The effects of oxidation on the photoelectron diffraction pattern originating from a silicon substrate were measured and simulated using the Monte Carlo method for calculating the path of scattered electrons in silicon oxide formed on Si(100). The results of these simulations revealed a total elastic scattering cross-section of 1.5 X 10(-20) m(2) and an inelastic scattering cross-section of 1.6 X 10(-20) m(2). In only particular photoemission directions, the effect of elastic scattering of electrons in silicon oxide is shown to be minimized on the basis of the results of these simulations, and the concept of escape depth can be used to determine the oxide film thickness.