On the Adsorption of Gases on Silicon Carbide: Simple Estimates

Resumo

The adsorption of atomic and molecular nitrogen and ammonia on silicon carbide is considered within two physically different (solid-state and quantum-chemical) approaches. In the solid-state approach, the Haldane–Anderson model is used for the density of states of the SiC 4H and 6H polytypes to demonstrate that the energy of binding to the substrate is 6 and 3 eV for N atoms and N₂ molecule, respectively. In the quantum-chemical approach, the model of a surface diatomic molecule is used to find that the binding energy of atomic nitrogen is 6 and 4 eV for adsorption on the C- and Si-edges, respectively. It has been established that the charge transfer between an adsorbate and the substrate may be neglected in all the considered cases. It has been hypothesized that the dissociation of a molecule with the further passivation of its dangling sp³-orbitals with hydrogen atoms takes place for silicon carbide as in the case of ammonia adsorption on Si(100).