is achieved through sub-monolayer coverage (0.5–3.0 molecules per μm²) of the dopants using the femtojet dispensing route. This approach is synergistically combined with the air-stability of n-GFETs to realise complementary, bottom-gated logic inverters exhibiting the highest gain of 0.275 (at 2 V) and lowest power dissipation (∼30 μW), to realise next-generation molecular electronic devices.