Abstract
Homoepitaxial SrTiO3(110) film is grown by molecular beam epitaxy in ultra-high vacuum with oxygen diffusing from substrate as the only oxidant. The resulted oxygen vacancies (VOs) are found to be spatially confined within few subsurface layers only, forming a quasi-two-dimensional doped region with a tunable high concentration. Such a δ-function distribution of VOs is essentially determined by the thermodynamics associated with the surface reconstruction, and facilitated by the relatively high growth temperature. Our results demonstrate that it is feasible to tune VOs distribution at the atomic scale by controlling the lattice structure of oxide surfaces.
Highlights
Transition metal oxide interfaces have exhibited a variety of novel phenomena, including the high-mobility two-dimensional electron gas,[1,2,3,4,5] superconductivity[6] and unusual magnetism.[7]
The films were grown on Nb-doped (0.7 wt. %) SrTiO3(110) substrates in a molecular beam epitaxy (MBE) system, following the recipe reported previously[22] as described in the supplementary material
Micrograph STEM images as well as the electron energy loss spectroscopy (EELS) were obtained by the aberration-corrected JEOL JEM-ARM200CF equipped with a cold field-emission electron source
Summary
Transition metal oxide interfaces have exhibited a variety of novel phenomena, including the high-mobility two-dimensional electron gas,[1,2,3,4,5] superconductivity[6] and unusual magnetism.[7]. Well-defined (4 × 1) reconstruction is maintained on the surface all through the growth [see Fig. 1 (a) and (b)], which compensates the polarity.[21] More importantly, the energy configuration associated with the surface reconstruction results in the spatial confinement of VOs within only few subsurface layers of the film, while their concentration remains extremely low on the topmost surface and in the bulk of STO substrate.
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