Graphene and chemically functionalized graphene are two-dimensional materials exhibiting fascinating properties. Technological applications of these materials can emerge only from understanding and controlling structure and properties at the layer/atomic level. In this talk, I will report on our recent atomistic studies of the chemical structure and mechanical properties of both pristine and oxidized multilayer graphene films on SiC. I will first focus on graphene oxide and present results of a density functional theory study undertaken to interpret puzzling X-ray photoelectron spectroscopy and X-ray diffraction measurements. Secondly, I will report on atomic force microscope (AFM) indentation measurements of the perpendicular-to-the-plane elasticity of graphene-based films, and after presenting selected experimental results, I will focus on the computations carried out to elucidate the elastic behaviors of both the pristine and oxidized graphene films. Key topics discussed in this talk include (i) the chemical structure and mechanisms underlying the metastable character of epitaxial graphene oxide [1,2], (ii) the role played by moisture to influence the elastic modulus and structure of the graphene oxide films [3,4], and (iii) the unusual mechanical response exhibited by a bilayer graphene film on SiC when indented by an AFM tip [4].

[1] S. Kim, S. Zhou, Y. Hu, M. Acik, Y.J. Chabal, C. Berger, W. de Heer, A. Bongiorno, and E. Riedo, Room-temperature metastability of multilayer graphene oxide films, Nature Materials 11, 544 (2012).
[2] S. Zhou and A. Bongiorno, Density Functional Theory Modeling of Multilayer “Epitaxial” Graphene Oxide, Accounts of Chemical Research 47, 3331 (2014).
[3] S. Zhou, S. Kim, E. Di Gennaro, Y. Hu, C. Gong, C.-Y. Chang, X. Lu, H.-C. Chiu, C. Berger, W. de Heer, E. Riedo, Y.J. Chabal, C. Aruta, and A. Bongiorno, Film structure of epitaxial graphene oxide on SiC: Insight on the relationship between interlayer spacing, water content, and intralayer structure, Advanced Materials Interfaces 1, 1300106 (2014).
[4] Y. Gao, S. Kim, S. Zhou, H.-C. Chiu, D. Nélias, C. Berger, W. de Heer, R. Sordan, L. Polloni, A. Bongiorno, and E. Riedo, Elastic coupling between layers in two-dimensional materials, NaturMaterials 14, 714 (2015).