Oxidation of polycrystalline and (111) lead surfaces studied by electron spectroscopy

Abstract

The initial oxidation of polycrystalline and (111) lead surfaces by oxygen has been investigated up to exposure of 10⁹ Langmuir at 295 and 425 K by X-ray and u.v. photoelectron spectroscopy. A single oxide species is found on both surfaces at all stages of the oxidation process and is interpreted as orthorhombic PbO in agreement with the work of Joyner et al. U.v. studies show that oxide formation occurs from the lowest oxygen exposure. Consideration of the escape depths of u.v. and X-ray excited photoelectrons suggests that the oxidation process occurs by oxide nucleation in islands which grow predominantly laterally to reach an average thickness of between 2 and 3 monolayers when the outermost layer is completely oxide.