Two additional mechanisms were found to contribute to the increased crystallization times. First of all, at pressures above 1*10−3, the silicon oxide thickness started to increase before start of the growth. This contribution was largely circumvented by starting the growth quickly after reaching the growth temperature. More importantly, the thickness of the silicon oxide after growth of YSZ depended heavily on the pO2, and showed a growth rate much higher than the growth rate on the as received silicon. Similar growth rate enhancement with over an order of magnitude has been described for thin metal overlayers of e.g. Ba32, Cu33, Sr34 and Y35. Apparently, YSZ catalyzes the absorption of oxygen by the silicon oxide. Therefore, silicon oxide regrowth is expected to compete with the scavenging process as soon a YSZ is present at the silicon surface. In the case of growth in a total pressure of 2*10−2 mbar, the optimum pO2 was found at conditions were severe regrowth of the silicon oxide was observed. Together with the observed partial oxidation of the plasma, the scavenging process in optimum conditions can now be summarized by the following reaction:2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$Zr{O}_{2-x}+xSi{O}_{2}+{O}_{2}+Si\to xSiO\uparrow +Zr{O}_{2}+Si{O}_{2}$$\end{document}ZrO2−x+xSiO2+O2+Si→xSiO↑+ZrO2+SiO2