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M. Wagner, F. Calcinelli, A. Jeindl, M. Schmid, O. Hofmann, U. Diebold:
"Adsorption configurations of Co-phthalocyanine on In₂O₃(111)";
Surface Science, 722 (2022), S. 1220651 - 1220657.

Indium oxide offers optical transparency paired with electrical conductivity, a combination required in many optoelectronic applications. The most-stable In2O3(111) surface has a large unit cell (1.43 nm lattice constant). It contains a mixture of both bulk-like and undercoordinated O and In atoms and provides an ideal playground to explore the interaction of surfaces with organic molecules of similar size as the unit cell. Non-contact atomic force microscopy (nc-AFM), scanning tunneling microscopy (STM), and density functional theory (DFT) were used to study the adsorption of Co-phthalocyanine (CoPc) on In2O3(111). Isolated CoPc molecules adsorb at two adsorption sites in a ∼7:3 ratio. The Co atom sits either on top of a surface oxygen (`F configuration´) or indium atom (`S configuration´). This subtle change in adsorption site induces different bending of the molecules and differences in their electronic structure. According to DFT, the lowest unoccupied molecular orbital of the undistorted gas-phase CoPc remains mostly unaffected in the F configuration but is filled by one electron in S configuration. At coverages up to one CoPc molecule per substrate unit cell, a mixture of domains with molecules in F and S configuration are found. Molecules in F configuration first condense into a poorly ordered F-(2 × 2) structure and finally rearrange into an F-(1 × 1) structure in which the molecules partially overlap. The only ordered structure of molecules adsorbed in S configuration is an S-(1 × 1) superstructure at full monolayer coverage.

Atomic force microscopyDensity functional theoryOrganic molecule on In2O3(111)Electronic structure of organic molecules

http://dx.doi.org/10.1016/j.susc.2022.122065

https://doi.org/10.1016/j.susc.2022.122065