Disentangling specific versus generic doping mechanisms in oxide heterointerfaces

High‐temperature 2D Fermi surface of SrTiO3 studied by energy‐filtered PEEM

“…Although annealing at 973 K clearly plays an important role with the appearence of IG intensity following oxygen loss, beam interaction with the surface also reduces Ti 4+ to Ti 3+ . It is the reduction under soft X‐rays that creates a 2D metallic surface state . As in Gonzalez et al, UHV annealing alone did not create a 2DEG.…”

Room temperature 2D electron gas at the (001)-SrTiO3 surface

“…This shows that the beam exposure has a greater effect on the creation of the 2DEG than the annealing used to prepare the surface and that the 2DEG is populated by electrons freed following the creation of oxygen vacancies at the surface. 9,10 Spectra of the Ti 2p core-level (not shown) exhibited a higher Ti 3þ component after the beam exposure, reinforcing the fact that the beam is responsible for reduced Ti 4þ rather than the annealing. 10 This sensitivity of the 2DEG to the oxygen partial pressure may limit the possibilities of realistic electronic devices to oxide structures with buried interfaces such as LAO/STO.…”

“…6 The existence of a low binding energy (BE) shoulder in the Ti 2p core level spectrum due to reduced Ti is a necessary condition for a 2DEG in STO; however, by itself it is not sufficient since the Ti 3þ shoulder may also be due to localized electrons which cannot contribute to the quasiparticle at the Fermi level (FL). 10 Here, we use photoemission electron microscopy (PEEM) and synchrotron radiation to characterize the Fermi surface (FS) of STO and to directly observe the existence of a 2DEG at room temperature, showing clearly the band structure of a highly mobile 2DEG, which can be obtained with a simple surface STO surface preparation. PEEM has the advantage of rapid switching between real and reciprocal space imaging, allowing correlation of surface chemistry with the electronic band structure on a microscopic scale.…”

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

“…To shed light on the detailed mechanism at work behind the formation of a conducting interface and to clarify the nature of the two-dimensional electron system our own research [91] combined two approaches: (i) full control of the oxygen vacancy concentration in the SrTiO 3 substrate and simultaneous monitoring of the microscopic electronic structure at the chemical potential by photoemission as described in Section 2.4 and (ii) comparison of epitaxial and amorphous heterostructures to emulate the toggling of the polar discontinuity [74,75].…”

“…The fully oxidized state is shown in blue, the one with saturated oxygen depletion in red. From reference [91]. (This figure is subject to copyright protection and is not covered by a Creative Commons license.)…”