Microstructure and surface evolution in the crystallization of α-Fe₂O₃/α-Al₂O₃(0001) thin films

We found the correlation between microstructure and surface evolution in the crystallization of amorphous α-Fe₂O₃/α-Al₂O₃(0001) thin films using real-time synchrotron x-ray scattering and atomic force microscope. The amorphous precursor is crystallized to the epitaxial α-Fe₂O₃ grains in three steps; i) the growth of the well aligned α-Fe₂O₃ interfacial islands on α-Al₂O₃(0001), ii) the growth of the misaligned, homoepitaxial, α-Fe₂O₃ grains on the well aligned grains (≥400°C), and iii) the nucleation of the heteroepitaxial misaligned grains directly on the α-Al₂O₃ substrate (≥600°C). The surface roughing is caused by the microstructure evolution during the crystallization of the amorphous precursor films.