Crystallization of Amorphous Thin BST/MgO(001) Films Grown by R.F. Magnetron Sputtering

ABSTRACTThe crystallization of amorphous BST thin films was studied in a synchrotron x-ray scattering experiment. At around 600°C, an intermediate phase, which was suspected to be a metastable pyrochlore phase, was formed. The x-ray reflectivity curves showed that the film-substrate interface became rough as the pyrochlore-like phase was formed. This suggests that the pyrochlore phase was nucleated near the interface area. Upon further annealing to higher temperatures, the film transformed to the crystalline perovskite phase. The crystallization was sensitive to the film thickness. In the thin 550Å thick film, the crystallization occurred at 750 °C with the <001> preferred orientation. On the other hand, the 5500Å thick film became crystalline even at 500°C with random crystalline orientation. The observed thickness dependence of the crystallization suggests that the crystalline perovskite phase was nucleated in the bulk of the film, rather than the near interface area.