The thermal stability of InSb/Al2O3 stacks has been systematically studied upon in situ post deposition annealing (PDA) at 300 degrees C and 400 degrees C. Atomic layer deposition (ALD) of Al2O3 (similar to 3 nm) has been grown on the native oxide and the HCl aqueous solution treated InSb (100) at 200 degrees C. The interface chemistry, elemental diffusion as well as elemental desorption are characterized by synchrotron radiation photoemission spectroscopy (SRPES) with the incident photon energy of 750, 600 and 500 eV. A Math model has been proposed to calculate the depth profile for In and Sb oxides based on the analysis from different incident energies. Indium atoms have re-oxidized during ALD process, and indium oxide has been observed to diffuse into the Al2O3 film upon PDA at 300 degrees C for the HCl pretreated sample. Indium oxide has desorbed and diffused upon PDA process for the native oxide sample. Sb oxide has been observed to desorb continuously as PDA temperature increases, for all samples. The surface has been torn up upon PDA at 400 degrees C from the morphology characterization. (C) 2017 Elsevier B.V. All rights reserved.