Solid state combinatorial synthesis of oxide thin films is an attractive proposition due to the large number of compositions that could have potentially useful proper-ties. Thin film growth, however, presents a unique set of problems related to the formation of heterointerfaces. Although this problem affects mostly the study of heterostructures, even simple film growth has to handle the substrate-film interface. We have developed a technique for growing lattice constant tunable Ba1-xSrxTiO3 (BSTO)/BaTiO3 (BTO) buffer layers on SrTiO3 (STO) substrates in order to study the effects of lattice strain in a systematic way in combinatorial thin film libraries. We show that by combining low temperature deposition and high temperature annealing, it is possible to grow buffers with an in-plane lattice constant gradient in the range of 3.9-4.02 Angstrom using a composition spread Ba1-xSrxTiO3 layer. (C) 2003 Elsevier B.V. All rights reserved.