Atomic structures of the isolated CuPc (top panel) and F16CuPc (bottom panel) molecules, and the corresponding charge density contour at 0.001 e/Å3 for the HOMO and LUMO states. C, H, F, N, and Cu atoms are denoted as green, white, pink, blue, and orange spheres, respectively.
UV-visible spectra of CuPc and F16CuPc molecules calculated from TDDFT. The two vertical gray lines show the absorption position and rescaled amplitudes of CuPc in the experimental spectrum (Ref. 49). The letters denote the absorption bands of CuPc (see text for details).
Density of states (DOS) of the F16CuPc molecule: solid lines show the LDA results and dashed lines show the corresponding HSE results. Black lines and red lines (upper and lower panels) denote the spin-up and spin-down components, respectively. The Fermi level is set to zero. Wavefunctions for the HOMO and LUMO states are also displayed on the right, and labeled according to their symmetry. The labels (1)-(4) identify the positions of these states in the DOS diagram.
Scanning tunneling microscopy (STM) images for F16CuPc molecules adsorbed on monolayer epitaxial graphene (MEG) and bilayer epitaxial graphene (BEG). Selective adsorption on MEG is evident. Characteristic STM images for the MEG, BEG,s and F16CuPc layers are also shown on the sides, enlarged.
High-resolution STM images of ordered F16CuPc patterns on epitaxial graphene. Simulated STM image for F16CuPc from the LUMO charge density is shown side-by-side (right panel) and overlaid onto the experimental images (left panel).
(a) The optimized configuration and (b) potential energy surface contours for the F16CuPc/gra[(3,4)×(4,3)] system. Graphene is shown as a gray sheet to distinguish it from C atoms in the Pc molecule. The unit cell is described by a red parallelogram. The potential energy surface is calculated by using a (4×5) grid sampling in the rectangular region marked in the lower right corner of (a).
Total DOS (thick black solid line) and projected DOS on the Pc molecule (blue solid line), on graphene (thin black solid line), upon F16CuPc adsorption on graphene, and the DOS of the isolated graphene (black dashed dotted line). The vertical dotted line shows the Fermi level.
Top view and side view of the charge density difference for F16CuPc/gra[(3,4)×(4,3)] (top panel) and CuPc/gra[(1,5)×(4,3)] (bottom panel) at contour levels of 0.003 e/Å3. The light blue and red clouds correspond to regions with electron accumulation and depletion, respectively.
(a) Geometry of CuPc molecules adsorbed on graphene[(1,5)×(4,3)]. (b) Corresponding density of states (DOS) plot projected on CuPc and graphene for the adsorption system, respectively. The vertical dashed line marks the Dirac point which is 10 meV below the Fermi level for CuPc/graphene. (c) One-dimensional charge density difference along the surface normal direction of graphene; vertical dotted lines mark the positions of graphene and the molecule planes. For comparison, the corresponding lines of F16CuPc (blue) are also shown in panels (b) and (c).
Geometries of uniform and non-uniform F16CuPc overlayers adsorbed on graphene[(3,4)×(8,6)]: (a) the α − α pattern; (b)-(d) the α − β stripes with relative azimuthal angles of: (b) 20°, (c) 30° and (d) 40°. The unit cell (red parallelogram) contains two Pc molecules.
Simulated STM images from the HOMO (left) and LUMO (right) states upon F16CuPc adsorption on graphene[(3,4)×(8,6)] (corresponding to applied positive and negative bias on the tip, respectively). The blue dashed lines indicate the orientations of molecular rows.
The calculated Fermi-level shift (ΔE F ) with respect to the Dirac point of graphene and the corresponding charge transfer (Δq) in the neutral and charged systems. The Dirac point is set to zero. N EG denotes the thickness of epitaxial graphene layers.
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