The Reaction of Clean Li Surfaces with Small Molecules in Ultrahigh Vacuum: I. Dioxygen

The creation of clean Li surfaces by vapor deposition and their subsequent interaction with oxygen have been studied by a combination of ellipsometry and Auger electron spectroscopy in ultrahigh vacuum. The ellipsometric parameters Δ and Ψ for Li thin films vapor‐deposited on a Ni substrate were monotonic functions of the film thickness, and in reasonable agreement with theoretical values calculated for dense (nonporous) films. The clean Li surface is very reactive toward oxygen, with essentially a sticking coefficient of unity at the initial stage of oxidation at Torr . Oxidation of the entire film (75 Å maximum) into proceeded with an approximately unit reaction probability. A model of oxidation with in‐plane contraction of the oxide film (continuously exposing fresh Li) is proposed to explain both the high rate of reaction and the observed variation of Δ and Ψ with time of exposure to .