Site-Specific Geometric and Electronic Relaxations at Organic-Metal Interfaces

Abstract

The correlation between the geometric and electronic structures of Zn-phthalocyanine (ZnPc) and F16ZnPc on Cu(111) were studied by x-ray standing wave and angle-resolved photoemission spectroscopy. We found evidence for a distortion of the planar molecules upon adsorption, with the central Zn atom in the molecule protruding towards the substrate. This modifies the energy levels of both the molecule and the substrate, which appear as interface states. The site-specific geometric and electronic relaxations are an important effect for organic-metal interface energetics.

Molecular distortion and charge transfer effects in ZnPc/Cu(111)

“…This fact indicates that the charge transfer governs the properties of this organometallic interface rather than structure effects as proposed in Ref. 21.…”

“…The different heights of the atoms relative to the substrate lower the symmetry upon adsorption. With vdW interaction we obtain atomic shifts of 0.31 Å for Zn and N, 0.43 Å for Zn and C, and 0.55 Å for Zn and H, while without vdW interaction we have 0.36 Å for Zn and N, 0.56 Å for Zn and C, and 0.71 Å for Zn and H. These values indicate that the molecular distortions are underestimated when the vdW interaction is included21. An increased molecule-substrate distance and flattened molecule, see Fig.…”

“…Yamane and coworkers have used a combination of the x-ray standing wave technique and angle-resolved photoemission spectroscopy for ZnPc on Cu(111) to analyze how the adsorbate configuration affects the chemical bonding at the interface and its electronic properties21. In addition, Gerlach and coworkers have shown experimentally that the adsorption distance on a Cu substrate is small because of the relatively low work function (as compared to Ag and Au, for example), pointing to a strong interaction23.…”

Inhomogeneous charge transfer within monolayer zinc phthalocyanine absorbed on TiO2(110)

“…Additionally, several reports have shown that when Pc are adsorbed on metal surfaces the molecular plane will experience distortion and deformation. [45][46][47][48] By using X-ray standing waves, Yamane et al 46 reported that ZnPc is buckled on Cu(111), with the zinc center pulled towards the surface, and the carbon periphery also bending downwards compared to the central pyrrole nitrogen ring. Pre-fluorinated Pc (ZnPcF 16 and CuPcF 16 ) deform in the opposite direction on metal surfaces with the fluorine atoms facing the vacuum.…”

“…Pre-fluorinated Pc (ZnPcF 16 and CuPcF 16 ) deform in the opposite direction on metal surfaces with the fluorine atoms facing the vacuum. [46][47][48] Thus, more theoretical and experimental work is needed to precisely determine the monolayer molecular configuration. At 3.8 ML, the line profiles in the π * region from the two polarizations resemble each other and are also consistent with previously reported results for ZnPc.…”