A quantitative method, using temperature-controlled friction force microscopy (FFM), has been developed to determine the frictional (dissipative) character of thin polymer films. With this method variations in friction are sampled over micrometer-scale regions and are reduced to “friction histograms,” yielding the distribution of frictional forces on the surface. The temperature dependence of the mean value of the frictional distribution is correlated to the known glass-to-rubber transition (T g) and/or secondary relaxation mechanisms in films of poly(methyl methacrylate) (PMMA), poly(ethylene terephthalate) (PET), and polystyrene (PS). The dominant contribution to friction, on polymer films, was attributed to viscoelastic mechanical loss. Using equivalent time scales, measured T g's were lower than bulk polymer values. The frictional response of PMMA displayed time−temperature equivalence upon variation of scan-velocity and temperature. The rate dependence of the hindered rotation of the −COOCH3 group (β relaxation) in PMMA was consistent with Arrhenius type behavior, allowing calculation of an activation energy. The activation energy of the thin film was found to be lower than measured bulk energies.

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A side-by-side comparison of the TiO2 deposition kinetics and the corresponding microstructures was studied. The two precursors were titanium(IV) isopropoxide and anhydrous titanium(IV) nitrate, and all depositions were conducted at low pressures (<10-4 Torr) in an ultrahigh vacuum chemical vapor deposition reactor. For both precursors deposition kinetics were qualitatively similar and exhibited three distinct regimes as a function of temperature. At the lowest temperatures, growth was limited by the rate of precursor reaction on the substrate surface. At intermediate temperatures flux-limited growth was obtained, and at the highest temperatures the growth rates decreased with increasing temperatures. The overall behavior was modeled quantitatively for each precursor using a two-step mechanism involving reversible adsorption followed by irreversible reaction. Titanium(IV) nitrate exhibited a lower activation energy of reaction (E r = 98 kJ/mol) which allowed deposition at lower temperatures compared to titanium(IV) isopropoxide (E r = 135 kJ/mol). The film microstructures were examined using transmission and scanning electron microscopy and X-ray diffraction. Comparison of the microstructures of films deposited at similar temperatures revealed significant differences in the reaction rate-limited regime. As the growth rates of the two precursors converged in the flux-limited regime, the respective microstructures became indistinguishable. The importance of precursor surface coverage and diffusion on this effect is described.