Electron escape depth variation in thin SiO2 films measured with variable photon energy

We have used a double crystal monochromator at the Stanford Synchrotron Radiation Laboratory to study the Si/SiO2 interface using photon energies of hν=1950–3700 eV. This photon energy range allows interfaces to be observed through oxide layers 50 Å thick or more. Variations in electron escape depth and/or oxide density as a function of distance from the interface are observed over the entire kinetic energy range (100–3600 eV). We attribute these differences to a strained oxide layer near the interface.