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Stöber silica nanoparticles of diameter about 45, 60 and 100 nm and different hydrophobicity are used to produce monolayers at a water-air interface. Both the surface pressure-area isotherms and the reflectivity angle of incidence curves of the layers have been measured in a Wilhelmy film balance. The contact angle of the as-prepared particles have been determined from the isotherms by two different evaluation methods, and compared to those obtained from in situ scanning angle reflectometry (SAR) measurements. SAR is proved to be an effective tool for the estimation of contact angles on nanoparticles of different wettability, using a modified version of the previously published gradient layer model (E. Hild, T. Seszták, D. Völgyes and Z. Hórvölgyi, Prog. Colloid Polym. Sci., 2004, 125, 61, ref. 1) for evaluation. The results are in fairly good agreement with those determined from the non-dissipative part of the isotherms of the as prepared particles, assuming a weakly cohesive film model (S. Bordács, A. Agod and Z. Hórvölgyi, Langmuir, 2006, 22, 6944, ref. 2). It seems that the traditional way to calculate the contact angle from the film balance experiments (J.H. Clint and N. Quirke, Colloids Surf., A, 1993, 78, 277, ref. 3) results in unreasonably high contact angles for the investigated systems and the homogeneous layer optical model gives unrealistic film thickness values in the case of hydrophobic particles.

Results of IR spectroscopic as well HVTEM investigations are given on the precipitation of oxygen in Si due to heat treatment within the temperature range 600 to 1275 °C. The initial oxygen concentrations of the Si samples are about 9 × 1017 cm−3 and about 1.5 × 1018 cm−3, respectively, with different concentrations of carbon within the range 1016 cm−3 ≦ [Cs]0 ≦ 1 × 1017 cm−3 in each case. It is shown that four different kinds of Si‐oxygen precipitates exist at least, in dependence on the temperature of heat treatment. [Oi]0, [Cs]0, and the thermal history of the samples heat treated. It is assumed that there is only heterogeneous nucleation within the whole temperature range. For temperatures T ≧ 900 °C the oxygen precipitation occurs by the growth of asgrown microprecipitates. The origin of various IR spectra and corresponding HVTEM microphotographs is interpreted as being caused by differences in the shape and size of the Si‐oxygen‐precipitates.