During growth of the films, RHEED movies were recorded with ~0.1 frame/s in order to obtain insights about the crystallization behavior in the different growth conditions. Figure 3a presents an example of the analysis performed on the RHEED data. Before start of the growth, the pattern of the crystalline surface buried beneath the amorphous silicon oxide was visible. This pattern faded when YSZ was deposited due to increased attenuation by the deposited material. After a certain deposition time, streaks or spots indicating epitaxial YSZ appeared. The intensity of a disappearing Si spot and evolving YSZ streak or spot was monitored over time. The minimum intensity was used as an indication of the crystallization time. This crystallization time serves as an indication of the efficiency of the native oxide decomposition and the following YSZ crystallization, and therefore reveals important details about the YSZ growth mechanism, as will be described in more detail in the discussion section. Figure 3b shows the crystallization times as well as the corresponding amount of deposited YSZ, determined for samples grown at different pO2 and total pressures of 2*10−2 or 1*10−1 mbar Ar. Similar trends were visible in the crystallization time for both total pressures. First the crystallization time decreased with increasing pO2, after which it increased again. At a total pressure of 1*10−1 mbar, the minimum in crystallization time was observed at the same pO2 as the optimum crystalline quality (see Fig. 2). At the total pressure of 2*10−2 mbar, a minumum was observed at a pO2 of 1*10−5 mbar, after which the crystallization time slightly increased. Crystallization times were notably larger at 1*10−1 mbar.Figure 3(a) Snapshots from a RHEED movie recorded during growth at 5*10−3 mbar O2 in a total pressure of 2*10−2 mbar Ar. Below the snapshots, the intensity profile derived from the blue box and the streak positions derived from the green box are presented. The dashed line indicates the minimum intensity, which is taken as a measure of the crystallization time/thickness. (b) Crystallization times/thicknesses derived with the method depicted in subfigure (a), for samples grown at different pO2 in total presures of 2*10−2 and 1*10−1 mbar Ar. The dashed lines are a guide to the eye.