One of the most used dielectric films for amorphous indium zinc oxide (IZO) based thin films transistor is HfO2. The estimation of the valence band discontinuity (Delta E-V) of HfO2/IZO heterostructure grown using the pulsed laser deposition technique, with In(In + Zn)= 0.79, was obtained from X-ray photoelectron spectroscopy (XPS) measurements. The binding energies of Hf 4d5, Zn 2p3 and In 3d5 core levels and valence band maxima were measured for thick pure films and for a very thin HfO2 film deposited on a thick IZO film. A value of Delta E-V = 1.75 +/- 0.05 eV was estimated for the heterostructure. Taking into account the measured HfO2 and IZO optical bandgap values of 5.50 eV and 3.10 eV, respectively, a conduction band offset Delta E-C = 0.65 +/- 0.05 eV in HfO2/IZO heterostructure was then obtained. (C) 2016 Elsevier B.V. All rights reserved.