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.