Monolayer oxidation on Si(001)-(2 x 1) studied by means of reflectance difference spectroscopy

Thermal growth of the first oxide layer on a single-domain Si(001)-(2 x 1) surface has been investigated by means of reflectance difference spectroscopy. The transition temperature between two different growth modes, namely, Langmuir-type adsorption and two-dimensional island growth, was identified from Arrhenius plots of the oxidation periods for the growth of an oxide monolayer. The activation energy for the growth of an oxide monolayer was estimated to be epsilon(1)=0.16 +/- 0.03 eV. The activation energy at low coverage was estimated to be epsilon(*)(1)=0.26 +/- 0.03 eV from analysis of the initial slope of the uptake curves. Our results demonstrate that a finite activation energy exists for monolayer oxide formation on Si(001)-(2 x 1) at high temperatures.