Polarity-induced persistent surface reconstruction in SrRuO$_{\mathrm{\mathbf{3}}}$\textbf{ (111) thin films}.

The surface structural and electronic properties of SrRuO$_{\mathrm{3}}$/SrTiO$_{\mathrm{3\thinspace }}$(111) as function of the film thickness are investigated. It is found that, though the interface of SRO/STO (111) has no polar mismatch and negligible lattice mismatch, the polar surface of SrRuO$_{\mathrm{3}}$ (111) thin films results in a persistent surface reconstruction. Above 2 unit cells, a $(\sqrt 3 \times \sqrt 3 )R30^{\circ}$ surface reconstruction is observed with both Low energy and reflection high energy electron diffraction. X-ray photoemission spectroscopy shows that the reconstruction is associated with the ordered oxygen vacancies on SrO$_{\mathrm{3-\delta }}$ terminated surface to compensate the surface polarity. Post annealing in oxygen/ozone mixture restores the $p$(1$\times$ 1) surface structure, but results in different surface relaxation and enhances the metallicity thus reducing the thickness of dead layer in this material.