Structural phase transition of ultra thinPrO2 films on Si(111)

Abstract

Ultra thin heteroepitaxial PrO2 films on Si(111) were annealed under UHV conditions and investigated by x-ray diffraction(XRD), x-ray reflectometry (XRR) and spot profile analysis low energy electrondiffraction (SPALEED) with regard to structural stability and phase transitionsdue to the high oxygen mobility of the oxide. This gives information about themanageability of the material and its application as a model catalyst system in surfacescience. While the samples are stable in UHV at room temperature, annealing at300 °C exhibits a terminatedphase transition from PrO2 and PrO2−Δ to cub-Pr2O3 with an increase in the silicate at the interface and a decrease in the crystalline praseodymialayer mainly due to atomic diffusion of silicon into the oxide film. Strain effects during thephase transition also cause mosaic formation at the surface. Further annealing up to600 °C shows only little change in the film structure. This will finally lead to a model of the filmstructure during the annealing process.