Initial stages of Zr single crystals oxidation at different oxygen pressures

C. OVIEDO; J. SACANELL

Sevilla, España

Conferencia; 8th European Conference on Applications of Surface and Interface Analysis (ECASIA 99); 1999

Numerous studies of the first stages of the interaction Zr - O have been carried out at low pressures and room temperature in polycrystalline Zr. In this work the oxidation behavior of two Zr single crystals with different orientation exposed to several low oxygen pressures is compared. Two pure Zr single crystals samples, one oriented with the normal to the surface parallel to the c-axis of the hcp structure (Z1) and the other with the normal perpendicular to c (Z2) were oxidated at 10^-8,10^-7 and 10^-6 torr and room temperature. XPS was the main technique used in this study. The kinetics observed correspond to a logaritmic type law, with a fast initial uptake of oxygen followed by a slower rate until saturation is achieved. For all the studied pressures the sample Z2 incorporated higher quantities of oxygen than the specimen Z1. The deconvolution of XPS 3d peaks indicated the formation of two Zr-O compounds before the formation of ZrO2. Varing the photoelectron take off angle, the compound distribution inside the oxide could be established. Thus, it could be confirmed that the most external oxide, in contact with the gas, was ZrO2. The other two Zr-O compounds were homogeneously distributed through the films. The thickness of the films grown at the different pressures was determined. Films of 1, 1.1 and 1.3 nm were obtained in Z1 specimen oxidized at 10^-8,10^-7 and 10^-6 torr, respectively. However, in the Z2 specimen, at the same pressures, the thicknesses measured were allways higher: 1.5, 1.7 and 1.8 nm.