Abstract
Artificial superlattices consisting of ferroelectric BaTiO3 (BTO) and conductive LaNiO3 (LNO) sublayers were epitaxially grown on SrTiO3 (001) single crystal substrates by a dual-gun rf magnetron sputtering system. The formation of superlattice structure was confirmed from the x-ray reflectivity curves and (0 0 L) Bragg reflection of x-ray. A partial but nearly constant relaxation of in-plane strain in the superlattices was observed, even though the sublayer thickness is below the critical value for the generation of misfit dislocations. X-ray reflectivity measurement reveals that the superlattices with stacking period below 20nm have about the same interface roughness of BTO/LNO. Consequently, nearly the same extent of dielectric enhancement results from the strained BTO layer, along with a highly conductive interface zone in the superlattiecs. On the other hand, in-situ, real-time synchrotron x-ray scattering experiment confirms the occurrence of lattice strain relaxation in the superlattice with stacking period below critical value (BTO-3nm/LNO-3nm), and the experimentally evaluated total thickness of the superlattice for the onset of strain relief is satisfactorily close to the prediction from theoretical calculation. Moreover, observation of roughness scaling behavior in the initial growth of epitaxial BTO/LNO superlattices indicates that the strain plays an important role in the evolution of microstructure in superlattices.