Is Due Principally to Electrons

This paper models damage induced by monochromatized Al Ka X-rays to organic thin films using self-assembled monolayers supported on Al, Ti, Cu, and Au. An X-ray photoelectron spectrometer is used both to conduct the X-ray irradiation and to analyze the damage. In all cases these monolayers comprised a trifluoroacetimido (CF3CONH-) group bound to the substrate through an undecyl tether to either a chemisorbed thiolate or carboxylate. This work extends a previous study of using trifluoroacetoxy-terminated SAMs on Au and Si. We find the X-ray-induced damage to the CF3coNH-terminated SAM is first order in the loss of fluorine. From a comparative study of the loss of fluorine from monolayers formed on these substrates with different electron yields, we show directly that electrons, not X-rays, are the principal cause of damage to the monolayer films. These results are relevant to the design of new materials targeted to fabrication at small dimensions by X-ray or electron lithography.