Atomic Structure of Epitaxial Graphene Sidewall Nanoribbons: Flat Graphene, Miniribbons, and the Confinement Gap

Irene Palacio (1) , Arlensiú Celis (2, 1) , Maya N. Nair (1) , Alexandre Gloter (2) , Alberto Zobelli (2) , Muriel Sicot (3) , Daniel Malterre (3) , Meredith S. Nevius (4) , Walt A. de Heer (4) , Claire Berger (4, 5) , Edward H. Conrad (4) , Amina Taleb-Ibrahimi (1) , Antonio Tejeda (2, 1)

1 SSOLEIL - Synchrotron SOLEIL
2 LPS - Laboratoire de Physique des Solides
3 IJL - Institut Jean Lamour
4 Georgia Institute of Technology [Atlanta]
5 NEEL - QuantECA - Circuits électroniques quantiques Alpes

Graphene nanoribbons grown on sidewall facets of SiC have demonstrated exceptional quantized ballistic transport up to 15 mu m at room temperature. Angular-resolved photoemission spectroscopy (ARPES) has shown that the ribbons have the band structure of charge neutral graphene, while bent regions of the ribbon develop a bandgap. We present scanning tunneling microscopy and transmission electron microscopy of armchair nanoribbons grown on recrystallized sidewall trenches etched in SiC. We show that the nanoribbons consist of a single graphene layer essentially decoupled from the facet surface. The nanoribbons are bordered by 1-2 nm wide bent miniribbons at both the top and bottom edges of the nanoribbons. We establish that nanoscale confinement in the graphene miniribbons is the origin of the local large band gap observed in ARPES. The structural results presented here show how this gap is formed and provide a framework to help understand ballistic transport in sidewall graphene.

Mots clés: Graphene; HR-XTEM; STM; atomic structure; band gap; ribbon

Domaines: Science des matériaux [cond-mat.mtrl-sci]

Irene Palacio, Arlensiú Celis, Maya N. Nair, Alexandre Gloter, Alberto Zobelli, et al.. Atomic Structure of Epitaxial Graphene Sidewall Nanoribbons: Flat Graphene, Miniribbons, and the Confinement Gap. Nano Letters, 2015, 15 (1), pp.182-189. ⟨10.1021/nl503352v⟩. ⟨hal-01271638⟩