Atomic-Level Electronic Properties of Carbon Nitride Monolayers
Dingguan Wang, Zishen Wang, Wei Liu, Arramel Arramel, Jun Zhou, Yuan Ping Feng, Kian Ping Loh, Jishan Wu, Andrew T. S. Wee
Abstract
Heteroatom-doped carbon-based materials are of significance for clean energy conversion and storage because of their fascinating electronic properties, low cost, high durability, and environmental friendliness. Atomically precise fabrication of carbon-based materials with well-defined heteroatom-dopant positions and atomic-scale understanding of their atomic-level electronic properties is a challenge. Herein, we demonstrate the bottom-up on-surface synthesis of 1D and 2D monolayer carbon nitride nanostructures with precise control of the nitrogen-atom doping sites and pore sizes. We also observe an electronic band offset at the C–N heterojunction. Using high-resolution scanning tunneling microscopy, the atomic structure of the as-prepared carbon nitride nanoporous monolayers are revealed, indicating successful and precise control of the structures and N atom doping sites. Furthermore, corroborated by theoretical calculations, scanning tunneling spectroscopy measurements reveal a valence band shift of 140 meV that results in an electric field of 2.9 × 108 V m–1 at the C–N heterojunction, indicating efficient separation of the electron–hole pair at the N doping site. Our finding offers direct atomic-level insights into the local electronic structure of the heteroatom-doped carbon-based materials.