HeteroepitaxialY2O3films were grown on Si(100) substrates by the technique of reactive ionized cluster beam deposition. The crystallinity of the films was investigated with reflection high energy electron diffraction (RHEED), glancing angle x-ray diffraction (GXRD), and the interface was examined by high resolution transmission electron microscopy (HRTEM). Under the condition of 5 kV acceleration voltage at the substrate temperature of 800 °C, theY2O3film grows epitaxially on the Si(100) substrate. RHEED and GXRD results revealed that the epitaxial relationship betweenY2O3and Si(100) isY2O3(110)//Si(100), and HRTEM observation showed a sharp interface without an amorphous layer. ©1997 American Institute of Physics.