Selenolate is considered as an alternative to thiolate to serve as a headgroup mediating the formation of self-assembled monolayers (SAMs) on coinage metal substrates. There are, however, ongoing vivid discussions regarding the advantages and disadvantages of these anchor groups, regarding, in particular, the energetics of the headgroup-substrate interface and their efficiency in terms of charge transport/transfer. Here we introduce a well-defined model system of 6-cyanonaphthalene-2-thiolate and -selenolate SAMs on Au(111) to resolve these controversies. The exact structural arrangements in both types of SAMs are somewhat different, suggesting a better SAM-building ability in the case of selenolates. At the same time, both types of SAMs have similar packing densities and molecular orientations. This permitted reliable competitive exchange and ion-beam-induced desorption experiments which provided unequivocal evidence for a stronger bonding of selenolates to the substrate as compared to the thiolates. Regardless of this difference, the dynamic charge transfer properties of the thiolate- and selenolate-based adsorbates were found to be nearly identical, as determined by the core-hole-clock approach, which is explained by a redistribution of electron density along the molecular framework, compensating the difference in the substrate-headgroup bond strength.

Topography and composition images of model thin films of deuterated polystyrene (dPS) and polyisoprene with different blend compositions were analyzed with an extension of integral-geometry approach. Surface patterns, formed in the course of spin-casting from toluene onto self-assembled monolayers (SAM), were recorded with scanning force microscopy. Their relation with lateral phase domain structures was demonstrated by dynamic secondary ion mass spectrometry, yielding maps of dPS distribution. Morphological measures, which cannot be provided by Fourier transform analysis (FTA), characterize individual images, compositional series of the surface patterns and individual features of the patterns. Different morphologies (nucleation-and spinodal-type and hole-and island-dominated ones) are consistently characterized by the Minkowski measures and related parameters. For instance, the latter can measure circular character of the individual features and estimate dominant lateral length (determined rigorously with FTA). Lateral morphologies are hardly affected when CH3-terminated SAM is exchanged for SAM with COOH end groups.

Blends of the low-bandgap polymer poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-5,5- (4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole] (APFO-3) and the fullerene derivative [6,6]-phenyl–C61–butyric acid methyl ester (PCBM) were spin-coated from chloroform solution into thin films, which were examined with dynamic secondary ion mass spectrometry. For blends with high PCBM content, the depth profiles show composition waves that were caused by surface-directed phase separation during spin-coating. The formation of such multilayer structures by spontaneous self-stratification is likely to have implications for optimization strategies for the performance of organic solar cells.