GROWING WETTING FILMS - AN X-RAY STUDY

The growth kinetics of thin liquid films, completely wetting a solid s ubstrate, are studied. The film thickness is perturbed and reduced by a short thermal pulse. Subsequently the time dependence of the growth process was monitored by x-ray reflectivity measurements in the region of total external reflection. The examined sample systems are CBrCl3 films on top of silicon, germanium, and glass wafers and CBrCl3 on gla ss/gold and glass/silver substrates. The observed growth kinetics of t he wetting layer are discussed in the framework of two models that wer e adapted to the experimental conditions, particularly the finite temp erature stability of the experimental setup. From the growth law l(t) proportional to 1-exp(-t/tau)(n) fitted to the data, time constants ta u and dynamic exponents n are determined. n depends on the dimension o f the growth mechanism. Various systems with quite different substrate -adsorbate interactions can be explained quantitatively within this mo del.