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Electron Transport Properties of Graphene-Graphyne-Graphene Transistors: First Principles Study

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.