Layer-by-layer heteroepitaxial growth of BaTiO3 thin films on single-crystal MgO (10 0) is demonstrated using a two-stage metal-organic chemical vapor deposition technique. Films grown using this technique are particularly well suited for photonic applications, with near atomically smooth surfaces and exceptional crystalline quality. Films with surface roughness as low as 0.23 nm RMS and X-ray rocking curve full-width-at-half-maximum values as low as 0.28degrees have been obtained. Refractive indices approaching those of bulk BaTiO3 are demonstrated, with deviations from bulk explained by strain-modified tetragonality and a polydomain structure. (C) 2003 Elsevier Science B.V. All rights reserved.