Self-assembled triangular graphene nanostructures: Evidence of dual electronic response Thais Chagas a , Marta Pelc b , Pedro H.R. Gonçalves a , Igor Antoniazzi a , Jhon W. Gonz  alez b , Andres Ayuela b , Jo ~ ao Marcelo J. Lopes c , Myriano H. Oliveira Jr. a , Rogerio Magalh ~ aes-Paniago a , Angelo Malachias a, * a Departamento de Física, Universidade Federal de Minas Gerais, Av. Pres. Antonio Carlos, 6627, Belo Horizonte, Brazil b Centro de Fisica de Materiales, CFM-MPC CSIC-UPV/EHU, Donostia International Physics Center (DIPC) and Departamento de Fisica de Materiales, Facultad de Quimicas, UPV-EHU, 20018, San Sebastian, Spain c Paul-Drude-Institut für Festk€ orperelektronik, Leibniz-Institut im Forschungsverbund Berlin e.V., Hausvogteiplatz 5-7,10117, Berlin, Germany article info Article history: Received 18 July 2018 Received in revised form 27 September 2018 Accepted 17 October 2018 Available online 24 October 2018 abstract Structural and electronic properties of bilayer graphene films and nanostructures obtained through the graphitization of SiC(0001) were investigated in this work using scanning tunneling microscopy and spectroscopy. We report on the observation of triangular nanostructures which result from extended stacking faults in the SiC substrate and their effects on graphene layers that are formed on top of them. Spectroscopic measurements revealed distinct electronic responses as a function of the local hydrogen intercalation. Spectroscopic signatures ranging from single- to double-layer graphene, as well as inter- mediate states were observed as a consequence of the (in)complete hydrogen intercalation process. High resolution topographic scanning tunneling microscopy images at resonant bias voltages inside triangular nanostructures reveal that the bottom layer of the bilayer graphene film is still bonded to the substrate. Therefore, the triangular nanostructures present edges and facets with the coexistence of carbon atoms in sp 3 and sp 2 hybridizations. Using atomistic calculations we have modeled the local density of states of these objects reproducing their electronic response. The generation of regions with distinct electronic responses is potentially interesting for high-density data storage with hidden bit capabilities. © 2018 Elsevier Ltd. All rights reserved. 1. Introduction Graphene has emerged as an extremely promising material for plasmonics and optoelectronics applications, which rely on the very singular properties of its surface plasmons, namely their tunable amplitude and wavelength [1], relatively long propagation distances [2] and electromagnetic energy confinement in small volumes [3]. Engineering of graphene electronic structures is currently mandatory for the understanding of novel phenomena as well as to develop new technologies based on this material. There are different approaches aiming the accomplishment of this task: stacking graphene layers, choosing an appropriate substrate (due to interface effects) and the fabrication of graphene nanostructures with deterministic behavior, for instance. Regarding the graphene stacking, the band structure of this material can be drastically changed, depending on the relative orientation and number of the stacked layers [4e6]. The role of interface effects is also extremely relevant, since all atoms of a graphene layer are directly exposed to the surrounding environment. This effect is clearly noticeable on monolayer graphene grown directly on top of a SiC(0001) surface, which results in lower carrier mobility due to its strong interaction with the substrate. In this particular case, the electronic properties of free standing graphene can be recovered by passivating the graphene/SiC interface with H atoms [7]. An intensive effort in plasmonics and nano-electronics has been directed to the study of nanostructures, such as metallic nano- particles [8e12], graphene/metals hybrid nanostructures [13e19] and graphene nanostructures [20e23]. In this context, graphene nanostructures became especially interesting, since their optical and electronic properties can be tailored by the influence of their shape, size and edge chirality, adding extra functionalities to the already very singular graphene properties [20,21]. Theoretical and * Corresponding author. E-mail address: angeloms@fisica.ufmg.br (A. Malachias). Contents lists available at ScienceDirect Carbon journal homepage: www.elsevier.com/locate/carbon https://doi.org/10.1016/j.carbon.2018.10.059 0008-6223/© 2018 Elsevier Ltd. All rights reserved. Carbon 142 (2019) 580e591