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Graphene on ferromagnetic surfaces and its functionalization with water and ammonia.

Böttcher S, Weser M, Dedkov YS, Horn K, Voloshina EN, Paulus B - Nanoscale Res Lett (2011)

Bottom Line: In this article, an angle-resolved photoelectron spectroscopy (ARPES), X-ray absorption spectroscopy (XAS), and density-functional theory (DFT) investigations of water and ammonia adsorption on graphene/Ni(111) are presented.ARPES and XAS data of the H2O (NH3)/graphene/Ni(111) system give an information regarding the kind of interaction between the adsorbed molecules and the graphene on Ni(111).The presented experimental data are compared with the results obtained in the framework of the DFT approach.

View Article: PubMed Central - HTML - PubMed

Affiliation: Fritz-Haber-Institut der Max-Planck-Gesellschaft, 14195 Berlin, Germany. dedkov@fhi-berlin.mpg.de.

ABSTRACT
In this article, an angle-resolved photoelectron spectroscopy (ARPES), X-ray absorption spectroscopy (XAS), and density-functional theory (DFT) investigations of water and ammonia adsorption on graphene/Ni(111) are presented. The results of adsorption on graphene/Ni(111) obtained in this study reveal the existence of interface states, originating from the strong hybridization of the graphene π and spin-polarized Ni 3d valence band states. ARPES and XAS data of the H2O (NH3)/graphene/Ni(111) system give an information regarding the kind of interaction between the adsorbed molecules and the graphene on Ni(111). The presented experimental data are compared with the results obtained in the framework of the DFT approach.

No MeSH data available.


Geometry of the H2O,NH3/graphene/Ni(111) systems investigated in this study. Graphene layer is arranged in the top-fcc configuration on Ni(111). Adsorbed molecules can be placed in three different highly symmetric adsorption sites: T, on-top; B, on-bond; C, center, with respect to the graphene lattice. Two examples of adsorption are shown: for NH3 in the on-top position with hydrogen atoms directed to the neighboring carbon atoms, and for H2O in the center position with hydrogen atoms directed to the C-C bonds.
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Figure 1: Geometry of the H2O,NH3/graphene/Ni(111) systems investigated in this study. Graphene layer is arranged in the top-fcc configuration on Ni(111). Adsorbed molecules can be placed in three different highly symmetric adsorption sites: T, on-top; B, on-bond; C, center, with respect to the graphene lattice. Two examples of adsorption are shown: for NH3 in the on-top position with hydrogen atoms directed to the neighboring carbon atoms, and for H2O in the center position with hydrogen atoms directed to the C-C bonds.

Mentions: As was previously found [8] and confirmed in the present calculations, the most energetically advantageous arrangement is the top-fcc arrangement of carbon atoms on Ni(111) (see Figure 1). For this structure, several high symmetry adsorption positions for molecules are possible. They are T, on-top; B, on-bond; and C, center and are marked by the corresponding capital letters in Figure 1. There are up to 42 and 16 possible configurations of H2O and NH3, respectively, on top of graphene/Ni(111), but in our calculations, the authors restrict the choice to only six arrangements where molecules are placed in the high symmetry positions (T, B, and C) with hydrogen atoms pointing upwards (UP) or downwards (DOWN). Two examples of possible absorption geometries are shown for H2O (C-DOWN--hydrogen atoms are pointed toward the direction of C-C bond) and NH3 (T-UP--hydrogen atoms are pointed toward the direction of the neighboring C atoms) in Figure 1. In these experiments, molecular layers (MLs) of adsorbate with the thicknesses ranging from approximately one third to one fifth of the thickness of ML (corresponding to the dense packing of molecules, when one molecule is placed in every carbon ring) are studied. For simplicity, in the calculations of this study, the concentration of the adsorbed molecules was chosen as 1/3 of ML that corresponds to the (√3 × √3)R30° overstructure with respect to the unit cell of graphene (shown in Figure 1 as dashed- and solid-line rhombus, respectively).


Graphene on ferromagnetic surfaces and its functionalization with water and ammonia.

Böttcher S, Weser M, Dedkov YS, Horn K, Voloshina EN, Paulus B - Nanoscale Res Lett (2011)

Geometry of the H2O,NH3/graphene/Ni(111) systems investigated in this study. Graphene layer is arranged in the top-fcc configuration on Ni(111). Adsorbed molecules can be placed in three different highly symmetric adsorption sites: T, on-top; B, on-bond; C, center, with respect to the graphene lattice. Two examples of adsorption are shown: for NH3 in the on-top position with hydrogen atoms directed to the neighboring carbon atoms, and for H2O in the center position with hydrogen atoms directed to the C-C bonds.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211271&req=5

Figure 1: Geometry of the H2O,NH3/graphene/Ni(111) systems investigated in this study. Graphene layer is arranged in the top-fcc configuration on Ni(111). Adsorbed molecules can be placed in three different highly symmetric adsorption sites: T, on-top; B, on-bond; C, center, with respect to the graphene lattice. Two examples of adsorption are shown: for NH3 in the on-top position with hydrogen atoms directed to the neighboring carbon atoms, and for H2O in the center position with hydrogen atoms directed to the C-C bonds.
Mentions: As was previously found [8] and confirmed in the present calculations, the most energetically advantageous arrangement is the top-fcc arrangement of carbon atoms on Ni(111) (see Figure 1). For this structure, several high symmetry adsorption positions for molecules are possible. They are T, on-top; B, on-bond; and C, center and are marked by the corresponding capital letters in Figure 1. There are up to 42 and 16 possible configurations of H2O and NH3, respectively, on top of graphene/Ni(111), but in our calculations, the authors restrict the choice to only six arrangements where molecules are placed in the high symmetry positions (T, B, and C) with hydrogen atoms pointing upwards (UP) or downwards (DOWN). Two examples of possible absorption geometries are shown for H2O (C-DOWN--hydrogen atoms are pointed toward the direction of C-C bond) and NH3 (T-UP--hydrogen atoms are pointed toward the direction of the neighboring C atoms) in Figure 1. In these experiments, molecular layers (MLs) of adsorbate with the thicknesses ranging from approximately one third to one fifth of the thickness of ML (corresponding to the dense packing of molecules, when one molecule is placed in every carbon ring) are studied. For simplicity, in the calculations of this study, the concentration of the adsorbed molecules was chosen as 1/3 of ML that corresponds to the (√3 × √3)R30° overstructure with respect to the unit cell of graphene (shown in Figure 1 as dashed- and solid-line rhombus, respectively).

Bottom Line: In this article, an angle-resolved photoelectron spectroscopy (ARPES), X-ray absorption spectroscopy (XAS), and density-functional theory (DFT) investigations of water and ammonia adsorption on graphene/Ni(111) are presented.ARPES and XAS data of the H2O (NH3)/graphene/Ni(111) system give an information regarding the kind of interaction between the adsorbed molecules and the graphene on Ni(111).The presented experimental data are compared with the results obtained in the framework of the DFT approach.

View Article: PubMed Central - HTML - PubMed

Affiliation: Fritz-Haber-Institut der Max-Planck-Gesellschaft, 14195 Berlin, Germany. dedkov@fhi-berlin.mpg.de.

ABSTRACT
In this article, an angle-resolved photoelectron spectroscopy (ARPES), X-ray absorption spectroscopy (XAS), and density-functional theory (DFT) investigations of water and ammonia adsorption on graphene/Ni(111) are presented. The results of adsorption on graphene/Ni(111) obtained in this study reveal the existence of interface states, originating from the strong hybridization of the graphene π and spin-polarized Ni 3d valence band states. ARPES and XAS data of the H2O (NH3)/graphene/Ni(111) system give an information regarding the kind of interaction between the adsorbed molecules and the graphene on Ni(111). The presented experimental data are compared with the results obtained in the framework of the DFT approach.

No MeSH data available.