Quasi-two-dimensional electron gas at the epitaxial alumina/SrTiO3 interface: Control of oxygen vacancies

abstract: In this paper, we report on the highly conductive layer formed at the crystalline γ-alumina/SrTiO[subscript 3] interface, which is attributed to oxygen vacancies. We describe the structure of thin γ-alumina layers deposited by molecular beam epitaxy on SrTiO3 (001) at growth temperatures in the range of 400–800 °C, as determined by reflection-high-energy electron diffraction, x-ray diffraction, and high-resolution electron microscopy. In situ x-ray photoelectron spectroscopy was used to confirm the presence of the oxygen-deficient layer. Electrical characterization indicates sheet carrier densities of ∼1013 cm−2 at room temperature for the sample deposited at 700 °C, with a maximum electron Hall mobility of 3100 cm[superscript 2]V[superscript −1]s[superscript −1] at 3.2 K and room temperature mobility of 22 cm[superscript 2]V[superscript −1]s[superscript −1]. Annealing in oxygen is found to reduce the carrier density and turn a conductive sample into an insulator.Copyright 2015 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. along with the following message: The following article appeared in JOURNAL OF APPLIED PHYSICS 117, 9 (2015) and may be found at http://dx.doi.org/10.1063/1.491386