SrAl12O19 thin films by chemical solution deposition and their use as buffer layers for oriented growth of hexagonal ferrites

• Two procedures developed for preparation of oriented SrAl12O19 thin films on Al2O3.
• (1) by high temperature topotactic reaction of thin SrO film with substrate
• (2) by nucleation and growth in amorphous SrAl12O19 film on Al2O3
• Used as a chemical buffer and structural template for growth of hexagonal ferrites
• Hexagon-on-hexagon epitaxy (001)subst ||(001)film and [100]subst ||[110]film

Thin films of SrAl12O19 were prepared on α-Al2O3(0001) substrates through the chemical solution deposition method and thermal treatment. Two types of precursor systems were used: stoichiometric mixture of strontium methoxyethoxide with aluminium iso-butoxide, and strontium methoxyethoxide topotactically reacting with Al2O3 substrate. Two distinctly different film-substrate orientation relationships were observed. In the latter case the orientation can described as perfect hexagon-on-hexagon epitaxy with 112−0SrAl12O19 || 101−0Al2O3 and (0001)Al2O3 || (0001)SrAl12O19. This relationship has 1.17% lattice misfit in the substrate plane. In the former case SrAl12O19 grains are rotated about the substrate normal and form more orientation variants that can be explained by the coincident-site lattice model for grain boundaries. We demonstrated that both types of SrAl12O19 films can be used as a chemical buffer and structural template layer for the growth of oriented hexagonal ferrite thin films. In both types of films the (BaSr)Fe12O19 phase cope the in-plane orientation of their respective templates.