Edge states and ballistic transport in zig-zag graphene ribbons: the role of SiC polytypes

• Published in: arXiv.org
• Main Authors: Miettinen, A L, Nevius, M S, W Ko, Kolmer, M, A -P Li, Nair, M N, Taleb-Ibrahimi, A, Kierren, B, Moreau, L, Conrad, E H, Tejeda, A
• Format: Paper Journal Article
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 12.03.2019
• Subjects: Bonding strength; Conductors; Graphene; Physics - Materials Science; Physics - Mesoscale and Nanoscale Physics; Polytypes; Ribbons; Tapes (metallic)
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.1903.05185

Zig-zag edge graphene ribbons grown on 6H-SiC facets are ballistic conductors. It has been assumed that zig-zag graphene ribbons grown on 4H-SiC would also be ballistic. However, in this work we show that SiC polytype matters; ballistic graphene ribbons only grow on 6H SiC. 4H and 4H-passivated ribbons are diffusive conductors. Detailed photoemmision and microscopy studies show that 6H-SiC sidewalls zig-zag ribbons are metallic with a pair of n-doped edge states associated with asymmetric edge terminations, In contrast, 4H-SiC zig-zag ribbons are strongly bonded to the SiC; severely distorting the ribbon's \(\pi\)-bands. \(\text{H}_2\)-passivation of the 4H ribbons returns them to a metallic state but show no evidence of edge states.