A similar trend was observed when the initial growth was performed at a total pressure of 1*10−1 mbar (see Fig. 2b). The growth rate per second was kept similar to the 2*10−2 mbar experiments by using a laser repetition rate of 12.5 Hz. Despite the equal growth rate, the lowest FWHM was observed at 5*10−4 mbar, which is one order of magnitude lower compared to the growth performed at a total pressure of 2*10−2 mbar. The lowest FWHM was 1.00°, while an optimum of 0.85° was obtained in the 2*10−2 mbar case. Furthermore, features indicating polycrystallinity started to dominate the RHEED pattern at 5*10−3 mbar, while streaks or spots indicating epitaxial phases were not observed at all at a pO2 of 2*10−2 mbar. This degree of polycrystallinity differed from the growth performed at a total pressure of 2*10−2 mbar, since only a small amount of polycrystalline phases was observed with XRD when 2*10−2 mbar O2 was used (see Fig. 2a).