Morphology evolution in spinel manganite films deposited from an aqueous solution

Spinel manganite films were deposited by the spin spray technique at low deposition temperatures (< 100 °C). It was found that the film microstructure depends strongly on the degree of supersaturation (S) of the cations in the aqueous solution. For S < 2, well-crystallized isolated particles were deposited on the substrate, suggesting that heterogeneous nucleation with a low nucleation density dominates under these conditions. For 10 < S < 200, the as-grown films were continuous, with some porosity confirmed by transmission electron microscopy (TEM); the films could be densified by post-deposition annealing at 400 °C for 1 h. As-deposited films under these conditions were X-ray amorphous but the nanocrystalline spinel phase was confirmed by TEM. In this region, both homogeneous and heterogeneous nucleation occur. For S > 1000, agglomeration of small particles was dominant, which suggests that homogeneous nucleation is dominant during deposition. Heterogeneous nucleation was critical to obtain dense films.