Effect of a NH co-adsorbate on the CH3 (or CH2) adsorption to a surface step on diamond (100)
2009 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 113, no 46, 19891-19896 p.Article in journal (Refereed) Published
This study reports upon the effect of a coadsorbed NH species on the binding of CH3 (or CH2) next to a step edge on the H-terminated (100)-2 x 1 surface, using density functional theory (DFT). It is a thermodynamic study where the CH3 (or CH2) species is assumed to be either directly chemisorbed to, or surface migrating to, the final position at the edge. Two types of frequently observed monatomic step edges on the (100) surface, have here been considered. For one of these edges, of type S-A, the carbon dimer row on the lower terrace is perpendicular to the step. While for step type S-B, the lower terrace dimer row is parallel with the step edge. The adsorption energy for CH3 (or CH2), adsorbed next to these steps and in the presence of an NH coadsorbate, were calculated and compared. Three different positions of the NH coadsorbate where chosen, in a neighboring position at the lower or higher terrace. Next to step S-A, the CH3 adsorption energy was not found to be significantly affected by the presence of NH in any of the three positions considered. However, the CH2 adsorption reaction was observed to be strongly improved in the presence of NH by the formation of a new interadsorbate C-N bond. The situation was found to be different for step type S-B, While the CH3 adsorption reaction was not significantly affected by the presence of NH further away from the chemisorbed CH3 species, the formation of a new C-N bond between the surface radical C and the closest NH coadsorbate, prior to adsorption, was found to seriously hinder the chemisorption. On the other hand, the CH2 adsorption reaction was found to be significantly favored by the presence of NH (for all three positions considered). The same trend in energetic results is expected for the situation with surface migration (instead of a direct adsorption) of CH3 (or CH2) toward to step edge.
Place, publisher, year, edition, pages
2009. Vol. 113, no 46, 19891-19896 p.
IdentifiersURN: urn:nbn:se:uu:diva-98007DOI: 10.1021/jp900853aISI: 000271583600020OAI: oai:DiVA.org:uu-98007DiVA: diva2:173160