  On the basis of first-principles computational approaches, we present a new
method to drive zigzag graphene nanoribons (ZGNRs) into the half-metallic state
using a ferroelectric material, poly(vinylidene fluoride) (PVDF). Owing to
strong dipole moments of PVDFs, the ground state of the ZGNR becomes
half-metallic when a critical coverage of PVDFs is achieved on the ZGNR. Since
ferroelectric polymers are physisorbed, the direction of the dipole field in
PVDFs can be rotated by relatively small external electric fields, and the
switching between half-metallic and insulating states may be achieved. Our
results suggest that, without excessively large external gate electric fields,
half-metallic states of ZGNRs are realizable through the deposition of
ferroelectric polymers and their electronic and magnetic properties are
controllable via noninvasive mutual interactions.
