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Ortho and Para Hydrogen Dimers on G/SiC(0001): Combined STM and DFT Study

2014; American Chemical Society; Volume: 31; Issue: 1 Linguagem: Inglês

10.1021/la504021x

1520-5827

Pablo Merino, Martin Švec, José I. Martínez, Pingo Mutombo, César González, José Á. Martín‐Gago, P. L. de Andrés, Pavel Jelı́nek,

Diamond and Carbon-based Materials Research

The hydrogen (H) dimer structures formed upon room-temperature H adsorption on single layer graphene (SLG) grown on SiC(0001) are addressed using a combined theoretical–experimental approach. Our study includes density functional theory (DFT) calculations for the full (6√3 × 6√3)R30° unit cell of the SLG/SiC(0001) substrate and atomically resolved scanning tunneling microscopy images determining simultaneously the graphene lattice and the internal structure of the H adsorbates. We show that H atoms normally group in chemisorbed coupled structures of different sizes and orientations. We make an atomic scale determination of the most stable experimental geometries, the small dimers and ellipsoid-shaped features, and we assign them to hydrogen adsorbed in para dimers and ortho dimers configuration, respectively, through comparison with the theory.