Epitaxial growth of LaAlO₃ on SrTiO₃-buffered Si (001) substrates by atomic layer deposition

Lanthanum aluminate (LAO) films were grown epitaxially on Si (001) by atomic layer deposition (ALD) using a buffer layer of strontium titanate (STO) grown by molecular beam epitaxy. The ALD growth of LAO was done at 250°C by using tris(N,N′-diisopropylformamidinate)-lanthanum, trimethylaluminum, and water as co-reactants. Reflection high-energy electron diffraction, X-ray diffraction and transmission electron microscopy were used to determine film crystallinity. The as-deposited LAO films were amorphous and became crystalline after vacuum annealing at 600°C for 2 h. In-situ X-ray photoelectron spectroscopy (XPS) was used to characterize the LAO/STO/Si interfaces at various stages throughout the growth and annealing process. XPS analysis showed minimal Si-O bonding at the STO/Si interface after the ALD process and after post-deposition annealing at 600°C for 2 h. The results demonstrate a method to integrate epitaxial LAO films on Si (001) substrates by ALD. © 2012 Elsevier B.V. All rights reserved.