MOCVD selective growth of orthorhombic or hexagonal YMnO3 phase on Si(100) 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.