The observed phenoma agree very well to the lateral overgrowth mechanism proposed by De Coux et al.20, since regrowth of silicon oxide does not necesseraly prevent lateral crystallization. The observed lattice relaxation from the start of crystallization fits this mechanism as well, and is in agreement with the observations made by Ishigaki et al.18. Lateral overgrowth is a well known method in growth of semiconductors, and proved to increase the crystalline quality due to avoidance of defect formation because of strain36,37. Similarly, the high YSZ crystalline qualities in conditions were residual SiO2 is expected, can be explained by this mechanism. As shown in Supplementary Fig. S3, a low surface roughness was obtained as well, as expected for high crystalline quality films. On the other hand, surfaces in silicide forming conditions were much rougher, due to a more local YSZ nucleation and lower crystalline qualities, as shown in more detail in the Supplementary Information (see Supplementary Figs S3–S5).