In Situ Control of Separate Electronic Phases on SrTiO₃ Surfaces by Oxygen Dosing

Abstract

Insulating SrTiO3 (STO) can host 2D electron systems (2DESs) on its surfaces, caused by oxygen defects. This study shows that the STO surface exhibits phase separation once the 2DES is formed and relates this inhomogeneity to recently reported magnetic order at STO surfaces and interfaces. The results open pathways to exploit oxygen defects for engineering the electronic and magnetic properties of oxides.

Oxygen partial pressure dependence of surface space charge formation in donor-doped SrTiO3

“…41,42 Similar intensity changes in the Sr core level, however, have also been assigned to SrO 17,43 or hydroxide (Sr(OH) 2 ) 41 surface phase formation. Neither the spectral differences in the O1s, 44 the Sr3d, 17,45 in the Ti2p 46 nor any spectral changes in the VB spectra 47 allow for an unambiguous interpretation as chemical changes. In fact, both scenarios (band bending and/or chemical changes) can describe the changes in the peak shapes equally well (cf., S6 in the supplementary material).…”

Oxide Materials at the Two-Dimensional Limit

“…interface bands compared to LaAlO3/SrTiO3 may reveal larger fraction of the nonconducting interfacial phase [209,210] Finally, Figure 5.4(f) shows the Fermi surface formed by the interface electrons.…”

Influence of oxygen vacancies on two-dimensional electron systems at SrTiO3-based interfaces and surfaces

“…Our own experimental work [57] in this context focused on the role of oxygen vacancies for the formation of a two-dimensional electron system at the surface of bare SrTiO 3 in (100) and (111) orientation. Using (angle-resolved) photoemission we got evidence for two separate electronic phases at the surface that are distinguished by a strong disproportionation of charge with respect to each other.…”

“…On the other hand, a metal capillary in front of the sample allows to direct a steady flow of oxygen onto the SrTiO 3 surface. Thereby, oxygen vacancies are annihilated and a certain concentration of oxygen vacancies can be adjusted in a dynamical equilibrium through the oxygen flow [57].…”

“…For details see text. From reference [57]. (This figure is subject to copyright protection and is not covered by a Creative Commons license.)…”