Nano-Scale Corrugations in Graphene: A Density Functional Theory Study of Structure, Electronic Properties and Hydrogenation Antonio Rossi, †,‡ Simone Piccinin, §,∥ Vittorio Pellegrini, ‡,⊥ Stefano de Gironcoli, ∥,§ and Valentina Tozzini* ,⊥,# † Dipartimento di Fisica ‘E. Fermi’, Universita ̀ di Pisa Largo B. Pontecorvo 3-56127 Pisa, Italy ‡ Graphene Laboratories, IIT Istituto Italiano di Tecnologia, Via Morego, 30 16163 Genova, Italy § CNR-IOM DEMOCRITOS c/o SISSA, Via Bonomea 265, 34136 Trieste, Italy ∥ SISSA, Scuola Internazionale Superiore di Studi Avanzati, via Bonomea 265, 34136 Trieste, Italy ⊥ Istituto Nanoscienze, CNR, Piazza San Silvestro 12, 56127 Pisa, Italy # NEST-Scuola Normale Superiore, Piazza San Silvestro 12, 56127 Pisa, Italy * S Supporting Information ABSTRACT: Graphene rippled at the nanoscale level is gathering attention for advanced applications, especially in the field of nanoelectronics and hydrogen storage. Convexity enhanced reactivity toward H was demonstrated on naturally corrugated graphene grown by Si evaporation on SiC, which makes this system a platform for fundamental studies on the effects of rippling. In this work, we report a density functional theory study on a model system specifically designed to mimic graphene on SiC. We first study the supercell geometry and configuration that better reproduce the corrugated monolayer. The relatively low computational cost of this model system allows a systematic study of the dependence of stability, structure, and electronic properties of graphene subject to different levels of stretching and corrugation. The most representative structure is then progressively hydrogenated, imitating the exposure to atomic hydrogen, and stability, structural and electronic properties are evaluated as a function of hydrogenation. Our results quantitatively reproduce the measured evolution of electronic properties as a function of hydrogenation, offering the possibility of evaluating the coverage by means of STS measurements. The dependence of hydrogen binding energy on coverage extends our previous results on reactivity of corrugated graphene, including the effect of H clustering. This work reports quantitative results directly comparable with experimental measurements performed on epitaxial graphene on SiC and reveals the quantitative interplay between local structure, electronic properties and reactivity to hydrogen, which could be used to design devices for flexible nanoelectronics and for H storage. 1. INTRODUCTION The interaction between hydrogen and graphene has recently received much attention, due to its potential interest for different technological applications. While graphene is a high mobility conductor, 1 its alkane counterpart, graphane, 2 obtained covalently bonding one hydrogen atom to each carbon site, is a wide band gap insulator. 3 Partially hydro- genated graphene displays intermediate properties: 4 stripped graphane/graphene hybrids are semiconductors with tunable band gaps; 5−9 different hydrogen decorations, such as graphane islands, 10 have potentially interesting transport properties and possible applications in nanoelectronics. Clearly, exploiting these properties requires a control of the hydrogenation at the nanoscale. Graphene hydrogen interaction is clearly also interesting for H storage applications. Because of its low molecular weight, graphene is potentially a storage mean with high gravimetric capacity. 11 However, molecular hydrogen is very weakly physisorbed by means of van der Waals interactions, 12 and although these are stronger in nanostructured 13,14 or multi- layered graphene, 15 low temperatures are necessary for stable storage. 16,17 Chemisorption was alternatively considered: the covalent bond of hydrogen to graphene is robust, leading to stable storage up to high temperature. But chemi(de)sorption of H 2 are high barrier processes (∼1−1.5 eV/atom 18 ) implying slow loading/release kinetics. Chemical (e.g., with Pd 19 ) or “alternative” catalysis (e.g., electric fields 20 or N-substitutional doping 21 ) were also suggested. We recently proposed that the two-dimensionality and structural/mechanical properties of graphene could be also Received: November 14, 2014 Revised: March 18, 2015 Published: March 18, 2015 Article pubs.acs.org/JPCC © 2015 American Chemical Society 7900 DOI: 10.1021/jp511409b J. Phys. Chem. C 2015, 119, 7900−7910