First-principle simulation and design of graphene nanoribbon-based devices

Graphene nanoribbons(GNRs) have very rich electronic properties that depend on their widths and edge types. The band gaps of armchair GNRs strongly vary with their widths, which facilitate their applications in electronics, e.g., enable double barrier tunneling devices. Using bottom-up synthesis with di-bromo-bi-anthracene molecules, we can fabricate 7 atomic-layer armchair GNR and heterojunctions consisting of polymer, GNR, and an intermediate state structure. Our STS measurements and calculations show that band gaps are significantly different in GNR and intermediate structure segments. Using the non-equilibrium Green’s function method within density functional theory, we systematically investigate transport properties of different GNR/intermediate-structure heterojunctions as double barrier devices. We find that the numbers and lengths of the segments play important roles in device functioning and its I-V characteristics. The band alignment between the segments is also critical to achieve negative differential resistance (NDR). Combining first-principles simulations with experiment, we design new experimentally realizable GNR-based NDR devices.