Alkali metal promoted oxidation of the Si(113) surface

We have investigated the sodium-promoted oxidation of the Si(113) surface b y using X-ray photoelectron spectroscopy (Mg K-alpha, 1253.6 eV). 0 1s, Si 2p and Na 1s core level spectra for the O-2/Na/Si(113) surface were measure d with increasing oxygen exposure and at several annealing temperatures. It was observed that sodium enhanced oxygen adsorption by about three times. When the 1.4 monolayer Na/Si(113) surface was exposed to oxygen at 150 K, t he sodium overlayer was oxidized but the silicon substrate was not. Subsequ ent annealing transferred oxygen atoms into the silicon substrate and desor bed sodium from the Si(113) surface. This oxidation process resulted in thi n silicon dioxide films at about 670 K. The results an consistent with thos e from low index silicon surfaces, Si(100) and Si(111), and are interpreted within a previously suggested sponge model fur the role of all;ali metal i n the: promoted oxidation. (C) 1999 Elsevier Science S.A. All rights reserv ed.