Photoemission study of oxygen adsorption on (001) silicon carbide surfaces

Abstract

X-ray photoemission (ZrMζ, hν=151.4 eV, and MgKα, hν=1253.6 eV) and electron energy loss spectroscopies, low-energy electron diffraction and work-function measurement have been used to study the initial adsorption of oxygen on cubic β-SiC(001) at room temperature. Three different SiC surfaces have been considered—Si-rich [two-domain (3×1) low-energy electron diffraction pattern], stoichiometric [two-domain (2×1)], and Si-deficient [c(2×2)]. Similar data have also been obtained for a Si(001)-(2×1) surface. For SiC the initial rates of O uptake are in the order (2×1)>(3×1)>c(2×2), and the rates for all three are much less than that for Si (2×1). A model for the initial adsorption of O on SiC is proposed in which the rates for the different SiC surfaces reflect the relative ease of formation of Si-O-Si bridges between surface Si atoms while the greater rate for Si versus SiC results from the difficulty in inserting O into SiC backbonds.