Large-Area Epitaxial Growth of Curvature-Stabilized ABC Trilayer Graphene with Tunable Band Gap*

The physical properties of epitaxially-grown layered van der Waals (vdW) materials can be engineered to an extraordinary degree by manipulating the number of atomic layers, their compositions, and their relative stacking configurations and twist angles. vdW trilayer graphene (TLG) can stack in either a semi-metallic ABA configuration or a semi-conducting ABC configuration with a gate-tunable band gap but to this point has only been produced via exfoliation, which greatly limits its scientific and technological development. Here we present a scalable approach to epitaxial TLG growth via chemical vapor deposition that reliably enhances the fraction and size of ABC stacked TLG domains compared to other methods. The key insight is that nanoscale substrate curvature can locally stabilize ABC domains, typically leading to alternating regions of ABC and ABA on topographically corrugated growth substrates. Unambiguous electronic signatures of ABC-TLG were revealed by nano angle-resolved photoemission spectroscopy and infrared scanning near-field microscopy. The ABC fraction remains high after transfer onto a device substrate, as confirmed by transport measurements showing a sizable and tunable ABC-TLG band gap.