| AVS 55th International Symposium & Exhibition | |
| Surface Science | Tuesday Sessions |
| Session SS-TuM |
| Session: | Dynamics at Surfaces |
| Presenter: | S.R. Bishop, University of California, San Diego |
| Authors: | S.R. Bishop, University of California, San Diego N.L. Tran, University of California, San Diego A.C. Kummel, University of California, San Diego |
| Correspondent: | Click to Email |
The investigation of the gas-surface reaction dynamics of NO with different iron phthalocyanine (FePc) thin films utilizing King and Wells sticking measurements is reported. Three surfaces were studied: a flat-lying monolayer FePc/Au(111) film, a crystalline flat lying multilayer FePc film, and a thick amorphous tetra-t-butyl FePc film. The initial sticking probability is a function of both incident molecular beam energy (0.09 – 0.4 eV) and surface temperature (100 – 300 K). For monolayer FePc/Au(111), NO adsorption onto FePc saturates at 3% of a monolayer at all incident beam energies and surface temperatures suggesting that the final chemisorption site is confined to the iron metal centers. At low surface temperature and low incident beam energy, the initial sticking probability is as great as 40% and decreases linearly with increasing beam energy and surface temperature. The results are consistent with the NO molecule sticking onto the monolayer FePc via physisorption to the aromatic periphery followed by diffusion to the Fe metal center. For the multilayer crystalline flat-lying film, the sticking probabilities are greater in comparison to the monolayer for the same incident beam energy and surface temperature, while the saturation coverage for the two films is identical. More efficient trapping onto the crystalline multilayer film is consistent with NO having improved mass-matching with the multilayer FePc surface compared to the monolayer FePc/Au(111) surface. A comparison between sticking to both crystalline and amorphous multilayer thin films is also presented. The initial sticking is similar for the monolayer FePc and amorphous tetra-t-butyl FePc surfaces. Furthermore, the saturation coverage is only 2% for the amorphous multilayer while 3% for the crystalline surface. The reduced saturation coverage in comparison to monolayer FePc is attributed to the reduced coverage of metal centers with the amorphous thin films.