Controlled Reorientation of CuPc Molecules in Ordered Structures Assembled on the TiO₂(011)‐(2×1) Surface

Scanning probe microscopy studies on the adsorption of selected molecular dyes on titania

“…In a few cases among these studies, scanning probe microscopy was used to examine the properties of the Pc/TiO 2 interface itself [33,43–47] and to investigate the heteromolecular systems in which phthalocyanine molecules formed a second layer [48–49]. Copper phthalocyanine (CuPc) appears to be the most extensively studied Pc derivative on titania surfaces [27,33,43,46]. Other accounts refer to CoPc/TiO 2 (110)[44], FePc/TiO 2 (110) [45], and metal-free Pc/TiO 2 (110) [47] systems.…”

“…At higher coverage, 2D self-assembled structures were reported for both surfaces [46]. Additionally, adsorption on the (011) face at different coverage densities has been investigated [33,43]. At a submonolayer coverage, molecules are predominantly found at the step edges and occasionally at the surface defects [33].…”

“…At monolayer coverage, the molecules form a quasi-ordered wetting layer that includes regions comprising parallel molecular lines and regions having chessboard-like structures [33]. The further increase in the amount of deposited organic material leads to the formation of the second layer [33,43]. When molecules are evaporated on the substrate kept at room temperature, the CuPcs in the second layer arrange in two coexisting phases with the majority of molecules lying with their plane parallel to the substrate surface.…”

“…When molecules are evaporated on the substrate kept at room temperature, the CuPcs in the second layer arrange in two coexisting phases with the majority of molecules lying with their plane parallel to the substrate surface. Post-deposition annealing at 200 °C leads to a reorientation of the molecules in the second layer into an upright geometry [43]. …”

“…We have already discussed the results of experiments on both CuPc and ZnTPP molecules deposited onto rutile surfaces [33,43,56]. In the former case, the CuPc molecules formed a wetting layer of flat-lying molecules on which ordered islands formed [33,43].…”