Epitaxial Growth of Iron Phthalocyanine at the Initial Stage on Au(111) Surface

Abstract

Growth behavior of iron(II) phthalocyanine (FePc) molecules on Au(111) surface at the initial stage is studied with low-temperature scanning tunneling microscopy. The FePc molecules are separately adsorbed on the face-centered cubic and the hexagonal close-packed regions at the submonolayer regime, indicating that the molecular adsorption is greatly affected by the molecule−substrate interaction. At the monolayer regime, the molecules can form a close-packed ordered structure. When the FePc goes further to the second layer, the unit cell of the formed molecular superstructure shifts compared with the unit cell of the first layer. Comparison of the growth behavior between the FePc and the CoPc also is made to understand the growth difference within the family of the phthalocyanine (Pc) molecules. And it is found that the central metal atom of the metal Pc makes a main contribution to the shift. Our results are helpful for understanding the growth of the Pc molecule family and controlling the related physical properties.

Metal-free phthalocyanine (H2Pc) molecule adsorbed on the Au(111) surface: formation of a wide domain along a single lattice direction

“…The ridge of the herringbone structure is perpendicular to one of these quasi-close-packed directions. For an MPc film, quasi-square lattices were commonly formed when the coverage was close to a monolayer, as clearly demonstrated for the molecules of CoPc [2,[13][14][15] and FePc [11,12].…”

“…Chen et al reported the adsorption of FePc on the Au(111) surface in a low-coverage regime (< 0.1 ML), in which FePc molecules were found only in the fcc region [12,23]. They concluded that the adsorption of FePc is more stable on fcc than that on the hcp domain.…”

“…Such bonding configuration (configuration I) has been proposed for the MPc adsorption on the Au(111) surface. Chen et al reported that for FePc adsorption on Au(111), 85% of the isolated FePc molecules have this configuration [12,23]; the rest assume configuration II, where the molecule is azimuthally rotated ∼15 • from configuration I. Hereafter we denote the alignment to the angles θ = 0, 30 and 60 • as Config I (C), Config I (A1) and Config I (A2).…”

“…In studying the adsorption of the double-layer molecules, it might be necessary to compare the results with those obtained on metal-free Pc, as the bottom Pc layer does not contain a metal atom. Contrary to numerous reports of MPc on the Au(111) surface [2,[11][12][13][14][15][16][17], the studies of metal-free Pc film growth in the low-coverage regime are scarce.…”

“…However, no areas with three coexisting domains were found for CoPc and FePc, and Cheng et al noted that only one lattice direction was observed even on a large terrace [12]. This is an unusual case of the lattice formation on the Au(111) surface-for example, six different domains could be observed on the Au(111) surface (three equivalent crystal directions and two chiral degrees of freedom in the molecule) as an ordered lattice of terephthalic acid molecules was forming through the head-tail hydrogen bonding between adjacent molecules [18].…”