Binding energies of CD4 and fragment species to Pt(111): Implications for measurements of anion electron stimulated desorption

Abstract

We consider the electron stimulated desorption, via dissociative electron attachment, of anionic species from thin condensed CD4 films deposited on a Pt substrate and compare experimentally observed desorption yields with density functional theory calculations of the binding energies of various anionic and neutral moieties to Pt(111). Certain species (which can be considered chemisorbed) exhibit very high binding energies and large charge transfer with the substrate. Other “physisorbed” species have much lower binding energies. Species that chemisorb have lower desorption yields than those that physisorb, especially at 1–2 monolayer coverage of the Pt substrate. The binding energy of D− to Pt is the weakest, and experimentally, the desorption yield is the highest regardless of the thickness of CD4. The calculations show that the formation and desorption of anionic species at a distance of 16 Å from the substrate, which is equivalent to the thickness of CD4 films of four monolayers, are not influenced by the short-range interactions between the substrate and the molecule and DEA products.