Scanning force microscopy investigations of (semi)conductive surfaces coated with Langmuir–Blodgett dye layers

The morphology of semiconducting (In2O3 and SnO2) and metallic (Au) surfaces without organic dyes and when coated with the Langmuir–Blodgett (LB) dye layer was investigated with the scanning force microscopy (SFM) technique. In the experiments the following dyes were used: magnesium tetranaphtylporphyrin (MgTNP), magnesium phthalocyanine (MgPc) and lead phthalocyanine (PbPc). On the ground of the SFM results the roughness parameter of the surfaces and its change upon dye deposition was estimated. It was shown that images of the surface morphology are closely connected with the relation between the magnitude of the substrate grains and the geometrical size of the dye molecules. The substrates of the large grains (Au and SnO2) preserve their own topography after coating with the dye layer whereas the change in the morphology was observed for the substrate of low granularity (In2O3). tion spectroscopy (also in the polarized light) was used to determine the dye spectral species when the dye LB layers were deposited on the surface and the dye orientation with respect to the substrate surface. It was showed that only MgTNP was kept in the monomeric form whereas PbPc and MgPc tend to form the aggregated species. The tilt angle between the dye layer and the substrate was estimated. It was shown that MgTNP is the in-plane arrangement and PbPc and MgPc are oriented perpendicularly to the substrate surface. The correlation between the topography of the substrate surface and the molecular arrangement of dyes (orientation, aggregation) was shown and discussed.