  High-quality BN-Graphene-BN nanoribbon capacitors with double side-gates of
graphene are experimentally realized. Graphene electronic properties can be
significantly modulated by the double side-gates. The modulation effects are
very obvious and followed the metallic electrode behavior of numerical
simulations, while the theoretically predicted negative quantum capacitance was
not observed, possibility due to the over-estimated or weakened interactions
between the graphene nanoribbon and side-gate electrodes.
