Chemical intermixing at oxide heterointerfaces with polar discontinuity

The stability of the (4 × 4) reconstruction is studied on SrTiO3(111) and LaTiO3(111) surfaces by scanning tunneling microscopy. While the reconstruction may effectively compensate the surface polarity, the associated large lattice distortion on SrTiO3 with relatively strong polarity has to be relaxed by extra adsorbates. Alternatively, substituting Sr by La can reduce the polarity and stabilize the clean reconstructed surface. This provides the driving force for La segregating towards the surface during the heteroepitaxy of SrTiO3 on LaTiO3-covered SrTiO3(111), and thus, the interface sharpness will be deteriorated. To improve the quality of heterointerfaces where the surface polarity of substrates tends to be increased by the epitaxial films, the growth kinetics must be optimized to play the major role.