Atomic layer epitaxy growth of LaGaO₃ thin films

Lanthanum gallate thin films were deposited by atomic layer epitaxy (ALE) at 325–425 °C from β-diketonate-type precursors, La(thd)₃ and Ga(acac)₃, and ozone. Films were grown on soda lime glass, Si(100), MgO-buffered Si(100), sapphire, MgO(100), SrTiO₃(100) and LaAlO₃(100) substrates. Good control of film stoichiometry was obtained by adjusting the La(thd)₃/O₃ to Ga(acac)₃/O₃ pulsing ratio. Stoichiometric LaGaO₃ films contained only 0.4 at.% carbon and less than 0.2 at.% hydrogen as impurities. Films were transparent and uniform and their thickness could be accurately controlled by the number of deposition cycles. The as-deposited films were amorphous and became crystalline upon annealing. The annealed films grown on sapphire and MgO(100) substrates were polycrystalline LaGaO₃ whereas a La₄Ga₂O₉ phase was formed when the films grown on Si(100) and MgO-buffered Si(100) were annealed. Epitaxial and smooth LaGaO₃ thin films were obtained on LaAlO₃(100) after annealing at 850 °C, verified by measurements of the X-ray rocking curve of the (200) reflection and the AFM surface roughness.