XPS study of Ge-Se-Te surfaces functionalized with organosilanes

Amorphous Ge25Se55Te20 chalcogenide thin films have been functionalized with three organosilanes: (3-aminopropyl)triethoxysilane, tetraethoxysilane and a mixture of tetraethoxysilane and octyl-trimethoxysilane. The functionalized films have been studied by X-ray photoelectron spectrometry, providing an interesting insight of the surface modification process and chemistry. First, the calculated stoichiometric ratios oxygen/silicon, carbon/silicon and nitrogen/silicon are in good agreement with the theory, demonstrating the effectiveness of the functionalization and relative precursors homocondensation. Secondly, the deconvolution of the 3d5/2 and 3d3/2 tellurium orbitals before and after functionalization show new oxidized environments. More specifically, the simultaneous disappearance of the bands at 573.0 eV and 583.4 eV attributed to TeGe and TeTe bonds (resp.) and appearance of a TeO environment (around 576.5 eV and 587.0 eV) strongly suggest covalent anchorage of the three precursors thanks to the formation of new TeOSi groups. This is the first report on tellurium anchorage of organosilane precursors onto chalcogenide surface.