Dissociation of perfluorinated ethers on Al2O3 thin films

We have observed dissociation of several small fluorinated ethers on an Al2O3 surface. The ethers studied were perfluoro-1,3-dioxolane (-CF2OCF2OCF2-), perfluorodiethylether (CF3CF2OCF2CF3), perfluorodimethylether (CF3OCF3), tetrafluorodimethylether ((CF2H)2O), and perfluorodimethoxymethane (CF3OCF2OCF3). Temperature programmed desorption determined that the fluorinated ethers bond weakly to the Al2O3 surface with desorption energies ranging from 8 to 10.5 kcal/mole. X-ray photoelectron spectroscopy revealed that a small fraction of a monolayer of adsorbed tetrafluorodimethylether decomposed thermally during heating. Although the decomposition is enhanced by electron irradiation or X-ray irradiation it will occur to a small extent in their absence. All the fluoroethers were observed to undergo some decomposition on the Al2O3 surface. None of the fluoroethers decomposed on the Al(110) surface even in the presence of X-ray irradiation.