Direct observation of the layer-by-layer growth of initial oxide layers on Si(100) surface during thermal oxidation

We present the results of an x-ray photoelectron spectroscopy investigation in the real-time regime of the kinetics of high-temperature oxidation of the Si(100) surface. The dependence of the net concentration of silicon atoms in all oxidation states (i.e., ${\mathrm{Si}}^{1+}$ ${\mathrm{Si}}^{2+}$, ${\mathrm{Si}}^{3+}$, ${\mathrm{Si}}^{4+}$) on oxygen exposure is found to exhibit a ‘‘step’’-like behavior, each ‘‘step’’ corresponding to one oxide layer. The results obtained suggest a mechanism of layer-by-layer growth of initial oxide layers, with oxide-phase formation taking place at the Si-${\mathrm{SiO}}_2$ interface.