We report on ZnO atomic layer deposition (ALD) with a precursor combination of diethylzinc as metal-precursor and pure oxygen (O-2) as oxidant as an alternative to H2O as oxygen precursor. The temperature region of self-limiting ALD growth (ALD window) is determined and shows an increase in growth rate of about 60% compared to water as oxygen-precursor. Finally, in situ X-ray photoelectron spectroscopy (XPS) and synchrotron-radiation photoelectron spectroscopy (SR-PES) have been used to analyze the initial growth and film properties of ALD-ZnO deposited in monolayer steps using both precursor combinations. (C) 2011 Elsevier B.V. All rights reserved.