Ti/Ni/Ti/Au Ohmic contact and Schottky transformation to Al-doped ZnO thin films

► A multi-layered Ti/Ni/Ti/Au Ohmic contact to Al-doped ZnO thin films was formed. ► The as-deposited metallic contact showed Ohmic behavior. ► The lowest specific contact resistivity was 6.69 × 10−5 Ω cm2 after 500 °C annealing. ► The contact annealed above 600 °C showed Schottky transformation. ► Interface diffusions induced by annealing resulted in the Schottky transformation.