MOCVD selective growth of orthorhombic or hexagonal YMnO3 phase on Si(1Â 0Â 0) substrate

Multiferroic YMnO3 (YMO) thin films were grown by pulsed injection metal organic chemical vapor deposition on (1 0 0)-oriented silicon substrate. The growth conditions were optimized in order to obtain either orthorhombic (o-YMO) or hexagonal (h-YMO) YMO phases. The most significant deposition parameters in the selective growth of these phases are the substrate temperature and the Y/Mn ratio in the precursor solution. Polycrystalline films with a preferential growth direction are obtained for h-YMO whereas grains with random orientation are observed for o-YMO as shown by X-ray diffraction and transmission electron microscopy. The h-YMO (300 nm thick) and o-YMO (450 nm thick) films present a columnar growth with column diameter comprised between 15 and 35 nm. The Raman spectrum of o-YMO film is reported and compared to the o-YMO bulk spectrum. The temperature-dependent magnetization curves display a λ-shape for both o- and h-YMO phases, indicating a spin-glass state.