A Theoretical Study Of The Reaction Mechanism On Cu₂O（111） And The Coverage-dependent Behavior On Chemical Functionalization Of X（100）（X=C, Si, Ge）

The research on the semiconductor surface can not only greatly promoteexploration, development and application of new-type semiconductor optoelectronicmaterials and devices, but also play a very important role on the development of surfacechemistry. Compared with other semiconductor materials, Cu₂O exhibits many uniquephysical and chemical properties due to its linear O-Cu-O bond and Wannier-excitonspectrum; group IV semiconductors C（diamond）, Si, and Ge are of great interestbecause they are comprised of X=X （X=C, Si, Ge） structural units that resemble theC=C bond of organic alkenes. Therefore, we selected Cu₂O and C, Si, Gesemiconductors as model systems to investigate semiconductor surface properties. Inthis work, we report a systematic study on the reaction mechanism of typical chemicalreactions on the Cu₂O（111） surface and the coverage-dependent behavior for chemicalfunctionalization of the X（100）（X=C, Si, Ge） surface, by using density functionalmethod with periodic slab models. Our work can provide rich theoretical informationfor the preparation of copper-based catalysts with high activity and help discover thebroader applications of C, Si, and Ge semiconductors. It is hoped that our theoreticalstudy would provide experiments with instructive information. All the research contentsand results are as follows:I. The investigation of the reaction mechanism of typical chemical reactions onCu₂O（111）（1） It is interesting to find that CO+NO on Cu₂O（111） could react to form adsorbedNCO surface species, but no CNO and CO2species are observed. Moreover,coadsorption of CO and NO could give rise to the formation of a O C N Osurface complex.（2） The mechanism of CO oxidation on Cu₂O（111） differs from the usual MVKmechanism. Our calculated results reveal that, on Cu₂O（111）, the oxidation is due to theoxygen atoms from the adsorbed oxygen molecule, not by the lattice O. In addition, wefound that CO oxidation on Cu₂O（111） can proceed along either ER or LH mechanism.And the ER mechanism is more favorable than the LH mechanism. II. The investigation of the coverage-dependent behavior on chemicalfunctionalization of X（100）（X=C, Si and Ge）Coverage-dependent behavior for chemical functionalization of the semiconductorX（100）（X=C, Si, Ge） surface by additions of carbenes and nitrene （CH2, SiH2, GeH2and NH） model molecules and by additions of transitional metal oxides （OsO4andRuO4） model molecules, has also been investigated. The results demonstrate that theadsorption energies decrease when coverage is increased. It is feasible to formmonolayer films of carbenes, nitrene and transitional metal oxides onto thesemiconductor X（100） surface and the as-formed monolayer structure among C（100）,Si（100） and Ge（100） is different. In addition, it has also been found that the band gapscan be finely tuned by modifying the coverage and type of the model molecules.