Incommensurate growth and interface stability in MgO/SrTiO3(001)

High quality MgO film has been grown on SrTiO3(001) by an oxygen-plasma-assisted molecular beam epitaxy system. Although the bulk mismatch of the two cubic structures is 7.8%, the surface lattice mismatch is as large as 23.7%. Reflection high energy electron diffraction (RHEED) provides direct evidence indicating that single crystalline MgO forms with nearly relaxed lattice constant from the first monolayer, The orientation of the MgO film is, however, rotated 45 degrees relative to the SrTiO3(001) surface structure. This incommensurate growth behavior, different from the inverted system SrTiO3/MgO(001), is believed due to the compression-expansion reversing effect. There is also indirect evidence showing that the mismatch interface energy can be removed through the relaxation along the perpendicular direction in a large misfit rocksalt/perovskite system. (C) 1997 Elsevier Science B.V.