Thermal stimulation of the surface termination of LaAlO3{100}

The surface termination, structure, and morphology of the LaAlO3{100} surface has been studied as a function of temperature by means of time-of-flight scattering and recoiling spectrometry (TOF-SARS), atomic force microscopy (AFM), low-energy electron diffraction (LEED), Auger electron spectroscopy (AES), and x-ray photoelectron spectroscopy (XPS). The results show that the surface is terminated in a Al–O layer from room temperature up to ∼150 °C and a La–O layer at temperatures above ∼250 °C. The surfaces are terminated exclusively in either Al–O or La–O layers, with mixed terminations observed only in the intermediate region of 150–250 °C. These surfaces exhibit ordered (1×1) LEED patterns and stepped AFM images with step heights of 3.9±0.5 Å and terrace widths of ∼1000 Å. A mechanism is proposed for this low-temperature surface stoichiometry change which is linked to the observation of the creation of surface oxygen deficiencies upon heating. The oxygen deficient Al–O terminating layer transforms to a La–O terminating layer, creating a near-surface vacancy in the twelve coordinate site of the perovskite structure.