We have investigated Cr solubility and secondary phase formation in metallorganic chemical vapor deposition (MOCVD) grown (Cr, Zn) O films on Si(100). Simultaneous deposition of 0.15 M Cr (TMHD) and 0.025 M Zn (TMHD) precursors in an oxidizing environment with a flow ratio of 1: 10 resulted in secondary phase formation rather than uniform Cr doping. Based on several surface and microstructural techniques, we have identified nanocrystalline ZnCr2O4 and disordered Cr2O3 as the secondary Cr-containing phases. Analysis suggests that ZnCr2O4 crystallites are dispersed throughout the film, and that disordered Cr2O3 layer may form at the interface. These results are consistent with the tendency of Cr to exhibit octahedral, rather than tetrahedral coordination with O. (c) 2007 The Electrochemical Society.