Diverse Transport Behaviors in Cyclo[18]carbon-Based Molecular Devices.

Scientists have been trying to synthesize ring-shaped pure carbon molecules for a half century. A breakthrough was made recently, and cyclo[18]carbon (C18) was produced successfully by bonding an 18-atom ring of carbon. Because of its potential application in molecular devices, it is natural and timely to study the transport behaviors of C18. Here we report the electron transport properties of the C18-ring connected to various electrodes, including 1D carbon chain, 2D graphene, and 3D silver electrodes, using density-functional theory combined with the nonequilibrium Green's function technique. Diverse transport behaviors are found for the C18 molecular devices, including an Ohmic characteristic, a quasi Schottky feature, and a current-limiting function. The origin and mechanism of unique nonlinear I-V characteristics are investigated by the transmission pathway, transmission spectra, density of states, and molecular frontier orbital theory. This study provides a theoretical guide for exploring the next-generation molecular devices based on this newcomer to the family of carbon allotropes.