Modification of an NF 3 film by sub-excitation electrons

Abstract

By applying the IRAS technique (infrared-absorption-reflection spectroscopy) and electron stimulated desorption (ESD) of negative ions we demonstrate that a 10 monolayer (ML) film of NF 3 is degraded in the course of low-energy electron irradiation in the range 0–5 eV which is far below the electronic excitation of NF 3. Degradation is accompanied by the desorption of F − fragment ions from the film and formation of NF 2 radicals and N 2F 4 molecules in the film. The energy dependence of the degradation cross-section follows that for resonant (dissociative) electron attachment in the low-energy region (≈0–5 eV) and increases above 6 eV. We therefore identify (dissociative) electron capture at low energy as the only initial reaction responsible for the chemical changes in the NF 3 film.