Atomic layer epitaxy growth of LaGaO3 thin films

Lanthanum gallate thin films were deposited by atomic layer epitaxy (ALE) at 325-425 degreesC from beta -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)/O-3 to Ga(acac)(3)/O-3 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 degreesC, verified by measurements of the X-ray rocking curve of the (200) reflection and the AFM surface roughness.