Crystalline quality of thin films can be mediated by their growth modes and crystallographic orientations. Normally, a growth mode of layer-by-layer can effectively suppress formations of defects (such as domain walls, grain boundaries, column-structures, dislocations, etc.) in thin films, reduce films' surface roughness, and consequently, promote films' crystallinity. Such a film grown by layer-by-layer growth mode may exhibit less defects and fiat surfaces, even presenting a single-crystalline nature (single domain). In this paper, we have characterized the crystallinity of pulsed-laser-deposited Ba0.6Sr0.4TiO3/Ir/MgO/Si heterostructures by X-ray diffraction, atomic force microscopy, reflection high-energy electron diffraction, Rutherford backscattering spectrometry and transmission electron microscopy. These investigations show that the heterostructures exhibit not only an epitaxial layer-by-layer growth mode but also a single-crystalline nature. This work demonstrates an effective way in monolithic integration of Ba0.6Sr0.4TiO3 with silicon for frequency agile devices. (c) 2005 Elsevier B.V. All rights reserved.