PNNL

Abstract

In a recent Letter, Yoshimatsu et al. [1] used soft x-ray photoemission to probe electronic structure at the buried epitaxial LaAlO3/SrTiO3(001) interface (LAO/STO). This system has been of significant recent interest because of reports of two-dimensional electron gas (2-DEG) behavior at the interface of two band insulators. Although oxygen vacancies in the STO can result in itinerant electrons, an intrinsic conducting layer appears to form, possibly originating with interface charge from LAO which allegedly alleviates the so-called “polar catastrophe” at the interface. The principal conclusions from [1] are: (i) there is no partially-reduced Ti at the interface, as expected if there is electron transfer from the LAO, and, (ii) band bending at the interface occurs and results in a quantum well which is populated with carriers in the case of the TiO2-terminated substrate, but not for the SrO-terminated substrate. While the first of these conclusions is defensible, the second is not.