No abstract

Thin films of both the hexagonal and orthorhombic forms of YMnO3 have been fabricated through atomic layer deposition (ALD) and subsequent heat treatment. ALD-type growth of essentially cation-stoichiometric YMnO3 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 YMnO3, whereas on LaAlO3(100) and SrTiO3(100) substrates, the metastable orthorhombic YMnO3 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.

Spinel-structured (Mn,Co) 3 O 4 thin films were reproducibly fabricated by atomic layer deposition (ALD) using Mn(thd) 3 , Co(thd) 2 , and ozone as precursors. A full control of the cation ratio was achieved in the temperature interval 140-160 °C within which also the growth rate remained constant. Precise control of the oxygen content of as-deposited MnCo 2 O 4þδ films was achieved through postdeposition heat treatments at prefixed temperatures in air and N 2 atmospheres, as evidenced from the monotonous increases of both the unit cell volume and the Curie temperature (T C ) with increasing annealing temperature/decreasing oxygen partial pressure. The T C value varied from 92 K for the as-deposited MnCo 2 O 4þδ films to 182 K for the films annealed at 700 °C in N 2 flow.

Atomic layer deposition (ALD) with subsequent annealing in N 2 gas flow was employed to fabricate an extensive series of both hexagonal and orthorhombic rare-earth manganate RMnO 3 thin films using R(thd) 3 , Mn(thd) 3 , and ozone as precursors. Excellent control of the R/Mn stoichiometry was achieved for all the rare-earth constituents studied at 275 °C. The formation of the metastable perovskites was elegantly enhanced through depositions on coherent perovskite substrates resulting in a complete series (from R = La to Lu) of single-phase RMnO 3 perovskites on LaAlO 3 substrates. The magnetic properties of the perovskite series exhibited expected antiferromagnetic behaviour at low temperatures (except for R = La which showed ferromagnetic interactions due to cation vacancies).