An XPS study of the initial stages of oxidation of hafnium

The oxidation kinetics of polycrystalline hafnium (Hf) at room temperature and low oxygen pressure ( P o 2 ∼ 10 −7 Torr) has been studied by x‐ray photoelectron spectroscopy (XPS). After a chemisorption stage for exposures ⩽ 5 L, Hf suboxides are initially formed and are dominant until ∼ 25 L. HfO 2 appears at ∼ 10 L. Above 25 L, HfO 2 grows by oxidation of the suboxides, whereas the oxide film thickness remains constant. Above 500 L, a saturation region is observed that corresponds to an oxide layer of 12 Å thick with an average composition HfO 1.8 .