X-ray photoelectron spectroscopic study of alternately layered zirconium and hafnium phosphonate thin films on silicon substrates

Multilayer films of alternately layered zirconium and hafnium phosphonates on silicon substrates were prepared and characterized by X-ray photoelectron spectroscopy. It is revealed that the multilayer film is built up layer-by-layer in the repeated order of a zirconium phosphonate layer and a hafnium phosphonate layer. The relative peak intensity of the Zr 3d line to the Hf 4d(5/2) line in the photoelectron spectra of the film takes a lower value as the take-off angle between the surface normal and the detector (alpha) increases. The mean free path of a photoelectron with an energy of ca. 1000 eV was estimated to be 70-90 Angstrom in the film by analyzing the alpha dependence of the relative peak intensities.