An anomalous surface X-ray diffraction study of the interface between SrTiO3(001) substrates and thin polar films of LaAlO3 revealed La/Sr interdiffusion leading to neutrally charged Sr1−1.5xLaxO layers. From a thickness of two unit cells, the LaAlO3 film's interior retains its polar stacking sequence, which was compensated by a cationic compositional change of the substrate's terminating TiO2 layer. While such valence-retaining A-site intermixing does not resolve the polar catastrophe, it may be a general feature at oxide interfaces influencing the electronic and magnetic properties.

Polar-Discontinuity-Retaining A-Site Intermixing and Vacancies at SrTiO3/LaAlO3 Interfaces. V.Vonk, J.Huijben, D.Kukuruznyak, A.Stierle, H.Hilgenkamp, A.Brinkman, S.Harkema: Physical Review B, 2012, 85[4], 045401