Atomic Layer Deposition of Hexagonal and Orthorhombic YMnO₃ Thin Films

Thin films of both the hexagonal and orthorhombic forms of YMnO 3 have been fabricated through atomic layer deposition (ALD) and subsequent heat treatment. ALD-type growth of essentially cation-stoichiometric YMnO 3 films was achieved in a reproducible manner in a temperature interval of 250−300 °C using Y(thd) 3, Mn(thd) 3, and ozone as precursors. The as-deposited films were amorphous, but a postdeposition heat treatment carried out in a temperature range of 750−900 °C depending on the substrate/polymorph yielded highly crystalline films. On Si(100) substrate, the product was the hexagonal phase of YMnO 3, whereas on LaAlO 3 (100) and SrTiO 3 (100) substrates, the metastable orthorhombic YMnO 3 phase was formed. On the perovskite substrates, the films were highly oriented, the direction of the orientation moreover depending on the choice of the substrate crystal.