  Atomically precise graphene nanoribbons (GNRs) are increasingly attracting
interest due to their largely modifiable electronic properties, which can be
tailored by controlling their width and edge structure during chemical
synthesis. In recent years, the exploitation of GNR properties for electronic
devices has focused on GNR integration into field-effect-transistor (FET)
geometries. However, such FET devices have limited electrostatic tunability due
to the presence of a single gate. Here, we report on the device integration of
9-atom wide armchair graphene nanoribbons (9-AGNRs) into a multi-gate FET
geometry, consisting of an ultra-narrow finger gate and two side gates. We use
high-resolution electron-beam lithography (EBL) for defining finger gates as
narrow as 12 nm and combine them with graphene electrodes for contacting the
GNRs. Low-temperature transport spectroscopy measurements reveal quantum dot
(QD) behavior with rich Coulomb diamond patterns, suggesting that the GNRs form
QDs that are connected both in series and in parallel. Moreover, we show that
the additional gates enable differential tuning of the QDs in the nanojunction,
providing the first step towards multi-gate control of GNR-based multi-dot
systems.
