Experimental realization of atomically flat and AlO2-terminated LaAlO3(001) substrate surfaces

Abstract

Oxide single-crystal substrates with atomically smooth and chemically uniform surfaces are indispensable for constructing sharp epitaxial heterointerfaces and investigating emergent interfacial physical phenomena. Here, we report a simple method to realize atomically flat and AlO2-terminated LaAlO3 (001) [LAO(001)] substrate surfaces. So far, the LAO(001) substrate has been utilized as a structural template for the epitaxial growth of a variety of oxide films. However, well-established methods for achieving atomically flat, singly terminated LAO(001) surfaces have rarely been reported. This is mainly due to the unstable charged surfaces of LaO+ or AlO2-, which hinders simultaneous stabilizations of atomic-scale smoothness and single termination. To overcome this problem, we combined thermal annealing and subsequent deionized water leaching to treat the LAO(001) surface. We used atomic force microscopy to investigate the evolution of the LAO(001) surface during the water leaching and confirmed the atomically flat surface of the 120-min-water-leached sample. We further demonstrated the uniform AlO2 termination of the LAO(001) surface via coaxial impact-collision ion scattering spectroscopy. Using the treated substrates, we are able to grow perovskite oxide films (i.e., SrRuO3) on the LAO(001) substrate with atomically sharp heterointerfaces. Our paper provides an effective means for controlling the surface and interface of transition-metal oxide heterostructures at the atomic scale. © 2019 American Physical Society