Optical and electrical measurements on CO2 covered copper films

Thin polycrystalline copper films are deposited in a special UHV cell on glass substrates and are covered step by step with CO₂. The optical and electrical properties of the films are studied in-situ by means of ellipsometry and resistivity measurements. The properties of the clean films correspond to literature data. In the case of monolayer adsorption of CO₂, the changes in the ellipsometrical angles are δΔ≈+1° and δψ≈+0.1°, similar to the Cu/O and Cu/CO systems. Three-dimensional island growth leads to a drastical increase of δΔ and δψ by several orders of magnitude. The resistivity first quickly decreases and then slowly reapproaches the initial value. This marked kinetics is quantitatively interpreted on the basis of a diffusion model.