Reaction mechanisms within aluminum-indium tin oxide (Al-ITO) metallization schemes were investigated in this work using Xray photoelectron spectroscopy and X-ray diffraction. Examination of A1-ITO, aluminum-nickel-indium tin oxide (Al-Ni-ITO), and aluminum-cobalt-indium tin oxide (Al-Co-ITO) interfaces reveals that considerable atomic rearrangement at the ITO interface with Al or with barrier layer transition (CO or Ni) metals occurs due to reaction. Metal-oxygen bonds in crystalline ITO are broken and the interface is rearranged. In Al-Co-ITO stacks, reduced intermetallic species were detected at the Co-ITO interface. In Al-Ni-ITO stacks, such species were not detected at the Ni-ITO interface, although Al3Ni formed at the Al-Ni interface. These reactions within metallization stacks are important because they determine the electrical quality of ITO contacts with Al alloy data lines in polysilicon thin film transistor displays.