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.

► Lanthanum aluminate (LAO) grown by atomic layer deposition at 250 °C.
► Single crystal strontium titanate on Si (001) used as the pseudo-substrate .
► Epitaxial, c-axis oriented LAO forms upon annealing at 600 °C.
► Approximately 1 nm-thick amorphous strontium silicate forms during 600 °C annealing.