The growth behavior and film quality of HfO2 deposited by atomic layer deposition (ALD) using HfCl4/H2O depends on the hydroxylation of the exposed surface. In this work, we investigate the dependence of the first HfCl4 chemisorption reaction at 300 degrees C on the OH density of the silicon surface. We observe that the hydroxyl density, and hence the Hf deposition, on O-3/H2O wet oxides depends on the initial preparation as well as on the stabilization time in the ALD reactor. A good understanding of the initial nucleation behavior is necessary because wet oxides are used in complementary metal-oxide-semiconductor transistors as surface pretreatment for aggressively scaled HfO2 gate dielectrics. Moreover, the HfCl4 chemisorption reaction is used to estimate the hydroxylated fraction of these surfaces by means of theoretical models. Finally, the temperature dependence of the OH density, as available in the literature, is applied to gain insight into the stoichiometry of the HfCl4 chemisorption reaction. (c) 2008 The Electrochemical Society. [DOI: 10.1149/ 1.2980427] All rights reserved.