Increase in yields of secondary ions by oxidation of zirconium at high temperatures and low oxygen pressures

Abstract

Secondary ion mass spectroscopy has been used to investigate the oxidation of zirconium at pressures of oxygen (6.7 × 10^–5–1.3 × 10^–3 Pa) and at high temperatures (773–1073 K). Existence of three sequential stages of the increase in the yields of the secondary ions Zr⁺, ZrO⁺ and ZrO⁺₂ has been found. The increase of the yield of the Zr⁺ ion is interpreted to be caused by the formation of oxide at the surface. By means of resonance tunnelling theory, the reason for the increase is explained by the downward energy shift of the highest occupied electronic level of the substrate.