In thin film geometry, the interplay between dewetting and phase separation or microphase separation controls the morphology of the polymeric structures resulting on a solid support. For the model system of polystyrene, polyparamethylstyrene and the diblock copolymer of the two homopolymers, the regime of ultrathin films is addressed experimentally. Evolving structures are probed with real and reciprocal space analysis techniques such as the optical microscopy, phase measuring interference microscopy, scanning force microscopy, neutron or x-ray reflectivity and grazing incidence small angle neutron or x-ray scattering approaches. The effective interface potential of the solid support is tuned by means of a change of the silicon substrate coating. Coating layers of silicon oxide, polyamide and polyimide are under investigation. A power law behaviour describing the most prominent in-plane length as a function of the initially prepared film thickness is observed. All reported structures have been prepared on large scale surfaces, such as typical Si wafers with 100 mm diameter.

factor of 7. This shows that solution-based silicon is a highly promising candidate for industrial-grade applications of solutionbased semiconductors. Evaluation of Precursors NPS and CPSIn literature, most groups reporting silicon fi lms fabricated from a liquid precursor use a cyclic hydridosilane, namely cyclopentasilane (CPS). We decided to use a branched molecule instead, namely neopentasilane (NPS). The molecular structures of CPS and NPS, as well as the process charts for obtaining solid amorphous silicon (a-Si) layers, are shown in Figure 1 . We characterized the NPS used in our process chain by NMR and by mass spectroscopy, showing the expected fi ngerprints mentioned in literature. [ 4 ] Employing NPS over CPS yields major advantages in processing effi ciency as well as in material quality. In general, branched molecules have a considerably better solubility in organic solvents, because the branches act as spacers, preventing strong interactions between the molecules and enabling better intercalation of solvent molecules. [ 5 ] The NPS material is therefore better soluble than CPS, which leads to improved fi lm homogeneity and uniformity. Moreover, in NMR measurements, we found that the NPS-oligomer bears 70% SiH 3 end groups, in contrast to 1.0% for the CPS-oligomer. Such end groups facilitate the cross-linking of the material to a solid network. Since this process is responsible for the formation of silicon-silicon bonds, we expect a positive effect on the coordination of silicon atoms, resulting in less dangling bonds and improved electronic properties. Until now, we have however not been able to demonstrate differences in nanoscopic amorphous silicon structure between CPS and NPS.Another major advantage of employing NPS instead of CPS lies in the differences in material synthesis. The synthesis of the CPS monomer involves a coupling reaction and subsequent chlorination of diphenyldichlorosilane to obtain decachlorocyclopentasilane. This process produces a large amount of various by-products, which are diffi cult to separate and recycle. However, in the synthesis of NPS, we use catalytic rearrangement of octachlorotrisilane to obtain dodecachloroneopentasilane,

The enhanced thermal stability of thin polymer bilayer films against dewetting is investigated. Stabilization results from the addition of a random functional copolymer. The model system consists of a silicon substrate covered with a bilayer of amorphous polyamide (PA), followed by a fully deuterated polystyrene (PSd). While the PA sublayer is stable against dewetting, the addition of a PSd homopolymer film allows dewetting to occur during annealing. By blending the PSd top layer with a fully protonated copolymer poly(styrene-co-maleic anhydride) (SMA2), containing 2% maleic anhydride groups in the chain, its dewetting process is retarded. This increase in stability is investigated as a function of copolymer and annealing time. Scanning force microscopy (SFM) is applied to determine the surface root-mean-square roughness and to check the stabilization effect. Information about the density profile is aquired from specular neutron reflectivity measurements. In addition, grazing incidence small angle neutron scattering (GISANS) is applied. GISANS utilizes the averaging capabilities of scattering methods, which is compared to local information obtained by SFM. Furthermore, GISANS enables the detection of buried structures in contrast to the SFM. An amount of 5% by volume SMA2 is sufficient to stabilize the bilayer film due to the creation of an enrichment layer of SMA2 at the PA:PSd interface. With creation of a brushlike interface, the mobility of the PSd molecules is decreased, which suppresses dewetting.

The surface topography and the chemical morphology of poly(styrene-block-paramethylstyrene) diblock copolymers confined within isolated drops are investigated. The drop geometry imposes a two-dimensional spatial restriction. With scanning force microscopy, the film thickness dependence of the mean drop distance as the basic topographical feature is determined. In addition to large drops, a second smaller droplet structure is observed among the drops. The comparison of grazing incidence small-angle scattering using X-rays and neutrons shows that inside the drops the diblock copolymer orients into perpendicular lamellae with respect to the substrate surface. Compared to the bulk, the lamellar spacing is stretched parallel to the substrate.