  A novel nanoelectronic device is constructed by graphyne that is robustly
connected between graphene electrodes, where graphyne is composed of hexagonal
carbon rings and carbon chains. Owing to similarities between the bond lengths
and unit cell shapes of graphene and graphyne, they have perfectly matched
interfacial structure at periodic locations, enabling the facilitated charge
transfer and heterostructural stability. Using a combined nonequilibrium
Green's function and density functional theory formalism, we have
systematically investigated the electron transport properties of
graphene-graphyne-graphene field effect transistors (FETs) by varying the
graphyne size and the carbon chain length. These devices exhibit excellent
switching behaviors with ON/OFF ratios on the order of 10^2-10^3. The ON/OFF
ratio increases as either of the graphyne size or the carbon chain length
increases. Noticeably, these devices sustain good FET features even at the
small graphyne size of 8.5 A, yielding ON/OFF ratio of 650 and transmission
energy gap of 0.8 eV, which suggests their potential applications for
fabricating highly-integrated circuits at the level comparable to molecular
devices. Their boron-nitrides analogues show similar qualitative behaviors for
the changes of the graphyne size and bias voltage, but they show higher ON/OFF
ratios for the smaller chain length in contrast to graphyne TFTs.
