Reactivity towards oxygen of surfaces investigated by ultraviolet photoelectron spectroscopy, X-ray photoelectron spectroscopy and low energy electron diffraction spectroscopy

Abstract

Very thin films of tellurium, with mean thickness up to 100 A, were deposited in ultra high vacuum at room temperature on a Si(100) 2 × 1 surface, and were exposed to different amounts of O 2 and to the atmosphere. Ultraviolet photoelectron spectroscopy, X-ray photoelectron spectroscopy and low energy electron diffraction spectroscopy were performed in order to investigate the reactivity of the Te Si (100) system towards oxygen. The Si(100) 2 × 1 surface is found to chemisorb O 2 and to saturate with ≈ 500 Langmuir. In contrast, the tellurium films are not active either towards oxygen or towards the atmosphere for a few minutes: no changes are detectable in the UPS and XPS spectra and LEED patterns of samples with the Si(100) surface completely covered by Te. With deposition of 1 A of tellurium the silicon substrate is not completely covered, and the sample can chemisorb a lower amount of oxygen with respect to the pure Si(100) 2 × 1 surface. The tellurium film thus acts as a protective barrier against the oxidation of silicon.