Ultrathin TiO2 films showing rich morphologies are prepared on Si(100) substrates using sol-gel chemistry coupled with an amphilic polystyrene-block-poly(ethylene oxide) (PS-b-PEO) diblock copolymer as a structure-directing agent. The block copolymer undergoes a good-poor solvent pair induced phase separation in a mixed solution of 1,4-dioxane, concentrated hydrochloric acid (HCl), and titanium tetraisopropoxide (TTIP). By adjusting the weight fractions of 1,4-dioxane, HCl, and TTIP, inorganic block copolymer composite films containing a variety of different morphologies are obtained. On the basis of the results a ternary phase diagram of the morphologies is mapped. By calcination, anatase TiO2 films are achieved. The morphologies and crystallographic phase of the films are studied with AFM, SEM, and XRD, respectively, and the formation mechanisms of the different morphologies are discussed.

To optimize the handling of fine powders in industrial applications, understanding the interaction forces between single powder particles is fundamental. The forces between colloidal particles dominate the behavior of a great variety of materials, including paints, paper, soil, and many industrial processes. With the invention of the atomic force microscope (AFM), the direct measurement of the interaction between single micron-sized particles became possible. The adhesional contact between a particle and a substrate is a parameter for analyzing pull-off force data generated by AFM. The aim of this study was to understand surface interactions between fine particles. I measured the adhesion forces between AFM tips or particles attached to AFM cantilevers and different solid samples. Smooth and homogeneous surfaces such as silicon wafer, mica, or highly oriented pyrolytic graphite (HOPG), and more rough and heterogeneous surfaces such as iron particles or patterns of TiO 2 nanoparticles on silicon wafer were used. First, I addressed to the wellknown issue that AFM adhesion experiment results show wide distributions of adhesion forces rather than a single value. My experimental results show that variations in adhesion forces comprise fast (i.e., from one force curves to the next) random fluctuations and slower fluctuations, which occur over tens or hundreds of consecutive measurements. Slow fluctuations are not likely to be the result of variations in external factors such as lateral position, temperature, humidity, and so forth because those were kept constant. Even if two solid bodies are brought into contact under precisely the same conditions (same place, load, direction, etc.) the result of such a measurement will often not be the same as for the previous contact. The measurement itself will induce structural changes in the contact region which can change the value for the next adhesion force measurement.In the second part I studied the influence of humidity on the adhesion of nanocontacts. Humidity was adjusted relatively fast to minimize tip wear during one experiment. For hydrophobic surfaces, no signification change of adhesion force with humidity was observed. Adhesion force-versus-humidity curves recorded with hydrophilic surfaces either showed a maximum or continuously increased. I demonstrate that the results can be interpreted with simple continuum theory of the meniscus force. The meniscus force is calculated based on a model that includes surface roughness and takes into account different AFM tip (or particle) shapes by a two-sphere-model.Experimental and theoretical results show that the precise contact geometry has a critical influence on the humidity dependence of the adhesion force.Changes of tip geometry on the sub-10-nm length scale can completely change adhesion force-versus-humidity curves. Our model can also explain the differences between earlier AFM studies, where different dependencies of the adhesion force on humidity were observed.Keywords: Atomic force microscopy (AFM), cantile...

During spin coating of very thin Ðlms from a solution of incompatible polymers quite interesting lateral structures are forming. From scanning force microscopy (SFM) and X-ray reÑectometry it is concluded that a surface height modulation is present, which reÑects at the surface the phase separated morphology of the blend in the Ðlm. Those structures depend critically on di †erent parameters like relative concentration of the components, spinning parameters, solvent quality or compatibility of the blend. In blends of di †erent statistical copolymers of poly-styrene-stat-para-bromo-styrene the compatibility between the blended polymers depends on the di †erence in the degree of bromination. This allows a variation of the interaction parameter within a wide range. Besides relatively incompatible materials, also weakly incompatible mixtures are of interest. Such a system with an almost vanishing but still positive interaction parameter is realized with blends of poly-styrene and poly-para-methyl-styrene. Ultra thin polymer Ðlms with thicknesses between 2 to 4 were prepared by solvent quenches from R G homogeneous solution. The lateral structures created during the quench are examined with SFM. The SFM pictures are statistically analysed in terms of their Fourier components. From the power spectral density function the most prominent in-plane length scale is extracted. This analysis of a mean distance is complemented by the use of Minkowski measures.

The long-range interface correlation in thin polymer films (polystyrene and fully brominated polystyrene) prepared by spin-coating is examined. Using diffuse X-ray scattering at small angles of incidence, the roughness correlation which dominates the surface morphology of the polymer film is probed from mesoscopic down to molecular in-plane distances. At the smallest replicable in-plane length scale, the crossover from a conformal to a statistically independent roughness spectrum is determined. The influences of molecular weight and film thickness are discussed. Compared to annealed samples, the as-prepared ones show a different scaling behavior, which is explained with simple models taking surface-bending rigidity into account. With a real-time annealing investigation, the decay of interface correlation after the onset of annealing has been followed. At annealing even below the glass-transition temperature, the roughness correlation is changing and disappears during sufficiently long annealing in the melt. Monitoring the changes with time probes the mobility of the polymer molecules at the polymer−vacuum interface. In thin films, the time constant is increased. The determined surface diffusion coefficient shows a slowing down as compared to the bulk behavior which may be attributed to the attractive, long-range substrate−interface interaction.