Dresden 2014 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 103: Graphene: Adsorption, intercalation, doping (organized by O)
HL 103.6: Talk
Thursday, April 3, 2014, 17:15–17:30, WIL C107
Charge doping induced phase transitions in hydrogenated and fluorinated graphene — •Tim Wehling1,2, Bernhard Grundkötter-Stock2, Bálint Aradi2, Thomas Niehaus3, and Thomas Frauenheim2 — 1Institute for Theoretical Physics, Universität Bremen, Otto-Hahn-Allee 1, 28359 Bremen, Germany — 2Bremen Center for Computational Material Science, Universität Bremen, Am Fallturm 1, 28359 Bremen, Germany — 3Department of Theoretical Physics, University of Regensburg, 93040 Regensburg, Germany
We show that charge doping can induce transitions between three distinct adsorbate phases in hydrogenated and fluorinated graphene. By combining ab initio, approximate density functional theory and tight binding calculations we identify a transition from islands of C8H2 and C8F2 to random adsorbate distributions around a doping level of ± 0.05 e/C-atom. Furthermore, in situations with random adsorbate coverage, charge doping is shown to trigger an ordering transition where the sublattice symmetry is spontaneously broken when the doping level exceeds the adsorbate concentration. Rehybridization and lattice distortion energies make graphene which is covalently functionalized from one side only most susceptible to these two kinds of phase transitions. The energy gains associated with the clustering and ordering transitions exceed room temperature thermal energies.