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The side views of (a) the fully optimized (0001) dense SiO2 surface, (b) the type I semi-hydrated SiO2 surface, and (c) the type II semi-hydrated SiO2 surface. The yellow, red, and white balls represent the Si, O, and H atoms, respectively.
(a) Three representative H, T, and B arrangements of graphene on top of the SiO2 surface, in which the red atom can be anywhere within the irreducible HTB triangle region; (b), (c), and (d) present the top views of the most stable configurations of a graphene layer on the siloxane, type I-OH, and type II-OH surfaces, respectively. The yellow, red, gray, and white balls represent the Si, O, C, and H atoms, respectively.
The electronic band structure of a graphene layer on the (a) siloxane and (b) silanol SiO2 surfaces, respectively. The insets in the right represent the enlargements of the bands around the K points.
The change in charge density upon the adsorption of graphene monolayer onto the SiO2 substrate; that is, . (a), (c), and (e) present the gain of charge density after the adsorption of a graphene layer onto the siloxane, type I-OH, and type II-OH surfaces, respectively; (b), (d), and (f) present the loss of charge density after the adsorption of a graphene layer onto the siloxane, type I-OH, and type II-OH surfaces, respectively.
The equilibrium distances do (Å), binding energies Eb (meV/Å2), and the induced band gaps Eg (meV) of a graphene layer adsorbed on various sites of the siloxane and silanol SiO2 surfaces calculated using LDA and vdW-DF methods, respectively.
The charge gain and loss of a graphene layer obtained by integrating the charge density difference around the C atoms within the distance of their van der Waals radii. The values of the charge gain and loss were averaged over all the C atoms in a 4 × 4 unit cell of graphene, respectively (32 C atoms, units = e/C atom). The sum of the charge gain and loss of a graphene layer indicates the amount of charge redistribution from the electrons of graphene to the interfacial region.
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