Ti Cx thin films were deposited on Al2 O3 substrates at 900 °C by using a multiple cathode high current pulsed cathodic arc. The Ti:C pulse ratio and, hence, the composition was varied from C rich to Ti rich. It is found that the Al2 O3 substrate is decomposed and reacts with the Ti Cx film to incorporate significant amounts of O and Al in the growing film. When the stoichiometry is suitable, epitaxially oriented Ti2 AlC MAX phase with significant O incorporated is formed. The results indicate that Al2 O3 is not an ideal substrate material for the growth of transition metal carbides and MAX phase thin films. © 2008 American Institute of Physics.