Phase transformations and selective growth in YMnO 3 films

An irreversible phase transformation from amorphous to crystalline orthorhombic YMnO3 (o-YMO) phase takes place in Y–Mn–O films deposited by pulsed-injection metal organic chemical vapor deposition (MOCVD) on Si(100) substrate. This phase transformation was studied through ex-situ and in-situ thermal annealings and the corresponding structural changes were analyzed by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and Raman spectroscopy. It was shown that it takes place at an almost constant temperature (~700°C) and in a short period of time (~min) and that the o-YMO phase thus obtained is stable at least up to 900°C. We also demonstrate that the selective growth of amorphous, orthorhombic or hexagonal films is made possible by adapting the MOCVD temperature according to the temperature stability region of the different phases.